Are There Dangerous Spiders in San Francisco?

Well, of course: the dreaded Black Widow, that infamous people-killer, shows up all over the San Francisco area! That’s dangerous right?

Well…sort of. That story is wrong for a few reasons. First, all forms of window spider are naturally shy — they don’t want to bite you! Researchers attempting to provoke several species of spider into attacking discovered that the black widow was among the least likely to bite. They’re far more likely to attempt to run, to play dead, or to attack with strands of silk. The only time they’re actually likely to bite is if they’re pinned entirely down — and even then, the chances of severe symptoms (beyond burning pain and nausea a little later) are very slim. (In 2013, there were 1,866 diagnosed black widow bites, and a mere 14 caused problems that required hospitalization; none were lethal.)

But that’s not all! The rash of scary “black widow” bites that killed a dozen or so people around 30 years ago and got this spider all up in the news weren’t even the same kind of black widow that lives around here. The Western Black Widow is the only “dangerous” spider in San Francisco — but the spider that caused the scare was actually the Mediterranean Black Widow a.k.a. the Steppe Spider. (They don’t even have the classic hourglass marking!) So not only are you unlikely to get bitten, and unlikely to have any long-term effects from getting bitten, but the bites you do get aren’t even the scary ones.

The fact is, most doctors will ask you, if you believe you have a spider bite, “Did you see the spider that bit you?” That’s because most presumed spider bites aren’t actually spider bites. There are a huge number of other things that can cause similar symptoms, from allergic reactions to infections to stings from other insects or arthropods.

Of course, if you have arachnophobia — quite common, all things considered — none of this is really going to help you. You’re going to quite rightly call a pest control outfit to come out and purge your property of the eight-legged horrors…and we’ll be happy to do it!

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