Far out on the ocean, when the vessel is laboriously making her way through the troughs and over the crests of the great waves, little birds, black save for a patch of white on the lower back, are a common sight, flying with quick irregular wing-beats, close to the surface of the troubled waters. When they spy some edible bit floating beneath them, down they drop until their tiny webbed feet just rest upon the water. Then, snatching up the titbit, half-flying, they patter along the surface of the water, just missing being engulfed by each oncoming wave. Thus they have come to be named petrels--little Peters--because they seem to walk upon the water. Without aid from the wings, however, they would soon be immersed, so the walking is only an illusion. But in our smallest ponds and brooks we may see this miracle taking place almost daily, the feat being accomplished by a very interesting little assemblage of insects, commonly called water skaters or striders. Let us place our eyes as near as possible to the surface of the water and watch the little creatures darting here and there. We see that they progress securely on the top of the water, resting upon it as if it were a sheet of ice. Their feet are so adapted that the water only dimples beneath their slight weight, the extent of the depression not being visible to the eye, but clearly outlined in the shadows upon the bottom. In an eddy of air a tiny fly is caught and whirled upon the water, where it struggles vigorously, striving to lift its wings clear of the surface. In an instant the water strider--pirate of the pond that he is--reaches forward his crooked fore legs, and here endeth the career of the unfortunate fly. In the air, in the earth, and below the surface of the water are hundreds of living creatures, but the water striders and their near relatives are unique. No other group shares their power of actually walking, or rather pushing themselves, upon the surface of the water. They have a little piece of the world all to themselves. Yet, although three fifths of the earth's surface consists of water, this group of insects is a small one. A very few, however, are found out upon the ocean, where the tiny creatures row themselves cheerfully along. It is thought that they attach their eggs to the floating saragassum seaweed. If only we knew the whole life of one of these ocean water striders and all the strange sights it must see, a fairy story indeed would be unfolded to us.