By Randy Deming
Last fall I spotted a baby dinosaur under a picnic table. I did not tell anyone because I was afraid I would repeat a mistake I made a few years ago before I learned to use the iNaturalist app. I once spent the good part of an afternoon watching cute little baby hummingbirds. I took some pictures and showed them to some friends. One of them laughed and said, “They are not birds. Not even closely related. They are sphinx moths!”
Before I repeated another mistake, I posted the picture of my baby dinosaur using iNaturalist and discovered that it was a wheel bug Arilus cristatus. This insect looks a bit cretaceous because of a spiked wheel on its back which makes it easy to identify. In my mind it looks like a 1.5-inch stegosaurus.
Wheel bugs belong to the order “Hemiptera.” Insects in this order are characterized by a triangular structure on their thorax called a “scutellum,” and by piercing, sucking mouthparts. Some species use these mouthparts to feed on the contents of leaves, stems, and seeds, while others, such as the wheel bug, feed on insects, drinking bodily fluids and liquified tissues. They are able to do this because they have a long sharp proboscis which they use to stab their prey and inject enzymes which liquify the innards which the wheel bug then sucks out.
Wheel bugs are beneficial insects for this reason. They prey on beetles, aphids, grasshoppers, crickets, caterpillars, and stink bugs. Gardeners are excited to find these guys because they not only feed on harmful pest, but their presence indicates a healthy environment. This is because wheel bugs are at the top of the food chain. Finding these insects means all the other food web levels are intact and pesticides are no longer necessary.
Though these friends of the garden are shy and retiring and seldom bite humans, they will defend themselves if mishandled. Bob Androw from the Carnegie Museum of Natural History described a bite on his thumb in this manner,
“The initial bite was not terribly bad, but unusual, feeling like a tiny electrical shock. In less than a minute, however, a sharp, burning sensation began spreading the length of my thumb. The pain reached a crescendo in about 5 minutes and stayed at that level for several hours. The next day the burning pain had subsided but was replaced with a dull throbbing ache that felt like I had hit my thumb with a hammer.”
We can avoid repeating Bob Androw’s experience by not handling these insects. The saying, “You leave them alone, they will leave you alone,” is especially true for wheel bugs.
In the spring, the female wheel bug will lay 40-200 eggs, which will then hatch as red and black nymphs ⅛ cm long. After laying her eggs, the female dies. The hatched nymphs will then go through five molting stages before becoming adults. The characteristic wheel is missing at the nymph stage. As they mature, they will lose their bright red color and take on a more greenish gray color which gives them good camouflage for stalking their prey.
I am thankful these baby “dinosaurs” are only 1.5 inches long and do not have an aggressive temperament. We do not need to build a “Jurassic Park,” or spray their environment with harmful chemicals. The key is to simply leave them alone so they can do their jobs of keeping harmful pests out of our gardens.
Resources:
• Androw, Bob, “So Just What is a Wheel Bug,” Carnegie Museum of Natural History. https://carnegiemnh.org
• Bohrod, Ryan, “The Wheel Bug in Your Garden,” https://insectslehighvalley.com/ April 20, 2016
• Wheel Bugs: “The Terminator in the Garden,” https://soilsalive.com/ March 26, 2015