Phoneutria is a genus of venomous spiders in the family Ctenidae of potential medical significance to humans. They are mainly found in northern South America, with one species in Central America.
The spiders in the genus can grow to have a leg span of 13 to 15 cm (5.1 to 5.9 in). Their body length ranges from 17 to 48 mm (0.67 to 1.89 in). While some other araneomorph spiders have a longer leg span, the largest Phoneutria species have the longest body and the greatest body weight in this group.
Wandering spiders are so-called because they wander the jungle floor at night, rather than residing in a lair or maintaining a web. During the day they hide inside termite mounds, under fallen logs and rocks, and in banana plants (hence the "banana spider" nickname).
Phoneutria are found in forests from Costa Rica southwards throughout South America east of the Andes including Colombia, Venezuela, the Guianas, Ecuador, Peru, Bolivia, Brazil, Paraguay, and into northern Argentina. Three species (P. reidyi, P. boliviensis and P. fera) are found in the Amazon region, one species (P. fera) is restricted to the Amazon, and one (P. boliviensis) ranges into Central America in Panama and Costa Rica.
The venom of Phoneutria nigriventer contains a potent neurotoxin, known as PhTx3, which acts as a broad-spectrum calcium channel blocker that inhibits glutamate release, calcium uptake and also glutamate uptake in neural synapses. At deadly concentrations, this neurotoxin causes loss of muscle control and breathing problems, resulting in paralysis and eventual asphyxiation. In addition, the venom causes intense pain and inflammation following a bite due to an excitatory effect the venom has on the serotonin 5-HT4 receptors of sensory nerves. This sensory nerve stimulation causes a cascading release of neuropeptides such as substance P which triggers inflammation and pain.
Aside from causing intense pain, the venom of the spider can also cause priapism in humans. Erections resulting from the bite are uncomfortable, can last for many hours and can lead to impotence.
These spiders' wandering nature is another reason they are considered so dangerous. In densely populated areas, Phoneutria species usually search for cover and dark places to hide during daytime, leading it to hide in houses, clothes, cars, boots, boxes and log piles, where they may bite if accidentally disturbed.
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