Brown-Tail Moth

Euproctis chrysorrhoea — the brown-tail moth — is one of the most medically-significant URTICATING-HAIR caterpillars in North America and one of about 200 species in genus Euproctis (the tussock moths and tussock-related moths). The species is native to Europe (where it has been a familiar nuisance moth for centuries), but was accidentally introduced to NA in the late 1800s (first detected in Massachusetts in 1897 — likely on imported nursery stock from Europe). The species spread aggressively across northeastern NA over the early 1900s but populations crashed by the 1940s due to combined parasitoid wasp introductions, fungal disease outbreaks, and habitat changes. The species persists in coastal Maine and parts of New England today, with periodic outbreak years causing significant human-health concerns. Adult moths are 3-4 cm wingspan, white with the species' diagnostic feature: a TUFT OF BROWN HAIR ON THE TIP OF THE ABDOMEN (the source of the 'brown-tail' common name). Females are the source of the brown tuft — they collect brown hairs from the abdomen and use them to cover egg masses for protection from predators (and to provide an early supply of urticating hairs for emerging larvae). Larvae are 3-4 cm long when fully grown, dark brown to black with red and white spots and the species' diagnostic feature: dense tufts of BROWN URTICATING HAIRS along the body. The urticating hairs are the source of the species' major MEDICAL SIGNIFICANCE. Each fully-grown brown-tail moth caterpillar carries TENS OF THOUSANDS of microscopic BARBED HAIRS — each hair is hollow with a barbed tip that can penetrate skin and detach in the skin tissue, where it causes intense allergic reactions through contact with toxic compounds in the hair. Reactions include SEVERE SKIN RASH (typically appearing 6-24 hours after exposure, persisting for 1-2 weeks), RESPIRATORY IRRITATION (when hairs are inhaled — coughing, watery eyes, asthma-like symptoms), and rare anaphylactic reactions in highly-sensitized individuals. The hairs persist in shed exoskeletons, in soil, in caterpillar nests, and on tree bark for MONTHS after the caterpillars are gone — so the human-health risk extends well beyond the active feeding period. Outbreak years cause widespread human-skin-rash incidents in coastal Maine — local public health departments distribute educational materials and shut down beaches and parks during peak hair-shedding periods. Larvae are gregarious and feed on a wide range of host plants (oak, willow, fruit trees, roses) and construct distinctive winter NESTS of woven leaves in host trees. The species is harmless to most NA ecosystem function but is a major human-health pest in Maine.