Daddy longlegs have been spotted devouring live frogs bigger than themselves in the tropical forests of South America, a new study reports. And this behavior might be more common than scientists expected.

"Finding these animals eating [live] frogs was a complete surprise, we didn't expect them to be able to capture them," study co-author Luís Fernando García, a biologist at the University of the Republic in Uruguay, told Live Science.

When arthropods, the group that includes animals like insects, spiders, centipedes and crustaceans, are observed eating vertebrates, it's typically treated as a rare or isolated phenomenon. But Jose Valdez, an ecologist at Martin Luther University Halle-Wittenberg in Germany who was not involved in the new study, has found that this type of predation — mostly on frogs, lizards, bats and birds — is actually quite common.

In reality, arthropod predation on vertebrates is under-documented, Valdez told Live Science in an email. Valdez's research has found it is most commonly spiders eating frogs, since frogs' soft bodies and thin skin make them relatively vulnerable.

Yet harvestmen (order Opiliones), also known as daddy longlegs, are not technically spiders; they are part of the arachnid class alongside spiders, but they are more closely related to scorpions, so observations like this new study are particularly noteworthy, Valdez said.

In the new paper, published April 21 in the journal Ecology and Evolution, the research team compiled 10 reports in South America of harvestmen eating frogs around their body size. The reports come from field observations in Ecuador and Colombia, scientific papers, and one from the citizen science platform iNaturalist, which lets anyone with a camera upload photos of wildlife and plants.

"The availability of good quality cameras on mobile phones has enormously helped in recording such interactions and making them available to specialists, sometimes through citizen science platforms," Olivier Pauwels, a conservation biologist at the Royal Belgian Institute of Natural Sciences who was not involved in the new study, told Live Science in an email.

Previous anecdotal reports of daddy longlegs eating frogs have been unclear about whether the arachnid had killed the frog or scavenged an already dead amphibian.

"What we found is that they are able to capture frogs, because many frogs were still moving" in these observations, García said, suggesting that the arachnids might be actively hunting frogs.

The researchers don't know exactly how harvestmen capture frogs, since the arachnids are rather slow and don't have venom, García said. They may be hunting sleeping or resting frogs, or grabbing them with their strong front limbs, known as pedipalps, which are similar to the forelegs of praying mantises and can grasp prey.

"The most surprising aspect is how these harvestmen are able to subdue their prey" without venom to chemically immobilize animals, Valdez said. "Instead, they must rely entirely on physical restraint," an impressive feat since some frogs were up to 1.29 times the size of the arachnids eating them, the study found.

"We now have a new field to explore: the feeding and behavior of these animals, which is basically unknown," García said. "We think it is opportunistic behavior, they are generalist predators."

New discoveries about arthropods' diets in the tropics, and their interactions with other species, can help scientists understand how to conserve these ecosystems.

"The fate of some species is often linked to others," Pauwels said.

Tiny tropical spiders in the Philippines and the Peruvian Amazon build giant, arachnid-like decoys in their webs to scare off predators, new research shows.

The outsize fake spiders are made of silk; plant debris; and dead, disembodied prey. Some decoys look rudimentary, but others accurately imitate the shape of a spider, according to a study published Nov. 6 in the journal Ecology and Evolution.

The builders of these decoy spiders are the orb weavers Cyclosa inca and Cyclosa longicauda, which measure just 0.1 inch (2.5 millimeters) long. Their spiderwebs are classic wheel shapes made of silk, but inside them lie important clues about spider survival strategies in a world filled with predators.

"They don't just decorate their webs — they meticulously arrange detritus, prey carcasses and silk into a structure that's not only larger than their own body, but clearly resembles the silhouette of a bigger, menacing spider," study lead author George Olah, a conservation geneticist at the Australian National University, said in a statement.

Unlike other orb weavers that build silken tubes to hide inside in their webs, the two Cyclosa spiders invest their time, energy and resources into crafting these decoys. This means the fakes are more than a quirky biological observation, study co-author Lawrence Reeves, an assistant professor at the University of Florida's Medical Entomology Laboratory, said in the statement.

"It illustrates a fundamental evolutionary trade-off in the spider world," Reeves said.

Researchers have known about Cyclosa spiders' strange antics for some time, but the new study is the first time the decoy-building behavior has been formally documented and interpreted.

The spiders turn their webs into "theaters of deception" to stave off would-be attackers, Olah said.

The decoys likely intimidate birds, lizards and other natural predators, prompting them to stay away. They may also provide camouflage for the small Cyclosa spiders, which have the same coloration as their creations and can therefore hide among the plant matter and prey remains.

The decoys may be as effective in defending Cyclosa spiders against predators as the retreats other orb weavers build, explaining why the spiders invest their energy into making them, according to the study. When predators approach the webs, Cyclosa spiders concealed within the decoys shake their abdomen to create vibrations in the fake spiders that make them seem alive.

The spiders do this day and night, the researchers wrote in the study. "When further approached, the spider jumped off from the web to the ground," they noted of a handful of observations in the Peruvian Amazon in 2022, adding that arachnids returned to their webs once the perceived threat was gone.

The decoys may also provide safe places for Cyclosa spiders to lay their eggs, Juan Carlos Yatto, a nature guide in Peru's Tambopata National Reserve who worked with the study's authors, said in a video. The spiders move the contents of their webs to new locations by building a single thread, along which they transport their eggs and all the debris and body parts used for their decoy. In this scenario, the disassembled decoy can camouflage the eggs during relocation, Yatto said.

Other benefits of building decoys could be that they attract prey and strengthen spiderwebs against adverse weather, the researchers wrote in the study. Further research is needed to understand these different advantages, Olah said.

Cyclosa spiders and their strangely decorated webs are featured in the documentary series "The Secret Lives of Animals."

Spider quiz: Test your web of knowledge

Researchers have discovered more than 111,000 spiders thriving in what appears to be the world's biggest spiderweb, deep inside a pitch-black cave on the Albanian-Greek border.

The "extraordinary" colony consists of a colossal web in a permanently dark zone of the cavern, according to a study published Oct. 17 in the journal Subterranean Biology. The web stretches 1,140 square feet (106 square meters) along the wall of a narrow, low-ceilinged passage near the entrance of the cave. It is a patchwork of thousands of individual, funnel-shaped webs, the researchers noted.

This is the first evidence of colonial behavior in two common spider species and likely represents the largest spiderweb in the world, said study lead author István Urák, an associate professor of biology at Sapientia Hungarian University of Transylvania in Romania.

"The natural world still holds countless surprises for us," Urák told Live Science in an email. "If I were to attempt to put into words all the emotions that surged through me [when I saw the web], I would highlight admiration, respect, and gratitude. You have to experience it to truly know what it feels like."

The spider megacity is located in Sulfur Cave, a cavern that was hollowed out by sulfuric acid formed from the oxidation of hydrogen sulfide in groundwater. While the researchers revealed tantalizing new information about Sulfur Cave's spider colony, they weren't the first to see the giant web. Cavers with the Czech Speleological Society discovered it in 2022 during an expedition in the Vromoner Canyon. A team of scientists then visited the cave in 2024, plucking specimens from the web that Urák analyzed before going on his own expedition to Sulfur Cave.

This analysis revealed that two spider species live in the colony: Tegenaria domestica, known as the barn funnel weaver or domestic house spider, and Prinerigone vagans. On their visit to the cave, Urák and his colleagues estimated there were about 69,000 T. domestica and more than 42,000 P. vagans specimens. DNA analyses for the new research also confirmed that these are the dominant species in the colony, Urák said.

Sulfur Cave's spider colony is one of the largest ever documented, and the species involved weren't previously known to assemble and cooperate in this way, Urák said. T. domestica and P. vagans are widespread near human dwellings, but the colony is "a unique case of two species cohabiting within the same web structure in these huge numbers," he said.

Scientists would normally expect barn funnel weavers to prey on P. vagans, but the lack of light in the cave may impair the spiders' vision, according to the study.

The spiders instead eat non-biting midges, which in turn feast on white microbial biofilms — slimy secretions that protect microorganisms against threats in their environment — from sulfur-oxidizing bacteria in the cave. A sulfur-rich stream fed by natural springs flows through Sulfur Cave, filling the cavern with hydrogen sulfide and helping microbes, midges and their predators survive, the researchers wrote in the study.

The spiders' sulfur-rich diet influences their microbiomes, causing them to be significantly less diverse than the microbiomes of spiders from the same two species outside the cave, gut content analyses revealed. Molecular data also showed that the spiders inside the cave were genetically different from their relatives living outside, suggesting the cave-dwellers have adapted to their dingy surroundings.

"Often, we think we know a species completely, that we understand everything about it, yet unexpected discoveries can still occur," Urák said. "Some species exhibit remarkable genetic plasticity, which typically becomes apparent only under extreme conditions. Such conditions can elicit behaviors that are not observed under 'normal' circumstances."

It's important to preserve the colony, despite challenges that might arise from the location of the cave between two countries, Urák said. In the meantime, the researchers are working on another study that will reveal further clues about Sulfur Cave's inhabitants, he added.

Nocturnal spiders have been filmed capturing fireflies and keeping them in their webs to attract more prey, even intermittently checking on them over the course of an hour, according to a new study.

When fireflies were kept on the webs, sheet web spiders attracted significantly more prey than without the bioluminescent beetles, leading researchers to think the spiders are purposefully using the fireflies as bait to increase hunting success.

"Our findings highlight a previously undocumented interaction where firefly signals, intended for sexual communication, are also beneficial to spiders," study lead author I-Min Tso, a researcher at Tunghai University who studies spider behavior, said in a statement.

"This study sheds new light on the ways that nocturnal sit-and-wait predators can rise to the challenges of attracting prey and provides a unique perspective on the complexity of predator-prey interactions," Tso added.

The researchers had noticed sheet web spiders (Psechrus clavis) — which build their sheet-like webs close to the ground — had accumulated a number of winter fireflies (Diaphanes lampyroides), and thought these glowing bugs may have been used as a visual lure. To find out, the team developed a series of field experiments, placing LED lights resembling fireflies and sheet spider webs, and left other webs empty as controls.

Related: Diving bell spider: The only aquatic arachnid that creates a web underwater to live in

The findings, published Thursday (Aug. 28) in the Journal of Animal Ecology, revealed the LED webs attracted three times more prey than the empty webs. When just looking at the number of fireflies caught, the LED webs snared 10 times more than the non-LED webs.

Sheet web spiders, found in subtropical forests of East Asia, normally sit in the dark, waiting for prey to approach. Footage captured by the researchers shows that if another insect, such as a moth, is caught, the spiders eat it immediately. But the fireflies were left for up to an hour before being consumed, which is about the same amount of time that a female firefly emits a glow in a fixed location, the authors wrote in the study.

Most of the captured fireflies were male, which the authors say may indicate males mistook the stationary glow for potential mates.

The researchers think the spiders — unlike other sit-and-wait predators that have developed their own bioluminescence, like anglerfish — have worked out how to exploit fireflies' sexual cues to their advantage.

"Handling prey in different ways suggests that the spider can use some kind of cue to distinguish between the prey species they capture and determine an appropriate response," Tso said. "We speculate that it is probably the bioluminescent signals of the fireflies that are used to identify fireflies enabling spiders to adjust their prey handling behavior accordingly."

Spider quiz: Test your web of knowledge

Scientists have had to create an entirely new spider genus after four new tarantula species were found to have such long genitalia that they couldn't fit into any pre-existing category.

The team believe the males have evolved this impressive appendage to keep themselves as far away as possible from aggressive females, which are known to eat their partners during mating.

Male tarantulas' genitals are typically 1.5 to two times the length of their head and thorax put together. But the newfound spiders' palps — specialized appendages to transfer sperm during mating — are four times as long as their upper bodies and almost half as long as their longest legs, according to a new study.

"The males of these spiders have the longest palps amongst all known tarantulas," study lead author Alireza Zamani, an arachnologist at the University of Turku in Finland, said in a statement. "Based on both morphological and molecular data, they are so distinct from their closest relatives that we had to establish an entirely new genus to classify them, and we named it Satyrex."

The name Satyrex is a combination of the words "satyr" and "rex." In Greek mythology, a satyr is a male nature spirit with the upper body of a human and the lower body of a goat or horse, and "rex" is the Latin word for king. According to the statement, satyrs are often depicted as having exceptionally large genitalia.

The newfound tarantulas live in burrows and cool spaces between rocks on the Arabian Peninsula and the Horn of Africa. Zamani and his colleagues first encountered Satyrex arabicus in Saudi Arabia, photographed Satyrex ferox in Yemen and Oman, and described Satyrex somalicus and Satyrex speciosus in Somaliland. They published their findings July 22 in the journal ZooKeys.

Related: We now know why tarantulas are hairy — to stop army ants eating them alive

Of the four newfound species, S. ferox stands out as the largest and fiercest, hence its name. Both males and females have leg spans of about 5.5 inches (14 centimeters), and males' palps stretch an incredible 2 inches (5 cm) long, possibly to provide a safety buffer against cannibalistic females during mating.

"We have tentatively suggested that the long palps might allow the male to keep a safer distance during mating and help him avoid being attacked and devoured by the highly aggressive female," Zamani said.

The species is also highly defensive. "At the slightest disturbance, it raises its front legs in a threat posture and produces a loud hissing sound by rubbing specialized hairs on the basal segments of the front legs against each other," Zamani explained.

Molecular and phylogenetic analyses, where scientists reconstruct the evolutionary history of a species through genetics, revealed that a tarantula previously assigned to the genus Monocentropus is in fact more closely related to Satyrex spiders, too. Researchers first described Monocentropus longimanus from Yemen in 1903, but the spider has now been reclassified as Satyrex longimanus.

"The much longer palps of S. longimanus and the four newly described species were among the primary characters that led us to establish a new genus for these spiders, rather than place them in Monocentropus," Zamani said. "At least in tarantula taxonomy, it seems that size really does matter."

Spider quiz: Test your web of knowledge

Filmmakers have captured first-of-its-kind, spine-chilling footage of young spiders cannibalizing their mothers and other elderly relatives en masse.

In the video, more than 1,000 young African social spiders (Stegodyphus dumicola) creep out of their nest in search of their next meal. The youngsters appear to play a macabre game of "statues" as they move, before suddenly freezing then moving again in unison.

The young spiders first attack and devour an insect caught in the giant web that holds their nest, tearing at its body while the insect is still alive. But when this source of food runs out, the spiders turn to one of the moms of the nest, whose condition is deteriorating fast after producing so many young.

"The demands of parenthood are finally taking their toll," British biologist and broadcaster Sir David Attenborough says in his narration of the clip, which is from a new five-part series from the BBC called "Parenthood."

Related: Starving cannibalistic spiders won't hunt their siblings, but they'll quickly dine on their corpses

But the dying spider mom has a departing gift: Trembling, she waits for her offspring and their cousins to swarm and cannibalize her. "Her's is the ultimate sacrifice, born out of a need to ensure the survival of the next generation," Attenborough says.

Scientists think African social spider moms tremble on purpose while waiting for their gruesome deaths. The vibrations they create may be similar to those made by insects that get caught in the web, so young spiders don't hesitate to attack their moms.

However, after eating the spider mom, the spiderlings still aren't satiated. They move on to their other surviving relatives, "eating every adult in the colony one by one until the next generation is all that is left," Attenborough says.

The clip is the first time TV cameras have captured this stomach-churning behavior, according to The Guardian. Attenborough was both "delighted and horrified" when he saw the footage, Jeff Wilson, the producer and director of "Parenthood," told the newspaper.

"When you step away from it and from the horror of it, it sort of makes sense," Wilson said.

An unusual fossil brain suggests that the ancestors of spiders and other arachnids may have once scuttled around the sea, rather than on land as was long thought, a new study finds.

The fossil shows that certain features of the brain of a now-extinct animal known as Mollisonia symmetrica are arranged backward compared with those of most modern arthropods, a large group of invertebrates that includes animals like insects, crustaceans and millipedes. However, M. symmetrica's brain is similar to those in one arthropod group: arachnids, a class that includes spiders, scorpions and ticks. This difference suggests that the marine-dwelling M. symmetrica is an early ancestor of modern arachnids, researchers reported Tuesday (June 22) in the journal Current Biology.

"It is still vigorously debated where and when arachnids first appeared, and what kind of chelicerates were their ancestors, and whether these were marine or semi-aquatic like horseshoe crabs," study co-author Nicholas Strausfeld, a professor who specializes in arthropod neuroscience at the University of Arizona, said in a statement. Chelicerates make up a major group of arthropods that includes arachnids and horseshoe crabs.

Chelicerates like M. symmetrica branched off from other arthropods by the mid-Cambrian period. The Mollisonia genus, which has four known species, lived between approximately 515 million and 480 million years ago. The species M. symmetrica had a segmented body like that of a scorpion, a round carapace and six pairs of appendages for moving and hunting.

Although scientists aren't sure exactly when arachnids branched off further from other chelicerates, arachnids have been around for some 400 million years. Until now, their fossil record suggested they lived exclusively on land.

In the new study, the researchers investigated the fossilized brain and central nervous system of a M. symmetrica specimen from the Burgess Shale formation of the Canadian Rockies. They found that the animal's brain was not organized like that of a horseshoe crab of the genus Limulus. Instead, certain regions of its brain appear to be arranged in the opposite direction compared with those of other arthropods, similar to how modern spiders' brains are laid out. This suggests that arachnids evolved and diverged from horseshoe crabs earlier than scientists had thought.

"It's as if the Limulus-type brain seen in Cambrian fossils, or the brains of ancestral and present [day] crustaceans and insects, have been flipped backwards, which is what we see in modern spiders," Strausfeld said.

Related: Why do spiders have 8 legs?

This opposite arrangement is exclusive to arachnid brains in modern animals, suggesting that M. symmetrica was an early arachnid and that this unique arrangement evolved in the ocean rather than later on land. Studies of existing spider brains suggest that the inverted setup allows spiders to coordinate many aspects of predatory movement, including their stealth, speed and dexterity.

"The arachnid brain is unlike any other brain on this planet, and it suggests that its organization has something to do with computational speed and the control of motor actions," Strausfeld said.

Spiders' stealth and speed as hunters on land may have contributed to the evolution of insect wings, which would have allowed prey to escape, Strausfeld added.

"Being able to fly gives you a serious advantage when you're being pursued by a spider," Strausfeld said. "Yet, despite their aerial mobility, insects are still caught in their millions in exquisite silken webs spun by spiders."

To figure out whether the similarities between M. symmetrica's brain and those of modern spiders came from a common lineage or mere coincidence, the researchers used a computer program to estimate the likelihood that the two were related. To do this, they compared brain and body traits of several living and extinct arthropods. The analysis suggested that the Mollisonia lineage eventually evolved into the arachnid group, meaning that it may have led to "the planet’s most successful arthropodan predators," the researchers wrote in the study.

Spider quiz: Test your web of knowledge

Spiders: they're creepy, they're crawly and they’re undeniably fascinating. With around 50,000 known species worldwide, spiders have adapted to nearly every environment on Earth; we're talking deserts, caves, rainforests and even underwater. Whether they send a shiver down your spine or make your senses tingle, there's more to these eight-legged enigmas than meets the eye.

As scary as they can appear — often starring in horror movies and our nightmares — most spiders tend to avoid humans and would much rather scurry away than attack. In fact, spiders are some of nature's most skilled engineers, survivalists and hunters. From questionable courtship rituals to elite hunting strategies, we can't help but be amazed by these adaptable arthropods.

So, are you a true arach-nerd or will you get caught in a web of lies? Brave this quiz to test your spider smarts, if you dare.

More science quizzes

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Young cannibalistic spiders give off social signals that stop siblings from eating each other alive, a new study finds. But the corpses of fallen brothers and sisters are fair game.

Labyrinth spiders (Agelena labyrinthica) live across Europe and spend most of their lives alone, dining on small insects and, if the opportunity arises, other labyrinth spiders. However, despite their cannibalistic tendencies, labyrinth spiderlings are content to share a web with their siblings at a young age.

