Their long, flexible legs are covered with micro-hairs that trap a layer of air so the bug can’t get wet and sink. If you watch a water strider you’ll see that they spread legs so their weight—as light as it is – is evenly distributed. Surface water tension supports this elegant design.
Water striders are insects, of the order Hemiptera – true bugs – with three pairs of legs.
Looking at this photo, you can see that the tips of the strider’s thin legs create little valleys. It rows the middle set of its three pairs of legs like oars, causing the water behind those legs to propel it forward as the surface of the valley rebounds like a trampoline.
The short front legs are used to catch prey. They eat any kind of aquatic insect or larvae they can find (mosquitoes and dragonflies are typical prey). Water striders are fearsome predators on any aquatic insects or larvae and other insects that fall into the water.
If a predator, like a bird, comes after a water strider it can jump nearly vertically off the water to escape. Jumping from the water surface is extremely rare and scientists wanting to understand how the water striders do it have created a water strider-like robot.
They are also extremely fast: Water striders can reach “speeds of a hundred body lengths per second. To match them, a 6-foot-tall person would have to swim at over 400 miles an hour.”
Watch this video about water striders