Brazilian Wandering Spider Hunts Instead of Waiting in a Web

The Brazilian wandering spider is part of a group of large, hairy spiders that can grow up to 7 inches (18 cm) across, including their legs. These spiders are typically brown or gray, with dark bands running along their legs, making them blend in perfectly with the forest floor.

One of their most noticeable features is their long legs, which they use to scurry across the forest floor at high speeds while searching for prey. The adult female spiders are usually larger than the males, but both sexes are equally dangerous.

In addition to being uncomfortably large, these spiders are fast, agile and pack a venomous punch (yes, venomous, not poisonous). Their venom contains a potent neurotoxin that can cause high blood pressure, blurred vision and severe local pain in humans who are unlucky enough to get bitten.

There are several subspecies of Brazilian wandering spiders, and they all belong to the genus Phoneutria. Some of the most well-known include Phoneutria fera, Phoneutria nigriventer and Phoneutria keyserlingi.

These spiders are often collectively referred to as "armed spiders" because of their aggressive defensive stance, in which they lift their front legs to appear more threatening to potential predators or attackers.

According to the World Spider Catalog, these spiders are considered one of the most dangerous spider genera, thanks to their highly toxic venom. Most spider species aren't nearly as dangerous to humans, but the Brazilian wandering spider stands out because of the potency of its bite.

Brazilian wandering spiders are loners. They're not particularly social with other spiders or animals and will defend themselves aggressively if threatened. Unlike some spiders that live in colonies, these spiders prefer a solitary life, moving from place to place in search of food.

They also don't spin webs to catch their food like other spiders. Instead, these wandering spiders actively stalk and ambush their prey, relying on their speed and powerful venom to immobilize victims quickly.

They're primarily nocturnal, meaning they're most active at night when they hunt for prey.

Brazilian wandering spiders are carnivores, feasting on a variety of insects, small amphibians, reptiles and even other spider species. They use their powerful legs to pounce on their prey, and once they make contact, their venomous bite quickly incapacitates the unlucky victim.

Once the prey is subdued, the spider injects digestive enzymes into the body, which breaks down the internal tissues, allowing the spider to suck up the liquefied remains. While they're known for their aggressive hunting style, they typically avoid humans unless they feel threatened or provoked.

These spiders are native to the tropical rain forests of Central and South America, including countries like Costa Rica, Brazil and Colombia. They prefer humid, dense environments where they can hide among fallen leaves, under rocks and inside logs.

You'll also find them on banana plantations, which is how they earned the nickname banana spiders.

Because they don't spin webs to catch their food, Brazilian wandering spiders are constantly on the move. Their wandering behavior means they can sometimes end up in human dwellings, where accidental encounters with people can lead to a spider bite.

The life cycle of a Brazilian wandering spider starts like most other spiders: with an egg sac. The adult female lays hundreds of eggs in a silk sac, which she hides in a safe place, such as under a rock or inside a log.

Once the eggs hatch, the spiderlings are tiny versions of the adults, and they quickly disperse to begin their solitary lives.

As the spiders grow, they molt their exoskeleton several times until they reach maturity. Once they're fully grown, they'll begin their wandering lifestyle, searching for food and mates. Unlike some spider species, Brazilian wandering spiders don't live very long — usually only about 1 to 2 years in the wild.

Brazilian wandering spiders aren't currently listed as endangered or threatened. However, habitat destruction — particularly the deforestation of the rainforests where they live — could pose a long-term threat to their populations.

As human activity continues to encroach on their natural habitat, these spiders may find themselves pushed into smaller and smaller areas, which could lead to more frequent encounters with humans.

Interestingly, scientists like Eduardo Mello de Capitani (who contributed to the field of toxicology) study the venom of Brazilian wandering spiders. Their venom contains toxins that could potentially be used in medicine, despite the extremely painful effects of their bites.

In fact, research into stonefish venom and other venomous animals has revealed potential uses for treating various human conditions, making these spiders a subject of ongoing interest in the scientific community.

So, even though people who are unlucky enough to get bitten by a Brazilian wandering spider experienced severe local pain and potentially dangerous symptoms like high blood pressure, understanding how these toxins work might help us unlock new treatments for medical conditions, proving that even the scariest creatures can have a silver lining.

We created this article in conjunction with AI technology, then made sure it was edited and fact-checked by a HowStuffWorks editor.