The Wheel bug (Arilus cristatus), in the family Reuviidae, is one of the largest terrestrial true bugs in North America, being up to 1 1/2 inches, or 38 mm, in length; it is the only member of its genus. A characteristic identifying structure is the wheel-shaped pronotal armour. They are predators upon soft-bodied insects such as caterpillars, japanese beetles, etc., which they pierce with their beak and inject salivary fluids that dissolve soft tissue. Because most of their prey are pests, wheel bugs are considered beneficial insects, although they can inflict a painful bite if handled carelessly.