June 27th, 2007
moms at work
For the past week or so, I’ve been meaning to write a couple of posts about spiders at the farm, but somehow it didn’t happen. Today is the day.
Since early June, I’ve been encountering female spiders guarding eggs cases. These are just a few of the spiders that I’ve seen (click on all photos for larger views).
I wish I could tell you the species of each of these spiders, but I’m just certain of a couple. The one in the top photo is a Xysticus crab spider found on the underside of a milkweed leaf. Unfortunately, I’m not sure just which species she might be. As some of you may remember, last year, I photographed a similar spider guarding an egg case. It’s possible that this one is the same species. Last year, I guessed that the spider on the case was a Xysticus emerteroni, and after reading the chapter on that species in Douglass Morse’s Predator Upon A Flower, I think that might be the correct ID. He writes that “Of these Xysticus species, only X. emertoni regularly occupies flowers frequented by Misumena.” He is writing about study plots in Maine, but I believe the species we would see here in Ontario would be much the same. Anyhow, last year’s spider was certainly cohabiting in a place where I would espect to see Misumena — the rugosa rose bushes that grow alongside my house. However, the above spider does seem a little different — to my eye, she looked considerably smaller (Xysticus emertoni is supposed to be quite large), and she had very distinct white and dark brown markings toward the rear of her carapace (see above image). I’ll continue to work on an ID for her.
The next spider was a very lovely crab spider which was also found guarding an egg case on the underside of a milkweed leaf. I can’t say I’ve ever seen one quite like her before. She has pinkish markings, with a couple of distinct darker markings along the sides of the abdomen. As in the case of the above Xysticus, she was quite determined to stay put and guard her egg case. I’ll be working on her ID as well.
The above spider was a new one for me — and I believe she might be a Theridion impressum — which is one of the Cobweb Weaver family (Theridiidae). She was very tiny but colourful. I found her among the smaller, central leaves of a milkweed plant. She stayed close to her spherical egg case, clinging to it with her hind pairs of legs.
The last spider was also found on the tip of a milkweed leaf a couple of days ago (please note how *IMPORTANT* milkweed is to all of these species of spiders!!). She’s an Oblong Running Crab Spider (Tibellus oblongus). I find these around the farm quite regularly throughout summer. They are extremely shy spiders, but the females will hang tough and stick with their egg cases even though they may feel threatened. I think this one might have just completed the webbing on the leaf, but not yet deposited eggs as the webbing looks thin and the spider’s abdomen looks larger than it probably would after ovipositing. What I find of particular interest is that I’ve photographed this species with egg cases right around this date in previous years. On June 30, 2004, I photographed this spider reaching out to shelter her egg case (note her slim abdomen). On July 6, 2006, I shot a couple of photos of one of these spiders clinging to a leaf to guard her nest. And on July 1, 2006, I photographed this gravid-looking female. It would be interesting to know if this species has a peak time for laying eggs. If so, the last few days of June and first few of July may be *it* for this region.
If you’re interested in egg-guarding behaviour of another species of spider, be sure to check out Wayne’s recent posts and photos of Pisaurina mira, one of what is known as the Nursery Web spiders, at Niches. Here is the first part, and here is the follow-up to the story.
NOTICE!! I’ve just this moment volunteered to host the June edition of Circus of the Spineless – the invertebrate blog carnival. I realize this is very short notice, but if you have an invertebrate post that you would like to have included, please forward links to me by the evening of June 30th. I hope to get the carnival posted on either July 1st or 2nd — so get busy sending in your links now!
Tags: Xysticus emertoni, Thomisidae, Theridion impressum, Theridiidae, Tibellus oblongus, Philodromidae