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Hobo Spider Q & A with Rod Crawford

I recently came across a blog and website by a fellow named Rod Crawford, who is the Curator of Arachnids at the Burke Museum at the University of Washington (check out his website here for LOTS of great info on spiders).  What I read challenged some of the ideas (quite erroneous I might add, but that’s not new to me!) that I’ve had about spiders, specifically Hobo Spiders.

I spoke with him on the phone, and he was kind enough share his over 44 years of spider experience in a Q & A with me!

Warning:  This gentlemen may make me look stupider than I am (by contrast), please remember that I really ain’t that dumb.

Is this a Hobo Spider? A positive I.D. "requires magnificaction. And even then, all you have is a good guess." says Rod Crawford, Curator of Arachnids at the Burke Museum in Seattle
Is this a Hobo Spider? A positive I.D. “requires magnification. And even then, all you have is a good guess.” says Rod Crawford, Curator of Arachnids at the Burke Museum in Seattle

Kirk:  In some of your research and blogs, you’ve mentioned that it’s possible that Hobo Spiders aren’t even poisonous, what data supports that idea?

Rod Crawford:  Poisonous is the wrong word. That would mean it was dangerous to eat one, like a poisonous mushroom. Hobo spiders (like almost all spiders) are definitely venomous, but we have no confirmed evidence that the venom has much effect on humans. The original research involved rabbits, and animal models aren’t a good guide for how a venom will effect humans. (We know that now, but didn’t know it then).

* Out of all the hundreds of cases of “horrible hobo spider bites”, NOT ONE initially healthy person ever developed the symptoms who could produce any spider that had bitten him/her. Based on brown recluse bite cases in Missouri, at least 20% should have the spider. Hobo spiders are pretty big, and there’s no way you wouldn’t notice one on you. And no, spiders don’t crawl into the beds of sleeping persons to bite them!

* Published research on biochemistry of hobo spider venom now shows that there is no unusual component that would account for its causing skin necrosis.

* Published microbiological study of hobo spider mouthparts shows they do not carry any bacteria that could cause skin necrosis.

* Some of us have been trying for many years to accumulate enough *real* human hobo spider bite cases (ones where the biting spider specimen exists and can be checked) to publish a study on the human effects. They are so rare that we have less than 10 cases so far (plus a couple on dogs). Not enough for a statistically significant study, but so far as it goes, in all the cases we have, the bite had little effect.

* I’m attaching pdf copies of some of the scientific papers:  Verified Spider Bites in Oregon with intent to assess hobo spider venom toxicityMisdiagnosis of Spider BitesAn analysis of venom of the spider Tegenaria agrestisDo Hobo Spider Bites Cause Dermonecrotic Injuries?An approach to spider bites.

* I’m quite sure many of your readers know someone with one of those “horrible hobo spider bite” cases. I don’t want to hear about it unless they *have the spider that bit them.* That is the only way to confirm the case is genuine.

Kirk:  If the necrotic lesions that people get aren’t from Hobo Spider bites, what do you think they’re from?

Rod Crawford:  There are at least 50 possible causes. These 4 articles discuss some of the common ones.

I cannot diagnose individual cases; my specialty is spiders, not bitten humans. Do not call me up and tell me your symptoms – I can’t tell anything from that, I have to have the spider!

Kirk:  Some people believe that you can identify a Hobo Spider from it’s coloration and markings, is that true?

Rod Crawford:  Spiders are very variable in color within a species and very similar between species. There are color features that can allow you to make a pretty good guess if you already know the spider is a Tegenaria/Eratigena (thus, already narrowing it down to only 3 possibilities instead of hundreds) but even those features require a specimen that is completely intact and fresh. And to tell what genus it’s in you need to look at the eyes, spinnerets and certain body hairs – all require magnification. And even then, all you have is a good guess, not a firm identification.

Kirk:  How then can you identify a Hobo Spider?

Rod Crawford:  The fine structure of the sex organs – located on the pedipalps of the males or the underside of the abdomen in females – is the final arbiter of species ID in these, as in most other spiders. Note, ALL male spiders of ALL species have enlarged “boxing glove” palps – you need to see the fine structure of that palp to ID the species.

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