In a new study, published in the April volume of the journal Animal Behaviour, researchers put spider sibling tolerance to the test by depriving lab-reared labyrinth spiderlings of food. The researchers wanted to see whether the hungry spiderlings would turn on each other, but, to the researchers' surprise, the spiderlings remained civil.

"Spiders, even when starving, can be highly tolerant of their living siblings, with strong signals that prevent cannibalism," study authors Antoine Lempereur, a doctoral student, and Raphaël Jeanson, a senior researcher, both at the University of Toulouse in France and the French National Centre for Scientific Research (CNRS), told Live Science in an email.

However, these signals only appear to be active while the spiders are alive, because the spiderlings happily fed on their brothers and sisters once they were dead, according to the study.

Related: Watch enormous deep-sea spiders crawl around sub-Antarctic seafloor

Labyrinth spiders live in webs with intricate tunnel systems, or labyrinths. Females lay and hatch their eggs — up to 130 of them — in the central chamber of these webs during the summer. The resulting hatchlings remain in the web with their mother over winter, before emerging in spring, according to the Southwick Country Park Nature Reserve in England, which is home to labyrinth spiders.

The spiderlings initially live off egg yolk from the eggs they're born in, which is kept in their abdomens, and will eat their mother if she dies. However, they can also catch flies within days of hatching, so they're capable of hunting at a young age.

To learn more about why siblings aren't hostile to one another, Lempereur and Jeanson collected labyrinth spider egg sacs in southwest France and hatched them in a lab. Some of the spiders were kept in groups of four, while others were kept alone. None of the spiders were fed during the experiment, and after 20 days, the researchers started putting two hungry spiders into small plastic "arenas" to see how they would interact, according to the study.

The spiderlings raised in groups were significantly less aggressive to one another than the spiders raised alone, something Jeanson has already demonstrated in previous studies. The researchers suggested this is because social isolation reduces sensitivity to social signals.

"In short, a spider living alone has no reason to respond to cues emitted by other spiders, as it will never encounter them again, except during reproduction when other signals, such as sexual pheromones, come into play," Lempereur and Jeanson said.

While the group-reared spiders were typically not hostile to each other, they fed on their dead siblings just as quickly as the socially isolated spiders, which the researchers said was surprising for two reasons.

"First, spiders are typically predators of living prey rather than dead prey," Lempereur and Jeanson said. "Second, and more importantly, as shown in our previous work, spiders can tolerate living siblings for weeks but will consume dead siblings within an hour of their death."

Lempereur and Jeanson wrote in the study that living siblings could be sending a "life signal" to one another through chemicals, which is one of the ways spiders communicate. The researchers will now investigate the makeup of this signal.

Until recently, scientists thought a rare and potentially deadly meat allergy was transmitted by just one species of tick found in the U.S. — the lone star tick (Amblyomma americanum). However, new reports of the allergy, called alpha-gal syndrome, show that the much more widespread black-legged ticks (Ixodes) can also transmit the disease.

Whereas lone star ticks are found mainly in the southern and eastern U.S., black-legged ticks (Ixodes scapularis), also called deer ticks, are present in the eastern half of the U.S. and the Midwest and the western black-legged tick (Ixodes pacificus) inhabits the West Coast, according to Mayo Clinic.

The new case reports suggest that people in a wide swath of the U.S. are at risk of tick-borne alpha-gal syndrome. However, "evidence continues to support that in the U.S., most alpha-gal syndrome patients develop the allergy after experiencing a bite from a lone star tick," Dr. Johanna Salzer, a veterinary medical officer and epidemiologist with the Centers for Disease Control and Prevention's (CDC) Division of Vector-Borne Diseases and a co-author of both case reports, told Live Science in an email.

Given that a variety of tick species have been linked to alpha-gal syndrome outside the U.S., scientists had long suspected that black-legged ticks in the U.S. also transmit the allergy.

"For us, it was never just the lone star tick," Jennifer Platt, co-founder of the nonprofit Tick-Borne Conditions United and an adjunct faculty member at the University of North Carolina at Chapel Hill, wrote in a blog post. "With thousands of Lyme [a tick-borne disease] patients telling us they can't tolerate red meat, we've long suspected black-legged ticks and other tick species in the US," she noted.

"Although our publications are some of the first reports linking blacklegged ticks in the US to alpha-gal syndrome, bites from these species in the U.S. leading to alpha-gal syndrome almost certainly have occurred prior to these reports," Salzer said.

In alpha-gal syndrome, the immune system overreacts to a sugar known as galactose-α-1,3-galactose, or "alpha-gal" for short. Those affected can develop severe allergic reactions not only to red meat but also to some medications, personal care products, and medical treatments containing ingredients from mammalian tissues, where this sugar is found.

Related: Tick season: What to know about bites, removing ticks and tick-borne diseases

The first case, reported in the April 4 issue of the CDC journal Emerging Infectious Diseases, described a Maine woman who developed alpha-gal syndrome after a confirmed black-legged tick (I. scapularis) bite.

The 45-year-old woman first experienced inflammation and itchiness at the bite site, followed by abdominal pain and malaise nine days later, after eating rabbit. Over the next two weeks, she continued having digestive problems after consuming red meat. A severe episode of diarrhea and vomiting hours after she ate beef prompted her to visit a health care provider 20 days after the tick bite. Blood tests revealed extremely high levels of alpha-gal-specific immunoglobulin E (IgE), confirming alpha-gal syndrome. Her allergy resolved after 10 months.

The second case of alpha-gal syndrome, reported in the same journal issue, involved a 61-year-old wildlife biologist in Washington. After a confirmed bite from the western black-legged tick (I. pacificus), she experienced a skin rash and lip swelling, followed by a severe allergic reaction 29 days later, after she ate red meat, and required emergency epinephrine (EpiPen) treatment. After being diagnosed with alpha-gal syndrome, she avoided meat and had no further reactions. Some years later, she got two more I. pacificus tick bites, which triggered a rise in alpha-gal IgE antibodies.

To date, why tick bites can trigger alpha-gal syndrome is poorly understood. "We are only beginning to delve into the science of this and other tick-borne diseases — there's so much we don't know," Platt said.

Research has shown that some tick species produce alpha-gal antigens — proteins that trigger an immune response — and secrete these antigens in their saliva during feeding. This may trigger the alpha-gal allergy in humans. "The ticks do NOT pick up [alpha-gal antigens] from animals and then transmit them to humans," Platt emphasized.

"More studies are needed to discover details about how a tick bite triggers alpha-gal syndrome in some people, and why bites from lone star ticks appear to cause the majority of the human cases in the United States versus blacklegged, western blacklegged, and other ticks," Salzer said.

Preventing tick bites is the best way to protect against alpha-gal syndrome and other tick-borne diseases, such as Lyme disease and Powassan virus. "When you anticipate being in areas where ticks may live, use an EPA-registered insect repellent and wear permethrin-treated clothing," Salzer advised.

Name: Asian hermit spider (Nephilengys malabarensis)

Where it lives: South, Southeast and East Asia (including India, Sri Lanka, the Philippines, China, Japan and Indonesia)

What it eats: Moths, beetles, flies, crickets and other small insects

Why it's awesome: The Asian hermit spider is no ordinary arachnid. This spider has evolved an adaptation that allows it to reproduce while escaping the threat of female cannibalism: It can detach its penis.

This spider species displays extreme sexual dimorphism, meaning that males and females have significantly different appearances. Females can grow up to around 0.59 inches (15 millimeters), while males are less than 0.20 inches (5 millimeters).

Males face considerable risks during mating due to aggression from females, which may kill and eat their partners before or after mating. Sex can be so treacherous for the males that they have developed the ability to detach their penis so they can leave it pumping sperm while they flee to safety.

In this process of "remote copulation," a male spider's palp — its sperm-delivering organ, of which it has two — can break off inside the female's reproductive tract. The broken-off palp can remain inside the female and continue pumping sperm into her even after the male has escaped.

While studying this "eunuch phenomenon" among orb-web spiders, biologists discovered that the longer the severed palp is left in the female genitals, the more sperm it transfers. And palp breakage induced by the female, instead of the male, led to faster sperm transfer.

The detachable penis also serves another important function: It acts as a mating plug. After breaking off, the embolus — a needle-like structure that delivers the sperm — stays lodged inside the female's reproductive opening to prevent other males from mating with her. This reduces sperm competition and increases the likelihood that the male's genes will be passed on.

After losing its penis, the male spider also becomes more aggressive and guards the female from other males that might try to dislodge the "palp plug" and inseminate the female.

According to a 2011 study in the journal Animal Behaviour, removing one palp reduces the spider's body weight and increases its endurance, thereby boosting its ability to fight. This finding supports what the researchers called a "gloves-off" mating strategy, where the spiders have nothing to live for other than protecting their potential offspring.

The male spiders also have another trick to prevent being eaten by the females: Sometimes, they offer one of their legs to the female as a distraction during mating. This act of self-amputation, known as autotomy, reduces the risk of being attacked or eaten during the mating process. It can also buy the male time to escape.

Scientists have captured stunning video of a dinner-plate-size sea spider crawling on the seafloor off the South Sandwich Islands, a chain of volcanic islands near Antarctica in one of the most remote areas of the world.

Sea spiders, also known as pycnogonids, are distant cousins of the creepy-crawly arachnids we see scuttling about on land. These creatures can have leg spans of up to 20 inches (51 centimeters) — nearly double those of the largest land spiders, whose leg spans top out at around 12 inches (30 cm).

According to the Schmidt Ocean Institute, which shared the footage, the spider's massive size is a result of deep-sea gigantism, the tendency for deep-sea creatures to grow significantly larger than their shallow-water relatives. In this case, the pycnogonid was filmed at a depth of 6,903 feet (2,104 meters).

Related: 32 truly bizarre deep-sea creatures

"Immense pressure and frigid temperatures, while insurmountable obstacles to land-lovers like humans, allow some animals to have very slow metabolisms and the ability to reach gargantuan proportions," Schmidt Ocean Institute representatives wrote in a Facebook post.

Larger animals can also move faster and farther to find food or to locate a mate, which is important when both are scarce.

Deep-sea gigantism is particularly prevalent toward the poles, where freezing temperatures facilitate slower metabolisms. Schmidt Ocean Institute representatives described sea spiders as both "abundant" and "abundantly large" in polar regions.

There are roughly 1,500 species of sea spider known to science and likely many more yet to be discovered, according to the post. Sea spiders inhabit oceans around the world and range just a few millimeters to the size of a serving platter. The species of spider in the video from the Schmidt Ocean Institute has not been specified.

The largest members of this group are usually found at depths between 7,200 and 13,100 feet (2,200 to 4,000 m), according to the Monterey Bay Aquarium Research Institute.

Instead of spinning webs or creating burrows as land spiders do, sea spiders use a specialized tube-like mouth structure, called a proboscis, to slurp up prey such as sea anemones, jellies and other invertebrates.

This latest footage was taken by remotely operated vehicle pilots as part of the Schmidt Ocean Institute's South Sandwich Islands expedition, a mission to locate and describe new species in these frigid waters. According to the institute, scientists have discovered only 10% of ocean life.

Scientists have discovered a never-before-seen mind-controlling fungus that creates spider "zombies" after it was stumbled upon in a Victorian gunpowder store on the grounds of a destroyed Irish castle.

The fluffy white fungus, similar to the zombie-ant fungus that inspired the "The Last of Us" video game and TV series, likely uses chemical signals to direct cave spiders out of their lairs and into the open. The fungus then kills the spiders and uses their corpses to release its spores, according to a new study.

Members of BBC's nature documentary TV series Winterwatch first discovered the fungus in a gunpowder storeroom at Castle Espie wetland reserve in Northern Ireland in 2021. Scientists analyzed the fungus and found it is new to science. They describe the species, named Gibellula attenboroughii to honor Sir David Attenborough, in a study published Friday (Jan. 24) in the journal Fungal Systematics and Evolution.

The G. attenboroughii found in the gunpowder store was on a dead orb-weaving cave spider (Metellina merianae). As their name suggests, these spiders usually live in caves but will also inhabit dark human-made areas such as cellars and old storerooms.

Related: Horrifying photo captures moment parasitic fungus bursts from huge spider's body

Following the chance discovery in 2021, study co-author Tim Fogg, a caving specialist, found more examples of the fungus in cave systems in Northern Ireland and the Republic of Ireland, including on another cave spider species, Meta menardi, according to the study.

Cave spiders are usually concealed in lairs or webs, yet all of the infected individuals were exposed on the roofs and walls of the caves in which they were found — the gunpowder spider was on the storeroom's ceiling. The researchers proposed that the fungus altered the spiders' behavior, sending them out into the open and exposing them to air currents that dispersed G. attenboroughii spores.

Study lead author Harry Evans, an emeritus fellow who researches fungi at CABI, an international nonprofit focussed on agriculture and the environment, told Live Science that the fungus infection process is complex and G. attenboroughii would have evolved alongside the cave spiders.

Evans explained that G. attenboroughii spores penetrate the spider and infect its hemocoel — a cavity that holds the invertebrate equivalent of blood. After the spider leaves its lair, G. attenboroughii produces a toxin to kill its host, then uses antibiotics — antimicrobial substances that kill bacteria — to preserve the corpse whilst mummifying it. The fungus absorbs all of the spider's nutrients and when conditions are right, like high humidity in the cave, G. attenboroughii grows long structures on the spider to disperse its spores.

"Medicinal treasure chest"

While the relationship between the fungus and spiders is interesting, Evans noted the endpoint of this research should be the potential human medicines that could come from the antibiotics and other substances the fungus produces. "It's a medicinal treasure chest," he said.

Evans and his colleagues extracted DNA from the fungus to confirm it was a previously unknown species. So far, it's only been found in Ireland, but the researchers also suspect that G. attenboroughii infects orb-weaving cave spiders in Wales, based on photographs of what appeared to be the same fungus.

The study highlighted that there is a hidden diversity of parasitic fungi in the British Isles and likely many more species to be discovered. Fungi are one of the five kingdoms that make up all living things — the other kingdoms are plants, animals, protoctista and monera.

"There's a lot more fungi to find," Evans said. "The fungal kingdom could be up to 10, 20 million species, making it the biggest kingdom by far, but only 1% have been described."

G. attenboroughii was originally going to be called G. bangbangus — "bangbangus" being a nod to the gunpowder store where the fungus was found. However, the study authors changed the species name to honor Attenborough instead.

A scientist has discovered the first species of South American scorpion that sprays its venom — a behavior previously only observed in two genera of scorpions found in North America and Africa.

Scorpions are known for their stings — the arachnids, of which there are more than 2,500 known species, use their venom to subdue prey and defend against predators. Their tails terminate in a structure known as a telson, which contains a bulb full of venom. The telson features a pointed aculeus — the stinger — which typically injects the poison.

The researcher published his findings Dec. 17, 2024 in a paper in the Zoological Journal of the Linnean Society. The new species, called Tityus achilles, was discovered in the Cundinamarca department of Colombia, in the mountainous Magdelena rainforest region. Only two other genera, found in Africa and North America, have previously been observed spraying venom.

"Most scorpions are likely capable of spraying venom. They just don't do it. This extreme behavioral response is only known to occur regularly in those two genera," author Léo Laborieux, who was a masters student at Ludwig Maximilian University of Munich at the time of the research, told Live Science.

"Venom-spraying is an inherently expensive strategy," he added. "There is likely a very intense selection pressure that would make it so that the behavior is more advantageous than it is disadvantageous. There has to be something going on with the predators in the environment."

Related: We now know why tarantulas are hairy — to stop army ants eating them alive

This technique for delivering toxins has been observed in other organisms — for example, spitting cobras can spray adversaries with venom too. Toxins that are externally applied in this fashion are called toxungens. A wide variety of animals, from arthropods to mollusks to mammals, use toxungens in defense and occasionally for hunting. These compounds may be sprayed, smeared or passively transmitted.

But unlike many other organisms that use toxungens, T. achilles is both toxungenous and venomous.. Poisonous animals transmit their toxins through external contact or ingestion while venomous animals inject them using their teeth or other specialized organs.

T. achilles can both inject and spray its venom. Direct injection of venom ensures that it is delivered and affects the target. But it comes at a physical risk — the target, whether predator or prey, may in turn defend itself.

Spraying venom is less risky — it does not require direct physical contact. But it is also less targeted and the effects of the venom are less severe. Still, a squirt of toxin to the face may be enough to deter a predator and allow the scorpion to escape. The angle of the toxic spray produced by T. achilles suggests that it may be targeted toward the eyes and nose of its attackers.

"These toxins need to reach very sensitive tissues to actually take effect," Laborieux said. "For this to make sense, the predator has to be a vertebrate." The toxins would be unlikely to penetrate the exoskeleton of another invertebrate, he noted, suggesting that the technique would be useless in securing prey.

Laborieux tested the ability of T. achilles to spray its venom by pinning specimens down with a drinking straw and recording their reactions. He tested 10 juvenile scorpions and recorded 46 ejections of venom, which reached a maximum distance of 14 inches (36 centimeters).

In some cases, the scorpions flicked small droplets of venom in response to the straw. In others, they issued a sustained spray. Most of the pulses of venom were directed forward, though some were also directed backward or upward.

The majority of venom flicks and sprays were transparent, suggesting that they consisted of pre-venom, a toxic liquid that is typically ejected prior to more potent true venom, which has a milky tint.

"The venom itself is usually composed of higher molecular weight peptides and proteins which are much larger, and for that reason, much more expensive to produce," Laborieux said.

A quick spray of pre-venom as a defense mechanism is thus a more conservative measure for a small organism that also uses these same compounds to subdue its prey — and will likely encounter additional predators in short order.

Editor's note: This story was updated on Jan. 22 at 3.00 a.m. to correct the spelling of Colombia in the headline.

One of Australia's biggest and deadliest spiders is actually three different species, researchers discover — and one of these behemoth arachnids is even bigger than the rest.

Sydney funnel-web spiders (Atrax robustus) are glossy black in color and grow to 1.5 inches (3.8 centimeters) long. The iconic arachnids are also among the most venomous spiders to humans.

Called funnel-web spiders after their long, narrow, silk-lined burrows these spiders can live in suburban areas and wander into houses during the summer when males leave the burrow to search for mates. Their venom contains a toxin that attacks the human nervous system, so bites need immediate medical attention — otherwise, a victim can die within 15 minutes.

The Sydney funnel-web spider was first described in 1877. Since then, scientists have developed a better understanding of funnel-web spiders and how they are related, describing more types of funnel-web spiders throughout Australia.

Related: What is the deadliest spider in the world?

Now, scientists have untangled how these species are related by collecting wild spiders throughout the Sydney suburbs and analyzing specimens from Sydney's Australian Museum, which has the largest collection of funnel-web spiders in the world. The scientists closely observed the specimens under a microscope and analyzed their genetics.

This revealed that the Sydney funnel-web spider is actually three species. The study was published Jan. 13 in the journal BMC Ecology and Evolution.

The "real" Sydney funnel-web spider (the creature originally described in 1877 as Atrax robustus) is found throughout the city and suburbs of Sydney. A second related species is Atrax montanus, which was first described about 100 years ago and then discarded as inaccurate, until the new research found it does exist. It mostly lives further south and west in rainforests. And a third, larger species, Atrax christenseni, can be found in a small region surrounding the city of Newcastle, around 105 miles (170km) to the north of Sydney.

Atrax christenseni was named for Kane Christensen, former head of spiders at the Australian Reptile Park, who first described it in the early 2000s and gave the spiders the nickname "big boys." These funnel-web spiders are the largest of the three species, growing up to 3.5 inches (9 cm) long.

Danilo Harms, co-author of the study and an arachnologist at the University of Göttingen in Germany, told Live Science his team was the first to systematically define these species' relationships. "You would think that a spider like that had been studied to death… because it's so relevant. There's practical relevance because people get bitten each year," Harms said. "Finding that very little had been done, looking into the very basic stuff you'd want to know, was surprising."

The first antivenom for funnel-web spiders was developed in 1981, and there have been no recorded deaths from these spiders since then. But confusion about the three species may mean that antivenoms are less effective than they could be.

