June 30th, 2007
a little special
Earlier this week, I posted several photos of female spiders guarding egg cases. Yesterday, I found yet another to add to my records. This spider is a Misumena vatia, a member of the Thomisidae Family (crab spiders). She’s a little special for a couple of reasons. It happens that she’s the first of this species that I’ve seen making an egg case here at the farm in 2007. I’ll see many more this season, but it’s nice to record a “first” date for this species. The other thing that is a bit special has to do with her markings (click on image for a larger view). Most females of this species have a pair of lateral pink to red bands on the abdomen. The rest of the abdomen is either white or yellow depending on whether the spider is in a white or yellow phase (these spiders gradually change their colour as they move between yellow and white flowers). Here is a photo of a typically marked spider. The spider that I found yesterday has an extra set of bright pink markings on the top of her abdomen. In checking through my images of this species, it looks like the only other similarly marked spider was photographed here at the farm on July 7, 2003.
Yesterday’s spider had made a chamber for her eggs within the folded central leaf of a Common Milkweed plant (see below). After folding, the leaf is carefully sealed with silk. Some spiders create such chambers and then hide within. However, I’ve found that most Misumena vatia remain on the exterior, perching upon it, or clutching their long raptorial legs around the chamber if they perceive any kind of threat. In a post that I wrote about these spiders back in January, I mentioned that I have observed these spiders staying with their eggs for weeks until they become desiccated from lack of food. I suspect that some must eventually expire while maintaining their vigil.
Misumena vatia is one of the nine species of spiders being tracked on the new Spider WebWatch citizen science site. If you happen to see one of these spiders, or any of the other eight spiders that are part of this program, please do enter a record, or better still, upload a photo to accompany your data. The site is easy to use and it just takes a moment to register so that you can begin entering data. It’s great to see some records now appearing in the database, especially for this species.
Reminder: Tonight is the deadline for invertebrate posts to be included in the upcoming edition of Circus of the Spineless. If you have a post that you’d like included, please email me.
Tags: Misumena vatia, Flower Crab Spider