Which Is The World’s Deadliest Spider, Really?

Cute monster: Phoneutria spider. dejeuxx, CC BY

Elise Andrew 13 Nov 2014, 19:44

It seems Ebola and terrorism may have lost their scare factor. That is because journalists have once again turned to arachnophobia. “Brazilian Wandering spider found under a bunch of bananas in Waitrose home delivery,” said one newspaper recently.

Every few months, almost like clockwork, a media hype about these arachnids surfaces in the press. But we rarely find a balanced story about deadly spiders. Just how toxic are they, really?

Trying to compare spider toxicities is like comparing apples and doorknobs. There are different levels of effects, some painful, others not so much. Probably the most reasonable way to compare would be to look at historic fatalities.

The most commonly reported group is the wandering spiders of the genus Phoneutria. These are traditionally the darlings of the media banana spider reports. Always listed as deadly but are they really?

A study in 2000, described 422 bites by Phoneutria spiders (pictured above), mostly P. nigriventer and P. keyserlingi in eastern coastal Brazil. Two children were seriously ill as a result of the bites – one died. However, more than 80% of the remaining bite victims had mild or no symptoms.

Another frequently cited dangerous species is P. fera, however, this spider lives in the Amazon, far from the banana growing areas in Brazil – and most of the people. And although Brazil produces large quantities of the fruit, most are eaten domestically so little exportation occurs.

Then there is the fact that most of the bananas shipped to North America originate from Central America and northwestern South America, far from areas containing large Phoneutria spiders. So these spiders pose little threat outside of Brazil (but there can be exceptional cases such as the one reported in the British supermarket Waitrose).

Hadronyche sp. lurking about. Marshall Hedin, CC BY-NC

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