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Myths about “Dangerous” Spiders

Myth: You can recognize the Hobo Spider by a chevron pattern on the abdomen, “boxing glove” shaped palps in front of the body, and funnel-shaped web.

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Hobo spider Tegenaria agrestis Real distribution in 2002; real bites do not occur outside pink area! Small dots are isolated populations. Click image to enlarge

Fact: This common idea is a misinterpretation of basically correct information found on the Internet about the hobo spider, a (possibly) medically important species of northwestern USA (see map, right) and Europe (and nowhere else). People will insist on finding a way (no matter how bogus) to “recognize” a spider by so-called markings… True, this species often has a pattern of chevrons on the abdomen, but they are worthless in identification. That is one of the commonest pattern types among spiders, and literally thousands of species have it. What’s more, it’s not always present in hobo spiders — like other species, they are variable in color! Again, hobo spiders do make a funnel web, but that is a characteristic of the entire spider family Agelenidae, with numerous species; even some non-agelenids make funnel-like webs; so the funnel does not mean hobo spider. And again, it’s true that male hobo spiders have enlarged pedipalps. But that doesn’t mean you can recognize the species that way; every male spider on earth has enlarged palps! Those are the male sex organs, and naturally, males all have them. The fine structure of the palps is indeed one of the keys to identification, but to see how a hobo spider’s palp differs from other male palps you need a microscope with at least 30x magnification. As with most spiders, a naked-eye view is simply not enough to identify a hobo spider. Whole body photos on web sites (including the old Hobo Spider Web Site) are only for illustration and have no identification value; around 200 other species in the same region appear similar. Please note that if you live outside its range (pink area on map), you don’t have hobo spiders! Update: It’s been 24 years since my late friend Darwin Vest found severe effects on laboratory rabbits bitten by male hobo spiders. His data led everyone to assume that hobo spiders caused many apparent human “spider bite” cases. However, over the past quarter century, not one patient has come forward who (1) was initially healthy, (2) developed the “typical hobo spider bite symptoms,” and (3) was able to produce any spider that had bitten him/her. Within the range of the brown recluse, genuine necrotic-bite patients recover the spider about 20% of the time, so “hobo spider victims” should have managed it at least once. On the other hand, several humans and dogs developed no significant symptoms when bitten by hobo spiders that were recovered and identified. Some such cases can be explained as “dry bites,” but it seems increasingly likely that these “hobo spider bite” cases, or most of them, are not actually being caused by a spider.

Hobo spider (drawing by Margaret Davidson) Click image to enlarge Hobo spider is not distinctive, but looks like hundreds of other species! (from Bob Thomson photo) Click image to enlarge Male spider Dictyna sublata Not a hobo spider! Typical funnel web Agelenopsis oregonensis Not a hobo spider web! (from a photo by Rod Crawford) Click image to enlarge Figures above: Some hobo spiders have a strong chevron pattern, some a weak one (far left), and some have none at all (near left). All male spiders have enlarged palps, from the tiny Dictyna (near right) to the largest tarantulas, without all being hobo spiders! Between 1000-2000 known spider species make funnel webs (far right), without all being hobo spiders!

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Myth: Hobo spiders are aggressive.

Fact: Once upon a time, an entomologist who shall be nameless wanted to write about the spider Tegenaria agrestis. “Agrestis” is a Latin word meaning “rural.” But this gentleman didn’t know much Latin, so he coined the name “Aggressive House Spider” for the species. Arachnologists suspected that the name was intended to encourage irrational fear of spiders, for reasons it is better not to speculate on. In any case, everyone who knew anything about the species realized how inappropriate that name was. The species is not aggressive, except in that any predator shows aggression toward its prey, and any spider is liable to bite when trapped against one’s skin. The species is not a true house spider; in fact, it cannot live permanently in buildings and is the only real example of that otherwise mythical idea that outdoor spiders wander into houses. Generally it is the males that do this wandering, and females are seldom found indoors. And finally, “aggressive” has nothing to do with the meaning of the scientific name. This unacceptable, fake name was firmly rejected by both the entomological and arachnological common-names boards, but nevertheless it’s been used in a number of publications. Evidently people would rather think that spiders are more dangerous than they really are! “Hobo spider” (from its common occurrence along railroad tracks and spread along transportation corridors) is the authorized common name.

Previous Myth Myths Home Web Resources Next Myth Text © 2003-2010, Burke Museum of Natural History & Culture, University of Washington, Box 353010, Seattle, WA 98195, USA Phone: 206-543-5590 Photos © as credited Queries to Spider Myths author, Rod Crawford This page last updated 10 September, 2010 This site best viewed at 800 x 600 using IE 5.0 or above.

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