Our insect of the week for September 28, 2026 is the wheel bug, Arilus cristatus. [HEMIPTERA: Reduviidae]. This species was described by Linnaeus in 1763. This is one of the largest terrestrial Hemiptera in North America (and is often encountered in central Illinois).

Adults are easily recognized by the wheel shaped cog (actually pronotal ridge). Nymphs lack this distinct structure. Adult males are smaller than females. I have often observed this species on tree trunks. They are also encountered on goldenrods and sunflowers. Adults and nymphs are predators. They use their beak to inject enzymes into the prey. This paralyzes the prey and dissolves the internal tissues. This fluid is then sucked up through the same beak. Common prey are insects (including caterpillars and beetles).

This species can produce an audible sound by rubbing its proboscis against a groove under its thorax. The purpose of this sound is not known.

Mating occurs in autumn with eggs overwintering in central Illinois. There are 5 nymphal stages before adulthood. Eggs may be attacked by parasitic wasps.

The specimen in this stacked photograph was collected in Tazewell County by Mark DuBois during the month of July.