any of a group of moths (order Lepidoptera), the common name for which is derived from the hair tufts, or tussocks, found on most larval forms. The family, which occurs in both Eurasia and the New World, includes several species that are destructive to shade and forest trees: the gypsy moth (q.v.; Lymantria dispar), browntail moth (Nygmia phaeorrhoea), satin moth (Stilpnotia salicis), and nun moth (Lymantria monacha).

The large larvae are hairy, with many species having stinging hairs. Most feed on foliage of trees and shrubs, sometimes foraging daily from a silken tent or colonial nest of webbed leaves. The larvae of certain species overwinter in these nests, whereas others overwinter as eggs. Pupation occurs aboveground in cocoons attached to tree branches or trunks.

The adults are medium-sized. Females range in colour from white to brown. Some, such as the white-marked tussock moth (Hemerocampa leucostigma), lack wings.