Steotoda grossa (The False Widow)


It’s been raining a lot in the Pacific Northwest. Between the deluge and the cool temps, it’s definitely not the season for bug viewing. Being indoors, in rainy winter weather, when you live on an island equals boredom, cabin fever, and winter blues. You have to make your own sunshine or you get SADD.

I found my sunshine today in the barn. I went down to take better photos of the spiders I discovered over the weekend residing in the well pump house (inside the barn). I get really excited finding any sort of invertebrate this time of year.

This shiny arachnid had me fooled the first time I found one. She’s not a real widow, but a False Widow (Steotoda grossa). False widow spiders are not native to Washington. They were imported from Europe, but are widely distributed and considered a cosmopolitan species. We have lots in the basement of our house!

When I was in the well pump house, I found three females, each in her own corner, tending her egg sacks.

A very shiny Steotoda grossa female

I also found a lone Callobius severus (male?) on the wall… just hanging out. He was alive. I gently blew on him to see if he moved. He did.

Callobius severus (male?)

Steotoda grossa spiders are actually quite beneficial, preying on invertebrates like pillbugs, but they are famous for eating other spiders that humans don’t particularly want to encounter, like Hobo spiders or Black Widows. They construct flimsy or loosely woven, somewhat messy webs and seem to love corners in outbuildings and basements (at least from my personal experience). Female Steotoda grossa spiders have been recorded living as long as 6 years, while males have a much shorter lifespan no longer than 1.5 years.

Loosely constructed Steotoda grossa web with round egg sacks

While not aggressive, Steotoda grossa spiders will sometimes bite people. They see very poorly and react mostly to vibrations when responding to threats. A bite from a False Widow is not life threatening, but some individuals may have a localized reaction to the bite.

Thanks for reading! πŸ•ΈπŸ•·

Steotoda grossa female with egg sack

Steotoda grossa female (upper center, above red mark) with egg sacks

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