Ohio State University Extension Fact Sheet

Ohio State University Extension Fact Sheet

Entomology

1991 Kenny Road, Columbus, OH 43210-1090


Stinging Hair Caterpillars

HYG-2130-95

William F. Lyon

Common Name Scientific Name
Saddleback Caterpillar Sibine stimulea (Clemens)
Io Moth Automeris io (Fabricus)
Puss Caterpillar Megalopyge opercularis (J.E. Smith)
Hagmoth Phobetron pithecium (J.E. Smith)
Buck Moth Hemileuca maia (Drury)
Hickory Tussock Moth Lophocampa caryae (Harris)
Silverspotted Tiger Moth Halisidota argentata
Stinging Rose Caterpillar Parasa indetermina (Boisduval)


Caterpillars or larvae of certain moths possess stinging hairs. These sharp hairs or spines are either hollow, connected to poison glands (venom flows on contact), or similar to glass fibers (hairs break off in skin easily) sometimes causing pain like a needle prick. Depending on the individual, reaction to the sting ranges from mild, with local reddening, swelling, burning and itching to severe pain. Hypersensitive persons may experience severe swelling, nausea and generalized systemic reactions, occasionally requiring hospital treatment. In severe cases, entrance of hairs into the eye can cause blindness.

Stings generally occur when accidentally brushing against one of these caterpillars or attempting to remove it by hand from clothing or on the body. Fortunately, stinging hair caterpillars are not a widespread problem (occur in small numbers). Complaints occur in late summer to early autumn and most are found on corn leaves, vegetable plants, shrubs and trees.

Identification

Saddleback Caterpillar

Larvae are slug-like, about one inch long and 3/8 inch wide full-grown, brown at both ends including hollow spine-covered tubercles (horns), green around the middle "saddle blanket", with a purple-brown oval spot "saddle" edged with white in the center of the back. The evenly rounded larva has groups of spines along the sides and two larger horns with spines at the front and rear of the body. The stiff hairs or spines are mildly poisonous. Abdominal prolegs (false legs on the abdomen) are absent and thoracic legs are very small.

Io Moth

Larvae are about 2 to 2-1/2 inches long full-grown, pale-green with a narrow, reddish stripe edged underneath with white that extends lengthwise along each side of the body. It appears spiny (numerous clusters of urticating hairs). Each body segment is equipped with several fleshy tubercles armed with numerous long, greenish venomous spines tipped with black. Pain is less severe than the puss caterpillar.

Puss Caterpillar

Larvae are about one inch long full-grown, broad and flat (pear-shaped) with a dense covering of long, silky, gray to reddish-brown hairs. Interspersed among the long body hairs are numerous short spines which discharge venom upon contact. The puss caterpillar sting is the most severe of these stinging caterpillars. Venom is discharged upon contact.

Buck Moth

Larvae are similar in size and appearance to that of the io moth but purple-black with a reddish head. They lack body stripes, but have numerous small, pale-yellow dots scattered over the body with reddish to black branches and stinging spines arising from tubercles. The prolegs are red and true legs on the thorax are glossy-black.

Hagmoth

Larvae are about 5/8 inch long full-grown, brownish with nine pairs of variable length lateral plume like processes upon which the stinging hairs are borne. Among the brown hairs of the plumes are longer, black, stinging hairs, curved and twisted, suggesting disarranged hairs of a hag, from which it is named. The sting is comparable to that of the saddleback caterpillar.

Hickory Tussock Moth or Hickory Tiger Moth

Larvae have different color forms. Some are white-haired with black spots clearly seen on each body segment whereas others are furry-white with a row of black, furry dots down the back with two long, black tufts of hair near the coal-black head. This caterpillar is basically white with a black head and when fully grown is about 1-1/2 inches long. Symptoms are usually a skin rash (poison ivy-like) and sometimes severe itching followed by a painful burning sensation.

Silverspotted Tiger Moth

Larvae are about 1 to 1-/2 inches long full-grown, densely covered with tufts of brown or black poisonous hairs.

Stinging Rose Caterpillar

Larvae are slug-like, about one inch long with narrow black stripes edged with yellow extending lengthwise along each side of the body. There are four black stripes lengthwise down the back with 12 pale-yellow tubercles armed with spines. There are clusters of spines on orange-red tubercles along each side.

Other Caterpillars

Larvae of the Gypsy Moth, Lymantria dispar (L.) and Browntail Moth, Euproctis chrysorrhoea (L.) are not listed as "stinging hair caterpillars," but their hairs can cause dermatitis, especially in sensitive persons.

Life Cycle and Habits

Saddleback Caterpillar

Adult moths fly in July and August in the North. Larvae feed on many hosts including corn foliage, apple, pear, cherry, rose, Pawpaw, basswood, chestnut, oak, plum and other trees. There is one generation per year with overwintering in a tough, brown, oval cocoon, retaining the stinging hairs for protection. Eggs are flat-like and laid singly or in groups on leaves. Children sometimes find larvae around shrubs and get stung by handling them. The stiff hairs, or spines, are mildly poisonous, with the sting somewhat less painful than other stinging caterpillars. Some individuals report severe irritation nevertheless.

Io Moth

Adult moths appear at lights from late-May through July. Larvae feed on corn foliage, cotton, roses and a wide variety of trees and shrubs. There is believed to be only one generation in most years with overwintering passed as a pupa inside a tough oval cocoon, often enclosed in leaves on the ground. Moths emerge in the spring and summer, mate and lay eggs. The sting mechanism is similar to the puss caterpillar, but usually less severe.

