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Brazilian Wandering Spider: Bites & Other Facts

Brazilian wandering spider, spiders
The Brazilian wandering spider seeks out its prey.
Credit: Nashepard | Shutterstock

The Brazilian wandering spider belongs to the genus Phoneutria, which means “murderess” in Greek. And it’s no wonder why — it’s one of the most venomous spiders on earth. Its bite can be deadly to humans, although antivenom makes death unlikely. The Guinness Book of World Records has named it the world’s Most Venomous Spider in multiple years.

There are eight species of Brazilian wandering spiders, which can all be found in Brazil. Some of the species can also be found throughout Latin America, from Costa Rica to Argentina. These powerful arachnids have been known to hitch rides internationally in banana shipments, for which they’ve been given the nickname “banana spider.”

In 2007, scientists discovered that in addition to intense pain and possible medical complications, the bite of a Brazilian wandering spider also deliver a long, painful erection to human males. The venom boosts nitric oxide, a chemical that increases blood flow. There has since been talk of incorporating the venom into drugs for erectile dysfunction.

Appearance

Brazilian wandering spiders are large, with bodies reaching up to two inches (5 centimeters) and leg spans reaching five or six inches (12 to 15 cm). The species vary in color, though all are mostly brown and may have a black spot on their bellies.

Their most distinctive physical characteristic is seen under threat: if frightened, Brazilian wandering spiders lift their two front legs up high in a dramatic and intimidating posture. This exposes the scarlet hair surrounding the fangs on some species. Their threatened stance serves as a “back off” gesture, indicating to predators that the poisonous spider is ready to attack.

Behavior

These arachnids are called “wandering” because of their hunting behavior. Unlike most spiders that catch their prey in webs, these spiders wander on the ground, searching for prey, which they kill by both ambush and direct attack. They spend most of their days hiding under logs or in crevices, and come out to hunt at night. They eat insects, other spiders, and sometimes, small amphibians, reptiles and mice.

Brazilian wandering spiders prefer forest floor environments with dark, moist leaf vegetation. They’re also often found at banana plantations, living under dried banana leaves. These spiders are known to come to cities and human dwellings, and there are known populations in Sao Paulo and Rio de Janeiro.

Because of the toxicity of their bite and their alarming-looking posture, these spiders have a reputation for being aggressive. But these are actually defense behaviors. They will only bite or raise their front legs if they feel threatened.

brazilian wandering spider, egg sac, spiders
A Brazilian wandering spider guards her egg sac.
Credit: Dr. Morley Read | Shutterstock

Mating

The female Brazilian wandering spider can be picky when choosing a mate, and once she does pick one, the male needs to watch out. Like many other spider species, females often attack the males once copulation is finished. The female stores the sperm in a separate chamber from the eggs until she is ready to fertilize them. The eggs are kept safe in a spun-silk egg sac.

Brazilian wandering spiders typically live for one or two years.

Bite

Scientists have been studying Brazilian wandering spiders’ bites since the 1920s, and have discovered that their venom is a complex cocktail of toxins, proteins and peptides. It affects ion channels and chemical receptors in victims’ neuromuscular systems, leading to symptoms such as paralysis, edema, inflammation of the throat and lungs, salivation, convulsions, and more —including priapism (painful erections mentioned above).

Children under 10 are at the greatest risk of death by Brazilian wandering spider bite. Regardless of age, if bitten, one should seek medical attention immediately. Not all bites have a full dose of venom, and if a bite is small painkillers may be prescribed. A 2008 Brazilian study revealed that only 2.3 percent of bites were treated with antivenom, and that as of that year, only ten deaths had ever been attributed to the spider’s bite in Brazil. According to the study, “Cases of serious envenomation are rare (0.5 percent).”

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