When Caterpillars Attack: The Buck Moth

The buck moth caterpillar (Hemileuca maia) is usually found in early to mid summer. It can be confused with spiny elm caterpillars and gypsy moth caterpillars which are also active at that time; but, the buck moth is such a rare species found in Pennsylvania, it is rearely found. Long branched spines and tufts of shorter spines cover the body.

The buck moth caterpillar is usually found on oak, especially the dwarf oak species. But willow, hazelnut, cherry, and rose are also suitable host plants. The poisonous hairs or spines are hollow and connected to underlying poison glands. Contact with them causes a burning sensation and inflammation that can be as painful as a bee sting. The irritation can last for a day or two and may be accompanied by nausea during the first few hours. The site of contact reddens and swells much like a bee sting.

A person "stung" by a poisonous caterpillar should immediately wash the affected area to remove any insect spines and poison that remain. An ice pack will help reduce swelling, and creams and lotions containing steroids will lessen the discomfort and promote healing. Persons known to be sensitive to insect stings should consult a physician. Stinging caterpillars rarely occur in sufficient numbers to be considered pests, but people who work with ornamental plants should learn to recognize them and avoid touching them. Having said all that, caterpillar stings are rare and not serious. These caterpillars are a fascinating example of protective strategies evolved by animals.

Reference: U.S. Department of the Interior.

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