Puss Caterpillar

Moths emerge from overwintering cocoons in late-spring and early-summer, mate and deposit eggs on various bushes, trees and shrubs. Eggs hatch in a few days (resemble small, white cotton tufts) with larvae maturing in a few weeks (color changes to reddish-tan). Hosts include hackberry, oak, maple, sycamore, elm, English ivy, rose and other plants. Stings can be quite painful. There is an intense local burning at the contact site, soon radiating a considerable distance as localized swelling occurs. The inflammation can spread several inches around the sting and, in sensitive persons, lymph nodes under arms and in the groin may enlarge. Victims may experience headaches, become weak and nauseated with shock-like symptoms usually within two hours after contact. Severity of symptoms depends on individual sensitivity, size of larvae, number of spines contacted, pressure against the caterpillar and sting site. These stings are considered the most severe of all the stinging caterpillars.

Hagmoth

Overwintering occurs as a bullet-shaped cocoon attached to a leaf or twig which is protected by the stinging hairs left behind from the larval skin. There is one generation per year. Larvae feed on various shrubs and lower branches of ornamental trees. There is a potential of accidentally brushing up against one.

Buck Moth

Adults fly in late-September and early-October during Indian summer. Peak moth activity coincides with the rutting season of whitetail deer, hence the name "Buck Moth." Overwintering occurs as tiny larvae inside egg cases with emergence in late-spring and summer. Larvae feed on oak and willow trees in groups.

Hickory Tussock Moth or Hickory Tiger Moth

Moths appear in May continuing into July. Eggs are laid in clusters of 100 or more on the undersides of leaves. Young larvae feed gregariously, later scattering to feed. Caterpillars require about three months to develop and cocoons are built on or near the ground in late-September and early-October. Host trees include walnut, hickory, butternut, apple, basswood, birch, elm, black locust, aspen and linden. Although not listed as a "stinging hair caterpillar," there are verified reports of school children and others developing rash and itching after playing with these immature insects.

Silverspotted Tiger Moth

Adults emerge in July and August and deposit eggs on needles or twigs of coniferous trees. Larvae feed on Douglas fir, true fir, pine and other conifers. Feeding occurs in clusters under a web formed with dead needles; overwintering occurs there in an early stage, and larvae disperse the following spring, feeding singly until mature. They spin cocoons of silk and body hairs, attaching them to twigs, needles, tree trunks or litter on the forest floor. Stings can be rather painful.

Stinging Rose Caterpillar

This insect is similar in habits to the hagmoth. It overwinters in a cocoon on the ground. Larvae feed on the underside of rose leaves and other low-growing shrubs.

Treatment for Caterpillar Stings

Diagnosis is usually simple since a rash generally breaks out where the hairs or spines have made skin contact. Immediate application and repeated stripping with adhesive or transparent tape over the sting site may be helpful in removing broken hairs or spines. Washing the affected skin area thoroughly with soap and water may help remove irritating venom. Prompt application of an ice pack and a baking soda poultice should help reduce pain and swelling. Household analgesics, such as aspirin, appear to be ineffective for reducing pain and headache. However, oral administration of antihistamines may help relieve itching and burning. Topical corticosteriods may reduce the intensity of inflammatory reaction. Desoximetasone gel applied twice daily to affected areas will help.

Prompt referral to and treatment by a physician should be made when severe reactions are evident. Some physicians reportedly have successfully treated severe cases with intravenous calcium gluconate codeine and prescription analgesics. Very young, aged or unhealthy persons are more likely to suffer severe reaction symptoms.

Control Measures

Prevention

Occasionally, these stinging hair caterpillars may drop out of trees onto people, crawl into clothing on the ground, occur on outdoor furniture or sting when brushed against on plant foliage. Be careful when attempting to brush them off. Never swat or crush by hand. Remove them carefully and slowly with a stick or other object.

Individuals, especially children, should be cautioned about handling or playing with any colorful, hairy-like, fuzzy caterpillars since it is sometimes difficult to distinguish between harmless and venomous insect larvae. Never handpick these hairy, fuzzy or spiny caterpillars except with heavy leather gloves if necessary. Wear long sleeve shirts, trousers and gloves when harvesting sweet corn in late-summer and early-autumn to reduce possible stings.

Insecticides

Usually, these stinging hair caterpillars do not occur in sufficient numbers to warrant the use of pesticide sprays. Should potential hazards exist around residences or schools, infested shrubs and trees may be sprayed to reduce or eliminate these caterpillars. Sprays of acephate (Orthene), carbaryl (Sevin), Diazinon, or chlorpyrifos (Dursban), in formulations labeled for bushes, shrubs and trees, can be helpful, if practical. Be sure to read the label, follow directions and safety precautions.


This publication contains pesticide recommendations that are subject to change at any time. These recommendations are provided only as a guide. It is always the pesticide applicator's responsibility, by law, to read and follow all current label directions for the specific pesticide being used. Due to constantly changing labels and product registration, some of the recommendations given in this writing may no longer be legal by the time you read them. If any information in these recommendations disagrees with the label, the recommendation must be disregarded. No endorsement is intended for products mentioned, nor is criticism meant for products not mentioned. The author, The Ohio State University and Ohio State University Extension assume no liability resulting from the use of these recommendations.


All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status.

Keith L. Smith, Associate Vice President for Ag. Adm. and Director, OSU Extension.

TDD No. 800-589-8292 (Ohio only) or 614-292-6181



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