Costa Rica has one of the most poisonous spiders in the world, as published by the famous book of Guinness World Records.

According to the latest report from 2013, the so-called Brazilian wandering (rocking or swaying Brazilian) of the genus Phoneutria, is the world’s most dangerous arachnid animal, especially the Phoneutria fera, located in the Brazilian Amazon region.

According to the famous book of world records, this spider can kill a mouse with only 0.00000021 ounces of venom.

“This is a highly aggressive creature that usually hides in clothes and shoes. And its attack brings hundreds of accidents every year. Fortunately, there is an antidote available and severe accidents occur with particular impact on children less than seven years,” writes the Guinness World Records.

The Costa Rican Spider

Costa Rica is home to the spider Phoneutria boliviensis and is widely distributed in the country, explained Carlos Víquez, INBio expert researcher in the arachnid world.

Víquez said that this spider is known for its venom, which has strong neurotoxic action on humans or other vertebrates. He indicated that cases of bites on humans have happened here and that required medical attention, but the use of the antidote was not necessary.

The Threat

A study in 1971 by Alfonso Trejos, Roberto Trejos and Rodrigo Zeledon described some of the effects of the bite of this spider on people: pain in the affected area, local edema, abnormal heart rhythm, respiratory and visual disturbances (including temporary blindness), sweating, sometimes slight fever and recurrent urine. After 24 hours there may be general prostration and muscle aches.

Treatment with analgesics and antihistamines is recommended in less severe cases, and a specific serum when symptoms are very marked.

“My consideration is that the spider is usually aggressive, and when it does bite a person, this person most likely needs to go to a medical center to receive basic medical care to minimize the symptoms associated with the bite,” said the specialist of INBio.

The specialist added that the spider is large (it can reach 9 inches in length), is brown, and the chelicerae (front of body) is pink.

If it´s angry, it normally lifts the front legs and opens its fangs menacingly.

Víquez added two fun facts about this poisonous spider: it distributes itself relatively easy in banana exports (which usually are controlled by packers), and there are two documented cases of these spiders biting dogs, and in both cases the animals died.