Wheel Bug

Arilus cristatus

By Scott Creary

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wheel bugSometimes we can’t help but judge a bug by its appearance, especially when the bug is big, spiny, and straight out of a horror movie. Take the wheel bug, which derives its name from the “wheel”—more like a circular saw—atop the adult insect’s thorax. Yet the wheel bug, despite its freakish exterior, is among the best bugs around, preferring to eat plant pests over fellow predators.

Related to assassin bugs, wheel bugs belong to the insect family Reduviidae, whose name translates to “hangnail.” They look innocent overwintering as clusters of barrel-shaped eggs under tree branches, and they’re downright cute when they hatch. Nymphs are endearingly gangly, inquisitive-looking creatures with bright red abdomens and a taste for aphids and other slow-moving herbivores. By midsummer, however, their charm has faded, and they become 11⁄2-inch-long giants with appetites to match.

Watching adult wheel bugs take down large grubs or caterpillars, their preferred prey, reminds us that nature can be gorier than science fiction. After locating a tasty morsel with its long antennae, the wheel bug approaches with slow, jerky movements, its drab color and jagged silhouette hiding it in plain sight until it is only inches away. Then it strikes, using its front legs to embrace and neutralize the target while stabbing down with daggerlike mouthparts. Lacking chewing mandibles, it injects prey with digestive enzymes and paralyzing venom that eventually end the struggle. Even envenomed, the prey will thrash for several minutes as its insides dissolve into paste, which the wheel bug then ingests.

Sometimes a fearsome exterior matches a fearsome disposition. Wheel bugs aren’t aggressive toward humans, though, and they try to avoid confrontation by excreting a foul-smelling musk from glands near their anus while they escape. They bite only if handled, which, now that you’ve read this far, you’re unlikely to attempt. But don’t let their lack of looks and social graces portray them as anything but what they are: good bugs of the highest caliber.

Illustration by Jack Unruh
Originally published in Organic Gardening magazine, August/September 2014

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