Entomology (Study of Bugs)/Black Widows


Hi Ed,

I live in a basement apartment that is invested with Black Widows.  Last summer I killed over one hundred of them . . . mostly in my bedroom!  I can't have poison spray.  Also, when the bug guy came to spray (I wouldn't let him), he said that it doesn't kill them right away . . . they have very small feet.  So I was figuring on half dead punch drunk Black Widows acting in uncharacteristic ways.  Because they were very "reliable" not on any poison.  I always knew where they were or where they might be.  They never were in my clothes or bed . . . always someplace that had an "angle" like a corner or something.  My question is: how reliable are those electronic spider repellents? Not the cheap ones, but the more expensive fancy ones? And since "my" black widows haven't returned this year yet, would it keep them from returning? And lastly, would it make them punch drunk like the poison or would it just make them stay away?

Thanks so much!

Dear JK - First off, how were these spiders identified? What you describe sounds rather unusual for black widows, and there are other species in the same family (Theridiidae) with a similar shape, but that lack the characteristic orange/red marking on the underside of the abdomen (http://tinyurl.com/akmtzl3). Then, the comment by the pest controller about the spiders having 'small feet' makes no sense to me, as this is not how the spray poison enters their body - it is by whole body contact. To the best of my knowledge, electronic devices advertised as repelling spiders are a waste of money. Although you will find many anecdotal testimonials on the internet, I do not know of any rigorous peer-reviewed studies supporting any such claims. The one study I found that appeared to show at least a short-term repellent effect by an electronic device on crickets and cockroaches had no effect on spiders. Should they return, I suggest simply vacuuming them up and disposing the bag in the trash after first placing the bag in a freezer overnight.

Hope this helps,

Entomology (Study of Bugs)

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Ed Saugstad


Will accept most questions in general entomology, including those related to medical entomology, taxonomy, ecology, arthropod surveillance, and pest management. If you are requesting a 'mystery bug' identification, PLEASE either attach an image to your question, or post an image on a web page (such as Flickr) so that I can look at it, as verbal descriptions frequently are insufficient for a definitive identification.


21 years in the U.S. Army as a medical entomologist; duties varied from surveillance of pest populations (including mosquitoes, cockroaches, ticks, and stored products pests) to conducting research on mosquito-virus ecological relationships and mosquito faunal studies. Ten years as a civilian analyst for the Department of Defense, primarily on distribution of vector-borne diseases worldwide. Limited experience on surveillance of agricultural insects in North Dakota and Indiana.

Entomological Society of America, West Virginia Entomological Society, Society for Vector Ecology, National Speleological Society, West Virginia Association for Cave Studies.

American Journal of Public Health, Contributions of the American Entomological Institute, Japanese Journal of Sanitary Zoology, Journal of Economic Entomology, Mosquito News, and Mosquito Systematics.

B.S. in entomology from North Dakota State University in 1963, M.S. in entomology from Purdue University in 1967.

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