Funnel-web spiders are not aggressive by nature but can attack when cornered, so it's a good idea for people to be mindful when they see one, Harms said. But in case of bites, investigating how these species differ, and how the structure of their venoms differs, can improve the specificity of antivenoms. For example, these species might have different levels of specific compounds in their venom that paralyze humans, which can help researchers tailor antivenoms to each species.

Editor's note: This story was updated on Jan. 21 at 9.20 a.m to correct an error in the headline that suggested A. christenseni is Australia's largest spider.

The biggest male funnel-web spider ever recorded — a deadly behemoth measuring 3.6 inches (9.2 centimeters) from foot to foot — has been handed into a zoo in Australia. The spider is so large, its fangs could pierce and deliver their lethal venom through a human fingernail, zoo keepers said.

Sydney funnel-web spiders (Atrax robustus) are some of the most venomous spiders in the world. If untreated, a single bite can kill a small child within 15 minutes and an adult within three days.

A member of the public caught and donated the giant arachnid to the Australian Reptile Park in Somersby, New South Wales. The zoo encourages donations to support its spider venom program, which produces life-saving antivenom against Sydney funnel-web spider and other spider bites.

Emma Teni, the spider keeper at the Australian Reptile Park, named the giant spider "Hemsworth" after the Australian actors Luke, Chris and Liam Hemsworth. Before Hemsworth, the record for the biggest male funnel-web spider belonged to a 3.1-inch (7.9 cm) arachnid called Hercules.

"We're used to having pretty big funnel-web spiders donated to the park, but receiving a male funnel-web this big is like hitting the jackpot," Teni said in a statement shared with Live Science.

Related: Drug inspired by spider venom aims to reverse heart attack damage

Male funnel-web spiders are typically smaller than females, but they are more dangerous due to a chemical in their venom called atracotoxin that affects the nervous system of humans and monkeys (it doesn't affect other mammals). Females lack this chemical, which likely explains why males are responsible for all 13 recorded deaths from funnel-web spider bites and most of the medically serious bite cases, according to the Australian Museum.

There have been no reported deaths from funnel-web spider bites since the introduction of an antivenom in 1981. The Australian Reptile Park is the only facility in Australia that milks funnel-web spiders for raw venom, and the resulting antivenom saves up to 300 lives per year, according to the statement.

The Australian Reptile Park has designated spider drop-off points dotted around Sydney, the Central Coast and Newcastle. Staff collect the spiders and milk them weekly before sending off the venom to a laboratory that makes the antivenom, according to the statement.

But milking spiders is a tedious process. "It takes about 150 to 200 milkings to create one vial of antivenom," Teni said in a video interview. "We can only milk the male funnel-web spiders, because of the presence of the atracotoxin in their venom."

Therefore, Hemsworth is a very welcome addition to the park's spider stock. "Because Hemsworth is so big, his fangs are massive and he produces so much venom," Teni said. When keepers first saw Hemsworth, "we thought for sure he had to be a female because of his size," she said, "but upon closer inspection, he's a boy."

Name: Hairy giant tarantula (Trichopelma grande)

Where it lives: Western Cuba

What it eats: Insects, lizards, frogs and other small reptiles

Why it's awesome:

Arachnophobes may not appreciate the discovery of a never-before-seen "giant" tarantula species, but for fans of these misunderstood creatures, Trichopelma grande is a special find. Not only is it larger and hairier than other spiders in its genus, it is the only kind with long, fluffy, "feather-duster" legs.

T. grande was first discovered in 2008 in Viñales National Park, a biodiversity hotspot in western Cuba. So far, only four specimens have been spotted: Three adult males and one juvenile male, all found in trap-door burrows on the ground.

The Trichopelma genus is made up of 23 species, with members all being very small tarantulas. As its name suggests, T. grande is the largest known member of the genus with a body length ranging from 0.33 to 0.44 inches (8.4 to 11.2 millimetres). However, the spider's most recognizable feature is its unusually hairy legs.

Hairy legs are typically associated with tree-dwelling tarantulas — called arboreal tarantulas — so this feature is very unusual for a ground-dwelling species.

David Ortiz, a researcher at Masaryk University in Czechia and lead author of the study describing the species, said having long, hairy legs may help the tarantulas defend themselves against predators like birds or snakes.

'Feather duster' legs

"The feather-duster legs are even more interesting, and might be associated with predator deterrence — the hairier the more impressive," Ortiz told Live Science in an email. "This might be particularly useful for males, because they have a 'wanderer' way of life, unlike females, who remain in their burrows almost at all times. Females might not be as hairy as males, but we are not sure yet. But these are just hypotheses."

Related: When stressed, these male spiders woo mates with empty 'take-out containers' instead of dinner

Having more leg hair likely also increases the spider's sensitivity to external stimuli, such as air currents, which helps them detect the movement of predators and prey. Being larger may also help the spiders to catch food, such as insects, frogs, lizards and other small reptiles.

These tarantulas likely aren't dangerous to humans. "Tarantulas usually have a very mild sting, probably less powerful than a bee sting. I expect the same from this species," Ortiz said.

The males are nomadic and abandon their homes to look for females to mate with. As of yet, no female tarantulas of this species have been discovered, so less is known about their behavior.

"I think that such a unique species deserves to be examined more deeply," Ortiz said. "The Viñales National Park is especially under threat by human activity (e.g., tree logging) and by extreme weather events like hurricanes. The valley of Viñales is deeply disturbed, and only forest patches remain untouched in the mogotes (hills) and sierras scattered along the valley."

There are an estimated 50,000 species of spider living on Earth, from behemoths like the giant huntsman and goliath birdeater, down to the tiniest, the dwarf orb weaver and Patu digua. In this extract from "The Lives of Spiders: A Natural History of the World's Spiders" (Princeton University Press, 2024), author Ximena Nelson looks at the three species with unusual diets — plants, blood and pill bugs.

Vegetarian spider

Scientific name: Bagheera kiplingi

Family: Salticidae

Body length: 1∕5–¼ in (5–6 mm)

Notable anatomy: Males have iridescent green markings on cephalothorax and abdomen

Memorable feature: Primarily vegetarian

A spider is an unlikely vegetarian, but Bagheera kiplingi almost fits the bill. Supplementing its diet with nectar, ant larvae, and nectar-feeding flies, this jumping spider feeds almost entirely on Beltian bodies, the detachable fat and protein-rich leaf tips of Vachellia acacia shrubs.

Bagheera is so dependent on Beltian bodies that it is an obligate resident of Vachellia plants, where it lives in areas that are not well patrolled by the resident Pseudomyrmex ants. There is such host specificity to the plant that the spider’s geographic range is limited by the presence of Vachellia.

Plant mutualisms

Ants can be helpful to plants because they tend to be aggressive and keep herbivorous insects away. Consequently, many plants make an effort to lure ants as bodyguards and keep them around by producing accessible nectar through extrafloral nectaries. This continuous source of food is irresistible to ants, but often is also exploited by spiders, especially wandering spiders that roam to hunt their prey.

This includes many species of jumping spiders, where nectarivory may be a common tactic to obtain a meal with less risk of injury than hunting. Nectarivory can increase spider longevity and reproductive output. Importantly, for the tiny spiderlings, nectar may provide much-needed energy that allows them to hunt prey inevitably larger than themselves. In addition to extrafloral nectar, Vachellia species produce nutritious Beltian bodies to keep Pseudomyrmex ants nearby.

Related: We now know why tarantulas are hairy — to stop army ants eating them alive

The defense put up by the ants is formidable, and few animals can encroach it. Bagheera exploits the mutualism by harvesting the Beltian bodies and extrafloral nectar produced by the acacia without providing defense to the plant. Being able to see ants from a distance, Bagheera largely seems to avoid encounters with them — unless craftily stealing a larva being carried by one.

An unusual diet

Depending on location, plant-derived food accounts for between 60 and 90% of Bagheera’s diet, making this the only near-herbivorous spider known and a rather extreme outlier in a group known for its predatory behavior. As spiders cannot ingest solids, the Beltian bodies must be enzymatically broken down prior to being consumed, which can happen in a matter of minutes. Although this may be an easily available source of food, the spiders appear to need a lot of it to get by: They feed on many Beltian bodies in a single feeding bout, and about 30 Beltian bodies are required to provide the nutrition of a single insect prey.

Vampire spider

Scientific name: Evarcha culicivora

Family: Salticidae

Body length: 1∕8–2∕5 in (3–10 mm)

Notable anatomy: Males have bright-red band under forward–facing eyes

Memorable feature: Specializes in hunting the vectors of Anopheles (malaria) mosquitoes

Living in the Lake Victoria region of Africa, Evarcha culicivora is possibly the pickiest animal on Earth. The media-named "vampire spider" does not feed directly on human blood, but does so indirectly by preying on blood-fed female mosquitoes. In fact, Evarcha actively chooses Anopheles mosquitoes, which are attracted to feed on human blood and are hence vectors of malaria.

By feeding on blood-fed female Anopheles at a time of day when the mosquitoes tend to rest after a blood meal, sexually mature spiders attain a "perfume" that makes them alluring to the opposite sex. This suggests that, unusually, their prey preference may be at least partly driven by sexual selection. As a coup, E. culicivora may play a small role in mitigating the transmission of malaria by preventing mosquitoes carrying the parasite from biting and infecting another person.

An affinity for blood

The vampire spider has an approximate hierarchy of preferences, with blood-fed female Anopheles at the top, followed by other kinds of local blood-fed female mosquitoes, then non-blood-fed female Anopheles, male Anopheles, and finally the most common prey type in its habitat: midges. Juveniles even have an Anopheles-specific method of hunting, which they don’t use for other prey. Odors associated with humans may attract the spiders to houses, where they are likely to encounter the Anopheles, but it is their visual decision-making that we understand best.

Anopheles has a specific resting posture, and Evarcha uses this to differentiate it from other mosquitoes. The spider judges how "fat" the abdomen appears as an indication that it is full of blood. To determine sex, it also looks at how feathered the antennae are, as female mosquitoes have barer antennae.

Paradoxical plants

Aside from houses, a popular hunting spot is on Lantana camara shrubs, where mosquitoes sometimes rest and eat nectar. The spiders also feed on Lantana’s nectar, which gives them a nutrition boost that allows them to hunt prey many times their size. Paradoxically, Evarcha’s prey preference is no longer expressed when the spider is exposed to the dominant volatile compound of Lantana, β-caryophyllene. This is because the plant odors reduce the time Evarcha spends visually assessing its prey. The fact that the spider is prone to identification errors of its preferred prey illustrates a trade-off in Evarcha’s ability to process information when faced with a diversity of stimuli involving multiple sensory modalities.

Woodlice-eating spiders

Scientific name: Dysdera crocata

Family: Dysderidae Females

Body length: Females c. ½–c. 3∕5 in (11–15 mm), males c. 2∕5 in (9–10 mm)

Notable anatomy: Has very noticeable and broad chelicerae

Memorable feature: Specializes in hunting woodlice

Woodlice are terrestrial crustaceans (isopods) with a thick carapace, which they use as a shield when they roll into a ball or cling to a surface to avoid attack. Despite being slow-moving, many species have noxious secretions, making them formidable foes. Some spiders in the genus Dysdera, the most famous being Dysdera crocata, are among the few predators to hunt them.

Pincer, fork and key

Species that specialize in catching woodlice have specially adapted chelicerae. Unlike nonspecialist Dysdera species, these specialists use one of three main tactics to grasp prey: the pincer, the fork, and the key. Each strategy is associated with a particular mouthpart morphology.

Species with elongated chelicerae, like D. crocata, use the pincer approach, rapidly penetrating the unprotected underside of a woodlouse with one chelicera before it can roll up and defend itself, while simply holding the armored side to keep the prey in place. If the woodlouse manages to roll into a ball or cling hard, the spider patiently waits, unmoving and ready, until it gets another chance to attack.

The fork tactic is used by species that have chelicerae with a concave upper surface. Here, attacks consist of quicky grabbing the woodlouse with its first pair of legs, slipping the chelicerae under the isopod, and rapidly biting the underside of the woodlouse before it has time to adopt a defensive posture. The key tactic requires flattened chelicerae. Like fitting a key into a lock, the spiders slide one chelicera between the armored segments of the carapace of the woodlouse, inserting its fang to bite — voilà!

Woodlice gradient

Of the Dysdera species that largely consume woodlice, there is variation in how much they rely on these prey. However, it is likely that all need to eat at least some woodlice to grow and develop quickly, suggesting a metabolic need for this food source. Furthermore, there is a correlation between the level of modification of the chelicerae and woodlouse specialization, with those that are almost obligate specialists having the most strongly reshaped mouthparts. This is matched by behavior, with species with less modified mouthparts exhibiting markedly less prey preference, and by their ability to extract key nutrients from their prey.

Adapted from THE LIVES OF SPIDERS: A NATURAL HISTORY OF THE WORLD’S SPIDERS. Copyright © 2024 by Ximena Nelson. Reprinted by permission of Princeton University Press.

Tarantulas are hairy so that the army ants cleaning their homes don't eat them alive, a new study suggests.

The study, published Aug. 6 in the Journal of Natural History, proposes several new ideas about tarantula relationships with other species, including their surprisingly passive but still occasionally violent interactions with predatory ants.

Predatory ants, or army ants, are known to hunt spiders alive, but when these ants were observed scavenging for food in South American tarantula burrows, the ants tended to ignore adult tarantulas as well as tarantula offspring. In the rare instances when the ants did attack, the tarantulas' stiff hairs offered adequate protection.

"The dense hair covering the tarantula's body makes it difficult for the ants to bite or sting the spider," study lead author Alireza Zamani, an arachnologist at the University of Turku in Finland, said in a statement. "Therefore, we believe that the hairiness may have evolved as a defence mechanism."

Related: Deadly male funnel-web spider 'Hercules' breaks record as biggest ever discovered

Zamani and his colleagues explored the complex relationships between tarantulas and other animals by reviewing previous scientific studies and gathering new observations from the field and social media.

The researchers found that army ants help fossorial tarantulas — those that live in burrows — by removing old food from their burrows. However, the spiders still needed protection in case the ants got bitey. This hair-defense hypothesis is supported by previous studies that suggested burrowing tarantulas cover their egg sacs in hairs to help stop ants from getting at them.

Furthermore, the team discovered that less hairy — and therefore potentially more vulnerable — arboreal tarantulas, including Avicularia hirschii in Peru, have developed different defense strategies against ants. For example, in one observation, the researchers watched A. hirschii hang from the tip of a leaf to escape ants on the hunt for prey, according to the statement.

While tarantula-ant relationships can get strained, the researchers found that tarantulas enjoy friendlier interactions with amphibians, which sometimes live in their burrows. The study described more than 60 partnerships between tarantulas and amphibians across 10 different countries, as well as relationships with snakes and other spiders.

"Apparently, the frogs and toads that live within the retreats of tarantulas benefit from the shelter and protection against their predators," Zamani said. "In turn, they feed on insects that could be harmful to the spider, its eggs, and its juveniles. It seems that tarantulas might not be as scary and threatening as their reputation suggests."

Giant, invasive Jorō spiders have spread across several U.S. states during the last decade. Now, scientists have discovered these palm-size critters are potentially much more tolerant to living in cities than other species and appear to thrive alongside major roads, which could help give them a foothold (or eight) in major cities along the Eastern Seaboard.

Jorō spiders (Trichonephila clavata) are a species of orb-weaving spiders — a group known for creating highly symmetrical, circular webs. Jorōs are easily recognizable thanks to the distinctive yellow bands that adorn their otherwise black legs. They also build unique webs that can be more than 6 feet (1.8 meters) across and appear golden when they reflect sunlight. 

Female Jorōs, which can grow to around 3 inches (7.6 centimeters) across — around double the size of males — also have blue stripes and red patches on their predominantly yellow abdomens. 

After mating in early autumn, female Jorōs lay large, web-bound clusters of up to 400 eggs before dying off at the start of winter, along with the males. When the eggs hatch in spring, the baby spiders create parachute-like webs that enable them to fly up to 100 miles (160 kilometers) away from where they were born. 

Jorō spiders are endemic to Asia, and until recently they were only found in Japan, Korea, Taiwan and China. However, in 2014, researchers spotted several Jorōs in the U.S. near Atlanta, Georgia. Experts believe these invasive individuals were accidentally brought to the U.S. inside a shipping container, according to a 2015 study. 

In the years since, Jorō spiders have quickly multiplied and spread in the U.S. thanks to their ability to widely disperse after birth. They are now found across Georgia, as well as in South Carolina, North Carolina and Tennessee. Additional sightings have also been reported in Alabama, Maryland, Oklahoma and West Virginia, and experts believe they could spread across the entire U.S. East Coast in the future.

Related: What is the deadliest spider in the world?

Since their arrival, researchers have noticed that Jorō webs are often located in close proximity to major highways. This is surprising because the vibrations caused by busy roads normally interfere with spiders' ability to hunt: When smaller critters get trapped in spider webs, they struggle to get free, which alerts the spiders to their presence, but busy roads can drown out these vibrations. Spiders are also very sensitive to vibrations in general.

In a new study published Feb. 13 in the journal Arthropoda, researchers investigated how vibrations impacted Jorō spiders. In the laboratory, the study team used tuning forks to simulate the vibrations given off by highways to see how it impacted the arachnids' ability to hunt simulated prey placed in their webs.

Across 350 trials, vibrated Jorōs attacked simulated prey 59% of the time, while non-vibrated Jorōs pounced on the dummy prey 65% of the time. The trials also showed that the "roadside" spiders were able to maintain a similar healthy body weight to the other spiders, indicating that the vibrations were not impacting them in the long term.

"The spiders seem to be able to make a living there," lead study author Andy Davis, an ecologist at the University of Georgia, said in a statement. They are surprisingly "urban tolerant," he added.

It is unclear what long-term effects Jorō spiders will have on the ecosystems they invade. Last year, researchers revealed that the spiders are unusually shy and non-aggressive toward other spiders. However, without a natural predator seeking them out, their numbers will likely continue to rise, which could help them outcompete other species for resources.  

But whatever their ecological effects, the new findings suggest these arachnid invaders aren't going anywhere anytime soon.

"I don't know how happy people are going to be about it, but I think the spiders are here to stay," study co-author Alexa Schultz, a third-year ecology student at the University of Georgia, said in the statement. And they could end up in places "where you wouldn’t imagine a spider to be," she added.

Name: Diving bell spider or water spider (Argyroneta aquatica)

Where it lives: Europe and Central and Northern Asia, with a separate subspecies in Japan

What it eats: Other aquatic invertebrates and small fish

Why it's awesome: As its name suggests, the diving bell spider lives almost completely underwater; it's the only spider to do so. It still needs to breathe air though, so it survives by creating a diving bell — spinning a web between underwater plants — and then carries air from the surface down to its web via its hairy body.

"It has developed an amazing adaptation for this aquatic life," Craig Macadam, conservation director of the U.K. invertebrate charity Buglife, told Live Science in an email. "The spider has numerous water-repellent hairs over its body which trap air from the water surface. The spider then spins a silk structure where it forms an air bubble, which it uses in the same way as a diving bell."

The bubble is expanded until the spider can fit inside. The chambers of females are double the size of those made by males, as they need it to serve as a nursing chamber, too. The air in the diving bell is regularly refreshed, and the spider carries a bubble of water around with it, giving it a silvery coloration.

Unusually for spiders, male diving bell spiders are larger and heavier than females. A 2003 study in the journal Evolutionary Ecology Research looked at why this might be and found that for the more mobile males, growing larger — and having longer front legs — meant they could move more efficiently underwater. By contrast, the size of females was constrained by the need to build a larger air bell in which they look after their young, and the energetic costs associated with more frequently transferring fresh air from the water surface to the bell. 

A follow-up study published in 2005 in The Journal of Arachnology by the same authors also revealed an interesting insight into the spiders' mating behavior: Females appear to prefer mating with large males, despite the hefty risks involved. 

The team discovered that larger males occasionally eat the females in a case of reversed sexual cannibalism. However, their experiments also showed that large males and females would also kill small males.

