They often drop from the defoliated twigs to the ground. Large caterpillars are solitary feeders, but commonly rest in large clusters. Mature caterpillars spin silk cocoons with white to yellow threads on vegetation, buildings and other stationary objects to begin pupation. This can occur from late May to late June. The pupae form inside the cocoons.
Adults emerge seven to ten days later.
The adult moth is buff colored and has a broad brown band across the front wings. FTC moths are night fliers and are attracted to lights in large numbers. As a result of this, it is common to find high populations of FTC near populated areas and along highways. Each female lays 150 to 200 eggs. A tough, bronze colored casing covers the egg mass and protects the eggs from drying out.