Fall webworm (Hyphantria cunea) is a moth in the family Arctiidae known principally for its larval stage, which creates the characteristic webbed nests on the tree limbs of a wide variety of hardwoods in the late summer and fall. It is mainly an aesthetic pest and is not believed to harm otherwise healthy trees.
The fall webworm feeds on just about any type of deciduous tree, where leaves are chewed; branches or the entire tree may become defoliated. Worldwide, it has been recorded from 636 species,and is considered to be among the most polyphagous of insects.
The adult moth lays her eggs on the underside of leaves in 'hair'-covered clusters of a couple of hundred. Eggs hatch in about a week.
The caterpillars are highly variable in coloration, ranging from a pale yellow, to dark grey, with yellow spots and long and short bristles. There are two cream stripes along the sides. There are two races, one more common in the north, the other in the south, differing in head capsule coloration.Maximum length, 35mm. Webs are progressively enlarged, and much messier looking than those of tent caterpillars (which occur only in spring and have shorter hairs and very little yellow on their bodies). Larvae feed inside the tents until the late instars. Very young larvae feed only on the upper surfaces of leaves. Later, they consume the whole leaf. The larval stage lasts about 4–6 weeks.
The adult is mostly white in the north, but in the south it may be marked with black or brown spots on the forewings. It is quite 'hairy', and the front legs have bright yellow or orange patches. The underwings will have less marking than the forewings, and the abdomen often has a sprinkling of brown hairs. Wingspan of 35-42 mm.