The brown tail moth, Euproctis chrysorrhoea, is an invasive insect in North America. Adult moths typically have white wings, sometimes with a single black dot on each forewing, fuzzy white legs, and a distinctive fuzzy reddish-brown abdomen, which gives them their common name. While the adult moths themselves do not pose a direct threat to human health, their caterpillar stage is a significant concern. The caterpillars possess a unique defense mechanism that can lead to adverse reactions in people.
Understanding the Hazard
The danger from brown tail moths stems from the microscopic, barbed hairs, known as urticating hairs, found on their caterpillars. These hairs are not merely irritating; they also contain a toxin. The caterpillars shed these toxic hairs from April to late June or early July. These hairs can become airborne, settling on outdoor surfaces, vegetation, and entering homes.
Exposure can occur through direct contact with caterpillars or indirectly by encountering airborne hairs or those deposited on surfaces. When these hairs come into contact with human skin, they can cause a highly irritating rash, similar to poison ivy. The rash results from a chemical reaction to the toxin and physical irritation as the barbed hairs embed in the skin. If the hairs are inhaled, they can lead to respiratory issues, including difficulty breathing, burning, irritation, or itchiness in the mouth or throat. Even after the caterpillar has died, these hairs remain toxic and can persist in the environment for up to three years, though their potency may decrease.
Symptoms and Treatment
Contact with brown tail moth caterpillar hairs results in a rash of small, red bumps, often clustered. This rash is intensely itchy, can be painful, and may become inflamed or blistered if scratched. It commonly develops on exposed skin areas and can last from a few hours to several days, though sensitive individuals may experience symptoms for several weeks. Beyond skin irritation, individuals might also experience eye irritation or, if hairs are inhaled, respiratory distress, which can be severe in some cases.
Upon exposure, wash the affected skin gently with soap and water to remove hairs. Applying tape to the skin can also help lift embedded hairs. For immediate relief, cool compresses, colloidal oatmeal baths, or cool baths with baking soda can soothe itching and swelling. Over-the-counter remedies like hydrocortisone cream, calamine lotion, or oral antihistamines can alleviate discomfort. If the rash is severe, persistent, or if respiratory issues develop, seek medical attention.
Minimizing Risk
Avoid direct contact with caterpillars or their nests. When performing outdoor activities like raking, mowing, or gardening, wear protective clothing. This includes long-sleeved shirts, long pants, gloves, goggles, a hat, and a respirator or dust mask. Tightly securing clothing around the neck, wrists, and ankles can further reduce exposure.
Conducting yard work on damp days or wetting down vegetation with a hose can help prevent hairs from becoming airborne. To avoid hairs clinging to laundry, dry clothes indoors, especially during peak caterpillar activity from June to July. Sealing windows and doors can help prevent airborne hairs from entering your home. For significant infestations or nest removal, particularly if nests are high in trees, seek professional assistance from licensed arborists or pesticide applicators.
Where They Thrive
The brown tail moth was accidentally introduced to North America in the late 1800s in Massachusetts. While its historical range covered much of New England and parts of Atlantic Canada, its distribution later receded. Currently, the moth is found primarily in parts of coastal Maine and Cape Cod, Massachusetts, with recent population expansion in Maine and confirmed sightings in New Hampshire.
The life cycle of the brown tail moth includes egg, larval (caterpillar), pupal, and adult stages. Larvae emerge from overwintering webs in spring to feed on new foliage, reaching full growth by mid to late June. Adult moths emerge in July and are active through August, laying eggs that hatch in late summer. Newly hatched larvae then build winter webs where they hibernate until the following spring.