City Creek Nature Notes – Salt Lake City

September 21, 2016

September 12th

Filed under: Dogs, Insects, People, Places, Stream, Water Skimmer — canopus56 @ 1:15 am

Kraken of the Water Striders

5:30 p.m. I’ve been following water striders (Gerris remigis) at a pool at picnic site 5 near mile 0.3. Today, about 25 water striders float on the pool and they are eliminated by low angle western sunlight. The water strider’s body are shaped like sculling boats. Their body rests primarily on four long stick legs. Under a microscope, the feet of these feet are covered with thousands of hydrophobic hairs. The low angle sunlight casts shadows on the bottom of the pond that shows the purpose of these hairs. Visually, their feet are sticks, but the shadows of the feet are surrounded by shadows of large elliptical pads. These elliptical shadows are diffraction patterns from the tensioned and depressed water tension surface underneath each foot. There is no similar depression underneath the body of the water strider, and this indicates that its body is suspended above the water surface like a catamaran sailboat. When startled, a quick flick of their legs immediately propels the water striders forward about 3 or 4 inches.

A family’s black Labrador runs into the pool and begins frolicking around. A half hour later, I return to the pool to check on fate of the water striders. They are still there, distributed around the outside edge of the pool. They are still waiting to see if this canine version of the Kraken will be released again.

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