Many people long to live near water for the pleasures of swimming, boating, fishing, or just to contemplate.

But, says Manu Prakash, a scientist at Stanford with broad interests, the surface of an alluring lake or pond, the boundary where water meets air , can be far less inviting for certain insects.

Water is about 100 times as viscous as air, and insects that live on its surface must somehow negotiate movement in both realms. Most seem to choose one or the other. Some, like long-legged water striders, maintain a small measure of distance from the water with a cushion of air that lets them skate on the surface. Others, like whirligig beetles, embrace the water and swim.

The lily pad beetle, which Dr. Prakash and his colleagues report on in The Journal of Experimental Biology, has evolved a unique solution to moving in water and air at the same time.