Hickory Horned Devil

The hickory horned devil is the larval stage of the regal moth, also called the royal walnut moth, and is widely regarded as one of the largest and most dramatic-looking caterpillars in North America. Its intimidating array of curved thoracic horns and sheer bulk make it an unforgettable sight, though the impressive appearance is purely for show.

Despite its size and fierce looks, this caterpillar is entirely without physical defenses beyond its intimidating posture, relying on its startling appearance to bluff potential predators away rather than any actual sting or bite.

• Body is blue-green to teal, thick and cylindrical, reaching up to 5-5.5 inches long in the final instar
• A set of long, curved orange-red horns tipped in black projects from the thorax just behind the head, resembling antlers
• Smaller black spines run in rows along the rest of the body
• Body surface has a granular or leathery texture
• Younger instars are much smaller and darker, lacking the full development of horns
• Unmistakable due to its combined size and horn arrangement; no other North American caterpillar closely resembles it

This species occurs throughout the eastern and southeastern United States, generally south of New England, in deciduous forests and wooded areas with suitable host trees. Caterpillars are found from summer through early fall feeding on the leaves of hickory, walnut, sumac, persimmon, sweetgum, and related trees.

The caterpillar is a solitary leaf feeder that consumes large quantities of foliage from a range of hardwood trees as it grows to its enormous final size. Its primary defense is its startling appearance, including the curved horns and large body, which can deter predators through intimidation alone despite the horns being soft and non-functional as weapons. When mature, it leaves the tree and burrows into the soil to pupate, an unusual habit among giant silk moth caterpillars that typically spin cocoons above ground.

Females lay eggs on the leaves of host trees, and larvae hatch to begin feeding, passing through five instars over roughly two months and growing dramatically in size with each molt. Unlike most large silk moth caterpillars, the mature hickory horned devil crawls down from the tree and burrows into loose soil to pupate rather than spinning a cocoon. It overwinters underground as a pupa, emerging as an adult regal moth the following summer, with typically one generation per year.