Brazilian Wandering Spider - Danger To Humans

Danger To Humans

Phoneutria includes some of the relatively few species of spiders known to present a threat to human beings. Danger to humans is not merely a question of toxicity, but requires the capacity to deliver the venom, a sufficient quantity of venom, a disposition that makes a bite likely and proximity to human habitation. The actual incidence of death or serious injury must also be considered.

Spider mouthparts are adapted to envenom very small prey; they are not well-adapted to attacking large mammals such as humans. A study in March 2009 suggests that Phoneutria inject venom in approximately one-third of their bites, and only a small quantity in one-third of those cases. Research in this area is hindered by the difficulty of identifying particular species. These spiders, however, almost never deliver dry bites, with 9 bites out of 10 being venomous. The aggressiveness of the spider is another issue, as it can bite several times in a row before fleeing.

Of the eight-described species, P. nigriventer and P. fera most frequently receive mention in mass-media publications. P. nigriventer is the species responsible for most cases of venom intoxication in Brazil because it is commonly found in highly populated areas of southeastern Brazil, such as the states of São Paulo, Minas Gerais, Rio de Janeiro and Espírito Santo. The species P. fera is native to the northern portion of South America in the Amazon of Brazil, Venezuela, Ecuador, Peru and the Guyanas.

The spider's wandering nature is another reason it is considered so dangerous. In densely populated areas, Phoneutria species usually search for cover and dark places to hide during daytime, leading it to hide within houses, clothes, cars, boots, boxes and log piles, thus generating accidents when people disturb it. Its other common name, "banana spider", comes from its tendency to hide in banana bunches or plantations, and it is occasionally found as a stowaway within shipments of bananas. These spiders can also appear in banana crates sent to grocery stores and bulk food centers around the world. One such instance happened in 2005 with a shipment of bananas arriving at Bridgwater, England, when a man was bitten by a P. fera; however, due to quick medical care he survived, taking nearly a week to recover from the bite following treatment.

Despite their reputation as the world's deadliest spiders, there are multiple studies that call into question their capacity for fatal human envenomation, though some of these are labeled with a level of uncertainty, as Phoneutrias can easily be confused with other species such as the Lycosides or other large labidognatha spiders. One study suggested that only 2.3 percent of bites (mainly in children) were serious enough to require antivenom. However, other studies, as cited in the Wolfgang Bücherl studies, showed that the toxicity of Phoneutria venom was clearly more virulent than both Latrodectus and Atrax. Many experts believe that various spiders like Phoneutria can deliver a "dry" bite to purposely conserve their venom, as opposed to a more primitive spider like Atrax that usually delivers a full load. Nevertheless, there are well-attested instances of death. In one case, a single spider killed two children in São Sebastião. The spider was positively identified as a Phoneutria by Wolfgang Bücherl.