Eight-Legged Beasties of the Hobo Persuasion, or not

This week, we were called out three times to retrieve a Possible Hobo Spider on campus. I’ve emphasized the name, because that’s how the callers invariably sound: frantic and hunted and ready to jump out of their skin.

I had the honor of going on retrieval runs with a trained entomologist who ID’d and handled the suspects.  Onlookers, including yours truly, were aghast. When she later opened the containers to study them while standing 6″ away from me in a closed elevator, I tried to be subtle in my writhing discomfort, but she noticed and I was duly ridiculed.

Back in the lab, we had a lengthy discussion about the nuances of Tegenaria identification, and then our professor arrived and we had a spontaneous workshop on handling them safely and differentiating species.

Here are eight legs of basics on ID, with an emphasis on ruling out Tegenaria agrestis, the Hobo Spider:

  • There is a lot of variability even within a species. Not every Tegenaria agrestis, the Hobo Spider, looks like every other Hobo Spider. Their sizes are widely variable, as are the patterns of their markings. Also, the different sexes of the same species often look unrelated.
  • A close relative and frequent doppleganger is the Giant House Spider, Tegenaria duellica. There’s a third spidery stooge, Tegenaria domestica, the Barn Funnel Weaver. Note that they are in the same genus and they are very similar in appearance. All three are from Europe in case you were wondering. You weren’t, were you?
  • People decide quickly that what they have found in their bathroom is a Hobo, but it’s often the House Spider. There’s no compelling reason to kill House Spiders; they are excellent predators and eat many of the other insects that are wont to wander your halls.
  • The males are generally much less aggressive than the females. It was a male that my associate casually picked up and flipped over. He clearly wasn’t happy, but he didn’t bite. Males are easily identified by the presence of large palps – short, leg-like appendages that extend from the front of the spider.
  • Hobo Spiders have a lighter colored stripe in the center of their sternum. This is the middle, underside portion of the spider, the section the legs attach to. In this same region, lighter colored spots mean it is not a Hobo Spider.
  • On the top of the spider, there are two main sections: the cephalothorax which is the head and “chest”, if you will, of the spider, and the abdomen, which is the back end of the spider. An obviously striped cephalothorax is not a Hobo Spider.
  • If there is a lighter patterning of color around the joints of the legs, that is also not a Hobo Spider.
  • Male Hobo Spiders have bluntish palps, whereas the male House Spider has very pointy tipped palps.

Here are the basics on safe handling:

  • Move faster than they do.

There is an excellent guide, with pictures, to use to convince yourself you do not have a Hobo Spider in your house, bathrobe, garden shed, or shoe. It’s here [PDF]. If after you’ve read it, you think you have a Hobo Spider, you can check in with your local extension service who likely has an entomologist or zoologist who can help you. If you live in the Pacific Northwest, OHSU wants your spider for their study.

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Note: I’m not including pictures in this post, because they do not represent a reliable way to identify Tegenaria agrestis.