When the delegation from our new Mexican sister city Patzcuaro arrived, one member happened to be hosted by a family with what I am sure is thought to be an American icon, the backyard swimming pool. He reported being a little cautious about going in it because his hosts had mentioned a problem with insects that swam in the pool. They were biters, he said, and he was very anxious to know what they were.

He reminded me of my own experience with such an insect, the "backswimmer", and the constant chore of trying to net them out of the family pool only to have them fly several yards and dive right back in. Research by Matt Evans, our summer intern, turned up some interesting information about them, and as usual even more wonder at the natural world we inhabit.

The "backswimmer" is really of a host of backswimmers. Its insect family, Notonectidae, has hundreds of species, and ten occur here. It is a true bug, which is one order of the insects. The Common Backswimmer, Notonecta undulata, is found throughout North America, and may be the most likely species to show up at your side in the pool.

As its name implies, a backswimmer spends much of its time on its back under the water, bouncing around a still pond or a slow, shallow creek using its long hind legs to row. As it surfaces it has long hairs and pockets along its abdominal area that are arranged to hold a silvery envelope of air that it uses to breath underwater. It can stay submerged for up to six hours if it is inactive. Very unusual for aquatic insects, it can adjust its buoyancy, so it can pause at any depth.

Like a fish it is camouflaged well, though its coloring is reversed from the fish. Its top or "dorsal" side is light and its bottom or "ventral" side is dark. When it is on its back then, it appears dark when viewed from above, so it blends in well with the bottom. It is similarly light when viewed from below. Its diet is typically insects that get caught in the film on the water's surface, though it also eats tadpoles and other small aquatic animals. Though shy, it will augment this diet with a bite to a human hand or leg that traps or threatens it, earning it another nickname of water bee or water wasp.

After their underwater routine, it is fascinating to see backswimmers exhibit yet another ability. They can rise to the surface, turn over and stand up, perfectly dry, ride on the surface tension of the water, and at some moment fly rapidly away. This strategy enables them to cover a good distance in search of habitat and food. It also enables them to fly right back into the swimming pool once you have carefully removed them.

We actually had trouble identifying research done on these insects and their strange relationship to swimming pools. Apparently pool chemicals don't harm them at normal levels because they breathe and envelope themselves with air from the surface. They seem hardy enough to survive most abuse that pool owners direct at them, and come right back for more, and at least one pool company claimed that it isn't worth the effort to try to get rid of them.

Though adults can be found here at any time in the water, summer is their peak season. Along with the marvels of summer, backswimmers are just one more reason to be in awe of the strange twists of nature that we ourselves are a part of.