The largest male specimen yet of the most venomous spider in the world has been found in Australia.

"Hercules," a funnel-web spider, is 3.1 inches (7.9 centimeters) from hairy foot to hairy foot, according to the Associated Press — about the same diameter as an Olympic gold medal.

The spider was found about 50 miles (80 kilometers) north of Sydney and taken to a local hospital. The hospital turned the giant arachnid over to the Australian Reptile Park, a zoo in New South Wales that runs a venom-milking program. Venom from spiders and snakes is used to produce antivenom for Australian hospitals.

"Male funnel-webs, once they reach maturity, their natural lifespan is only around one year," Emma Teni, a spider-keeper at the park, said in a video provided by the AP. "So we need to constantly have them handed in by the general public, because we need them for our lifesaving antivenom program."

The male Sydney funnel-web spider (Atrax robustus) has one of the most toxic-to-humans venoms of any spider, according to the Australian Museum. Male spider venom contains a neurotoxin that affects the nervous systems of primates, including humans. Females are also venomous, but their venom does not contain this neurotoxin, according to the museum. Only male bites have caused human deaths.

Since the Australian Reptile Park launched its spider antivenom program in 1981, no one has died from funnel-web spider bites, according to the park. Every week, park staff use glass pipettes to urge spiders to bite so they can suck up droplets of venom. The venom is then frozen and used by supplier CSL Seqirus to make antivenom that can be given to patients who have been bitten.

Related: Why does Australia have so many venomous animals?

Funnel-web spiders are burrowers. They get their names from the networks of "trip wires" they spin at the entrances to their burrows, which are often shaped like a funnel of silk, according to the Australian Museum. They like moist, vegetated areas and are often found in the forested Sydney suburbs. Humans are probably most likely to encounter deadly male spiders, which leave their burrows in the summer months to look for mates.

Hercules is bigger than the Australian Reptile Park's previous record-holding male funnel-web, a specimen nicknamed Colossus who lived at the park in 2018.

Female funnel-webs are typically larger than males, and the largest the park has ever held was "Megaspider," a female donated in 2021 with a leg span of 3.14 inches (8 cm).

Funnel-webs defend themselves aggressively when threatened, rearing up on their hind legs and showing off their 0.8-inch-long (2 cm) fangs. According to the Australian Museum, they are also capable of surviving up to 30 hours underwater by trapping air bubbles around the hairs on their abdomens. Spiders are sometimes found at the bottom of pools and presumed dead, only to recover and scurry away once they dry out.

Tarantulas are hair-covered beasties. But most spiders don't have such "furry" bodies. So why do tarantulas look so hairy? 

These hairs are more important than you might think.

"Unlike the very limited functions of human hairs, hairs on tarantulas (and other spiders) can do so very many different things," Jerome Rovner, former associate editor of the Journal of Arachnology by the American Arachnological Society, told Live Science in an email.

Sensing the world

Tarantulas are hairy for several reasons. Unlike mammal hair, which is made of keratin, tarantulas' hairs, called setae, are made of chitin, a derivative of glucose that also makes up the structure of a spider's exoskeleton. 

Some of these hairs act as sensory organs, helping tarantulas smell, taste, touch and detect vibrations from the world around them. These sensory hairs are found mainly on the spiders' legs and mouthparts and feed into sensory nerves located in the spider's "skin" or cuticle..

The most sensitive hairs, called trichobothria, detect even the smallest changes in air movement because of their "ball and socket" attachment to the membrane in the cuticle. These hairs help guide tarantulas in capturing or responding to escaping prey. In 1883, German zoologist Friedrich Dahl named these "hearing hairs" when he observed that they moved to the sound of a violin.

The chemically sensitive hairs used for smell and taste are blunt and hollow. They also play a role in reproduction and help the tarantula look for a mate. "Male tarantulas wander in search of a female's burrow. If they walk near such a burrow, their contact chemosensitive hairs are stimulated by the sex pheromone that is bound to silk lines near the burrow's entrance, thereby enabling the male to find the female," Rovner explained, adding that these hairs could possibly detect chemicals left by  nearby prey.

 Related: Why do spiders have 8 legs?

Tarantula hairs serve three other functions. First, they help tarantulas, which are cold-blooded, regulate their body temperature. 

"The hairs trap a layer of air against their body and appendage cuticle, creating a kind of insulation," Rovner said. "With a thick coat of hair, tarantulas can remain active throughout cool nights in tropical rainforests and deserts." 

The long hair also serves as a sort of waterproof coat that can "repel water if the tarantula is submerged by flooding," Rovner said. 

Finally, the undersurface of their leg hairs are "sticky." This helps tarantulas climb smooth vertical surfaces. These dense networks of bristles are called scopulae and also help with capturing prey.

Many tarantulas in the Western Hemisphere also have up to 1 million deadly sharp hairs on their abdomen that they use for defense. These barbed, or urticating hairs t "can embed in the skin, eyes, and mucosal membranes of predators, causing irritation," Rovner said. 

When threatened, tarantulas use their hind legs and rub against their abdomen to detach these urticating hairs, creating a mist of stinging spines that penetrate the predator so they can escape. 

When people are hit by urticating hairs, they can cause redness, stinging and itching —and even blindness if they strike the eyes. 

Tarantulas native to the Eastern Hemisphere, by contrast,  do not have urticating setae. Instead they have more potent venom and use an aggressive stance to warn predators before they bite.

A strange, yellow, spider-like creature with four near-black eyes and large bulbous claws has been pulled from the depths of the ocean off Antarctica.

The never-before-seen animal is a sea spider — a distant relative of horseshoe crabs and arachnids that live on the ocean floor, eat through a straw-like proboscis instead of a mouth and breathe through their legs.Scientists have discovered more than 1,000 species of sea spiders all over the world.

The newfound species, Austropallene halanychi, was pulled from the ocean floor in the Ross Sea, about 1,870 feet (570 meters) below the surface. In addition to all the other weird things about sea spiders, the new species has large claws that look like "boxing gloves," which it likely uses to grab hold of soft foods like anemones and worms, study co-author Andrew Mahon, a biologist at Central Michigan University, told Live Science. The study was published Nov. 28 in the journal ZooKeys.

A. halanychi's body is about 0.4 inches (1 centimeter) long, but its legs stretch nearly 1.2 inches (3 cm) long. That gives the species the spindly look typical of many sea spiders — though some species can grow much larger, reaching nearly 2 feet (60 cm) wide.

Related: Sea spiders can regrow their anuses, scientists discover

What's more, this new species is likely just a drop in the bucket when it comes to the undiscovered wildlife living at the bottom of the Southern Ocean — an ecosystem home to everything from brightly colored sea stars and otherworldly marine worms to sponges and cold-water coral.

"The benthic environment in Antarctica is an area of science that we need to keep exploring," Mahon said. "There's so much down there that every time we go, we find new things."

To learn more about this environment, researchers drop nets deep underwater to pick up whatever might be hanging around at the bottom. After pulling the nets up, they sort everything they caught and preserve each specimen before shipping them back to labs for further analysis.

But with so many potentially new species to describe, it can take time to go through all the samples. A. halanychi was first pulled up in 2013 by the Nathaniel B. Palmer, a U.S. research vessel. Recently, Mahon and his colleague Jessica Zehnpfennig took it out of storage and identified it as a species new to science by analyzing its body shape and genetics.

Yet researchers may also be running out of time to study the Antarctic seafloor. As the climate keeps changing, warmer waters may threaten the future of some of the species living in this isolated and unique ecosystem, Mahon said. One of the reasons that researchers keep studying the Antarctic seafloor, he said, is to help describe and protect this biodiversity before it’s too late.

A stunning photograph has captured a wolf spider wearing a hat of her own babies in Maryland. The image, titled "Wolf Spider Mama" was named the winner of the insects and arachnids category of The Nature Conservancy's 2023 Global Photo Contest.

The image, taken by photographer Benjamin Salb, shows a wolf spider (of the family Lycosidae)  carrying its spiderlings. Salb spotted the spider in the middle of an asphalt path early in the morning.  

"What’s special to me about this recognition is that this mama spider and her spiderlings were just [in] my neighborhood park," he wrote in an Instagram post after the winners were announced. "I wasn’t on a safari nor in the jungles of Madagascar (not hating, I’m just jealous). I was in suburbia."

Related: Horrifying photo captures moment parasitic fungus bursts from huge spider's body

Wolf spiders are unique in that they carry their egg sac on the bottom rear of their abdomens. They can lay around 100 eggs at a time and are fiercely protective of their young. "After hatching, the spiderlings climb on their mother's back, and she carries them around for several days," Jo-Anne Nina Sewlal, an arachnologist at the University of the West Indies in Trinidad, previously told Live Science. Within a week, the spiderlings become independent and they climb off and leave.

The overall winner of the contest was Tibor Litauszki from Hungary, who captured the moment a newt feasted on newly laid frog eggs underwater. 

In total, more than 80,000 photographers submitted nearly 189,000 photos to the contest. "Photographers from all walks of life helped give voice to nature by showing us what mattered to them," Alex Snyder, judging coordinator for the competition, said in a statement.

A psychedelic image of the spider web-like network of tiny vessels in the back of a rat's eye has won this year's Nikon's Small World photography competition.

Hassanain Qambari, a diabetes researcher at the Lions Eye Institute in Australia, was awarded first prize for the detailed image of a rodent's optic nerve head. Along with Jayden Dickson, Qambari submitted the image to the competition "to showcase the complexity of retinal microcirculation," Qambari said in a statement.  

The researchers study diabetic retinopathy, a condition in which long-term high blood sugar levels damage the small vessels of the eye, potentially causing complete vision loss. 

"Current diagnostic criteria and treatment regimens for diabetic retinopathy are limited to the late-stage appearance of the disease, with irreversible damage to retinal microvasculature and function," Qambari said. 

One of the challenges they faced was locating these tiny vessels, which are around 0.004 inch (110 micrometers) in diameter. To create the intricate image, Qambari collected and stacked hundreds of single images taken with confocal and fluorescence microscopy. 

Photographer John-Oliver Dum, with the company Medienbunker Produktion in Germany, was awarded fourth place for his terrifyingly beautiful shot of venomous tarantula fangs. In the haunting close-up, the large, rounded black fangs of a Caribena versicolor glow red at the tips and are surrounded by a dense collection of pink hairs. The picture was taken in collaboration with the Museum of Natural History in Chemnitz, Germany.

"We had planned that I would give pictures for a lecture about the microworld of their insects and spiders, to show the unknown world," Dum told Live Science in an email. But due to the COVID-19 pandemic, this project was never finished. 

Photographer Sherif Abdallah Ahmed, from Tanta University in Egypt, was awarded 12th place for a stunning photo of an iridescent, emerald-green cuckoo wasp (Chrysididae) perched on a mass of purple flowers. Much like cuckoo birds, cuckoo wasps are kleptoparasites —  they lay their eggs in other wasps' nests. The larvae of the thieving wasps then devour all the food stored in the nest, sometimes along with any other eggs there.

Yuan Ji, from the World Expo Museum in Shanghai, was awarded 17th place for a colorful, ethereal photo of a Chinese moon moth's (Actias ningpoana) wing scales. These moths live in the mountainous cloud forests in China. Bats hunt these moths, but the moths use their twisted tails to sabotage the bats' echolocation, lowering the risk of being caught.

Other noteworthy images included a colorful view of defensive hairs covering the surface of a leaf, a glimpse into the development of a mouse embryo and an intricate view of cell division in a myoblast stem cell.

Nikon's Small World photography competition showcases the beauty of scientific imagery captured through the lens of a light microscope. This year's winners were announced Oct.17.

Nikon's Small World competition also includes an award for videography. On Sep. 26, the Nikon Small World in Motion video competition top prize was awarded to Alexandre Dumoulin for his 48-hour time-lapse video of developing neurons in the central nervous system of a chick embryo.

Certain male spiders in South America usually give their partners a tasty snack before mating. But in stressful environmental conditions, males may "cheat" in their mating ritual by offering females a useless ball of silk instead of a nutritious meal, a new study has found.

The research shows how spiders may adapt their behavior to reflect changes in their environment.

When a male Paratrechalea ornata spider wants to mate, he'll snag an insect and prepare it for a female, said study co-author Maria Albo, a biologist at the University of the Republic in Uruguay.

Related: Female spiders play dead during sex so males don't have to worry about being eaten

The spider starts by wrapping the insect in silk over and over until it forms a nice, little ball with a juicy treat hidden inside. "And then they start to walk along the river, along the stones," Albo told Live Science.

If a female takes the bait, she'll grab onto the gift with her mouth and slowly digest the silk to reach the food inside. While that's happening, the male mounts the female and they mate.

But some P. ornata males try to mate without going through the hassle of giving a gift. Instead of packaging a piece of food, these males will wrap up something not so tasty, like a leaf or even the leftover bits of an insect they've already eaten.

Albo knew that some males offered "worthless" gifts, but in the new study, published July 27 in the journal BMC Biology, she and her colleagues compared the prevalence of worthless-gift giving in two distinct habitats in Uruguay. One, in southern Uruguay, has a relatively stable climate. The more northern habitat is more affected by El Niño and is a more variable and unpredictable — and, therefore, more stressful — climate for a spider. In addition, the southern habitat had vastly more prey than the northern one did.

The team collected spiders along the river and checked what was inside their silk balls. In the less-stressful, southern population, males carried worthless gifts just 38% of the time. But in the more-stressful, northern population, males had worthless gifts a whopping 96% of the time.

Albo offered a couple of theories that might explain this discrepancy. For one, spiders in the stressful habitat might have to be more focused on survival, because the amount of nearby food is lower. So, the stressed-out males may be more tempted to keep the food to themselves instead of giving it away to females.

In addition, spiders in the stressful habitat were smaller, perhaps as a result of having less food around. So smaller-bodied females may not need any extra food to stay healthy. But larger females in the less-stressful habitat may need the extra food the males provide to produce healthy offspring.

These kinds of gifts given before mating, known as "nuptial gifts," occur in many different animals. In many scorpionfly species, males offer females either a dead insect or a ball of saliva to eat while they mate. Male great gray shrikes (Lanius excubitor) — a species of small, carnivorous bird — often offer their potential mates a dead mouse or lizard. And katydids have combined mating and feeding — as they copulate, the males will also provide the females with a "spermatophylax," a gelatinous ball of nutrients that the females will eat after they've finished mating.

A rare image has captured the moment a huge spider is "defeated" and engulfed by a parasitic fungus, with spores bursting from the arachnid's back, legs and head 

The striking photo is one of the winning images from the BMC Ecology and Evolution photography competition. The picture, taken by evolutionary biologist Roberto García-Roa, was named runner-up in the Plants and Fungi category. 

"While it is not uncommon to encounter insects parasitized by 'zombie' fungi in the wild, it is a rarity to witness large spiders succumbing to these fungal conquerors," García-Roa wrote in a BMC Ecology and Evolution editorial released Friday (Aug. 18). "In the jungle, near a stream, lies the remains of a conquest shaped by thousands of years of evolution." 

Related: In a 1st, man catches 'silver leaf,' a tree fungus never before seen in humans

Many species of fungus are known to parasitize spiders, and instances of parasites bursting from the bodies of dead arachnids have been recorded across the globe. Most species belong to the Cordycipitaceae and Ophiocordycipitaceae families. The species of spider and fungus in García-Roa's image are not known, but the fungus appears to have entered its host and taken over the spider's body.

The BMC Ecology and Evolution photography competition invites researchers from around the world to put forward images that capture the natural world. The winning entry in the Plants and Fungi category shows an ant that had been taken over by a zombie fungus —Ophiocordyceps — which was, in turn, parasitized by another fungus. Ophiocordyceps is a genus of parasitic fungi known for its ability to turn ants into zombies, controlling their bodies before killing them.

"The forests these fungi inhabit are also shared with mycoparasitic fungal lineages that can parasitize, consume and even castrate Ophiocordyceps," João Araújo, a mycologist at the New York Botanical Garden who submitted the category-winning photo, wrote in the editorial. "Only recently scientists have started to catalogue and describe these still unknown fungi that can kill other fungi."

The overall winner of the 2023 competition was an image of the invasive orange pore fungus (Favolaschia calocera). The species was first identified in Madagascar and has since spread across the world. The photograph shows the fungus growing on deadwood in the Australian rainforest.

"Despite its innocent and beautiful appearance, the orange pore fungus is an invasive species that displaces other fungi and is spreading throughout the Australian rainforest," Cornelia Sattler, from Macquarie University in Australia, who took the photo, wrote in the editorial. "It is important to closely monitor this fungus, whose spores are often transported by humans, in order to safeguard the biodiversity of Australia."

The overall winner of the 2022 competition also featured a parasitic fungus. García-Roa's winning image, taken in the Peruvian jungle, shows spores of the zombie fungus Ophiocordyceps erupting from the body of a fly. 

A supermarket in Austria was evacuated following reports of a spider whose bite can cause hours-long, painful erections. But media claims that the erections are permanent are not supported by science.

The spider was discovered in a discount store in Krems an der Donau, 45 miles (72 kilometers) west of Vienna, and is believed to be a Brazilian wandering spider (Phoneutria nigriventer), leading to a flurry of media reports claiming that its bite could cause permanent erections.

The 4-inch (10 centimeters) spider's potent venom gives it a nasty — and occasionally, fatal — nip that increases the victim's blood pressure and causes hours-long erections. However, there is no evidence that these erections are ever permanent.

Related: What is the deadliest spider in the world?

Past studies in rats have revealed that the Brazilian wandering spider's venom works by causing nitric oxide to be released in the brain. This chemical leads to a biochemical cascade that ends in the production of an enzyme called cyclic guanosine monophosphate (cGMP), which causes the muscles in the penis to relax, enabling 10 times the blood to rush into it. 

A few hours later, however, another compound, called PDE-5, arrives to break down cGMP and return the penis to its previously limp state.

The spider's tumescent trick works from the opposite end of the biological pathway than drugs such as Viagra — which blocks the production of PDE-5 — leading scientists to study it in hopes of an application in future drugs to treat erectile dysfunction.

Following the spider's reported discovery, the store was closed and fire brigades were called — but the arachnid is still nowhere to be found.

"Despite an extensive search, no spiders have been found to date," Austrian authorities said. It is assumed that the store won't open again until next week, after the conclusion of a thorough search.

Two new species of blind and colorless daddy longlegs spider have been discovered — one in the dry western region of Australia, and one on the lush tropical island of Réunion.

Both of the species live in underground habitats, which likely led to their colorless bodies and blindness. And researchers believe that both of these subterranean spiders could tell us an interesting story about the way species evolve and move over time.

This study "really highlights why it is that biodiversity discovery matters and how it is that you can find really unusual species in some of the strangest places that you look," Prashant Sharma, a biologist at the University of Wisconsin-Madison who was not involved in the new research, told Live Science.

Spiders in the Pholcidae family are found all over the world and are notable for their long, spindly legs,  which earned them the common nickname "daddy longlegs." Because they tend to live in dark places, such as basements, they're also often called "cellar spiders." The researchers published descriptions of these two new Pholcid species on July 24 in the journal Subterranean Biology.

Related: Are daddy longlegs really the venomous spiders in the world?

These daddy longleg spiders should not be confused with harvestmen, another type of arachnid often referred to as daddy longlegs. Unlike these Pholcid spiders, which look like regular spiders with two distinct body sections, harvestmen often look like they have a single, round body section hoisted aloft by their wire-thin legs.

The first new Pholcid spider was discovered in mining boreholes of the Pilabra, a dry and rocky habitat in a remote corner of Western Australia. The species belongs to the genus Belisana, which — prior to this study — was thought to only live hundreds of miles away, in Asia and the more vegetated northeast region of Australia.

Because this spider lives so far away from other members of its genus, the researchers think that Belisana spiders may have once been much more widespread in Australia. They speculate that the genus may have lived all across the continent about 60 million years ago, when it was covered by forests. But as western and central Australia grew drier, many of the Belisana spiders living there could have died out — except for this newfound species, Belisana coblynau, which had by then adapted to live in underground environments that hadn't changed as drastically as the surface ecosystem.

