Lesbian spiders? Dimorphic males? Precocious adolescents?

Yesterday, I set up a cage for Steatoda borealis. I haven’t successfully raised them in the lab, probably because I haven’t fine-tuned their environment, but I thought I’d give it another try. I caught these individuals living in a communal environment (my compost bin), so I made a substrate of moss, for burrowing in, and added 5 females, all in the same confined space.

I came in today, and what do I find? They’ve built a communal web and they’re all perched on it, spaced about 2cm apart. This is already interesting.

Something to know about S. borealis: the adult males are distinctive, they have palps that look like massive medieval instruments of war, while the females have slender palps. I was pretty confident I’d segregated them by sex accurately, on the basis of casual inspection.

So I added a male this morning. All the spiders seemed somewhat agitated, there was much scurrying and tapping and exploratory sensory behavior, as I would expect. The male was courting the biggest, plumpest female in the cage.
Then, to my immense surprise, two of the females (I think) paired off, and one of them was aggressively thrusting its skinny little palps at the others genitals. Whoa, what? Did I misgender them, or was this some kind of social behavior?
Then I get dragged away to attend some fucking meeting, and couldn’t inspect them more carefully. This was extremely annoying, as you might guess.

Now I’m intensely curious. I’ve searched the literature, there is no mention of male dimorphism in this species, but it’s an interesting possibility that warrants further investigation. The other possibility is female:female sexual behavior — these spiders are somewhat social compared to others I’m working with, so it could be some kind of bonding behavior? Another possibility is that I’m fooled by juvenile males that exhibit typical sexual behavior but just haven’t completed their final molt to acquire their gloriously developed sexual organs.

I’ll be putting them under the microscope tomorrow to find out.


  1. Dennis K says

    @2 Artor — Never go by what them so-called scientists say, lessen’ you wanna turn gay. Go by what ya feel, ya know, in yer gut.

  2. scuba says

    “Did I misgender them…?”

    Oh please, this is just tragic.

    Spiders have sexes, not genders.

  3. IX-103, the ■■■■ing idiot says

    Since it sounds like things didn’t really get started until you added the male, it seems possible there is a chemical trigger released by the male that triggered this behavior. So we can hypothesize that spiders accultured to low levels of such a chemical may display frenzied sexual activity when exposed to it.

    So it is obvious from evolutionary pSychologY thAT WOMEN GO CRAZY WITHOUT THERE MEN1!1!1!!!

  4. raven says

    Some spider species are hermaphrodites.

    I’ll let PZ tell us if that…doubles their chances on a weekend.

    Solved III. You are working with a species of spiders that

    Chegg https://www.chegg.com › questions-and-answers › iii-…

    You are working with a species of spiders that have only 2 autosomal chromosomes and no sex chromosomes (the spiders are hermaphrodites, meaning each spider …