The Large Whirligig Beetle is 9 mm to 15 mm long. It often has a bronzy shine to its black body. Adults live through the winter on plants or in the mud. The Small Whirligig Beetle is 3 mm to 7 mm long. It is shiny black above and black or yellowish brown on the sides and below.
Adults live through the winter in leaf litter near ponds.
There is only one generation of Small Whirligig Beetles each year. Whirligig Beetles are useful in keeping the water's surface clean and keeping the numbers of smaller insects down. They are food for many larger insects and animals.