The other new species described in the paper was also found underground, but this time in a lava tube — a tunnel formed by molten lava — on Réunion, a French island off the coast of Madagascar in the Indian Ocean.

This spider is in the genus Buitinga, with its closest relatives living on the African mainland. But no Buitinga spiders are known to live on Madagascar, despite the fact that Madagascar is closer to the African mainland and much larger than Réunion. Complicating the mystery, daddy longleg spiders don't "balloon," a process in which baby spiders weave parachutes out of silk to let the wind blow them around — and a great way to travel from island to island.

Because of this, the researchers speculate that these Réunion Buitinga spiders likely ended up on the island due to a single, one-off event, like a log carrying a group of spiders across the sea or a storm carrying the spiders off the mainland in hearty gusts of wind.

Cave-dwelling animal species, including spiders, often lose their eyesight and their color as they adapt to underground habitats, Sharma said. Maintaining eyesight and producing body pigmentation requires a lot of energy, he added, and in a dark environment where there's little or no light, like a lava tube or a mining borehole, animals are often better suited putting their energy elsewhere.

For example, some animals that live underground evolve a keen sense of smell, Sharma said, which can help them get a sense of what’s happening in the dark around them.

Throughout history, tales of giant spiders have gripped the human imagination — from Arachne, the half-woman, half-spider figure in Greek mythology to J'ba Fofi, the rumored monkey-size spider of the Congolese rainforest and Shelob, the monstrous arachnid who keeps Frodo the hobbit on his toes in "The Lord of the Rings." 

But are there real-life spiders that inspired these stories and myths? What, in fact, is the biggest spider in the world?

While none are quite as enormous as those fictional beasts, the real world contains giant spiders galore. Just take giant huntsman spiders (Heteropoda maxima), which are the world's largest spiders by leg span. Measuring 11.8 inches (30 centimeters) across, these arachnids can reach the size of a dinner plate. 

But another spider species is so large it's closer to the size of a puppy. "If we're talking about the largest species of tarantula, that would be a species called Theraphosa blondi," said Ray Hale, a wildlife lecturer, arachnologist and vice chairman of the British Tarantula Society. "That is, the goliath bird-eating spider."

Related: What is the deadliest spider in the world?

How big is it?

Most spiders can be split into two broad groups, Hale told Live Science: araneomorphs (also known as 'true spiders', a group that includes 90% of spiders on earth) and mygalomorphs. Tarantulas are mygalomorphs, a group that's considered more primitive than true spiders. This means that they have evolved less since ancient times, and have therefore maintained certain features that true spiders have since shed — such as downward-pointed fangs, and their large size. 

This is why tarantulas feature the biggest spiders on Earth, including the West African Hercules baboon spiders (Hysterocrates hercules) — hefty creatures whose legs stretch to about 8 inches (20 cm); and face-size tarantulas Poecilotheria rajaei, which can also reach 8 inches in diameter and are native to Sri Lanka. Even larger are Brazilian salmon pink bird-eaters (Lasiodora parahybana), whose legs can reach 11 inches (28 cm).

But none of these beat goliath bird-eaters, which live in dense rainforest in northern South America. While these spiders have slightly shorter legs than their huntsman cousins, stretching to 11 inches — their weight gives them the edge. 

At 6.17 ounces (175 grams), and with bodies measuring 5.1 inches (13 cm), they are double the weight of their salmon pink relatives, making them the largest spiders in the world by mass. In 2014, an entomologist roaming the jungles of Guyana came across a goliath birdeater that was so big, it rustled the undergrowth and was equivalent in size to a young puppy — though a bit less cuddly, perhaps.

What does it eat?

The goliath bird-eater's name is a bit of a misnomer. "Yes, it is a big spider. Does it eat birds? Not really," said Hale. There are different theories on where the name came from. It was possibly inspired by a 19th-century engraving that showed these arachnids feasting on birds, while Hale said the name came from the accounts of 16th-century explorers to South America who put two-and-two together when they discovered some chicks that had fallen into the silk-lined burrows of this ground-nesting tarantula. 

But Hale noted that while the nocturnal hunters might opportunistically pounce on vulnerable birds — and the occasional mouse — the bulk of their diet is made up of crickets, lizards and frogs. The spiders are near-blind, so they use extremely delicate bristles on their legs and abdomen to sense slight vibrations that guide them to their food. Their prey meet the sharp end of the tarantulas' 1 inch-long (2.5 cm) fangs, which inject a lethal amount of neurotoxic venom, followed by digestive juices that liquefy prey's tissues so that the spiders can slurp it up. 

Goliath bird-eaters have their own predators, including snakes, wasps and humans — who report that the spiders have a delicious prawn-like flavor when roasted in banana leaves. 

Is this spider harmful to humans?

Goliath bird-eaters are more likely to scurry away from a human than attack. And while there's nothing nice about receiving a nip from their needle-like fangs — an experience that's been compared to a wasp sting — their venom isn't potent enough to harm us. "You're not going to die from it. They're not dangerous," Hale said. 

They do, however, have a secret weapon to ward off unwanted attention: By rubbing their hind legs against their abdomens, they release a flurry of hook-shaped bristles called "urticating hairs" that, once airborne, can become lodged in the skin and eyes and cause enough irritation to drive a predator away. That only happens after these spiders have delivered a warning: Threatened tarantulas will rub their front legs together to produce a high-pitched hissing sound that warns uninvited animals away. Called "stridulation," it's loud enough to be heard from up to 15 feet (4.6 meters) away.

And if that's not enough, these spiders can live for an extraordinarily long time. Along with their huge size, female goliath bird-eaters can live for up to 25 years, Hale said. Alongside the other wonders of their biology, this strikingly long lifespan is perhaps another reason that these behemoths deserve our respect and admiration, more than our fear.

There seems to be no ideal number of legs. Humans have two, dogs have four, insects have six and millipedes can have over 1,000. So what made spiders settle for eight legs? 

"I think the best answer and the simplest answer is that spiders have eight legs because their parents did," Thomas Hegna, an assistant professor of invertebrate paleontology at the State University of New York at Fredonia, told Live Science. "But then that gets into sort of a regress, and somewhere this all had to start."

If we follow the succession of eight-legged spider parents back to about 500 million years ago, during the middle Cambrian Period, we arrive at the root of the chelicerate lineage, the group of arthropods that contains spiders. If we go even further back, to 541 million years ago, we find the ocean-dwelling lobopods, the ancestors of all arthropods. 

The name "lobopod" doesn't refer to a single species but rather a large variety of species with rather simple bodies. Basically, they were wormlike creatures with segmented bodies. Each segment featured roughly identical pairs of short, stubby legs, and this pattern continued along the lengths of their bodies. 

Related: What is the deadliest spider in the world?

As the lobopods evolved, they began specializing their legs and fusing body segments. The early chelicerates seem to have fused their small body segments into two big ones: the head and the abdomen. Scientists aren't sure why, but the head kept the legs, and the abdomen lost them. By the time spiders appeared 315 million years ago, they inherited a body plan that was likely already 150 million years old.

It's unclear which environmental pressures, if any, caused chelicerates to settle on their eight-legged arrangement. However, we know a great deal about where their legs came from — and it's weird.

"Those legs are actually part of their mouth," Nipam Patel, a developmental biologist and director of the Marine Biological Laboratory, which is affiliated with the University of Chicago, told Live Science. 

Because spiders, insects, crustaceans and millipedes all evolved from an ancestor that likely had a segmented body with a set of appendages on each segment, these species are just highly modified riffs on that basic plan. According to Patel, all arthropod appendages — including legs, antennae and even mandibles (the jaws) — can be traced back to a stubby lobopod appendage. 

Take a mantis shrimp. It swims with a bunch of little legs on a segmented abdomen. On the cephalothorax (a fused head and thorax) are its walking legs, and then near its mouth are little appendages that not only make up its jaws but also sweep food into its mouth to help it eat. 

Compare that to an insect, whose abdomen doesn't have appendages. But it has six legs on its thorax, while its head and mouth are basically set up like the mantis shrimp's.

Then, there are spiders.

"If you look at a spider embryo, it looks exactly like an insect embryo," Patel said. "Except it only grows the legs on its head. But instead of using those as mouthparts, it uses them to walk."

The reason spiders walk with appendages from their faces goes back to lobopods and the original chelicerate body plan. While modern arthropods are spoiled for specialized appendages, the lobopods were wormlike creatures with many sets of roughly similar appendages. 

Related: What is the largest arachnid to ever live? 

"Initially, all of the legs were the same," Heather Bruce, a research associate at the Marine Biological Laboratory, told Live Science. "But then the first appendages became differentiated for being a sensory appendage, like for sensing and grabbing food."

From that point, the spider's chelicerate ancestors began to diverge from the other groups. In the ancestors of insects and crustaceans, the lobopod's multitasking front appendages lost their grabbing and feeding ability and became specialized sensory structures called antennae. But for chelicerates, those same appendages lost their sensory capabilities and became fangs. 

Meanwhile, chelicerates' second leg pair evolved into a set of grabby appendages called pedipalps; the following four sets of legs remained in their role as walking legs, and all appendages after that were lost. 

Well, not all of them. "Spinnerets evolved from spider legs," Bruce said. "There are really cool fossils in amber of a species that looks to be an ancestor of both spiders and scorpions, so it has some intermediate traits between the two. And on that fossil, there are very clear legs hanging off of the abdomen."

Fuzzy, long-legged spiders may attack their prey with an ingeniously gruesome tactic — by covering them in toxic digestive fluids.

Unlike most other spiders, feather-legged lace weavers (Uloborus plumipes) don't have venom-producing glands or a way to inject their prey with toxins through their fangs. Instead, these spiders seem to produce neurotoxins in their gut, which may help explain their unusual hunting strategy of dousing their victims in fluids from their digestive system, researchers have discovered. The findings were posted as a non-peer-reviewed preprint on BioRxiv on June 28.

"It really looks like there's something in these digestive fluids that kill the prey,” which could be the toxins found in this study, co-author Giulia Zancolli, an evolutionary biologist at the University of Lausanne in Switzerland, told Live Science.

When most spiders trap an insect in their web, they inject it with venom from their fangs to paralyze it. They then cover each bite with digestive fluids to help break the insect down before consuming it.

But spiders in the Uloboridae family, such as feather-legged lace weavers, wrap their victims in a copious amount of silk — sometimes more than hundreds of feet of it — before covering them in fluids and eating them.

Related: What is the deadliest spider in the world?

While scientists already knew about this unusual behavior, they weren't exactly sure how the victims actually died, the new paper said.

To investigate, Zancolli and her colleagues extracted RNA — a cousin to DNA — from different parts of feather-legged lace weavers. RNA can contain instructions for cells on how to make different materials, so by extracting RNA from different areas of the spiders' bodies, the researchers could see what kinds of compounds the animals were producing and where they were being produced. The researchers then looked at the structure of each of those compounds to determine whether they were likely to be toxic.

The team didn't find many potential toxins near the spiders' heads, nor did they find many in their silk. But they did find RNA for multiple potential toxins in the midgut gland (an organ that produces digestive fluids) — indicating that the digestive fluid may be toxic. In addition, the team found no evidence of venom glands or a typical venom-delivery system through the fangs.

The team didn't actually examine what was in the digestive fluid itself. But Zancolli noted that in another recent study, scientists did find toxins in an Uloborus digestive system. 

This discovery could show that while spiders in the Uloboridae family may not be able to inject venom through their fangs, they may still be using toxins — in a unique, vomit-y way.

When male spider mites are ready to mate, they strip off the skin of maturing females as part of a freakish mating ritual.

Scientists in Austria uncovered the creepy act for the first time while studying spider mites, the dust speck-size relatives of arachnids such as spiders and scorpions, in their lab. The researchers found that the males would guard the females, which typically reach sexual maturity at 10 days of age, and wait until their potential mates began molting their exoskeletons, according to a study published Friday (June 7) in the journal iScience.

"The males will guard the females for hours," study co-author Peter Schausberger, a zoologist and professor in the Department of Behavioral and Cognitive Biology at the University of Vienna, told Live Science. "The males are able to recognize when the premature females start molting because their exuvia [old, outer skin] turns silvery as air lodges between it and the new skin."

And this is when things get really weird. To make the female ready for mating sooner, the male then slips beneath the female and uses its pedipalps (needle-like mouthparts) to pull the skin off the female. Once the exuvia is removed, the male can insert his aedeagus (reproductive organ) into the female, according to a statement.

Related: Strange love: 13 animals with truly weird courtship rituals

The researchers also noticed that at times the males would use their forelegs to "drum" against the female, perhaps to trigger them to begin the molting process, according to the study. 

"It only takes a couple of seconds for copulation," Schausberger said. "This guarding behavior is high in energy and time, so the males want to ensure that another male doesn't take over a female."

This dedication to ensuring a mate is pivotal for the males, since the "first copulation partner of a female is the one that sires all the offspring," according to a statement.

Interestingly, the researchers discovered that at times the female spider mites would "undress" themselves when it came time for them to molt. However, the females pulled off the skin beginning from their heads, whereas the males would remove the hind part of the skin first.

While this is the first time that this skin-stripping behavior has been recorded in any species, spider mites aren't the only ones that conduct creepy mating rituals in the animal kingdom.

For instance, male butterflies will "penetrate the casing" of a female pupa, the stage in a butterfly's life cycle after it's a caterpillar and cocoons itself into a chrysalis, Schausberger said.

Both of these instances "show that intense mate competition can arise" and that these "sophisticated behaviors are driven by sexual selection even in the tiniest of animals," Schausberger said. 

The scientists hope to expand their research by seeing what happens when males have to contend with rivals during this undressing act.

Giant, invasive Jorō spiders that are spreading throughout the southeastern United States could be the "shyest ever documented," meaning they don't owe their success to aggression, a new study finds.

Jorō spiders (Trichonephila clavata) first appeared in the U.S. in 2013, when they were accidentally brought across from eastern Asia in a shipping container, according to a study published May 15 in the journal Arthropoda. The yellow and blue-black critters are now found all over Georgia and its neighboring states, where they weave exceptionally large webs measuring up to 6.5 feet in diameter (2 meters) that are sometimes interlinked to form "colonial" webs.

"Most people think 'invasive' and 'aggressive' are synonymous," study co-author Amitesh Anerao, an undergraduate biology major at the University of Georgia, said in a statement. "People were freaking out about the Jorō spiders at first."

The species' explosive spread suggested it could be innately combative and threatening. "One of the ways that people think this spider could be affecting other species is that it's aggressive and out-competing all the other native spiders," lead author Andy Davis, an assistant research scientist at the University of Georgia's Odum School of Ecology, said in the statement. 

But it turns out that Jorō spiders, whose bodies without the legs can measure up to 1.2 inches (30 millimeters), are quite the opposite — and possibly the shyest spiders on record.

Related: What is the deadliest spider in the world? 

To determine their boldness and resilience to mild stress, the researchers collected Jorō spiders and exposed them to two consecutive, gentle puffs of air from a turkey baster. They measured the duration of the spiders' freeze response, or thanatosis — when spiders remain still for a period of time after a disturbance — and compared it with that of nine other North American spiders.

The researchers were baffled to find that Jorō spiders remained motionless for more than an hour after the disturbance. The shortest freeze responses lasted 11 minutes, which was still seven times longer than the average response of other spiders (one to two minutes). "They basically shut down and wait for the disturbance to go away," Davis said.

Only one other species closely related to Jorō spiders, the golden silk spider (T. clavipes), displayed a similarly lengthy startle reaction. "We ourselves were surprised when conducting the tests because the reactions of the Trichonephila spiders differed so greatly from the published literature," the researchers wrote in the study. "We hypothesize that this prolonged response must be an innate trait of this genus."

Spider freeze time is a good estimate of how threatened they feel, according to the study. Spiders that stay still for longer are thought to be shyer, and those that resume activity soon after a disturbance, bolder. "Our paper shows that these spiders are really more afraid of you than the reverse," Davis said.

Despite their timidity, Jorō spiders appear to be highly tolerant to human environments and to have successfully expanded their range. 

So instead of aggression, their spread could be down to their "incredible reproductive potential," Davis said. "They're simply outbreeding everybody else. It's not because they're displacing native spiders or kicking them out of their own webs."

Arachnophobes might hate the look of them, but Jorōs are relatively harmless and don't bite unless they are cornered. The giant spiders are unlikely to budge from the southeast. "They're so good at living with humans that they're probably not going away anytime soon," Anerao said.

Scientists have discovered the survival secret of a brightly colored spider that mimics ants to deter predators: the imperfection of its impressions.

The tiny jumping spider Siler collingwoodi lifts its front legs to form mock antennae while swinging its legs and jiggling its abdomen to copy an ant's gait. Ants often possess spiny defenses and venomous jaws, so the spider's act is intended to discourage potential predators that may be more wary of an ant. 

Now, a new study reveals that S. collingwoodi's impersonation is far from perfect — but that its imperfect performance is no bad thing, enabling the amateur performer to mimic multiple ant species and deter most of its predators. The researchers published their findings May 17 in the journal iScience.

Related: Bold jumping spiders can literally go blind with hunger

"S. collingwoodi is not necessarily a perfect mimic, because its gait and trajectory showed high similarity with multiple ant species," study first author Hua Zeng, an ecologist at Peking University, said in a statement. "Being a general mimic rather than perfectly mimicking one ant species could benefit the spiders by allowing them to expand their range if the ant models occupy different habitats."

To investigate how the ant-mimicking spider fools its predators, the researchers collected S. collingwoodi along with five ant species and another type of non-mimicking jumping spider from four locations across southern China's Hainan island. By comparing S. collingwoodi's ant impersonations to the movements of real ants, the researchers found that the spider's gait was a good all-around impersonation of all of them and most closely resembled the gaits of the three smaller ant species that were closer to its size. The non-mimicking spider, in comparison, showed no resemblance to the ants.

The true test came with how S. collingwoodi's performance was received by its harshest critics: two of its likely predators, the praying mantis Gonypeta brunneri and the predatory jumping spider Portia labiata, which is similar in size to S. collingwoodi. The mantis was unconvinced by S. collingwoodi's thespian bobbling and snacked on it, as well as the non-mimicking spider.

However, the predatory spider did not attack the spider mimic — a sign that its performance does work on some occasions and is possibly most effective at deterring predators that are less willing and capable of fending off an ant's counterattack.

But this thespian spider doesn't rely on its acting abilities alone: Another layer to the spider's defenses is its costume — the brilliant flecks of metallic oranges, reds and blues that mark its head and abdomen. The researchers modeled these patterns with the known visual systems of the mantis and predatory spider, along with two plants — the Chinese Ixora (Ixora chinensis) and the Fukien tea tree (Carmona microphylla) — that S. collingwoodi lives on. These plants helped camouflage the mimic spider, with the jasmine plant successfully hiding it from both predators.

In a follow-up investigation, the researchers said they will investigate whether the spider's performance is genetic or acquired by learning — which will reveal even more about the dancing spider's usefully imperfect display.

Spiders are common critters. And, as almost all of Earth's 43,000 known spider species are venomous, it is likely that most people have encountered a venomous spider at one point or another. 

So that's the bad news. The good news, however, is that of these, only 25 species are known to have killed or caused serious harm to humans. But which spider is the deadliest?

The deadliest spiders — or at least those most frequently cited as having caused death or serious injury to humans — are funnel-web spiders (Atrax), redback and black widow spiders (Latrodectus), banana and wandering spiders (Phoneutria) and recluse spiders (Loxosceles). 

But even these deadly spiders, with potent venom and fangs primed for piercing skin, are not particularly dangerous to humans. The American Association of Poison Control Centers (AAPCC) tracked only one death caused by a spider bite in the U.S. in 2021. Australia, home to some of the most venomous spiders in the world, hasn't reported a single spider bite death since the 1980s. 

"It is incredibly rare to have a deadly spider encounter," said Rick Vetter, a retired research associate with the Department of Entomology at University of California, Riverside, whose research focused on medically important spiders. "Considering all the bad things that could happen to you, if spiders are your biggest concern, then you are living the good life."

