The Wheel Bug is a species of Assassin Bug found in North America with a painful bite. Scientifically known as Arilus cristatus, they have a semicircle spiny ridge behind their head which resembles a cogwheel or gear protruding up from their back. One of the largest Assassin Bugs, they grow upwards of 1.5″ (~38mm) by late summer and feed on garden pests.
It wasn’t until I was well into my native plant journey that I first took note of this strange looking insect. It wasn’t even in my garden, but had managed to crawl atop of a bench near my lawn. Since then I frequently encounter (or rather notice) adult Wheel Bugs throughout my yard & garden.
The Wheel Bug’s strange alien-like appearance and large size are hopefully a sufficient warning not to touch them. Although generally docile and slow moving, you should not handle Wheel Bugs as they have a very painful bite, likely similar to the sting of a Saddleback Caterpillar. Fortunately the Wheel Bug primarily lives in our flower beds and gardens where it feeds on insects and garden pests.
In this article:
- Bite information about the Wheel Bug
- What is an Wheel Bug
- Identification of Wheel Bugs
- Native Range of Wheel Bugs
- What do Wheel Bugs eat
- What attracts Wheel Bugs
- Should you control Wheel Bugs?
Bite information about the Wheel Bug
Are Wheel Bugs harmful to humans
In general Wheel Bugs are not aggressive nor harmful to humans, preferring to stay hidden among plants where they stealthily stalk their prey. If you accidentally touch a Wheel Bug, it may sting you with it’s beak / proboscis. 
The venom from a Wheel Bug is painful, but it will not kill you. That being said, there is always a risk of anaphylactic shock, so one should be aware.
Common Wheel Bug bite symptoms
The overall severity of the bite is highly dependent on individual sensitivity. The main symptom of being stung by a Wheel Bug is pain. The bite/sting of a Wheel Bug has noted to being similar to a wasp sting and lasting 3-6 hours.  Numbness may follow the pain lasting for some time, and the bite location may feel hot. Lesions may persist at the site of the bit for six to nine months until dissipating. 
The YouTuber Jack’s World Of Wildlife willfully stung himself and stated that the sting was “similar to a paper wasp”. If you want to see Jack get stung by a wheel bug, you can view it below (as well as understand why women live longer than men).
Treatment of Wheel Bug Bites
Washing of the wound is with soap and water is recommended. One can also apply an icepack to help relieve pain or any swelling.
What is the Wheel Bug
Considered a beneficial insect in the garden, the Wheel Bug is a predator of other soft-bodied insects and arachnids that inhabit leaflitter, trees, and plants. They have been known to eat caterpillars, tomato hornworms, cucumber beetles, squash bugs, etc. 
Slow moving and living for only one season, it is unlikely you will notice any until late Summer or Fall when they make their final molt, when they will be about 1.5″ long.
Wheel Bug Identification
Adult Wheel Bugs are approximately 1-1/2″ long, gray in color, and have tiny hairs on their bodies. Their antennae may be red. It will have a large cogwheel protruding from their back, that appears to almost be lifting a sheet of armor. It is believed that this feature dissuades predators from attacking. The six legs are kind of strange looking, as the ‘upper thigh’ portion of the leg is quite large and robust, while the lower portion is very thin. 
The Wheel Bug has a narrow dark grey head with two large eyes. Adult Wheel Bugs also have wings and are capable of flying, even if they don’t do so very well. They seem to prefer to slowly walk/creep stealthily up the stalks of plants, on leaves, or the sides of buildings stalking their prey.
At the bottom of it’s head you will find it’s proboscis / beak. The Wheel Bug uses this to stab it’s prey. It then injects venom into the body of the insect it is attacking. The venom paralyzes it’s prey very quickly, then dissolves the innards, which the Wheel Bug then drinks via the same beak / proboscis it used to kill it’s victim. Pretty slick and horrifying eh?
