The wheel bug (Arilus cristatus) is a very common beneficial insect found in vegetable gardens and in many home landscapes across the United States. This distinctive insect gets its common name from a large, prominent, cogwheel-like crest or projection on its back (or thorax), making identification of the adults very simple. Anyone who has ever seen an adult wheel bug will never forget it. It is that unique.
Wheel Bug I.D.
The wheel bug is the largest type of assassin bug (family Reduviidae) found in North America. Adult wheel bugs have a gray to dark-brown armored body and can reach between 1 and 1¼ inch long. It has long legs, lengthy antennae, and a narrow head with prominent eyes. It uses a large sucking/piercing mouthpart at the front of its head that to inject toxins into its prey, both paralyzing the captive insect and liquefying its internal organs.
A Garden Friend
This aptitude for eating pest insects is exactly why you should encourage the wheel bug in your garden. Adult wheel bugs like to feed on a range of pest insects, from medium-sized stink bugs and beetles to much larger grasshoppers and caterpillars, which can be bigger than the wheel bug itself. Immature wheel-bug nymphs are also voracious predators that eat many smaller pests, such as aphids.
When Wheel Bugs Bite
Wheel bugs are quite timid and wary, so even though they are quite common, there’s a chance you’ve never actually spotted one. If approached they will often move to back side of leaves to stay out of sight. While gardeners should take time to observe these shy insects, they should never attempt to directly handle the wheel bug with their bare hands. If threatened, the wheel bug will pierce your skin with its mouthpart, and the bite is a particularly painful. While a wheel-bug bite doesn’t typically require medical care unless an allergic reaction occurs, it will often cause some localized swelling and acute pain that many consider to be much worse than a bee sting. Once bitten, you’ll learn to leave the wheel bug alone and let these helpful creatures hunt for their prey.