The brown-tail moth is a moth of the family Erebidae. It is native to Europe, neighboring countries in Asia, and the north coast of Africa. Descriptions of outbreaks, i.e., large population increases of several years duration, have been reported as far back as the 1500s. The life cycle of the moth is atypical, in that it spends approximately nine months as larvae (caterpillars), leaving about one month each for pupae, imagos and eggs. Larvae (caterpillars) are covered in hairs. Two red spots on the back, toward the tail, distinguish these species from other similarly hairy moth larvae. The winged adults have white wings and a hairy white body with a tuft of brown hair at the tip of the abdomen. Females lay one egg cluster, usually on the underside of a leaf of a host plant. The species is polyphagous, meaning that it feeds on many different species of trees, including pear, apple, maple and oak.

Compsilura concinnata is a parasitoid native to Europe that was introduced to North America in 1906 to control the population of an exotic forest, univoltine, spongy moth named Lymantria dispar. It is an endoparasitoid of larvae and lives with its host for most of its life. Eventually the parasitoid ends up killing the host and occasionally eating it. It attacks over 200 host species, mainly insects from the Orders: Coleoptera, Lepidoptera and Hymenoptera. Since this parasite has the ability to attack many different types of hosts, the organism has spilled over from the intended forest systems into other areas, like agricultural fields, affecting cabbage pests including the cabbage looper (Trichoplusia); the cabbage worm ; and even other invasive species such as the brown-tail moth. However, it also attacks native, non-pest insects such as the Cecropia moth and American moon moth.