Arilus cristatus, commonly known as the Wheel Bug, is one of the biggest, baddest, and neatest looking true bugs that can be frequently found here in Virginia. It is something out of a steampunk enthusiast’s best nightmare; it is relatively large, has a dark brown and black exoskeleton sometimes tinged with red, has long, gangly appendages, and moves with a jerky, robotic gait. Best of all, it has what appears to be a large, jagged gear protruding dramatically from its pronotum. It is one of the largest terrestrial true bugs in its native range which stretches coast to coast across southern North America, reaching up to 1.5 inches in length. The wheel bug is very rarely found on the ground, preferring to stay in trees, plants and bushes above the ground and in wooded areas where its prey is easier to find. Wheel bugs can fly, but do so clumsily and produce a very conspicuous buzzing sound as they fly.
The wheel bug is found in the order Hemiptera, the true bugs. True bugs are characterized by their having what appears to be “half wings”, where the front half of their forewing is hard and leathery and the rear half is thin and membranous. The hind wings are entirely membranous. This order is also characterized by piercing-sucking mouthparts, often used to suck the sap of plants or to predate upon other small animals. Wheel bugs are further classified into the family Ruduviidae, which includes all the other so called “assassin” bugs, a group of terrestrial predatory Hemiptera. This group is interesting as most hemiptera are phytophagous, meaning that they feed on plants, and most of the predatory groups are aquatic, not terrestrial.
Wheel bugs are fairly common in their native range across the United States and south into Mexico and Central America. They are commonly thought of as friendly garden guests due to their habit of feeding on annoying pests such as caterpillars and other plant-eating insects. Their pest-control abilities rival even that of the notorious ladybug beetle.
Wheel bugs are definitely generalists when it comes to their diet, which includes most other insects that they can get their beak-like rostrum into, even being shown to eat insects known to be unpalatable such as stink bugs, (another kind of hemipteran insect,) and insects that are much larger than themselves such as caterpillars and grasshoppers. It is generally an ambush predator, stabbing its prey with its rostrum and injecting a paralyzing toxin. Once the prey is subdued, the wheel bug sucks the fluids out using its straw-like mouthparts.
Like all hemipterans, wheel bugs have a hemimetabolous developmental cycle, going through several nymphal instars before finally molting into its adult form. The nymphs appear similar to the adult with small differences in anatomy and color. Both the adults and the nymphs are completely predacious, eating only other insects and invertebrates.
As beneficial as wheel bugs can be with regard to pest control, they pack a painful punch. When threatened or handled, it will deliver a painful bite with its rostrum, which has been likened to a bee sting. The pain is moderately worse than the pain felt from a bee sting, and is longer lasting. Both the adults and the tiny nymphs can bite and handling them should be avoided when possible.
Overall, wheel bugs are one of the biggest and definitely the baddest terrestrian hemipterans in North America, and are one of my favorite species by far.