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“Huntsman Spider” Olios sp. (Family Sparassidae) in her silk retreat. Click here for a close-up of the face

This rather large spider (which is 25 mm (1 in) long, not counting the legs*) was collected in Wisconsin, but does not actually occur here. In fact no spiders in this family are found in the Great Lakes states. It was found on a bunch of bananas purchased in Grant County, and the country of origin of the bananas was Columbia. This spider is a “huntsman spider” (Family Sparassidae). It isa species in the genus Olios.

It is common in and near human habitations throughout the tropics and is often carried on bananas and other produce to distant locations (like Wisconsin). Various spiders have biological characteristics that predispose them to this kind of long-distance human dispersal. Ctenids (or wandering spiders) are another group of large spiders that often “hitchhike” to new areas aboard produce. Neither type of spider is likely to become established in Wisconsin, though, because they are tropical animals and unable to survive our cold winters, even inside. There’s simply not enough living insect food in a Wisconsin house in the winter to support such large spiders. Both spiders are large enough to bite humans if provoked. The venom is commonly no more toxic to humans than a honeybee sting, but not all species in the tropics have been investigated for their toxicity, so exercise common sense if you should encounter one in your next pineapple!

Sparassids are sometimes called "giant crab spiders" because they have their legs all turned sideways and forwards so that the spider can move laterally (sideways) as well as forward or backward. The outer segments of each leg have dense scopulae or hairy brushes or facilitate lateral movements. Some species have the ability to hyperextend their tarsi, which also makes them more maneuverable.

The somewhat flattened morphology of huntsman spiders makes them especially good at “hitchhiking.” Not only are they flat, but their legs work efficiently in a flattened stance, too. They can easily hide inside silken retreats in produce, and can are often found in houses in Central and South America. Likely due to its ability to hitchike it is found around the world in tropical and subtropical areas, including Florida, Texas, and California. It is believed to have been introduced to the Americas from Asia. Perhaps surprisingly, most people in tropical areas welcome these large fast spiders inside! Why? Because they are voracious predators of a much more disagreeable houseguest: Cockroaches.


Contributed by Dr. Michael Draney with thanks to Rick Vetter at UC-Riverside help with identification.

*Its common to hear a spider described as "big as a hockey puck" or farther south as "big as a dinner plate", but there are no spiders that big as far as an arachnologist is concerned. Spiders are only measured from the tip of the head to the end of the abdomen because leg size varies considerably.

 

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Last updated on April 15, 2014