Wheel bugs are big, armored, and dangerous.
When disturbed, these slow-moving giants can inflict a painful bite that starts out feeling like a bee sting, followed by days of numbness. But that’s okay because wheel bugs more than make up for that possibility by the number of garden pests they hunt down and devour.
Native to North America, wheel bugs (Arilus cristatus) are a type of assassin bug. At up to 1½” in length, they are one of our largest true bugs. True bugs (Hemiptera) have piercing and sucking mouthparts and they go through an incomplete metamorphosis. Unlike aphids and leafhoppers, which feed on the sap of our plants, wheel bugs pierce, liquify, and consume other insects.
Wheel bug identification
Wheel bugs are easy to identify but they are shy. Besides being large, they don’t move very quickly. This makes it easy to take the time to see details. They do fly, however, so don’t startle them. The first thing you will notice about a wheel bug is its dorsal crest. Dorsal crests are raised ridges along the back. In the case of wheel bugs, that crest looks like part of a cog or spoked wheel. And when they fly, wheel bugs make a buzzing noise and are easily mistaken for grasshoppers
Wheel bug adults are usually gray to brown. They may look nearly black right after molting. And males are slightly smaller than females. Wheel bug nymphs do not have the cog-shaped crest. Instead, they look more like spiders with red or orange abdomens.
Wheel bug lifecycle
Wheel bugs mate in autumn. Females lay clusters of 40-200 brown, cylindrical eggs on bushes, trees, and other surfaces. After laying eggs, the female eventually dies. Eggs hatch in spring and the nymphs go through five molts before reaching adulthood.
Wheel bug diet
Wheel bugs feed on a variety of garden pests, including cabbageworms, caterpillars, Japanese beetles, Mexican bean beetles, and tent caterpillars. Wheel bugs are usually active during the day but may hunt at night in areas with lights. When they hunt, they capture their prey with their front legs and inject it with paralyzing and dissolving enzymes.
While wheel bugs also prey on honey bees and ladybugs, they are considered highly beneficial. Their presence indicates a healthy environment with abundant biodiversity. To encourage wheel bugs in your landscape, avoid using broad-spectrum pesticides and insecticides, and add some goldenrod and sunflowers.
You can grow a surprising amount of food in your own yard. Ask me how!