Wheel Bugs lifecycle begins as eggs, then as small nymphs, and finally to adults in Summer or Fall.
A female Wheel Bug will lay eggs in Fall on a hard surface. These eggs are spherical and will overwinter until Spring. When temperatures begin to warm up, the eggs will hatch and small black and red nymphs will emerge.
Wheel Bugs will have five nymph stages. The time between each molting varies between 14 to 30 days, totaling roughly 100 days to reach adulthood.  Adults will then live on for several months until Winter. Roughly 10% of the nymphs survive to adulthood. 
Native Range of the Wheel Bug
The Wheel Bug inhabits much of North America East of the Rocky Mountains. From as far North as Vermont and Maine, South to Florida & New Mexico, and up to Colorado and South Dakota. Beyond the US and Southern Ontario, the Wheel Bug is also native to Mexico and Guatemala. 
What attracts Wheel Bugs to your yard or home
What do Wheel Bugs eat?
Wheel Bugs are a generalist predator of soft-bodied insects. [gen book] [eating bugs] They have been reported to frequently eat caterpillars (even Monarchs), tomato horn worms, spiders, and even bees. And while some say they are primarily ambush predators, I have witnessed them stalking and killing a Bumblebee on Blue Lobelia in one of my flower gardens. 
[Watch] How a Wheel Bug hunts insects
In the below video you can see a Wheel Bug stalk and kill a Bumblebee. I apologize for the quality of the video, but I was trying to capture footage of a hummingbird so I just set the camera up and let it roll. It was only when I was reviewing the footage I noticed the Bumblebee murder. I edited the video and zoomed in on the action so you could better see the hunt, so the footage is a bit grainy.
Should you get rid of Wheel Bugs?
Wheel bugs are not aggressive, and are generally docile. They move very slowly, and aren’t going to jump at you. Since they help control garden insects, you should not try to control or eliminate them. If you happen to see one near a door, window, or patio, simply put on some leather gloves and gently relocate it to the garden.
Nonetheless, if you are clearing brush in late Summer or performing an early Fall Cleanup you may inadvertently contact one. Although it would be rare, it would still hurt. But some risks cannot be avoided when you have a garden, as you are just as likely to contact a pus or Saddleback Caterpillar.
 – Biery, Terry L. Venomous Arthropod Handbook: Envenomization Symptoms/treatment, Identification, Biology and Control. No. 43. Disease Surveillance Branch, Epidemiology Division, USAF School of Aerospace Medicine, Aerospace Medical Division (AFSC), 1977. Accessed 10DEC2022
 – Mead, Frank Waldreth. Wheel Bug, Arilus cristatus (Linnaeus)(Insecta: Hemiptera: Reduviidae). University of Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, EDIS, 1999.
 – Hall, Maurice C. “Lesions due to the bite of the wheel-bug, Arilus cristatus (Hemiptera; Reduviidae).” Archives of Internal Medicine 33.4 (1924): 513-515.
 – Sams, Travis SamsTravis. “This Assassin Bug In Indiana Has A Bite That Can Take Months To Heal”. 99.5 WKDQ. Retrieved 2022-03-31.
 – Clawson, John R. The Crested Assassin. Audubon Magazine September-October 1958: Vol 60 Iss 5. pp221.
 – Kneidel, Sally Stenhouse. Stinkbugs, stick insects, and stag beetles : and 18 more of the strangest insects on Earth.
 – Giraldo-Jaramillo, Marisol, Dimitri Forero, and Pablo Benavides. “The Wheel Bug Arilus gallus (Hemiptera: Reduviidae): Life History and Description of Immature Stages.” Proceedings of the Entomological Society of Washington 123.3 (2021): 551-563.
 – Cator, Elizabeth. “The Last Days Of An Assassin”. American Museum of Natural History; Natural History Magazine, Inc, New York, N.Y. : American Museum of Natural History, 2004, v.110, no.9, Nov 2004, pp 94.
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