Last October my daughter phoned me at the office to report the presence of a “big, weird-looking bug” on our front porch—long-legged, slow moving, and unlike any she’d ever seen. She texted me a photo of the creature. I told her to get inside and lock the door.
The image captured a wheel bug, a little-known, seldom-seen beast that seems more an evil steampunk contraption than anything conjured by nature. Abdomen flared like the hull of a speedboat. Large fin shaped like a cogged wheel rising from its back. Skinny, dowel-like head. And tucked beneath that head, a mouth in the form of a powerful syringe, with which the bug injects its prey with an enzyme-busy squirt of saliva that liquefies meat—then sucks up the resulting goo like a milkshake.
By the already brutal standards of the insect world, it’s an apex predator, one of the most vicious, pitiless hunters around. Few of our crawling brethren—bees, wasps, even the redoubtable praying mantis—are good bets against it. And that meat it liquefies includes ours. The critter delivers a bite that one victim likened to a gunshot wound. Your own results may vary, but rest assured: it hurts.
Even so, until now you’ve probably not heard of the wheel bug, and odds are even better that you’ve not seen one. It populates woodlands, fields, and gardens from Massachusetts to New Mexico, but it’s a secretive animal, wary of man; one can spend a lifetime outdoors and miss it. So I was surprised and a little alarmed when, in the two weeks after my daughter snapped that portrait, five other wheel bugs turned up on our porch—specifically, on and around the front door—and a sixth juvenile materialized in our living room. I sought expert insight into what was going on.
The answer: in some parts of the country, the once-invisible wheel bug is stepping out.
And that’s worth your attention and respect.
First things first: Arilus cristatus won’t come looking for trouble. Though the largest of the accurately named “assassin bug” family—carnivores that lie in ambush until prey happens by—it bites humans strictly in self-defense.
The problem is that, despite its size and bizarre appearance—and it looks and moves like a robot assembled from wristwatch parts—its dusty brown-gray armor blends well with tree trunks, branches, and weathered lumber. You can all too easily touch it before you see it.
So it was for Richard “Bugman” Fagerlund of Las Cruces, New Mexico, a pest management consultant, columnist, and blogger who, while inspecting a property in Albuquerque, “put my hand in some bushes and kind of grabbed” a wheel bug. It stabbed the back of his hand.
Fagerlund, now 73, told me he’s been bitten nine times by poisonous snakes and stung by scorpions and centipedes, and that the wheel bug’s bite equaled the worst of them. In fact, he wrote in a 2002 column for the San Francisco Chronicle, his “first impression after the bite was the feeling of being shot.” He confided that he had experienced that brand of injury, too.
“It was painful,” he told me earlier this year. “It was about as equally as painful as a snakebite, but it didn’t last as long. I didn’t panic or anything. I knew what had bit me, and I knew they weren’t poisonous. I do recommend that people not try to pet them.”
It’s possible that Fagerlund’s experience was atypical—the bug “could have hit a nerve, or something,” he allowed. That would explain the somewhat less dramatic description of a bite offered by Michael J. Raupp, a professor of entomology and extension specialist at the University of Maryland, and a well-established authority on the wheel bug in particular.
Raupp, who’s known as “the Bug Guy” (not to be confused with Fagerlund’s “Bugman”), says that on the Doberman Scale, with 0 representing easy comfort and 10 the pain you’d experience in a full-on mauling by said attack dog, the wheel bug manages “less than a 5.”
Not even half as bad.
“Once they get to be adults, they can definitely give you a bite,” he told me, but he ranked its wallop below that packed in the notoriously painful sting of the bald-faced hornet. Any other comparisons were beyond his expertise: “I have to be honest with you,” he said. “I’ve never been bitten by a rattlesnake, and I’ve never suffered a gunshot wound.”
All of this would be academic had the wheel bug remained in hiding. But over the past few years, entomologists in the Mid-Atlantic have received anecdotal reports of the insect’s growing prevalence. Raupp attests to it, as well: Until recently, he and his students rarely encountered wheel bugs on their forays into the woods around UM's campus, even when they were hunting specifically for them; the ever-reclusive insects "rarely showed themselves." Nowadays, however, "it's no surprise to encounter a wheel bug," he said.
The difference, he believes, is a jump in the predator’s food supply, especially an entrée called the brown marmorated stink bug. Native to Asia, this distant cousin of the wheel bug apparently snuck into the United States in shipboard freight, and first drew the notice of Pennsylvania scientists in the late nineties. It has since spread to more than 40 states, feasting on fruits, vegetables, and ornamentals.
Nowhere is the invader a bigger pest than in the states of the coastal Mid-Atlantic, where it has proved a scourge to farmers and homeowners alike: the stink bugs, which use their probosces to suck up plant innards rather than meat, wreak havoc on croplands and, with the cooler evenings of autumn, invade homes, offices, classrooms and shops in search of warmth. Where I live in Virginia’s Blue Ridge Mountains, they slip around screens and under doors and seemingly through walls, becoming ubiquitous inside and out by early October.
And right behind them, Raupp believes, are wheel bugs, which happen to love the taste of their foreign kin—an assertion borne out by Raupp’s own experiments in which he and his students have baited trees with stink bugs and watched as wheel bugs turned up for a feed.
That and other experiments have led Raupp to theorize that we’re witnessing what he describes as a “numerical response, where you see the increase of a predator population in response to an increase in its available prey.” In other words, the wheel bug has not simply shifted its distribution to take advantage of a new food source—an ungainly flyer, it’s not mobile enough for that. Rather, it appears that its numbers have swelled to fill a natural void.
Which means, Raupp said, that as long as we’re stuck with the stink bug, we’re likely to see more of this formidable creature both in the woods and on the porch. “Because the stink bug can be a very urban and suburban pest—because people have vegetable gardens and there are overwinter shelters,” he said, “it makes sense that the wheel bug would appear with greater frequency in and around our homes.”
That might seem a bad thing, especially after you take in a nightmarish installment of Raupp’s “Bug of the Week” online video series starring a wheel bug wielding its wicked beak on a hapless caterpillar—a clip Raupp himself calls “awesome and gruesome at the same time.”
But, no—both he and Fagerlund say that the bug’s voracious habits make it an ally in the garden and orchard. It’s considered a beneficial insect. Scary though it is, you should let it be.
Bottom line: give the wheel bug plenty of room. And be advised that it acquires its telltale wheel only as an adult, after five molts. As a smaller nymph, it passes through some stages, or "instars," with bright orange-red markings, which you should recognize as a warning if you see it trying to slip into home or tent. It packs a bite, even as a tyke. Watch where you put your hands.