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|Tip of leg of orbweaving spider, showing claws
Illustration: J.H. Comstock, 1913
Myth: Spiders have oil on their feet that keeps them from sticking to their own webs.
Fact: Everyone who educates about spiders has heard the question "why don't spiders stick to their webs?" many times. Who first came up with the oil-on-the-feet idea is unknown, but it must have originally been a perfectly reasonable guess, or hypothesis. Since the decades-old origin of this idea, in some circles it's become a dogma. It's been repeated countless times in print and online. There are even classroom lesson plans built around this false "fact".
To quote two of the world's leading experts on spider silk use (Fritz Vollrath and Edward Tillinghast) writing in 1992: "Ecribellate spiders simply tiptoe around the glue, which they deposit in spheroidal globs. When a spider accidentally steps into one of these glue balls, as it sometimes does, it suffers no more inconvenience than a human stepping into a wad of gum. When a fly slams into the web, however, it hits about 50 of the droplets, enough to make it stick." I might add that most spiders don't even make sticky silk, and those that do (mainly orbweavers and cobweb weavers) still have many non-sticky threads in various parts of their webs.
To clinch the matter, investigators have found no oil-secreting glands opening on spider tarsi (end segments of legs). One unique feature web-making spiders do have on their tarsi is a third claw opposable to certain specialized bristles, enabling them to grasp individual threads. No insect has more than two tarsal claws per leg, and most are helpless in a web.
I'm indebted to Ohio University arachnologist Jerome Rovner for the germ of this article.
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2008, Burke Museum of Natural History & Culture,
University of Washington, Box 353010, Seattle, WA 98195, USA
Photos © as credited
to Spider Myths author, Rod Crawford
This page last updated 2 September, 2010
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