The Wheel Bug (Arilus cristatus) is the largest assassin bug in North America, measuring 28-36 mm with females larger than males. Instantly recognizable by the prominent cogwheel-shaped crest on the thorax, this predatory insect ranges from Ontario to Florida, west to Iowa, Kansas, New Mexico, and California, and into Central America. Most common in the eastern U.S.

Adults hunt on flowers, trees, and shrubs where prey like caterpillars, aphids, bees, and sawflies abound. Nymphs hatch in spring from hexagonal egg clusters laid on trees or structures within 4 feet of the ground. The eggs, resembling tiny brown bottles with ornate stoppers, overwinter. One generation develops per year, taking about three months to maturity.

Nymphs are red and black, progressing through red/gray and gray/black stages. They actively stalk prey, even within caterpillar tents, and face threats from cannibalism and parasitoids. Molting leaves behind empty exoskeletons with inverted tracheal tubes. Adults appear from late spring through early winter, mating in fall; males guard females against rivals.

Despite chemical defenses, some succumb to parasites. Others survive with deformities, including malformed wheels. All life stages are voracious predators, using a stout beak to inject paralyzing saliva and digestive enzymes into prey.

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