Row, row row your bug...

As kids my friends and I called them “water spiders.” We were wrong linguistically and taxonomically. They were actually water striders, and they not spiders but insects -- quite amazing insects at that. For one thing, like the whirligig beetles I posted about earlier, they were (and are) nigh impossible to catch – they move on the water’s surface with incredible agility.

Most interesting, though, is how they move. They have six legs like other insects, but they use them differently. The front pair catch prey. The middle (much longer) pair act like oars, for propulsion. The hind pair provide steering (like a rudder).

But how do they stay afloat as they do, legs in contact with the water, body elevated like that of a four-wheeled crop sprayer going over a field? It has to do with my previous post about the surface tension of water. Surface tension keeps the legs from sinking below the surface. One thing you notice if you watch striders in shallow water are the four roundish shadows the front and hind “feet” cast on the bottom. Those are from the dimples the feet make in the “skin” of surface tension. The surface tension bends, but doesn't break, under the striders' weight.

Of course, closer examination has shown that striders’ high flotation is not all about surface tension. The legs are covered with microscopic hairs that trap tiny air bubbles, which provide buoyancy. Scientists say studying and replicating these hairs could lead to development of better water-resistant fabrics.

As described on the website Livescience (www.livescience.com): “Microscopic images of the insect’s legs revealed that the otherwise invisible hairs, called microsetae, are oriented in one direction and involve several layers. The needle-shaped microsetae are each less than 3 micrometers in diameter (a human hair is 80-100 micrometers wide).

“The microsetae are scored with grooves measured in nanometers, even smaller units that represent billionths of a meter. Air gets trapped in the spaces among the microsetae and nanogrooves to form an air cushion, which prevents the legs from getting wet.”

The science is interesting, but mainly it’s treat just to watch these creatures and, if your eyes are quick enough, capture the swift, sure rowing strokes by which they move. You can find water striders on almost any body of water. Look for them on your lake.