Wheel Bug

Arilus cristatus — the wheel bug — is the largest assassin bug (family Reduviidae) in North America and one of the most morphologically distinctive insects on the continent. Adults measure 28-38 mm. The defining feature is a half-circular cog-toothed crest mounted on top of the thorax that resembles half a gear-wheel; the function of this structure is not definitively known, though hypotheses include defensive armor, species recognition, or visual disruption against bird predators. Like other Reduviidae, the wheel bug is a stalking ambush predator that uses a long curved rostrum to stab prey, inject paralytic and digestive enzymes, and drink the liquefied internal tissue. Wheel bugs are voracious predators of caterpillars, beetles, stink bugs, and other large garden insects — making them important biocontrol agents in vegetable gardens and orchards. The bite to humans is rare (the bug is shy and not aggressive) but severe: pain is reported as among the most intense of any North American insect bite, comparable to a copperhead snake bite, with slow healing over 1-3 weeks. The species is found across the eastern and central US, from southern New York and southern Wisconsin south to Florida and Texas. The eggs are bottle-shaped and laid in tight hexagonal clusters that overwinter on bark and emerge as 50-150 nymphs in spring.