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Bug of the Week: Crab Spider Camouflage

We haven't had a spider lately for Bug of the Week.

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How about a crab spider waiting for a meal?

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Crab spiders are known for using camouflage. In fact, adult female crab spiders have been shown to be able to change color to match the color of the flower they are sitting on.

So, why isn't this crab spider purple, or sitting on a white or yellow flower? Isn't being white going to wreck its chances of catching prey?

As this article from Wired points out, color matching does not necessarily help the spider to catch prey. One reason may be because bees can see ultraviolet light. Some spiders may reflect ultraviolet light, so even though the crab spiders look like they are matching the flower to our eyes, to the bees they stand out against their background.

This video suggests that standing out against the background may attract prey rather than dissuade it (it also shows crab spiders hunting).

Why would bees be attracted? The video does not explain this, but flowers have patches of ultraviolet that serve as beacons to the nectar. These patches are contrasting, and are thought to act like "signposts" directing the bees to the good stuff. Crab spiders may be trying to change the signs to direct flies and bees to themselves instead.

Now we are back to the question, why do female crab spiders change colors to match the flowers as we see them? Do you have any ideas?

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