Brazilian Wandering Spider: The World's Deadliest?

There are three candidates for the world's most deadly spider: the Brazilian wandering spider, the Australian funnel-web, and the Black widow. This business of "the Daddy long-legs is the world's most venomous spider, but its teeth are too small to bite humans" is strictly an urban legend, by the way. Science has never tested the venom of any Daddy long-legs species, so we don't know how venomous it is.
The Brazilian walking spider is exceptionally large, with a leg span of 4-5 inches. It gets its name because unlike other spiders, this one is not content to sit back in a web and wait for prey. Instead, it spends its nights hunting prey, and its days holed up in a safe sanctuary. In the wild this may be a pile of damp leaves or a termite mound, but in urban areas it may hide in stray shoes, wood piles, and - most notoriously - in bundles of bananas.
Brazilian walking spiders are a curse of the banana plantation. They like to hide in damp crevices, and a bundle of bananas fits that to a "T." Not only are they hazardous to the people who work on the plantations, they can also occasionally find themselves being boxed up and shipped around the world. Only to deliver a nasty surprise to the store clerk who unpacks them, or the customer who unwittingly takes them home!
In fact, this exact scenario played out recently in England. Luckily the pub owner in Bridgewater received prompt medical attention, and recovered after a week spent in the hospital. Brazilian wandering spiders have "wandered" in this way as far afield as Cornwall (2005), Manitoba (2009), Oklahoma (2009), and the Netherlands (2008).
The Brazilian walking spider's venom is about ten times more deadly than that of the second runner-up, the Black widow spider. However, there is some debate about the Brazilian wandering spider's standings because it is less likely to bite, and it can deliver a "dry bite," where it holds back its venom. In fact, when hunting, the Brazilian wandering spider controls the amount of venom it releases, using only the tiniest bit when subduing prey.
By comparison, the other two runners-up (the Australian funnel-web and the Black widow) have venom that is only a fraction as potent. However, they are much more likely to bite, more successful at puncturing the skin when they do bite, and both species deliver their entire "payload" of venom in every bite.


Photo credit: Flickr/Alejandro Soffia Vega