Vector Spotlight: “Wheel Bug”


Adult wheel bug preying upon a bottle fly. Photo by Nathan D. Burkett-Cadena, AVMS member

SCIENTIFIC NAME: Arilus cristatus
By Nathan D. Burkett-Cadena, AVMS member
The wheel bug is a large, predatory insect native to North America and is a common inhabitant of gardens and yards. Wheel bugs get their common name from the large, rounded extension of the exoskeleton that protrudes from the dorsal thorax. This wheel-shaped extension is said to resemble a cog or gear embedded in the insect’s back. The body of wheel bugs is usually gray with brownish legs and antennae. The head is long and slender and has a long “beak” which it uses to stab its prey (mostly caterpillars and other soft-bodied insects) and then drink the prey’s bodily fluids. The beak is folded under the head at rest, but is held downward or in front of the head during feeding.
Many people only learn about wheel bugs after being bitten by one. While humans are far too large to be preyed upon by a wheel bug, these bold insects are not above biting to defend themselves or out of  curiosity. People are usually bitten as they put on a glove or boot that has a wheel bug inside it. The bite is described as being quite painful, but is not considered dangerous to people unless a severe allergic reaction occurs. The bite from a nymph can be equally painful.
Adult wheel bugs are seen in summer and autumn. After mating and laying eggs the adults will die. The eggs will pass the winter and hatch the following spring. The nymphs (immature stages) will grow and mature through the spring and summer, completing the life cycle. Wheel bugs belong to the family Reduviidae, a group that also includes the “kissing bugs”, so called for their habit of biting people on the lips and face while they sleep. Kissing bugs, unlike wheel bugs, are parasitic and feed on the blood of mammals (including humans) and birds. Kissing bugs of tropical America (Mexico through Argentina) can transmit a parasite that causes a deadly disease: Chagas disease.

The parasite that causes Chagas disease is passed to humans through the feces of kissing bugs. As the bugs feed, they defecate. The parasite-laden feces is then accidentally scratched or rubbed into the bite site by the person being bitten. Thankfully, wheel bugs do not feed on blood and do not carry the parasite that causes Chagas disease. In fact, since wheel bugs prey upon plant-feeding insects such as caterpillars and Japanese beetles,
many people consider wheel bugs as beneficial and welcome them in their gardens. For some people, protecting their roses from Japanese beetles may be worth the bite of a wheel bug.

Wheel bug nymph close-up. Photo by and (c) 2007 Derek Ramsey, GFDL v.1.2 license applies