The whirligigs are oval, flattened, and black with a metallic sheen. The larger species are about a half inch long and the smaller ones about a fourth inch. The second and third pairs of legs are short broad paddles. The front legs are used for holding the mosquitoes, midges, and other surface insects on which they prey. The eyes are one of their most interesting features.
Some kinds give off a protective milky fluid with an odor like apple seeds.
The Diving Beetles are adapted for a life in water but are awkward and almost helpless on land. The flattened hind legs are used together like oars. A number of different local species range from one-eighth inch to over an inch in length. They are oval in shape and colored shiny black or brownish. At rest they hang head down with the breathing pores on the tip of the abdomen above the water surface.