Two species of whirligig beetles, belonging to the Gyrinidae family and differentiated by their different sizes, swim about in erratic patterns on the surface of the water. These aquatic predators are thought to stay in nearly constant motion searching out prey items that may have fallen into the water, and as a means of defense from other predators. When alarmed, they will dive beneath the water's surface. The larger specimens featured here measure about 15 mm in length.