Here is a little quiz for you. Is this a good bug or bad bug?
It’s quite possible that you’ve never spotted this well-camouflaged bug called a Wheel Bug (Arilus cristatus) in your garden, one of the largest of the assassin bugs. It is fairly common in the eastern part of the country, a slow-moving member of the Hemiptera (half wings) order of True Bugs that includes stink bugs for one. The adult pictured is resting on the outside of our screened porch. A semicircular structure appearing much like a cogwheel on the thorax gives the Wheel Bug its nickname. No one knows the function of this armor-like wheel but it is thought to add protection from predators.
The answer is: this is a GOOD BUG for the garden but it comes with a caution.
All True Bugs have long straw-like mouthpieces that fold up beneath their body that most insect pests use to suck up juices in plants. Not so with the Wheel Bug or other assassin bugs in this order. Their mouthparts are used to suck the body juices of other insects. In the photo above, the Wheel Bug’s mouth is visible as a red tube beneath its long head. It waits in ambush to prey upon caterpillars, aphids, Japanese beetles, sawflies, stink bugs and other pests of the garden. It plunges the tube into an insect, injecting an enzyme and within seconds, the prey’s organs have been dissolved. It then sucks out all fluids much like a spider does. A little gruesome sounding, yes?
It is an especially beneficial bug in the garden and should be ignored when seen around the yard. Don’t run and fetch a pesticide. Maybe you’ll see one this fall as numbers of Wheel Bugs have increased, perhaps due to the proliferation of its pest cousin, the stink bug. Where there is an abundance of a pest, we are lucky that Mother Nature supplies us with an effective predator.
A word of caution: do not handle the Wheel Bug. It is a benign insect and seeks out quiet, hidden spots, however it is not particular where it will stick its sharp tube when it feels threatened. And due to the enzyme, it is a painful poke.
Ann Hohenberger, The Garden Club of Gloucester