Brown Crab Spiders

2012 July 14

There are quite a number of medium-sized brown crab spiders about, we regularly find them on flowers, on the side of the house, hiding in crevices, and similar places. Like this one, that we found on the kids’ plastic slide in the yard in the spring, on May 30, 2010:

The fact that she was so big so early in the year is a pretty clear indication that she overwintered as a nearly-mature adult. She probably spent the winter in the “subnivean environment”, the thin layer between the snow and the soil where it isn’t quite freezing, and the grass props up the snow enough that creatures down there can move around.

Look how friendly she is! See? She wants to give you a hug!

Here’s another one that Sam found on our hanging-basket fuchsia on June 4, 2011 (she is sitting on a dried fuchsia petal). She may or may not be the same species. Most spider species have such variable coloration that it is hard to tell from pictures, so the fact that they have different markings may not actually mean anything. She has a practically identical body shape to the first one, so they are likely to be close relatives, at any rate.

I say “she” because she is clearly gravid with eggs. She was so swollen that she wasn’t actually bothering about going into much of a hunting pose. At this point, she had other things on her mind than food.

We kept her in a jar, and a bit later she made an egg case inside of a bundle of leaves, which she then guarded. Here she is on June 25, 2011, making sure that her eggs stayed safe. That snow-white lump she is sitting on is her egg case.

We ultimately decided to let her and her egg case go, because if they hatched in the house the babies would be small enough to escape through the screen lid of the jar, and a house is not really a good environment for crab spiders.

So, given that the eggs probably hatched by the beginning of July, the babies would have had plenty of time to eat and grow to adulthood before winter. At which point they could spend the winter under the snow until spring. One thing I’m not sure about, though, is when they mate. It is possible that the males mate with the females in the fall and then die before winter, but it is equally possible that they hang around until spring and mate then. Doing it in the fall would make more sense, though, because getting through the winter is a pretty risky business, so one is really better off getting things taken care of before the snow flies.

4 Responses
  1. Katbird permalink
    July 14, 2012

    Love your spider pictures and lore- subnivean was new to me- thanks.

  2. July 14, 2012

    That pregnant crab spider is quite possibly the most expectant looking spider I have ever seen. We have a few spiders on and about our deck and every time I see them I avoid them. It is remarkable that you and your offspring do not do the same. My older son (on being forced to view this beastie) said weakly “Oh, she’s beautiful” and got away as soon as he could from the vicinity of the photographs.

    The bit in your post about “one is really better off getting things taken care of before the snow flies” seems rather a clinical way of referring to the delicate and possibly elegant matter of spider mating (perhaps she ate her mate for extra protein before the snow flew and integrated him into her bulk—see how romantic that is? Not to mention practical, as must be the female of the species intent on survival of the species).

    You will be happy to know that I will now be checking all playground equipment for spiders after reading your post.
    If I had one of these gigantic friendly creatures about a slide, I don’t think I’d want to shake hands with her or give her a hug.
    But she does remind me of Charlotte of pig fame.
    The only thing I’m disappointed about is that you did not take a more scientist stance and hatch the babies for us.
    Maybe next time?

  3. July 16, 2012

    Julie, if I ever suggested that my wife might want to integrate me into her bulk, I would most certainly end up killed. Maybe eaten, too, but only in an offhand, absent-minded way as she pondered what to do with the body.


  4. July 16, 2012


    I actually did keep a previous crab spider egg case until they hatched. The babies are just about as cute as you probably imagined.

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