Everything you need to know about Brazilian wandering spiders

The large and intimidating Brazilian wandering spiders, which also go by the names of “banana spider” or “armed spider,” are famous for being the most venomous spiders in the world. Their venom can actually kill humans, though they are much more likely to kill children than adults.

That being said, labeling an animal as deadly might be misleading. In the case of Brazilian wandering spiders, the amount of damage they cause is determined by how much venom they inject when they bite, which is typically not much. Also, despite being known as an aggressive species, Brazilian wandering spiders do not usually attack humans. When they do bite us, it is out of self-defense.

Classification and taxonomy of Brazilian wandering spiders

Eight species of Brazilian wandering spiders exist in total, all part of the Phoneutria genus. Their full taxonomy is as follows:

Kingdom: Animalia
Subkingdom: Bilateria
Infrakingdom: Protostomia
Superphylum: Ecdysozoa
Phylum: Arthropoda
Subphylum: Chelicerata
Class: Arachnida
Order: Araneae
Family: Ctenidae
Genus: Phoneutria
Species: Phoneutria bahiensis, Phoneutria boliviensis, Phoneutria eickstedtae, Phoneutria fera, Phoneutria keyserlingi, Phoneutria nigriventer, Phoneutria pertyi, or Phoneutria reidyi.

In Greek, Phoneutria means “murderess.” No doubt, they were given their official name because of their ability to kill people. Still, just because they have the power in their venom to cause serious harm does not mean they often do it.

Where do they live?

All eight species of Brazilian wandering spider can be found in Brazil. Some of them can also be found throughout the rest of Latin America, as far north as Costa Rica and as far south as Argentina. Most commonly, they reside in Brazilian, Costa Rican, Colombian, Peruvian, and Paraguayan forests.

Phoneutrians sleep during the day. They like to be well hidden in dark and moist locations as opposed to in webs like many other arachnids. In nature, it is common that they will hide in termite mounds, beneath logs and rocks, and in banana plants. However, if they have made their way to civilization or civilization has made their way to them, they could easily be found in woodpiles, cupboards, garages, clothing heaps, and shoes. Their propensity to hide is part of what makes them so dangerous.

Phoneutrians sleep during the day well hidden in dark and moist locations as opposed to in webs like many other arachnids

At night, Brazilian wandering spiders live up to their name. They wander the jungle floor, mainly hunting insects and other spiders. Sometimes they also hunt small mice, amphibians, and reptiles thanks to the deadly potency of their venom, particularly when injected into a little creature.

It is extremely rare to find spiders in the Phoneutrian genus outside of those Latin American regions, though it is not impossible. They have made their way to North America and Europe by way of banana shipments since they are known to sleep inside of banana bunches. For this reason, one of their nicknames is “banana spider.”

What do they look like?

Brazilian wandering spider
Flickr

The body of a Brazilian wandering spider can reach up to two inches. Their legs make them look much more substantial, giving them a span of up to six inches. Most of the eight species of Phoneutria are mainly brown in color, some with black spots on their bellies. All Brazilian wandering spiders are hairy.

Many reported cases of Brazilian wandering spiders outside of their natural habitats have been due to misidentification.  Phoneutria spiders are often confused with the Cupiennius species. The two look similar, but Cupiennius spiders are harmless.

Are Brazilian wandering spiders deadly?

If you look in the Guinness Book of World Records for the most venomous spider in the world, you’ll find the Brazilian wandering spider. It is true. They have the most active neurotoxic venom of all living spiders. Their venom contains toxins, proteins, and peptides mixed together that affect the neuromuscular system of their victims.

If bitten by one of these tropical spiders and it injects a large quantity of venom, it can cause excruciating pain, sweating, local swelling, abdominal cramps, dizziness, impaired vision, convulsions, hypothermia, goosebumps, trouble breathing (which can be fatal), and paralysis.

A Brazilian wandering spider bite requires immediate professional medical attention.

It can also destroy skin cells and lead to painful erections in males that can last as long as four hours. Because of the latter effect, scientists have looked into using Brazilian wandering spider venom to treat erectile dysfunction.

A Brazilian wandering spider bite requires immediate professional medical attention. Their bites have been reported to kill people within an hour. Typically, deaths occur in children under seven years old because of their small size. However, with professional medical attention, anti-venom will be administered, which is useful in eliminating toxic and fatal effects.

Brazilian wandering spider bites are rare and kill few

Brazilian wandering spider bites may be deadly, but very few people die from them. This is mostly because an effective anti-venom can be found in Brazil. More than 7,000 cases of Brazilian wandering spider bites have been recorded with only been ten reported deaths. Furthermore, only two percent of people bit have severe enough cases to require anti-venom. This is why calling the Brazilian wandering spider deadly is quite misleading.

Their venom’s toxicity has given Phoneutrians a bad reputation for being aggressive. On the contrary, outside of hunting, they typically only bite as a defense mechanism. If they feel threatened, they elevate their first two pairs of front legs. This posture looks pretty scary as it exposes the red hair around their fangs. It is this attacking stance that has given the Brazilian wandering spider the nickname “armed spider.”

Unfortunately, because these spiders hide in clothing piles, shoes, garages, and other dark areas in houses, people can easily startle them unintentionally. This will put them into self-defense mode where they are more likely to bite. However, their defense posture can act as a warning that it is about to attack, giving a human a chance to get out of the line of fire.

Most bites are mild

It might be hard to believe that a bite from the most venomous spider in the world could be mild but believe it. As it turns out, Brazilian wandering spiders don’t usually inject all of their venom when they bite. They prefer to conserve it for practical reasons.

It takes a lot of energy and time for the spider to replace its venom after using it, so it makes sense that it would only inject large quantities when absolutely necessary. Plus, a Brazilian wandering spider without its venom becomes a vulnerable creature, another situation nature tells them to avoid.

Only one-third of human Brazilian wandering spider bite victims are injected with venom.

A 2009 study into the behavior of Phoneutria found that they most commonly deliver what is called a “dry bite” to humans. These are bites where no venom is injected into the victim. Only one-third of human Brazilian wandering spider bite victims are injected with venom. Even in those cases where venom is inserted, the typical quantity of venom injected is small.

Of all the recorded Brazilian wandering spider bites, they have only injected fatal amounts of venom, amounts that require the anti-venom, a half of a percent of the time. In other words, that situation is very rare. Because of the nature and rarity of their bites, labeling these spiders as deadly to humans seems like a gross misrepresentation.

For those seeking out Brazilian wandering spiders

If you want to see a Brazilian wandering spider in the wild, you’ll have to go to the rain forests of Latin America, namely in Peru, Costa Rica, Brazil, and Colombia. Hire a trained guide to take you on a night hike, as this is when they are actively wandering and not hidden. It is at night when Brazilian wandering spiders aggressively hunt their prey, such as larger insects, mice, and small reptiles and amphibians.

If you want to see a Brazilian wandering spider in the wild, you’ll have to go to the rain forests of Latin America

Your chances of getting bitten by one of these spiders are extremely low, perhaps even lower when you are seeking them out than when you accidentally find one in your Costa Rican home. In fact, the only reason they would bite you is if you try to pick one up or foolishly reach your hand under logs, termite mounds, or other places they would likely hide in during the day.

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