Related: Are daddy longlegs really the most venomous spiders in the world?

Funnel-web spiders top the list of deadliest spiders, if only for their storied venom. Native to Australia, these spiders boast venom that's so potent their bite can kill within minutes. "The deadliest is probably the funnel-web spider and its relatives. The Sydney funnel web spider (Atrax robustus) can kill a toddler in about 5 minutes and a 5-year-old in about 2 hours," Vetter told Live Science. Although no one has died from these spiders since the advent of antivenom in the 1980s, it is difficult to imagine a toddler receiving treatment soon enough to recover from a funnel-web bite.

Phoneutria spiders, the most common of which are often referred to as banana spiders or wandering spiders, are native to Brazil and have the most neurologically active venom of any spider. But they rank a bit lower on the list of the world's deadliest spiders because their venom works relatively slowly, leaving ample time for treatment. And Loxosceles spiders, the most familiar of which is the brown recluse (L. reclusa) found in the U.S., may be one the most common causes of spider-related injuries, with painful bites that can cause body aches and fever and take months to fully resolve. But they are very rarely deadly. 

The only arachnid genus that gives the funnel-web a real run for its money as the deadliest spider is Latrodectus, which includes the Australian redback (Latrodectus hasselti) and the more familiar black widow spider in the U.S. These spiders have a slight edge because they bite humans more frequently than funnel-web spiders, with comparably potent venom. "The most venomous species (Sydney funnel-web spiders, Brazilian wandering spiders) don't kill or impact that many people," Linda Rayor, a behavioral ecologist at Cornell University who focuses on spiders, told Live Science in an email. "It is the more widely-distributed black widows that are going to be the stars of your story."

It's important to note that, while AAPCC's annual reports carve out a section for spider bite statistics, it isn't easy to get a real handle on spider bite mortality or morbidity. 

"A number of human deaths each year are attributed to spiders," Rod Crawford, curator of arachnids at the Burke Museum at the University of Washington in Seattle, told Live Science in an email. "However, from a scientific viewpoint, almost none of these attributions are evidence-based." 

Related: 11 deadliest spiders

It is exceedingly rare, Crawford explained, for a victim to see a spider on their skin, feel a bite, capture that same spider, and then bring the offending spider to a physician (let alone a spider specialist) for analysis. "Practically all of the 'spider bites' you hear about, including those reported to poison centers originate from the belief that if you didn't see what bit you, it was a spider," Crawford said. 

Rayor echoed this sentiment. "I have spent a surprising amount of time trying to track down the human mortality rate from spiders and it is miniscule," she said. "This isn't reliably reported, but it is clear that not that many people get killed by spiders."

Keeping in mind the flawed nature of spider bite statistics, The Australian Museum claims that about 2,000 people are bitten by redback spiders each year, and that the antivenom to treat funnel-web spider bites has been given to about 100 patients since 1980. AAPCC's annual report tracked about 3,500 spider bites in the U.S. in 2021, with about 40 "major" clinical outcomes. Nine of those serious outcomes were attributed to black widows; 29 major outcomes and the only death that year were attributed to brown recluses. There were no spider bite deaths in AAPCC's 2020 report, which tracked seven "major" black widow bites and 23 "major" brown recluse bites.

This means that the deadliest spiders are, in fact, not very deadly. "True human spider bites of any kind — dangerous or harmless — are vanishingly rare," Crawford said. "Take me as an example: Over a long career I have handled tens of thousands of live spiders with my bare hands. Only 3 actual bites resulted; none of the 3 had any significant effect. So when people tell me spiders crawl into their beds at night and bite them while they are asleep, I just roll my eyes."

Vetter agreed. "In reality, spiders are way down the list of things to be concerned about."

Spiders have a keen sense of sight, but once they begin to starve they also start to go blind.

Biologists made the startling discovery while studying the eyes of bold jumping spiders (Phidippus audax) in the lab. They found that when they decreased the diets of these tiny hunters, the spiders' vision decreased too, according to a study published in the May issue of the journal Vision Research.

"We started looking at their eyes and noticed dark spots that suggested degeneration," study co-author Elke Buschbeck, a professor in the department of biological sciences at the University of Cincinnati, told Live Science. "We were really surprised and not expecting that."

Jumping spiders have high-resolution color vision, which they see with their principal, forward-facing eyes. (They also have side eyes for black-and-white vision.) Buschbeck thinks that studying these spiders could provide insight into the role nutrition plays in human eye diseases such as macular degeneration.

The spiders’ degenerating eyesight was initially spotted by one of Buschbeck’s undergraduate students, Miranda Brafford, who was examining the eyes of several of the wild-caught spiders using the lab's custom-built ophthalmoscope — a device designed to take fluorescent images of the retinas of animals with teensy eyes, such as spiders and insects. Brafford, who is a co-author of the study, noticed that some of the spiders had developed spots on their photoreceptors, which are cells that convert light into signals that are sent from the eyes to the brain. The spots suggested that the spiders' eyesight had degenerated. They then used electron microscopy to examine thin cross sections of the photoreceptors to confirm that the cells were indeed dying, according to an April 20 statement.

Related: Female spiders play dead during sex so males don't have to worry about being eaten

To test their theory that poor nutrition was the culprit, the team divided the spiders into two groups: One was fed a normal diet of crickets and bee pollen while the other received half portions.

"The condition of the eyes of the spiders with less nutrition was much worse," Buschbeck said. "We could tell just by looking at them with the ophthalmoscope that some of their photoreceptors had died." 

The researchers think that this shift in vision could be because photoreceptors require a lot of energy in the form of nutrients to function optimally, and if they don't receive a sufficient energy supply "the system fails," according to the statement.

While humans aren't spiders, "the photoreceptor mechanism is very similar" between the two species. So something similar could be at play in people with macular degeneration, though more research would be needed to show that, Buschbeck said.

"In both cases, it has something to do with energy metabolism and those photoreceptor cells, which are extremely energetically costly," Buschbeck said. "It's not easy for an organism to keep up with their energy needs [when nutritionally deprived]."

Female funnel weaving spiders engage a bizarre behavior to mate: They play dead during sex so males are less worried that they might be eaten when the deed is done, a new study shows. That, in turn, makes it easier for females to choose the best mates, by playing dead for appealing partners and fighting off the scrubs.

Some funnel weaving spiders (also called funnel weavers and funnel web spiders) — a family of fast-moving, slender spiders that build their webs in a distinctive funnel shape — are known to engage in sexual cannibalism, when females kill and eat the males after the pair has finished mating. Naturally, this makes sex a much less appealing for the males, which are literally risking their lives every time they want to hook up. 

To get around this, some species have developed an unusual behavior known as sexual catalepsy, in which the female curls up its legs and stays immobilized as if it had died. This allows males to go about their business without having to worry about becoming a post-sex snack for the female.   

Researchers have known about sexual catalepsy in spiders for some time, but until now, it has not been clear if the females are voluntarily immobilizing themselves for the benefit of the males or if the males have some control over the behavior, either through some behavioral trigger or via a chemical cue.

To understand what was going on, researchers conducted experiments on funnel weaving spiders from the species Aterigena aculeata to compare sexual catalepsy with similar behaviors to see if it was controlled by males or females. Results were published March 21 in the journal Current Zoology.

Related: Male spiders drum out mesmerizing syncopated beats to woo mates 

During the experiments, the team observed A. aculeata females during one of three scenarios: engaging in sexual catalepsy naturally during mating; playing dead, also known as thanatosis, after being shaken in a test tube; and being put to sleep by anesthesia, to mimic a potential male-produced chemical cue. 

Afterward, the spiders were frozen to death and their bodies were ground up so the researchers could analyze the chemicals being used to coordinate the spiders' actions. This allowed the researchers to look for physical and chemical similarities among the behaviors. 

If sexual catalepsy closely mimicked thanatosis, it was probably being controlled by the female. But if it was more similar to anesthesia, then it suggested that it was not in the female's control and could have been influenced by the male, study co-author Mark Elgar, an evolutionary biologist at the University of Melbourne in Australia, told Live Science in an email.

The results showed that sexual catalepsy appeared almost identical to thanatosis. Individuals that had experienced both behaviors had chemical profiles much more similar than those that had been anesthetized. 

This finding strongly suggests that sexual catalepsy is controlled by females and acts as a way for them to choose their mates, Elgar said. "Mating occurs only when the female enters sexual catalepsy, so if she doesn't behave that way, then mating doesn't proceed," he added.

Although the females may appear to be dead during the mating process, the males are fully aware that they are faking. Shortly after mating has finished and the male has backed away, the female will get up and scurry away. 

Sexual catalepsy also occurs in several other species of funnel weaving spiders, but it is too soon to tell if the technique works the same way across the rest of the group, Elgar said. "It isn't clear yet whether it has consistently evolved as a female mechanism of mate choice or a male mechanism of protection against sexual cannibalism," he added.

Playing dead is not the only behavior spiders use to escape sexual cannibalism. In April 2022, researchers revealed that males from Philoponella prominens, a type of orb weaving spider, use a catapult-like mechanism in their legs to immediately launch themselves away from females after they finished mating. 

Deadly spiders that can survive underwater for over 24 hours are turning up in people's swimming pools in Australia after parts of the country were hit by heavy rain and floods over the past week. 

These swimming pool interlopers include funnel-web spiders, which are members of the Araneida family, with around 40 known species. The Sydney funnel-web spider (Atrax robustus) is one of the most deadly spider species, with males being responsible for most fatalities, likely because it evolved more potent venom to protect itself while wandering around looking for females to mate with. While no deaths have been recorded since antivenom became available in the 1980s, if untreated a bite can kill a child in as little as 15 minutes. 

Heavy rain and thunderstorms have hit parts of New South Wales since March 23, with a severe weather warning still in place for northern parts of the state. Sam Herrmann, a reptile keeper from Australian Reptile Park, told 9news that the rain has set funnel-web spiders "on the move."

"They're often seeking shelter, so the lip under the pool creates a great environment for them to hide and stay dry," he said. "However, sometimes they can accidentally fall into the pool."

Related: 11 deadliest spiders

Dan Smith, from the southern Sydney suburb Engadine, spotted one of these deadly spiders in his pool in the same spot he had found a trapdoor spider just a few days earlier. 

"It was quite an awakening event," he told 9news. "It was very active, very fiery." 

Vasilios Basil Haddad, from Sydney, also found a "nasty" male funnel-web spider in his empty pool and posted a video of it to Facebook. 

Meanwhile Lynda Smith, who lives on the northern New South Wales coast, found four eastern mouse spiders (Missulena bradleyi) in her pool. This species is similar in appearance to funnel-web spiders, with bulbous heads, powerful jaws and a venom of similar potency to their better-known counterparts. According to 7NEWS, she posted a warning about the presence of spiders to Facebook. "Please always check your pools before jumping in especially after rain," she wrote, adding they are "not to be messed with."

Funnel-web and mouse spiders are able to survive underwater by trapping an air bubble to the hairs on their underside, Helen Smith, the arachnology collection manager at the Australian Museum, told 7NEWS. She said spiders breathe differently than humans do, so it takes them much longer to drown. Most spiders have a dual respiratory system made up of a trachea and an organ called a book lung, which consist of a series of plates stacked up that allow for the diffusion of oxygen. The trachea carries oxygen to the tissues, while book lungs oxygenate hemolymph — the spider equivalent of blood. 

"They can survive for several hours and sometimes a thoroughly dead-looking spider can suddenly twitch or come back to life slowly," she said, adding they can also bite underwater. "But to bite they need to grip onto something — so don't poke them."

Smith captured the funnel-web spider in his pool and contacted expert Scott Johnson, who offered to take it to the Australian Reptile Park, which has the facilities to milk it to make antivenom. 

Herrmann told 9news that if people find spiders in their pools, they should scoop them out with a net. "If you so happen to get bitten, seek medical attention immediately," he said.

Black widow spiders in the U.S. are being killed off by an unexpected rival: their invasive relatives, but the motivation behind the highly aggressive attacks is not yet clear, a new study finds. 

The perpetrators, brown widow spiders (Latrodectus geometricus), likely originated in Africa or South America but have since spread to every continent on Earth apart from Antarctica. Brown widows are from the same genus as black widows, of which there are five species, including three that are native to North America: southern black widows (Latrodectus mactans), western black widows (Latrodectus hesperus) and northern black widows (Latrodectus variolus). But unlike black widows, which can all inflict extremely painful and occasionally lethal bites on humans, brown widow bites rarely cause significant harm to people, likely because they inject less venom into their bites despite having venom that is "drop-for-drop" just as toxic, according to the Center for Invasive Species Research (CISR) at the University of California, Riverside. 

In the U.S., brown widow spiders were first spotted in 1935 in Florida, and have subsequently spread across the southern states and into California, according to CISR. Since the invasive species was introduced, southern and western black widow numbers have plummeted, particularly in Florida, where southern black widows have gone "locally extinct" in certain areas.

However, scientists are unsure exactly why this is happening: Other spider species have not been affected by the brown widow's arrival, and there does not appear to be any competition for resources that would force the two widow species to fight one another.

Related: False widow spider preys on baby bat in never-before-seen encounter

In a new study, published Monday (March 13) in the journal Annals of the Entomological Society of America, researchers put solitary brown widows into laboratory tanks with one of three individuals from another spider species — a southern black widow, a red house spider (Nesticodes rufipes) or a triangulate cobweb spider (Steatoda triangulosa), which all overlap with brown widows in the wild — to see how the brown widow reacted to cohabiting with each of the species. 

When paired with the non-widow spiders, the brown widows peacefully cohabited with their tankmates in 50% to 80% of the tests. The rest of the time, one spider would kill and eat the other, but there was little difference between which species would end up victorious.

But when adult brown widows were paired with adult black widows, the invasive species killed and consumed the black widows 40% of the time, the pair peacefully cohabitated together 30% of the time, and in the remaining trials the black widows ended up victorious — but only after defending themselves from an initial brown widow attack. However, when sub-adult individuals of both species were mixed, the brown widows killed and ate their counterparts 80% of the time. Overall, brown widows were six times more likely to kill black widows than the other two spider species. 

In separate experiments, the team also showed that brown widows produce more offspring than black widows and that those offspring begin to reach maturity faster than black widows. This could explain why sub-adult individuals were so adept at killing younger black widows, which in turn would explain why black widow populations are collapsing in areas where brown widows have invaded, the researchers wrote. However, the researchers were surprised at the stark behavioral differences between brown and black widows.

Related: 11 deadliest spiders

"Brown widows are boldly aggressive and will immediately investigate a neighbor and attack if there is no resistance from the neighbor," study co-author Deby Cassill, an ecologist at the University of South Florida (USF), said in a statement. "But the black widows are extremely shy, counterattacking only to defend themselves against an aggressive spider."

The researchers are unsure why the closely related species react so differently to one another and plan to study brown and black widows in other parts of the world, such as Africa, to see if the same trends apply.

"I would love to see if their [brown widows'] behavior and displacement of black widows is something that they have adapted here in North America, or if this behavior is something they exhibit naturally even in areas where they have coevolved with black widows for much longer periods of time," study lead author Louis Coticchio, a doctoral student of conservation biology at USF, said in the statement.

Sea spiders possess a remarkable, previously unknown ability: They can regrow their rear ends.

In a series of experiments, scientists discovered that juveniles from the sea spider species Pycnogonum litorale were able to fully regenerate a number of amputated body parts from their lower body, including hind limbs, parts of their guts, reproductive organs and even their anuses. 

Sea spiders, which belong to the class Pycnogonida, are a group of around 1,300 marine arthropods with eight legs. While they look similar to terrestrial spiders they are only very distantly related to them. Other arthropods, such as spiders, centipedes and crabs, can also regenerate body parts, enabling them to escape predators that have taken a bite out of them. However, it had long been assumed that sea spiders didn't possess this ability because scientists had never observed the animals doing it, and because sea spiders have evolved hard exoskeletons to protect them from predators, which suggested they might not need any other form of defense.

In a new study, published Jan. 23 in the journal Evolution, researchers tested this assumption by amputating body parts from 23 juvenile and 23 adult P. litorale sea spiders. The adults were unable to regenerate any of the lost body parts, but surprisingly a majority of the juveniles eventually regrew the missing parts.

"We were the first to show that this is possible," Gerhard Scholtz, a zoologist at the Humboldt University of Berlin in Germany, told French news agency AFP. "Nobody had expected this."

Related: 10 bizarre deep sea creatures found in 2022

During the experiments, the sea spiders had varying parts of their posterior sections removed, such as their back legs, hindgut, anus, various muscle regions and reproductive organs, which include gonoducts in females and gonopores in males. 

The adults were unable to regenerate the lost body parts and most died from their injuries, although a couple of individuals that sustained less-extensive damage were able to survive for up to two years after the experiments. However, 16 juveniles survived their amputations and 14 were able to fully regrow their lost body parts, although some individuals that had all four rear legs removed only regrew two replacement legs. 

The adults' inability to regrow lost body parts is likely why the juveniles' regenerative skills have gone unnoticed until now, researchers noted in the paper.

The team now wants to discover the exact mechanism that triggers the regeneration in sea spiders and compare it with other arthropods' regenerative abilities.

"We can try to find out on the cellular level and the molecular level what initiates the regeneration," Scholtz said. It is possible that it involves stem cells, or undifferentiated cells that can transform into any other type of cell, he added. 

Related: Could humans ever regenerate a limb?

While this is the first time sea spiders' regenerative powers have been documented, scientists have observed more extreme versions of regeneration in other animal groups. 

In March 2021, researchers serendipitously discovered that photosynthetic sea slugs (Elysia cf. marginata) could deliberately decapitate themselves and regrow an entirely new body from their severed heads, with some individuals performing the trick twice in their lifetime. In September 2022, another team revealed how axolotls (Ambystoma mexicanum) — aquatic salamanders that were already known to regenerate their limbs, heart and spinal cord — can regenerate damaged parts of their brain. 

Studying the regeneration abilities of arthropods and other animals could one day lead to a breakthrough in regrowing lost human body parts, the team wrote in the new study. 

"In the end, maybe the mechanisms we detect in arthropods may help medical treatments of limb loss or finger loss and so on in humans," Scholtz said. "This is always the hope."

Two people who were bitten by brown recluse spiders developed a rare condition in which their immune systems destroyed their red blood cells, a new case report shows. 

In the first case, a 30-year-old man came to the hospital because he was nauseous, vomiting, had muscle aches, and had a painful lesion on his left shoulder. In the other case, a 28-year-old woman came in for bad low back pain. They both had strange-looking lesions. The man’s, on his left shoulder, was small and irregularly shaped, with a black scabby portion on one side; the woman’s, on her upper back, was target-shaped and larger. Both were painful to the touch.

In both cases, doctors noticed that the whites of the patients’ eyes were yellowish. The condition, called scleral icterus, is caused by a buildup of a pigment called bilirubin in the blood, which is made when red blood cells break down.

Based on blood testing, both patients were diagnosed with a condition called warm autoimmune hemolytic anemia — something was causing their immune systems to destroy their red blood cells. In both cases, that something was systemic loxoscelism, a body-wide reaction to a bite from the venomous Loxosceles reclusa spider, otherwise known as the brown recluse.

Though brown recluse bites can be painless, the bite can become itchy, red, and inflamed shortly after the bite occurs, according to the National Capital Poison Center (NCPC). It may eventually become more painful, darker, and form a blister. A bite can also cause necrosis, or tissue death, surrounding it, and can eventually form a black, scab-like area called an eschar. Brown recluse bites are difficult to diagnose, according to the NCPC — doctors make the diagnosis based on a patient’s history and symptoms, if they have any. 

Related: The 11 deadliest spiders

The patients in the report were treated with intravenous fluids and corticosteroids, which suppress the immune system. Both were also given blood transfusions, and eventually recovered enough to leave the hospital. 

