This aquatic insect (also called electric light bug) is up to two and a half inches long, dark brown and leathery. The hind legs, which are used for swimming, are flattened and have a hairy fringe. This insect has a beak for injecting anesthetic saliva into its prey and sucking out the contents while holding the prey with its forelegs. There are two breathing tubes at the rear end so that the insect can obtain air by raising its abdomen to the water surface. Eggs are attached in rows of about a hundred to plants above water.

Toe-biters eat insects, tadpoles, small fish and salamanders. As implied by their name, they can also give humans a hearty nip. Toe-biters also fly, and are attracted to light, hence their alternate name.

Lethocerus americanus (toe-biter) can be distinguished from Benacus griseus (eastern toe-biter) by a groove in each front femur into which the tibia fits when the leg is folded. Its range extends west of the Mississippi River.