Older caterpillars develop a deep blue velvet coloration with a sparse covering of long brown hairs. A line of white to cream colored spots runs down the back. These spots often look like footprints or a series of keyholes. As the caterpillars get larger, they consume increasing amounts of leaves and can wander widely in search of more food. 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.