SCOTT SHALAWAY A devilish caterpillar

If reader response is any indication, it seems to be a good year for hickory horned devils. In the last week I've received daily letters and phone calls about this ferocious-looking backyard monster. Its looks, however, are deceiving; it's harmless.
The hickory horned devil is the caterpillar of the royal walnut or regal moth, a large and beautiful silk moth. Luna and cecropia moths may be more familiar, but the royal walnut moth is equally impressive. With wings that span almost 6 inches, its brown wings are marked by orange veins and large golden spots. In midsummer, they are sometimes attracted to porch lights.
But like many large moths, adult regal moths are short-lived. Their sole function is to reproduce. Their mouth parts are nonfunctional, so they can't even eat. Females lay eggs on the leaves of walnuts, hickories, sweet gum, persimmon and sumacs. The eggs hatch within a week to 10 days, and the larva spend the rest of the summer growing into the hickory horned devils people are now beginning to notice.
Impressive looks
Mature devils are huge, the largest caterpillar most of us will ever see. And their horny ornaments justify the devilish moniker. It's difficult to imagine a more spectacular caterpillar. By summer's end, the body measures close to 6 inches long. Each segment of the green fleshy body is equipped with several short, black, spiny horns. Curiously, the hickory horned devil was known nearly 70 years before the adult moth was described in 1793.
But the long thoracic horns that adorn the area near the head are the most distinguishing and fearsome feature. These black-tipped orange horns can be up to three-quarters of an inch long and appear to be terribly dangerous. They are not. If handled carelessly these spikes might prick tender skin, but the hickory horned devil is harmless.
After a summer of gorging on host tree leaves, the mature caterpillars are now moving down tree trunks to the ground, where they will burrow into the ground to pupate. The reports I've received have come from people who have noticed this earthward movement. If disturbed or picked up, the devil will thrash its head violently from side to side.
As the caterpillar prepares for pupation, its body color morphs from green to a beautiful turquoise. It then burrows a few inches beneath the surface and forms a chamber in which it pupates. Exactly how it survives subfreezing winter conditions remains unclear.
Beware others
Sometime the following summer, the adult moth emerges and the life cycle repeats itself. Beware, however; not all spiny caterpillars are harmless. The io moth is found across the eastern half of the United States and is easily recognized by its prominent dark eyespots on its hind wings. Its caterpillar, which feeds on a wide variety of tree species, is green and fleshy and marked by reddish and white stripes the run along the length of the body on each side. And each body segment has several sets of branched spines. If handled, these spines can penetrate human skin and be quite irritating. When disturbed, io moth caterpillars fall to the ground and roll into a ball, much like woolly bears.
The saddleback caterpillar is another strikingly marked moth larva that invariably attracts attention. The adult moth is inconspicuous and rarely noticed. But the caterpillar, which gets to be about an inch long, is lime green with brown ends and a white-rimmed brown saddle. But like the io moth caterpillar, the saddleback is covered by clusters of branched spines. Just brushing against these spines can be quite painful, so resist the urge to handle saddlebacks. And make it a point to warn children of this danger.
Looks can be deceiving. The hickory horned devil appears to be a backyard monster, but it's harmless. Saddleback caterpillars, however, are almost cute, but a close encounter is surely one you'd never forget.
sshalaway@aol.com