Thursday, October 13, 2011

Spied a spider?

I recently had the pleasure of spending the night on an island in Indian Lake in the Adirondacks. While foraging for firewood on the northeast end of our island, my son and I found a large fishing spider sitting on a rock. She was carrying an egg mass under her body and sat still for some photographs.

Somewhere I had read that fishing spiders ran across the water surface to prey upon invertebrates trapped in the surface film. I assumed that with a 6.7 cm leg span, this must be the largest spider in our region. But with a little digging, I learned that at least one local wolf spider species is larger.

Far more interestingly, the fishing spider does not limit its menu to invertebrate prey. While they typically consume invertebrates, they are occasionally true to their name and can actually catch fish more than four times their body weight (Bleckmann and Lotz 1987). The spiders use ripples on the water surface to detect prey, including water striders. They move rapidly across the water surface by rapidly retracting their legs and then gliding before again making water contact. All of this happens so rapidly that Gorb and Barth (1994) who described the behavior could see it only using high-speed photography.

View Indian Lake in a larger map

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