Brown-tail Moth

The brown-tail moth is a member of the subfamily Lymantriinae within the family Erebidae, native to Europe but established as an introduced species in parts of North America, particularly along the northeastern coast. It is named for the tuft of brown hair at the end of the adult female's abdomen, used to cover her egg mass after laying.

Adults are entirely white-winged moths with a compact, fuzzy body, making them fairly distinctive among white moths due to the contrasting brown tail tuft, most visible on females. The caterpillars are gregarious, living communally in silken winter nests woven into the branch tips of host trees, and are covered in dense hairs.

As an introduced species in North America, the brown-tail moth has drawn attention due to periodic population outbreaks affecting deciduous trees and shrubs in coastal New England, making it a notable subject of regional monitoring.

• Adult wings and body are almost entirely snow-white, with a dense covering of white scales.
• A conspicuous tuft of brown hair sits at the tip of the abdomen, more prominent in females than males.
• Wingspan roughly 3–4 cm; body compact and moderately furry in appearance.
• The caterpillar is dark brown with two conspicuous orange-red spots near the rear and a broken white stripe along each side, densely covered in short hairs.
• Distinguished from other white moths by the brown tail tuft, and from other hairy caterpillars by the paired orange-red dorsal spots near the tail end.

Native to Europe, North Africa, and parts of Asia, with an established introduced population along the coast of the northeastern United States, particularly Massachusetts and Maine. Found in deciduous woodlands, coastal shrubland, orchards, and hedgerows. Caterpillars overwinter in silken communal nests at branch tips and become active again feeding on new foliage in spring, while adults fly in mid-summer.

Adults are nocturnal fliers attracted to light, with a relatively short flight period in summer focused on mating and egg-laying. Caterpillars feed gregariously on the leaves of a wide range of deciduous trees and shrubs, particularly in spring, and construct dense communal silk webs at branch tips for overwintering shelter. The caterpillar's body hairs are a notable defensive feature, readily detaching and dispersing to deter predators.

Females lay egg masses on leaves in mid-summer, covering them with brown hair from the tip of the abdomen for protection. Eggs hatch into small caterpillars that feed briefly before constructing a communal silk nest in which they overwinter as partially grown larvae. In spring the caterpillars emerge to resume feeding, molting through several instars before pupating within the shelter of leaves or bark crevices. There is one generation per year, with adults emerging in summer to mate and restart the cycle.