8-Legged Nightmares? The World's 3 Deadliest Spiders

Brazilian wandering spider, spiders
The Brazilian wandering spider seeks out its prey. (Image credit: Shutterstock)

Nothing strikes fear into the hearts of more people than spiders. The eight-legged beasts boast a menacing appearance, and some pack a deadly, poisonous bite.

Spiders form the largest part of the arachnid family, with about 40,000 different species of spiders crawling the planet. And about a dozen of these species are deadly enough to kill a human. We take you on a tour of three of the deadliest spiders in the world, which can lurk anywhere from a forest floor to your own backyard.

Brazilian wandering spider

The Brazilian wandering spider, or banana spider, has repeatedly ranked as the world's most venomous spider in "Guinness World Records." Fittingly, it belongs to the genus Phoneutria, which means "murderess" in Greek. [Creepy! Amazing Photos of Spiders]

The spider's bite is potent enough to kill a human within minutes if antidote isn't delivered. Even with antivenom, on rare occasions, the bite can still prove deadly. Just 6 micrograms of venom are enough to kill a 20-gram mouse, and the spider carries more than 10 times that amount of venom in reserve.

In addition, the spider's bite can cause a long, painful erection in men, scientists discovered in 2007. The venom boosts levels of nitric oxide, a chemical that increases blood flow, and some have considered using the venom in drugs for erectile dysfunction.

Found mostly in South America, the large brown spider, which sometimes sports a black spot on its belly, can reach up to 2 inches (5 centimeters) in body length, with a leg span of 5 to 6 inches (12 to 15 cm).

The spider has a trademark move, raising its two front legs in an intimidating pose when frightened. This pose reveals the arachnid's red-haired fangs. The "wandering" part of its name comes from the spider's hunting habits. Instead of using a web to catch prey, the Brazilian spider "wanders" around and hunts on the ground.

Related: World's deadliest spiders a toxic myth?

Black widow spider

The ominously named black widow is a shiny black spider, but the females have an even more ominous hourglass-shaped mark on their abdomens, as if to say "time is running out." They earned the name "widow" because the females of many species eat the males after mating. Several species of black widow spiders exist, residing in temperate areas around the world. They are the most venomous spiders in North America. Before the antivenom was discovered, about 5 percent of black widow bites proved fatal.

These spiders like to lurk in woodpiles, sheds, outdoor furniture and chain-link fences, but they have a special predilection for old-fashioned outhouses. (Perhaps that's where these lyrics from the Australian country song about the black widow's cousin the redback spider come from: "There was a redback on the toilet seat/When I was there last night. I didn't see him in the dark/But boy, I felt his bite!") Fortunately, modern home plumbing and heating make such outhouse encounters rare.

Funnel web spider

The deadly Australian funnel web spiders owe their name to the conical webs these creatures use as burrows or prey traps. In fact, there are three different families of funnel web spiders, only some of which are dangerous to humans. The Hexathelidae family — the dangerous variety — includes about 40 species in Australia, such as the notorious Sydney funnel spider and its tree-dwelling cousins.

These spiders are usually black or brown; sport a shiny, hard, slightly hairy covering called a carapace on the front of their bodies; and range between 0.4 and 2 inches (1 to 5 cm) in body length. Nocturnal creatures, they prefer humid climates. Most live on the ground, but some dwell in trees. The bite can be life-threatening, especially in children, but is usually nonfatal if antivenom is administered.

So be careful of these little, leggy beasts. But if all these eight-legged horrors scare you, keep in mind that most deadly spiders are shy and attack only when threatened.

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Tanya Lewis
Staff Writer
Tanya was a staff writer for Live Science from 2013 to 2015, covering a wide array of topics, ranging from neuroscience to robotics to strange/cute animals. She received a graduate certificate in science communication from the University of California, Santa Cruz, and a bachelor of science in biomedical engineering from Brown University. She has previously written for Science News, Wired, The Santa Cruz Sentinel, the radio show Big Picture Science and other places. Tanya has lived on a tropical island, witnessed volcanic eruptions and flown in zero gravity (without losing her lunch!). To find out what her latest project is, you can visit her website.