The man’s recovery was uncomplicated, the woman’s less so for reasons apparently unrelated to her spider bite. She was six weeks pregnant and had a miscarriage, and also developed a brain condition called acute metabolic-toxic encephalopathy while in the hospital. This condition can also be caused by withdrawal from alcohol and drugs, and the woman had a history of drug abuse. But she eventually also recovered enough to be discharged with oral corticosteroids.

The treatment course went well for these patients: some people who develop autoimmune hemolytic anemia must take a blood cancer drug with potentially severe side effects if corticosteroids don't work, and some may even need to have the spleen removed, according to the study.

The brown recluse spider, a small, brownish or tan spider with a dark brown “violin-shaped” marking on its head, lives in several parts of the United States, but is most common in Texas, Missouri, and Illinois. 

Most people shouldn't lose sleep worrying about brown recluse bites, as they are rare, and 90% of them don’t cause any major complications. 

Children, as well as African American and Hispanic people, are at greater risk for having systemic reactions, according to the study. The American Association of Poison Control Centers reported that in 2019, out of 802 reported brown recluse bites, only 24 people had major reactions, and no deaths were reported. 

The brown recluse bites were described in a report published in the journal Hematology.

Spiders are some of the most successful arthropods on the planet, having colonized every continent except Antarctica. Not all of these eight-legged arachnids are venomous, but some can be deadly to humans. From the notorious black widow to the ultra-deadly funnel web spider, here are some of the deadliest spiders on Earth.

Brown recluse spider

As their name suggests, brown recluse spiders (Loxosceles reclusa) have a shy nature and tend to hide away in dark, sheltered places. However, the brown recluse spider will bite if they feel threatened, and their bites can be deadly. They are usually found in the south and central United States, spanning southeastern Nebraska to southwestern Ohio, south to northwestern Georgia and into Texas.

The brown recluse spider can be dangerous to people because their venom contains a toxin that can cause skin necrosis (rotting). For the most part, symptoms, such as burning and itching at the bite site, as well as fever and nausea, develop a few hours after a bite. In extreme cases, the venom can lead to serious reactions or even death, especially to more vulnerable groups such as young children and the elderly.

Hobo spider

Part of the family of spiders known as the funnel web spiders, the hobo spider (Eratigena agrestis, formerly Tegenaria agrestis) can be recognized by it's light to medium brown coloring and the multiple chevron patterns (v-shaped) on its abdomen pointing toward their head. They are often confused with the brown recluse spider (and vice versa), but the brown recluse is much more dangerous to humans. While hobo spiders have been known to bite if they feel threatened, there is much debate about how venomous they actually are. So much so that the Center for Disease Control and Prevention has removed them from their venomous spiders list. However, it's still wise to be cautious as hobo spider bites result in swelling and redness around the area, and can have more severe effects in young children.

Hobo spiders are not great climbers, so you'll find their funnel-shaped webs at ground level. Geographically, they can be found in western North America, in the Pacific Northwest and Great Basin, as well as distributed throughout Europe to Central Asia.

Black widow spider

In the genus Latrodectus, the black widow is one of the most venomous spiders and is found on every continent except Antarctica. In North America, they're commonly found in southern Canada and in the northeastern United States. You can identify the female black widow spider by its shiny black body and distinct red hourglass-shape on the underside of the abdomen. The male black widow is smaller in size, brown or gray in color with small red sports and does not have the hourglass marking.

While both male and female black widows are venomous, only the female is dangerous to humans. The venom of a black widow is reported to be 15 times stronger than that of a rattlesnake, although they don’t deliver as much venom in their bite, so fatalities are rare. That’s not to say a black widow bite isn’t painful! Those unlucky enough to be bitten by a black widow will experience nausea, fever, sweating, restlessness, muscle cramps and labored breathing, and these symptoms may last for several days.

Brazilian wandering spider

Commonly referred to as armed spiders or banana spiders (as they tend to be found hiding within shipments of bananas), the Brazilian wandering spider is one that you'll definitely want to avoid. They belong to the genus Phoneutria, Greek for "murderess," which is quite apt as they are one of the most venomous spiders on Earth.

This arachnid is aggressive, and rather than camping out, the Brazilian wandering spider actively hunts its prey, searching the jungle floor at night. If you ever find yourself in Central and South America, such as Costa Rica or Argentina, watch out! Their neurotoxic venom is extremely painful and affects the nervous system, causing increased sweating and drooling, loss of muscle control, breathing problems, and, in some cases, unwanted prolonged erections.

Yellow sac spider

The yellow sac spiders (Cheiracanthium) are in the family Cheiracanthiidae and they probably account for more human bites that any other type of spider. These arachnids are distributed all over the globe, from America to Northern Europe, South Africa to India, and even Australia and Japan. They’re nocturnal predators and during the day they hide in small white web cocoons.

Mildly venomous to humans, the yellow sac spider bite can be painful and sometimes misdiagnosed as brown recluse bites. Their venom can cause necrotic legions, as well as redness, swelling and sores around the bite site.

Brown widow spider

Latrodectus geometricus is the scientific name for the brown widow spider. It looks similar to its infamous "cousin" the black widow, right down to the hourglass-shaped marking on its abdomen, but there are some key differences. The brown widow’s marking is orange and yellow rather than red, and as their name suggests, they predominantly have tan and brown mottling and a spiky, rather than smooth, appearance. Believed to originate in South America, the brown widow spider is found all around the world.

The brown widow's venom is less toxic than that of its black cousin. However, it can still be deadly. Although they don't deliver as much venom as a black widow, the brown widow's bite can still cause latrodectism due to its neurotoxic venom. Symptoms of lactrodectism include pain, perspiration, muscle rigidity and vomiting.

Red widow spider

Living mostly in sand dunes in Central and Southern Florida, the red widow spider (Latrodectus bishop) is another member of the notorious "widow" family. Their venom is just as lethal as brown and black widows, but as they live so far from human contact there has been no recorded bite in medical literature. The female red widow spider's venom is a neurotoxin which is thought to cause prolonged muscle spasms.

The red widow spider has a red-orange head and legs and a black abdomen with yellow rings around red dots. Rather than an hourglass marking like its "cousins," the red widow usually has one or two red marks.

Redback spider

Due to its strikingly similar appearance, the redback spider (Latrodectus hasselti) was once thought to be a sub species of the black widow spider, but it is a distinct species. Also known as the Australian black widow, you can find this creepy crawly throughout Australia, Southeast Asia and New Zealand. The redback spider has even been found in Japan, the United Arab Emirates and Belgium due to inadvertent introductions.

Highly venomous, the bite from the female redback spider can be life-threatening. Using its fangs, it injects a complex venom that causes intense pain at the bite area, in addition to sweating and goosebumps. As time goes on, these symptoms worsen and there may also be redness and swelling, as well as nausea, muscle twitching, headache and fever. Respiratory failure may occur in severe cases. Thankfully, in 1956 scientists released a redback spider antivenom which is very effective, even when used several weeks after the initial bite. No deaths have been reported since.

Funnel-web spiders

Normally in the world of spiders it is the female that is more deadly, but for funnel-web spiders (Atrax) the male has the more toxic bite. Any attack must be treated quickly with antivenom, especially if a child has been bitten. There have been several recorded fatalities due to the venomous bites of the funnel-web spider, with death occurring within the hour after being bitten. However, since the development of the antivenom in 1981, there haven’t been any more recorded deaths. Predominantly located in southeast Australia (Sydney), funnel-web spiders are also found in New Zealand, Chile and Europe.

Interestingly, animals such as cats and dogs can actually survive a funnel web bite – it takes about 30 minutes for their body to neutralize the toxin – it's just humans who have such a severe reaction. This venom effects the nervous system and causes symptoms such as an elevated heart rate, numbness/tingling of the mouth and difficulty breathing.

Six-eyed sand spider

Found in deserts in southern Africa, the six-eyed sand spider (Hexophthalma hahni) buries itself in the sand to ambush unsuspecting prey. The small, stiff hairs that cover the spider helps to hold sand particles in place, adding to its camouflage. It's otherwise known as the six-eyed crab spider due to its crab-like legs.

Another arachnid that produces venom with necrotic effects, the six-eyed sand spider is the most venomous of any of its arachnid relatives, toxicology studies reveal. Scientists have found that there are proteins within their venom that can cause tissue destruction, blood vessel leakage, and thinning of the blood. No antivenom currently exists.

Mouse spider

Black in color with stocky, thick legs and a distinctively bulbous head and jaw regions, the mouse spider (Missulena) looks a lot more frightening than its name sounds. One species is located in Chile, another in South America and the rest distributed throughout Australia. They live in soil-covered burrows, popping out the hinged trapdoor top to attack prey.

Their hard, large fangs can cause a deep and very painful bite. However, while scientists believe that the venom of the mouse spider is very toxic, it is rarely injected. As so few cases have been reported, it is thought that mouse spiders don't use a lot of venom or may even "dry bite." Fortunately, funnel-web spider antivenom has proven effective in cases of mouse spider bite.

The brown recluse spider is the most common and widespread of the brown spiders, but it is usually found only in the South and Central United States. It is a small species, with a violin-shaped body that can grow up to 0.5 inches (1.2 centimeters) long. It's bite, however, can pack a powerful, venomous punch. 

Brown recluse bites can cause necrotic (rotting) skin lesions and lead to serious reactions or even death in some people, especially children, according to MedlinePlus, a service of the National Library of Medicine. 

But about 90% of brown recluse bites are not medically significant, and they "heal very nicely, often without medical intervention and treatment," Rick Vetter, a retired research associate of entomology at the University of California, Riverside, wrote on the university's entomology department's website. 

After seeking emergency help, people with less severe bites will usually see their wounds heal quickly after they clean it and apply the RICE method — rest, ice, compression and elevation — to the affected area, he said. 

Where do brown recluse spiders live?

Brown recluse spiders (Loxosceles reclusa) are native to a region comprising Kansas, Oklahoma, Texas, Louisiana, Arkansas, Missouri, Mississippi, Alabama and parts of Georgia, Tennessee, Kentucky, Ohio, Indiana, Illinois, Iowa and Nebraska, according to Vetter. If you do not live in those areas, "it is HIGHLY UNLIKELY that you have a recluse spider," according to Vetter. "It is POSSIBLE but incredibly unlikely."

Appearance: How to identify a brown recluse spider

The brown recluse is part of the Loxosceles genus of spiders. Members of this group have violin-shaped markings on the top of their cephalothorax (fused head and thorax, where the legs are attached) and may be informally referred to as fiddleback or violin spiders, according to Oklahoma State University.

The brown recluse's violin markings can vary in intensity depending on the age of the spider, with mature spiders typically having dark brown violin shapes. The neck of the violin shape points toward the spider's rear, or bulbous abdomen. However, the violin shape is easy to misinterpret, so it is best to look at the eyes when determining whether a spider is a brown recluse.

The recluse's eyes are one of its most distinctive physical characteristics. "They have six eyes, instead of eight like most spiders," entomologist Christy Bills, the entomology collections manager at the Natural History Museum of Utah, told Live Science. Other types of spiders have eight eyes arranged in rows of four. Recluses, however, have six equal-size eyes arranged in three pairs, called dyads, in a semicircle around the front of the cephalothorax.

Another distinguishing characteristic of the brown recluse spider is its uniformly colored abdomen (though the shade of brown varies from spider to spider) covered in fine hairs, which give it a velvety appearance. Their long, thin legs are also covered in fine hairs, not spines like some non-recluse spiders, Bills said. According to the Integrated Pest Management Program at The University of California, Berkeley, the genus name Loxosceles means "slanted legs," and refers to the fact that recluse spiders hold their legs in a slanting position when at rest.

The brown recluse's body (not including its legs) is typically between 0.25 and 0.5 inches (0.6 and 1.2 cm) long, according to Oklahoma State University.

In short, brown recluses have all five of these features, according to the Integrated Pest Management Program:

1. Six eyes in dyads (pairs)
2. Uniformly colored abdomen with fine hairs
3. No spines on the legs
4. Uniformly colored legs (no patterns, such as stripes or spots)
5. Body isn't more than 3/8-inch (1 cm) in length

Classification/taxonomy

According to the Integrated Taxonomic Information System (ITIS), the taxonomy of brown recluse spiders is:

• Kingdom: Animalia
• Subkingdom: Bilateria
• Infrakingdom: Protostomia
• Superphylum: Ecdysozoa
• Phylum: Arthropoda
• Subphylum: Chelicerata
• Class: Euchelicerata
• Subclass: Arachnida
• Order: Araneae
• Family: Sicariidae
• Genus & species: Loxosceles reclusa

Brown recluse behavior and mating

The brown recluse gets its name from its color and its "shy nature," Bills said. "Most spiders go out of their way to avoid humans, which makes sense, considering we are thousands of times larger than they are and don't have a great record of behaving politely toward them."

These primarily nocturnal spiders build webs that serve as shelters as well as trigger systems, alerting them when prey is passing nearby so they can actively hunt it down, according to the Integrated Pest Management Program. They typically eat insects, such as silverfish and crickets, according to Oklahoma State University. 

As dawn nears, brown recluses find dark, sheltered hiding places; in nature, they may find refuge in rock cracks and crevices, but if they're near humans, these spiders may camp out in places such as shoes or around human-altered environments, including trash cans, rubber tires or tarps, a quirk that can put them in close contact with people. Male brown recluse spiders may also cross humans' paths when they search for female mates.

This is why brown recluse spiders are considered "house spiders," according to the Integrated Pest Management Program. 

Brown recluse spiders get around by hitchhiking on furniture boxes and other items from infested structures, according to the Illinois Department of Public Health. These long-lived spiders, who live an average of 2 to 4 years in the wild and up to 7 years in laboratories, have remarkable survival skills, and can go for six to 12 months without eating. 

Egg laying season lasts from April to July, but a female brown recluse needs to mate only once to produce fertilized eggs throughout her life, and she can produce 150 or more spiderlings in a year and up to five egg sacs in her lifetime. Thus, a single female hitchhiking into a human-made structure is enough to establish an infestation — a fact that may compel people who are moving around or from recluse spider territory to check their belongings before they leave.

Examples of brown recluse spiders living with people

Brown recluse spiders tend to head indoors during the winter as they search for warmth and food. They are drawn to clutter, often being drawn to attics and basements, where items are left for long periods of time. According to the University of Missouri, they are attracted to boxes of papers and files, which have lots of crevices in for hiding. 

"They really are shy, thus the name recluse," Wizzie Brown, an entomologist at Texas A&M University, said in a statement. "They come out to hunt insects, even other spiders, at night, but otherwise they like hidden areas where they aren’t bothered."

She said any seasonal clothes that have been stored away should be shaken out or put in a dryer on a high heat before being worn. She also said shoes that have been sitting in a closet for a long period should be checked. 

Once established within a structure, brown recluses are often difficult to control. Though hundreds of brown recluses may be present in a house, they may not be easily observed because of their reclusive, nocturnal habits. Therefore, if you see one brown recluse spider, chances are there are more nearby.

Examples of brown recluse populations around human structures include the discovery of 52 spiders at a dilapidated homesite in Mississippi in the early 1970s and 44 caught in sticky traps under a couch in a Tennessee home in just 24 hours, according to the Integrated Pest Management Program. In a wild case, eight 13-year-olds collected about 60 brown recluse spiders from a pile of bricks (the children didn't realize the arachnids were brown recluse spiders) in Oklahoma, but none of the children were bitten.

Even wilder still, a family living in a 19th-century home in Kansas collected 2,055 brown recluse spiders during a six-month period in 2001, according to a study in the Journal of Medical Entomology. The family had lived in the house for about 10 years, and although they regularly found brown recluse spiders, they only had one instance of getting bitten — when one individual's finger turned red for several days and then healed. "In fact, on many evenings, this family collected more brown recluse spiders per hour in their home than the entire California human population has ever been able to find in the state," according to the Integrated Pest Management Program.

Even if there is an infestation, Brown said people should not be overly concerned about bites. "If there is a recurring problem with brown recluse spiders in a location, I could see the need for action." she said. "But I know of a house that has regular pest control and would catch hundreds of them, but no one had ever been bitten. They want to avoid an encounter with us as much as we want to avoid an encounter with them."

Brown recluse bites and symptoms

Like most spiders, the brown recluse typically only bites when disturbed — though it is possible to inadvertently threaten them. The Texas A&M AgriLife Extension Program reports that this may happen if a spider is caught in bedding or clothing.

If the venomous brown recluse bites you, you might not feel a thing, although some people remember feeling a sharp sting, according to MedlinePlus. Bites sometimes, but not always, become painful within a few hours. The reaction the bite causes may range from mild to severe, especially in children.

Related: 11 of the deadliest spiders

"People react differently to bites," Bills said. About 10% of brown recluse bites cause moderate or greater tissue damage and scarring, according to Vetter. But the vast majority of bites result in inflammation, can heal without medical intervention and do not leave scars.

For those with higher sensitivity levels, victims might develop a necrotic lesion that looks like a "dry, sinking bluish patch with irregular edges, a pale center and peripheral redness," Michael F. Potter, an extension entomologist at the University of Kentucky (UK) College of Agriculture, wrote for the UK Entomology Department. These bites often develop a central blister. If the venom begins to destroy surrounding tissue, the wound may expand several inches over the next few days or weeks. Sometimes, this necrotic ulcer can remain for several months and leave a deep scar, Potter wrote.

According to MedlinePlus, symptoms of a brown recluse bite may include itching, chills, fever, nausea, sweating and a general feeling of discomfort or sickness. More severe symptoms include coma, blood in urine, yellowing of the skin and the whites of the eyes (known as jaundice), kidney failure and seizures.

In rare cases, the bite can cause systemic loxoscelism, a severe illness that involves a blood clotting disorder and destruction of red blood cells, according to a 2017 study in the journal PLOS One. "Children are much more likely to develop this systemic syndrome," study senior author Dr. Jeremy Warner, a hematologist at Vanderbilt University, said in a statement. In severe cases, treatment requires hospitalization, blood transfusions and other supportive measures, he said.

Brown recluse bite treatment

There is no effective commercial antivenom approved for use in the United States. If you are bitten, MedlinePlus  recommends calling 911 or poison control (1-800-222-1222) or getting to an emergency room immediately.

The NIH says you should wash the area of the bite with soap and water, then wrap ice in a washcloth and place it on the bite area for 10 minutes. Remove the washcloth for 10 minutes, and repeat the process.

Then, go immediately to the emergency room and bring the spider, if possible, for identification purposes.

Brown recluse management

To decrease your odds of becoming an unwitting host to these six-eyed spiders, remove or reduce outdoor trash and unneeded outdoor structures, such as wood piles or boxes, especially those near the house, according to the Integrated Pest Management Program. You can also seal cracks around doors, electrical conduits and plumbing fixtures with caulk, expandable foam, weather stripping or other materials to prevent the spiders from entering the house.

If you're in brown recluse territory, move your bed away from the wall, remove bed skirts and clear away items stored under the bed. These moves will reduce the chances that a brown recluse will set up shop around your sleeping area and possibly bite you during the night. Moreover, don't leave clothes and shoes on the floor, or make sure to shake them out before putting them on. Store outdoor equipment, such as gardening gloves and baseball mitts, in tightly sealed bags or bins.

Sticky traps laid down on floor boards are a great non-chemical way to catch brown recluse spiders. Chemical control can be difficult, as these spiders can be challenging to find during the day. If used, liquid, aerosol and dust-based insecticides should be applied to cracks and other places where the spiders might be hiding, Potter wrote for the UK entomology department. But bug sprays are not effective against the brown recluse spider, as the long hairs on the bottom of their feet enable them to walk on treated surfaces without getting a lethal dose.

Brown recluse fangs are short and can't bite through clothing, so wearing long sleeves, pants and gloves can help protect you when you're working outdoors.

Originally published on Live Science on Nov. 14, 2014 and updated on March 5, 2024.

Additional resources

Watch "How to catch a spider" on YouTube that the University of California Statewide Integrated Pest Management Program produced.

Learn more about brown recluse spiders on the Missouri Department of Conservation website.

Read about ways to protect yourself from brown recluse spider bites from the Occupational Safety and Health Administration.

