Common Name: Puss caterpillar or “asp”
Scientific Name: Megalopyge opercularis (J. E. Smith)
Description: The caterpillars grow to about 1 inch long and are furry in appearance, being completely covered by thick tan to grayish-white hairs that taper toward the back end. Among the long body hairs are shorter spines that discharge venom upon contact. The head and legs are not visible from above. The night-active adults known as flannel moths are rarely encountered.
Other stinging caterpillars include larval stages of: the io moth, Automeris io (Fabricius) (Lepidoptera: Saturniidae); the hag moth, Phobetron pithecium (Abbot & Smith) (Limacodidae);the saddleback caterpillar, Sibine stimulea (Clemens) (Lepidoptera: Limacodidae); and the buck moth, Hemileuca maia (Drury) (Saturniidae). However, many hairy or spiny caterpillars may produce a similar skin irritation, and care should be taken to avoid skin contact with them. The io moth caterpillar is pale green with yellowish and maroon stripes edged with white along each side of the body. The body is adorned with clusters of stiff spines. They can grow to be about 2 ½ inches long. The buck moth caterpillar resembles the io moth caterpillar but is purple-black with a reddish head and lacks the body stripes. The saddleback caterpillar is an unusual looking caterpillar with a brown body marked with a bright green area resembling saddle blanket with an oval purplish-brown spot in its center. Fleshy protuberances bearing spins occur the sides of the body, with larger pairs near the front and rear. They grow to be about 1 inch long before pupating. The even weirder hag moth caterpillar is about 5/8 inch long when fully grown and has nine pairs of curved and twisted fleshy projections arising from the sides of the body bearing stinging hairs.
Life Cycle: The winter is spent in the cocoon or pupal stage. Adult moths emerge in late spring or early summer and lay eggs on host plant leaves. Tiny whitish fuzzy larvae hatch from eggs and develop through several stages or instars between molts over a period of several weeks before they pupate.
Habitat and Food Source(s): Caterpillars have chewing mouthparts. Adults have siphoning mouths. Caterpillars feed on leaves of many shrubs and bushes, such as hollies. Adults moths can be collected at lights.
Pest Status: The caterpillar is called an “asp” by Texans, although there are other caterpillars that also produce a painful skin rash from contact with venom containing spines. Hypersensitive individuals may experience a generalized systemic reaction requiring medical attention.
WARNING: Do not handle caterpillars (larvae) with bare hands!!
For additional information, contact your local Texas A&M AgriLife Extension Service agent or search for other state Extension offices.
Literature: Hamman 1981.