Shy and nesting

A while back, I told you I had a slight problem: I probably had two nearly indistinguishable Parasteatoda species in my colony, P. tepidariorum and P. tabulata. The way to tell them apart is by close examination of their genitals, or by dissection, and a) I don’t have the skill to do that, and b) I’m trying to maintain a live, breeding colony, so taking individuals apart to figure out their sex is off the table.

I did hatch a cunning plan, however, to get a provisional identification. P. tabulata is known to build nests from scraps of debris and wind-blown litter, so I thought maybe I could get a tentative guess at their taxonomy by cluttering their cages with scraps and seeing who built homes for themselves. It’s not at all definitive, especially since they’re all living in a sheltered environment right now and even P. tabulata might find nesting superfluous, but I raided the department’s paper shredder and hole punch for little bits, and scattered them in all the tanks.

Most of the spiders ignored them. They couldn’t eat them, after all. But a few have slowly dragged bits and pieces of paper towards their roost and built little hidey-holes. Here’s Melisandre:

So maybe I can put together a rough behavioral test to estimate who is who? I don’t think a real taxonomist would be satisfied with it at all, but it’ll be useful for me, making it less likely that I send a P. tepidariorum male off to mate with a P. tabulata female, which probably wouldn’t go well.

By the way, P. tepidariorum is thought to be native to the Americas, that is, it hitch-hiked here with the first humans to move here; it colonized Europe when the human colonizers boats sailed back home. P. tabulata is probably native to Asia, and emigrated to the Americas and Europe much more recently. Both are thriving almost everywhere humans live now, but the timing would suggest that the two species diverged at least 15,000 years ago…or about 15,000 generations ago. It’s kind of neat how their morphology hasn’t drifted apart much, but their distinct genitalia make an uncrossable reproductive barrier.


  1. =8)-DX says

    Why yes, Mr Darcy is a handsome-looking prospect, with a generous income. But their distinct genitalia make an uncrossable reproductive barrier!

  2. davidc1 says

    Off topic ,but the snatch snatcher has left the NATO summit because all the others were mean and making fun of him .
    Do you think he will nuke GB to get back at us ?

  3. says

    I suppose if your behavioral test worked you could destructively examine offspring and build a probability that your behavioral test was reliable. Or you could wait until they pass on and then examine them more closely and then build your probability model that way. I wonder what’s an acceptable likelihood?

  4. says

    I was not referring to Trump in my comment but it works that way, too. Rather than dissecting Barron, wait till he dies of heart failure; it might be soon.

  5. says

    PZ– Are there any arachnid genomic resources available? Even if not, it may be possible to identify a collection of diagnostic marker assays (SSRs, SNPs) useful for typing the spiders in your collection– provided that you could non-destructively extract gDNAs. Maybe you could get them to pee into a cup?

  6. magistramarla says

    I thought of you as I was cleaning up my patio today, PZ. After our recent move to California, my husband left a mound of packing paper piled on the patio. The recent rain drenched it and it resembled used toilet paper, so I took some garbage bags out and attacked the mound today. I found a lot of spiders that closely resembled yours in that mound. I think that they, and the bugs they feed upon, had believed that they had found the perfect place to spend the winter. I tried to gently send the spiders on their way before stuffing the wet paper into the bags. Wish you could come out here to collect some California spiders, PZ!

  7. jamiejag says

    @Scott Woody, #6

    Guessing there’d be a reasonable source of spider DNA somewhere in their molted exoskeletons, or in the left-overs from feeding time? How about their webs?