The wheel bug (Arilus cristatus) is a species of large assassin bug in the family Reduviidae (literally, "hangnail"). It is one of the largest terrestrial true bugs in North America, reaching up to 1.5 inches (38 mm) in length in its adult stage. It is sexually dimorphic, in that males are somewhat smaller than the females. A characteristic structure is the wheel-shaped pronotal armor. Wheel bugs prey on caterpillars and beetles, such as Japanese beetles, the cabbage worm, orange dogs, tent caterpillars, and the Mexican bean beetle, all of which they pierce with their beak to inject salivary fluids that dissolve soft tissue.