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Myths about "Dangerous" Spiders

Myth: "I just know the dreaded Brown Recluse spider is in this area. Why? Because people have been bitten by them!"

Thumbnail version of brown recluse distribution map
Brown recluse spider
Loxosceles reclusa
Real distribution in 2002; real bites do not occur outside green area!

Click image to enlarge

Fact: Unless you live in the south-central USA (see map, right), where Loxosceles reclusa actually lives, human bite cases are reported from your area because of the incompetence of those reporting them, not because of actual spiders biting people. In the USA generally, there are hundreds of these cases reported each year, and at least 80% of them are false reports from areas where the spider supposedly responsible does not exist.

"Brown recluse bite" has become medical shorthand for "this patient has a mysterious sore or lesion." In such areas as the Pacific coast states, it is safe to say that 100% of these reports are errors, and the vast majority (80-95%, depending on locality) are not spider bite cases of any kind. It goes with the almost universally believed superstition, "if you didn't see what bit you, it was a spider." In reality, a variety of medical conditions (see this article, also this one) cause these mystery lesions, including lymphatic disorders, bacterial and fungal infections, and delayed-hypersensitivity allergic reactions; in addition to bites of ticks and other bloodsucking arthropods.

For a detailed analysis of the "bite" misdiagnosis problem in California, which has reached major proportions, see Rick Vetter's excellent web page: Myth of the Brown Recluse. A list of publications in medical journals on the epidemic of "brown recluse" misdiagnosis is available on request. Another brown recluse myth follows.



Disclaimer: Information on this web site is not a substitute for professional medical advice, and should not be used to diagnose or treat a medical or health condition. You should consult a physician as to any symptoms that may require diagnosis or treatment. Genuine spider bites can sometimes require medical attention, but beyond that, several medical conditions commonly mistaken for spider bite can be even more serious. If you have what appears to be a serious spider bite, please contact your health care provider or local emergency services. If you have the actual spider that bit someone, always save it for identification by a professional arachnologist.

Text © 2003, 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 2 September, 2010

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