Wednesday, August 12, 2009

Misumena vatia, the flower crab spider

These pictures are all of a single individual but taken over several days. The prey changes.

I had started out looking for flies to photograph, and almost immediately spotted one, lying on its back on some tall cilantro flowers, and wondered why:

I'd snapped my first picture before I realized:

Although crab spiders in drab browns and greys are found all over the world, Misumena vatia, the flower crab spider, lives only in North America, usually on flowers—and you can see why. Apparently it has the power to change colour over several days from white to yellow or vice versa to match the flower it's on. This one was about 6mm from fangs to anus, and is female—the males are much smaller and less stupendous.

She waits patiently on her flower in her "crab" posture:

When prey arrives, she moves quickly, paralyzing it (or killing it; none of the prey insects I saw moved at all). She holds the immobilized (or dead) prey in her pedipalps while she works on it with fangs to loosen up the liquid contents, which she drinks:

I watched this for awhile, then went away and did something else. When I returned, she had dropped or finished with her fly, but I took a few more of her lovely coloured eyes and gleaming fangs:

This is a tiny creature, but in my camera's viewer at high magnification these things look like monsters. Suddenly the fangs began to open:

They opened very wide indeed, and the spider stalked forward. The ant which had crawled carelessly up there scrambled back into free fall and got away. I was scrambling back too—that thing was scary!

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