They are also known as eggers, the name eggars come from the neat egg-shaped cocoons of these moths. American Lappet Caterpillars are large in size and are hairy, especially on their sides. They feed on leaves of many different trees and shrubs and often use these same plants to camouflage their cocoons. They are in the same family as tent caterpillars.
The American Lappet Moth has a wingspan of 2.5 to 5 cm. The coloring of the fore wing can be from reddish to light brown and marked with white and violet. Both their wings have white scalloping on the outer edges. They look strange when at rest as the fore wings are folded over the abdomen and the hind wings protrude out.
The caterpillar can grow to 4.5 cm in length. The body is gray with white markings and is covered with soft gray hairs, the longest of these protrude from lappets on the sides of the body. There are 2 reddish orange bands on their backs, just behind the head section, these red bands are more visible when they are in motion and almost disappear when at rest.
The larval food plants in the Pacific Northwest are alder, apple, cherry, oak, and willow. The larvae feed at night, so they are seldom encountered. They overwinter as a pupa.