Adult Wheel Bug (Arilus cristatus, family Reduviidae) are now roaming landscapes and forests in southwest Ohio. The immatures (= nymphs) have been with us for some time lurking among the leaves of trees and shrubs on the hunt for soft-bodied insects.
The “wheel” in the bug’s common name only appears on adults and refers to the peculiar morphological feature that rises from the top of the adult bug's pronotum which is the first thoracic segment behind the head. The distinctive structure looks like half of a cogwheel, with the gear teeth clearly visible. Wheel bug adults are big, measuring over 1 1/4" long, and their color varies from light gray to bluish-gray to grayish-brown.
Wheel bug nymphs look nothing like the adults. They hold their curved abdomens upright as they parade around on their long, spindly, spider-like legs. Indeed, the nymphs are commonly mistaken for spiders. We normally don’t see the big adults lumbering around in groups. However, it’s common to find several nymphs patrolling the same branch of a tree or shrub in search of prey.
Insects that belong to the heteropteran family Reduviidae are collectively known as Assassin Bugs. The family includes over 190 species in North America, and they are all predators. The common name for the family clearly describes how these stealthy hunters make a living and wheel bugs serve as an ideal poster child for assassin bugs.
Wheel bugs and other family members sport two features that support their predatory lifestyle. They have raptorial front legs designed for grabbing and holding prey in death's embrace.
Their piercing-sucking mouthparts are housed in a structure called a beak. It swings into action (literally) to inject paralyzing and pre-digestive enzymes into prey which is most often another insect. Like miniature vampires, they then suck the essence-of-insect from their hapless victims.
Caterpillars and sawfly larvae are the favored table fare of these voracious predators; however, they will not turn their beaks up at other arthropod meat morsels. Indeed, they will even nail the probing fingers of uninformed gardeners!
While these are beneficial insects, they should not be handled. All members of the family are capable of delivering a painful bite to people. The pain of a bug bite has been described as being equal to or more powerful than a hornet sting, and the wound may take over a week to heal. It is best to appreciate these beneficial insects from afar.
A Kissing Cousin Creates Confusion
Wheel bugs are sometimes mistaken for Kissing Bugs (family Reduviidae, subfamily Triatominae). Identification errors are understandable given the family resemblances. Both types of bugs share a general body plan with long spindly legs, large bodies, and narrow heads with beady eyes. However, no kissing bug species has a wheel-like structure rising from their thoracic pronotum.
Unfortunately, misidentifications have occasionally induced rounds of entomo-panic owing to concerns over kissing bugs being capable of vectoring the protozoan pathogen behind Chagas disease. On the other hand, Ohio is in fact home to a native kissing bug with a horrible-sounding common name, the Bloodsucking Conenose (Triatoma sanguisuga).
However, the bloodsucking conenose focuses its blood-sucking attention on small animals rather than humans, and equally important, Chagas disease is not endemic to Ohio. So, we don’t have infected people providing a reservoir for the pathogenic protozoan that causes the disease.
I’ve received verified reports over the past couple of weeks of bloodsucking conenose bugs being found in a few homes. Thus, this bug is the subject of my next BYGL Alert.