Arilus cristatus

The adult is gray to brownish gray in color and black shortly after molting, but the nymphs (which do not yet have the wheel-shaped structure) have bright red or orange abdomens. Like other species of wheel bugs, A. cristatus have a characteristic dorsal crest, shaped like a wheel or cog. They move and fly slowly, and in flight produce a noisy buzzing sound. As with other assassin bugs, the proboscis arises from the anterior end of its long, tubular head and unfolds forward when feeding. A. cristatus possesses two scent glands (red-orange in color) that can be ejected from its abdomen with two distinct chemical functions; one gland used for defense and one gland utilized for breeding behaviors. North American wheel bugs exhibit armored forewings and membranous hind wings which allow this species to take flight. As a result of its inability to move swiftly, A. cristatus rely heavily upon camouflage, the effect of their bite, or the production of unpleasant odors in order to avoid predation. ==Distribution==

North American wheel bugs are most common in eastern Canada and the United States, and their range extends into Mexico and Guatemala. a western hemisphere genus, only A. cristatus is found in the United States. ==Behavior==

North American wheel bugs initiate predation by gripping and pinning their prey with their front legs. The bug plunges its beak into its victim before injecting it with enzymes, paralyzing it and dissolving its insides, and proceeds to drain the resulting fluids. The North American wheel bug commonly preys on caterpillars and beetles, such as Japanese beetles, the cabbage worm, orange dogs, tent caterpillars, and the Mexican bean beetle. A. cristatus is also noted to be very aggressive in the wild, and cannibalistic behaviors between them have been noted; for example, nymphs may prey on one another and the female may feed on the male after mating is concluded. Additionally, like many reduviids, the species is capable of producing audible sound by rubbing the tip of its proboscis in a groove under its thorax. The purpose of this sound is unknown and may serve as a means of communication between members of the species. File:Wheel bug catch attempt.webm|thumbtime=0|American wheel bug attempts capture of spotted cucumber beetle and captures and rejects an ambush bug File:Wheel bug assassin bug vs. silver-spotted skipper caterpillar.webm|Arilus cristatus vs. Epargyreus clarus caterpillar File:Wheel bug grooming.webm|North American wheel bug grooming ==Reproduction==

The reproductive cycle of A. cristatus initiates in autumn. After mating, the female will lay 40 to 200 small, brown, cylindrical eggs, and eventually die. Females lay eggs on trees, bushes, twigs, and other objects. Secreted glue serves as an adhesive which maintains the cluster formation of the eggs. The eggs will hatch in the following spring into eight-millimeter-long, red nymphs, which will undergo five molts until they reach the adult stage the following summer. After the nymphs hatch, the average length of each molt is roughly 18.8 days, though the interval of the 5th and final molt prior to the adult stage is the longest. Eggs generally hatch in the beginning of May and finally mature into adults by July. Overall, it takes roughly 94 days for nymphs to reach maturity. However, the phenology of this life cycle varies, based upon the climate which the population occupies. For instance, communities in warm climates may not overwinter as eggs. Of the 12 clusters of eggs monitored in the lab, 10 were ravaged by parasites which prevented the eggs from hatching normally. A. cristatus is predatory immediately upon hatching, but the distinctive wheel unique to the species derives only after the bug reaches the adult stage following the final molt. ==Ecological significance==

North American wheel bugs are highly regarded by organic gardeners because they consume a variety of insects and their presence indicates a healthy, pesticide-free ecosystem. "They're the lion or the eagle of your food web," Dr. Michael J. Raupp, an entomologist at the University of Maryland, notes. "They sit on top. When you have these big, ferocious predators in your landscape, that tells me that this is a very healthy landscape, because all these other levels in your food web are intact." Although A. cristatus is a welcome agent of pest control, this species also preys on several ecologically beneficial species, such as lady beetles and honey bees. ==Interactions with humans==

The species is generally indifferent concerning the presence and interruption of humans. Although evidence suggests that A. cristatus can seemingly be tamed in controlled environments, if provoked or mishandled, they may attack in an act of defense. Their bite is generally considered to be of greater severity in terms of the level and duration of pain than the sting of common insects, such as wasps. Furthermore, the vicinity of the injury is known to become heated and irritated. A white crust sometimes forms around the wound during the healing process, though it eventually deteriorates, leaving the small puncture wound visible. Discomfort may persist for two weeks and up to six months in some cases. However, the latter timeline is frequently attributed to allergic reactions or recurrent infections of the original wound. ==Gallery==

File:Wheel Bug Arilus cristatus Nymph 2053px.jpg|Arilus cristatus nymph closeup File:Wheel Bug on pool skimmer (NW Arkansas, July 2012).png|Arilus cristatus on pool skimmer, Arkansas File:Wheel bug assassin bug vs. silver-spotted skipper caterpillar.webm|Arilus cristatus vs. Epargyreus clarus caterpillar File:North American Wheel Bug 02.jpeg|Arilus cristatus adult found in Fort Worth, Texas File:Wheel Bug & Prey Japanese Beetle.jpg|Arilus cristatus consuming a Japanese beetle File:Wheel-bug-nymph.jpg|Older nymph walking atop a fence File:Arilus cristatus emerging adult.jpg|An adult Arilus cristatus emerging from its nymphal skin File:Matingwheelbugs.png|A mating Arilus cristatus pair File:Wheel bug on roystonea regia.jpg|Arilus cristatus on juvenile Roystonea regia, Maryland ==References==