Bibliography

Medline Plus. National Library of Medicine. Brown recluse spider. Reviewed June 30, 2019.

Rick Vetter. How to Identify and Misidentify a Brown Recluse Spider. Updated January 2005.

Rick Vetter. Brown Recluse Spider Map

Oklahoma State University. Brown Recluse or Fiddleback Spider, Loxosceles reclusa 

Rick Vetter. Integrated Pest Management Program at The University of California, Berkeley. Brown Recluse and Other Recluse Spiders. Revised November 2018.

Integrated Taxonomic Information System - Report. Loxosceles reclusa. Generated Feb. 16, 2022.

Illinois Department of Public Health. Brown Recluse and Black Widow Spiders. 

Michael F. Potter. University of Kentucky College of Agriculture, Food and Environment. Brown Recluse Spider. Revised July 12, 2018.

Texas A&M AgriLife Extension. Field Guide to Common Texas Insects: Brown Recluse

Robinson, J.R. et al. PLOS One. "Defining the complex phenotype of severe systemic loxoscelism using a large electronic health record cohort" (2017)

Imagine a spider hanging from a silky thread, as still as a corpse, until its eight legs unexpectedly tremble. While this might sound like a horror movie, it's actually a nightly experience for jumping spiders (Evarcha arcuate) who can reach rapid eye movement (REM) sleep, the stage in which most dreaming occurs, a new study finds.

In the study, published Aug. 8 in the journal Proceedings of the National Academy of Sciences, researchers used cameras to examine jumping spiders while they slept, watching the motions of the arachnids’ eyes and bodies throughout the night. The twitching movements the team witnessed as the spiders snoozed was similar to that seen in humans and other mammals such as dogs, as well as nonavian reptiles and cephalopods during REM sleep.

The discovery came about unexpectedly for lead study author Daniela C. Rößler, a behavioral and evolutionary ecologist and postdoctoral fellow at the University of Konstanz in Germany. She was originally planning to study the arachnids' reactions to 3D-printed models of predatory spiders. But her research took a swift detour when she observed the spiders while they slept; at one point, she thought they were dead.

"They were all hanging from the lids of their boxes," Rößler told Scientific American. "I had no idea what happened."

Related: Dead spiders reanimated as creepy 'necrorobots'

With a "cheap night-vision camera" equipped with a magnifying lens she attached with duct tape, Rößler focused her lens on one of the females. At first, it simply hung there, immobile. But eventually, its legs began twitching, along with its abdomen and silk-producing spinnerets. At one point, its legs curled upward. The entire display lasted about a minute and "repeated periodically throughout the night," Scientific American reported.

"They were just uncontrollably twitching in a way that really looked a lot like when dogs or cats dream and have their little REM phases," Rößler told Scientific American.

For the study, Rößler and her team used an infrared camera to record 34 spiderlings (juvenile spiders). They witnessed "unmistakable eye-tube movements" that didn't occur at other times throughout the spiders' sleep cycles. According to the paper, jumping spiders have movable retinal tubes that help them redirect their gaze, and in spiderlings, these movements can be seen through their exoskeleton, which remains translucent during their youth.

The spiders' retinal movements occured at the same time as the leg curling and jerking, which are similar to limb movements seen in other animals experiencing REM sleep, according to a statement. And while the scientists couldn't easily observe retinal movements in adult jumping spiders, they did document similar leg movements happening at regular intervals during sleeping bouts.

Prior to this research, not much was known about the sleep patterns of spiders and other invertebrates, since the study of REM sleep is still largely focused on mammals and birds. However, scientists have already recorded similar actions in two other invertebrates: octopuses and cuttlefish, Live Science previously reported. 

While Rößler cautioned that it's too soon to say for certain that jumping spiders are dreaming, the evidence looks promising. To broaden her research, she and her team must conduct brain scans to prove that the spiders' brains are actually in a REM-like state. That's a tricky undertaking, considering that these tiny spiders, which measure about a quarter of an inch (6 millimeters) long, have brains the size of poppy seeds. To record the spiders' brain activity, scientists will need to insert an electrode into each spider's brain without crushing it.

Until then, scientists might find themselves dreaming about spider dreams.

"I personally think they are dreaming — just like any person watching a dog or cat sleep and kick their leg will think that they're dreaming — but being able to scientifically prove that is a whole different story," Rößler told The Harvard Gazette. "I don't think we can say they are, and I'm not even sure we will ever be able to say it, but the fact alone that we're thinking about it is already quite amazing."

Originally published on Live Science.

Taking a dead spider's lifeless body and reanimating it as a robot is an idea that would be the stuff of nightmares for most people. But scientists aren't most people. Recently, a team of researchers turned the corpses of wolf spiders into arcade-style claw machines that could pick up and move a variety of objects — including other dead wolf spiders.   

The idea for the mechanized arachnid grippers, or "necrobots," first came about when researchers noticed a dead spider curled up in a ball in a corner of their engineering lab. After looking up why the legs of dead spiders always seem to end up pulled tightly toward their abdomens, the scientists learned that spider joints were controlled through a hydraulic pressure system that fails when the arachnids die. The team then realized that they could reverse engineer this hydraulic system to hijack the spider's corpse and give it a second life as a machine.

By puffing air into wolf spider cadavers, the team found that all eight legs could be simultaneously straightened out and curled up again to create a grabbing motion that could then be used to lift up objects. Wolf spiders — a group that comprises nearly 2,400 species in the Lycosidae family — can carry objects much larger than themselves and have tiny hairs on their legs that give them extra grip. This means the necrobots could pick up a wide variety of objects, including delicate electrical components, irregularly shaped meshes and, yes, dead wolf spiders, the researchers explained in a new study. 

The researchers believe their work could inspire the creation of other necrobots from the corpses or individual body parts of other dead animals. "It's something that hasn't been used before, but it has a lot of potential," senior study author Daniel Preston, an assistant professor of mechanical engineering at Rice University in Houston, said in a statement.

Related: Millions of palm-sized, flying spiders could invade the East Coast, scientists say 

In humans and other vertebrates (animals with backbones), most joints are controlled by antagonistic muscle pairs, which are opposing muscles that pull a joint in different directions. An example of an antagonistic muscle pair in humans is the bicep and tricep: When the bicep contracts and the tricep relaxes, our arm bends at the elbow; when the tricep contracts and the bicep relaxes, our arm straightens out again. 

However, spiders only have a single flexor muscle in their joints that allows them to bend their legs. To straighten their legs again, spiders use a hydraulic pressure system, which involves forcing blood from a chamber near the thorax, known as the prosoma, into the legs. The blood acts as the antagonist to the single flexor muscle and pushes the joint back open. But when the spider dies, there is nothing to push against this muscle, and the joints close.

"When they die, they lose the ability to actively pressurize their bodies," lead study author Faye Yap, a doctoral candidate in mechanical engineering at Rice University, said in the statement. "That's why they curl up."

To transform the wolf spiders into necrobots, the researchers recreated the arachnid hydraulic system, substituting air for blood. The team inserted a needle into the prosoma of a dried-out spider corpse and superglued it in place. When they blew air into the chamber through the needle, the air flow activated the hydraulic system just as a spider's flowing blood would, forcing the legs to straighten. When the air was sucked back out through the needle, the legs returned to their naturally curled-up position.

Normally, spiders control each individual leg through valves that adjust the flow of blood into each limb. The researchers were worried about how this would affect the mobility of their reanimated spiders, as there was no easy way to open the corpses' leg valves. But it turned out that in dead spiders, the valves were permanently stuck in the "open" position, Preston said. This allowed the researchers to control all of a necrobot's legs simultaneously, making them perfect for grabbing objects, he added.

The dead wolf spiders were so well suited to their new task that the researchers were able to create a working necrobot on their first attempt. "We took the spider; we placed the needle in it not knowing what was going to happen," Yap said. "And when we did, it worked the first time, right off the bat." It is extremely rare for engineers to succeed so quickly when doing this type of trial-and-error experiment, she added. 

Further experiments with the necrobots showed that they could reliably lift objects that weighed more than 130% of their own body weight, and occasionally, they could lift even more. However, after around 1,000 cycles of opening and closing their legs, the necrobots became less efficient and showed signs of damage. 

"We think that's related to issues with dehydration of the joints," Preston said. However, the researchers think they can eventually overcome this problem by coating the legs with special polymers, which would extend the life span of the necrobots, he added.

The necrobots have a wide range of potential applications, according to the statement. The team has already shown that the spider grippers can be used to move fragile components in electrical circuits without damaging them, which hints at their usefulness for assisting in the assembly of microelectronics and other small-scale construction projects. And if the scientists can replicate their work with other species, that could further extend the range of projects that could benefit from a necrobot's delicate touch, the team reported in the study. 

Ecologists also could utilize necrobots to collect live insects to study from the wild without damaging them, Yap said. The reanimated spiders are likely to be highly effective tools for capturing insects because their legs have evolved specifically to catch tiny arthropods, and their natural camouflage could help keep them hidden in the field, she added.

Using necrobots instead of mechanical constructs made of metal and plastics  could also help to reduce the waste produced during tool manufacturing. "The spiders themselves are biodegradable," Preston said. "So we're not introducing a big waste stream, which can be a problem with more traditional components."

Wolf spiders are extremely common, widespread and easy to collect, so there would be a cheap and plentiful supply of spider corpses for engineers to transform into necrobots — as long as those engineers aren't arachnophobic, that is.

The study was published online July 25 in the journal Advanced Science.

Originally published on Live Science.

Male wolf spiders (Schizocosa stridulans) that improvise intricate dance moves are big winners in the mating game, wooing females with showstopping tap routines. Now, new research finds that the more complex the dance, the more likely the spiders are to find love. 

The study researchers found that improvised steps benefited the spiders, which live in humid, mostly forested areas worldwide. The ability to bust a complicated move wasn't associated with size or strength in males, but it may hint to females that the male possesses a certain athleticism and grace.

"Females aren't necessarily looking for the biggest male or the loudest male or the strongest male," study co-author Eileen Hebets, a biologist at the University of Nebraska–Lincoln (UNL), said in a statement. "But maybe they're looking for a male that is really athletic and can coordinate all of these different signals into one display."

Feel the noise

S. stridulans are brownish-gray spiders that can grow to be 1.4 inches (35 millimeters) in body length. But behind that drab coloration lies a flashy and flamboyant performer, with mating dances that involve males tapping their forelegs and vibrating their abdomens. Females feel these vibrations and decide whether or not to let the suitor get close enough to mate.

Recent UNL doctoral graduate Noori Choi, a student of Hebets', wondered what exactly the females found so intriguing about the mates that they eventually chose. He analyzed one of Hebets' experiments in which ready-to-mate female spiders were put in a soundproof chamber with one amorous male at a time. The researchers placed the spiders on top of thin filter paper, which easily transmits vibrations, and monitored them with cameras and a laser to detect every last shiver and twitch created by the male's dance.

Related: These male spiders use built-in leg catapults to escape sexual cannibalism

Out of 44 hopeful males, nine spiders were deemed acceptable by the female test subjects. The spiders that successfully mated also had the most complex dances, Choi found.

Getting into a groove

Choi analyzed the complexity of the spiders' dances with computer-science analyses that have been used to quantify the complexity of patterns in data signals, part of the process of data compression. These methods have never before been applied to arachnid vibrations. Previously, Hebets said, scientists looked at features of a spider's dance individually, focusing just on factors like vibration alone, or looked at very basic interactions, such as those between visual signals and vibrations. 

"Now we're at the point, with some really talented people who have quantitative skills, of coming up with computational ways to look at how all of these things might interact, and how the entire package might be important in ways that we would never understand if we were just looking at components A, B or C," Hebets said. 

Males danced with more complexity for heavier females, which are desirable mates because they're likely to be able to bear and take care of large broods of spiderlings, the researchers found. Successful males also amped up their dance complexity as the courtship went on — dances can last up to 45 minutes —which may have indicated that the females were communicating their interest in some way. 

"When you're talking about spiders," Hebets said, "I think that's something people don't tend to appreciate; that signalers are paying attention to the receivers, they're paying attention to their environment, and they're adjusting accordingly."

The complexity of these spiders' moves is the equivalent of a person dancing on a syncopated beat, changing up the tempo, or otherwise making unpredictable artistic choices. These moves didn't correlate with spider size or a male's ability to produce loud vibrations, the researchers reported May 18 in the journal Biology Letters. Instead, the important qualities seemed to be related to vigor and skill, the researchers said. 

Or maybe these males just stood out from the crowd by abandoning preplanned choreography and thinking on their feet.

"There are a lot of studies that show that animals prefer novelty, in some capacity," Hebets said. In the case of the lovelorn wolf spiders, "the males constantly changing things up" might be the best way to catch — and keep — females' attention, she added. 

Originally published on Live Science. 

The term "arachnids" likely conjures up visions of spiders: from creepy, crawly things silently spinning webs in the corner of the room to big, hairy creatures with fangs — the likes of the mythical Shelob or Aragog — stalking you in the dark. But just how big (and ferocious) can these arachnids get? Even better, what was the largest one to have ever lived?

Answering this question is deceptively simple. Arachnids are eight-legged arthropods, which means that this group not only contains spiders but also scorpions and ticks among other, much smaller and rarer groups. Of these, spiders are the most diverse group of arachnids (the 50,000th species was discovered recently, and that number is expected to grow). The problem is that exactly what counts as an arachnid is a bit of an open question.

Arachnids are part of a larger group of arthropods called the chelicerates. The chelicerates are subdivided into smaller groups, with arachnids being one group and horseshoe crabs (in the order Xiphosura) and sea scorpions (Eurypterida) being separate but related to the arachnids.

According to Russell Bicknell, a paleontologist at the University of New England in Australia, this is the traditionally accepted phylogeny. "But a paper came out recently that suggested this is wrong, and suggested that horseshoe crabs and sea scorpions are actually nested within arachnids."

Related: Why do Cambrian creatures look so weird? 

Thomas Hegna, an assistant professor of paleontology at the State University of New York (SUNY) at Fredonia, who was not involved in the new study, told Live Science in an email that the new phylogeny, which is based on molecular analysis, implies some groups of land chelicerates (spiders and scorpions) came before marine ones (horseshoe crabs and sea scorpions). However, despite the fact that this claim is well supported by genetic evidence, it is inconsistent with the fossil record. 

This might seem like paleontological pedantry, but it actually makes a huge difference when it comes to determining the largest-ever arachnid. 

According to the traditional view of the arachnid family tree (ignoring horseshoe crabs and sea scorpions), the largest living arachnid is likely to be a spider. 

There are two spiders that make great contenders for the title of "world's largest spider." The largest known spider by mass is the Goliath Birdeater (Theraphosa blondi), a 6-ounce (170 grams) spider whose body can reach up to 5 inches (12 centimeters) in length, a number that grows to 11 inches (28 cm) when its legs are included, according to the American Association for the Advancement of Science (AAAS). 

If one is to judge the size of a spider instead by the diameter of its leg span, then the largest spider may very well be the Giant huntsman spider (Heteropoda maxima), which has a leg span of about 1 foot (30 cm) in diameter, making it about the size of a dinner plate. Despite its size, this spider wasn't discovered until 2001. 

When we dive into the fossil record, we find that the largest-ever arachnid was likely not a spider, but a scorpion. Brontoscorpio anglicus was a scorpion that lived during the Silurian-Devonian era (between 350 million and 450 million years ago) and reached lengths of nearly 3 feet (1 m) long — five times longer than the longest scorpion alive today. However, the caveat here is that the one example of this species was described from a single fossilized finger, so the animal's actual size is an educated guess. 

Related: Is every spider web unique?

These animals are the largest-known arachnids, both living and extinct, as arachnids are traditionally defined. But if sea scorpions and horseshoe crabs are indeed considered arachnids, as new research might suggest, then the largest living arachnid is no longer a spider, but is instead a horseshoe crab.

The largest living species of horseshoe crab dramatically surpasses the largest living spiders. Tachypleus tridentatus, the largest of this group, can reach sizes of 31 inches (79.5 cm) and weigh as much as 9 pounds (4 kilograms), according to research published in 2017 in the Journal of Asia-Pacific Biodiversity.

As far as the largest-ever species goes, the title would likely go to a member of the now-extinct sea scorpions, a group scientifically known as eurypterids. Fossils suggest that many of these ancient marine predators would even rival humans in size. 

The largest species from this group was Jaekelopterus rhenaniae, a species discovered in 2007 that had claws up to 18 inches (46 cm) long. From the claws, researchers estimated that its body was roughly 8 feet (2.5 m) long, making it not only the largest potential arachnid, but the largest-ever member of the entire group that contains arachnids, the chelicerates. 

Originally published on Live Science.

For a type of orb-weaving spider, mating has a spectacular finale: The male catapults off a female's body at a speed too fast for a human to see with the naked eye. 

These amorous acrobatics aren't meant to impress the spiders' partners; rather, a male springs into action to escape the female's hungry mandibles, as sexual encounters for these arachnids would otherwise end with the male being eaten.

They leap for their lives by using a mechanism that has never been seen before in spiders, involving a joint in their front legs that enables them to launch their bodies dozens of centimeters in a split-second by storing kinetic energy and then suddenly releasing it, according to a new study.

Prior to mating, male spiders would secure themselves to the female's web with a silk "safety line," so that after catapulting they could climb back up to mate again. Males sometimes mated with the same female up to five times; and with the risk of being cannibalized looming in every encounter, post-sex catapulting likely evolved as a means of survival, the researchers reported.

Philoponella prominens spiders are tiny — males' bodies measure about 0.1 inches (3 millimeters) long, while females are about twice that size — and they live in colonies that can contain more than 200 spiders in a vast network of webs. When the study authors observed a colony of the orb-weavers in Wuhan, China, in 2019, they noticed that mating always ended with the males catapulting off the females so quickly "that common cameras could not record the details," said Shichang Zhang, lead author of the study and an associate professor at Hubei University's School of Live Sciences in Wuhan. That prompted the researchers to take a closer look at what was going on while the spiders were mating, Zhang told Live Science in an email.

Related: Weird and wonderful: 9 bizarre spiders 

But taking a closer look turned out to be exceptionally challenging. Because the spiders were so small and mating was over so rapidly (lasting only about 30 seconds from copulation to catapult), the study authors struggled to focus their high-speed camera's macro lens in time to film the mating act and its aftermath. In many cases, the males finished and sprang away before the camera lens was focused and ready.

"That's the most difficult part in this research," Zhang said.

The scientists collected around 600 P. prominens spiders and conducted 155 successful mating trials. In spite of the photography challenges posed by the speedy spiders, the researchers captured images with a camera shooting 1,500 frames per second, and then used software to measure the energy and speed of the male spiders' catapulting escapes. After the first mating, 97% of the males catapulted — and all of them survived. Males that failed to catapult "were captured, killed and consumed by the females," the study authors reported. When the scientists prevented 30 males from springing away by disrupting the catapult mechanism in the spiders' legs, all of those males were also devoured.

But when the spiders were able to fling themselves away, the stored energy in their legs propelled their tiny bodies at remarkable speeds: up to 2.9 feet per second (88 centimeters per second). That's the equivalent of an adult human taking a flying leap and landing one second later at a distance of nearly 1,740 feet (530 meters), Zhang said. 

"We hypothesized that the mechanism of the catapulting is that the legs are folded against the female, and then when released the hydraulic pressure causes the legs to rapidly expand," the scientists reported.

Similar mechanisms using hydraulic energy storage and release for rapid limb movement are found in other animals, such as the mantis shrimp's knockout punch and the blink-and-you'll-miss-it speedy snap of a trap-jaw ant's mandibles. "But they use the fast actions to either capture prey or escape predators," Zhang said. By comparison, the wee orb-weavers are the only known animals to use the technique as protection against sexual cannibalism, catapulting to safety so that they may live to mate another day. 

This could be a way for the males to signal their fitness as mates, as males that are physically superior to their competitors can perform multiple catapults while mating, "thereby increasing their chance of paternity," the study authors concluded.

The findings were published April 25 in the journal Current Biology.

Originally published on Live Science.