Recently a friend showed me a hickory horned devil caterpillar, a monstrous caterpillar and the scariest I had ever seen. The Regal Moth or Hickory Horned Devils are commonly found on walnut, hickories, persimmon, sweetgum, and sumacs. It’s said that larvae grow faster and larger on persimmon.
The moth lays up to four tiny yellowish eggs on the upper surface of the host plant that hatch 7–10 days later. After hatching, the small black larva feeds at night and sleeps the day, using leaf tops as hammocks and masquerading as a bird dropping. The larva molts four times, enlarging with each molt and changing colors, wearing shades of yellow, brown, and bright orange before the final coat of green. It spends about forty summer days devouring foliage.
The larva, mistaken for bird poop, mushrooms into the largest North American caterpillar at six inches long and fat as a hot dog with a massive reddish-orange headpiece of horns with black spikes up to an inch long. Enhancing fear are two long and two shorter red spikes protruding from the next two segments, and four short black spikes on the abdominal segments. Big black spots on the body mimic eyes. Chickens shy away, but other birds devour them. Pick them up without fear, but picking them up is the hardest part.
The caterpillar’s spikes neither pierce nor sting; its bright colors are just for show; and its ruse of rearing its horned head and vibrating violently to create a buzz resembling that of a rattlesnake’s is but a scam.
Before pupation, the larva expels its gut and changes color from green to turquoise. They crawl down the host and burrow in the ground five or six inches deep and pupate in a earthen chamber, rather than spinning a cocoon. The devils are transfigured into glossy brown pupae, which will spend winter entombed like mummies. Some pupae overwinter two seasons.
From the tomb arises the adult regal moth, giant cousin of the silk moth and the largest moth north of Mexico. When the orange veined, greenish-gray wings dotted with creamy yellow are smoothed open, they measure up to six inches across. After mating, the female spends her life laying eggs. Adults have vestigal mouths, mouthparts are reduced, and they do not eat and only live about a week. It’s a midsummer moth, on the wing from late June through August with larvae peaking August through October. Remember, they may look creepy, but they’ve got nothing.