Each time the larva grows it sheds its skin and a new larger skin forms. The larval stage lasts for about 7 weeks. In June and early July full-grown larvae may leave the host plant and seek out protected places to form the pupa or resting stage. At this time, the large caterpillars may be seen crawling across walkways or roads, or up the side of a house. The pupal stage lasts about two weeks.
Moths emerge from the pupae - the males usually emerge first.
Males are strong fliers and may be seen flying in a zig-zag pattern during the daytime. After mating she deposits her eggs in a single mass and then dies. There is one generation per year. Before mid-April look for overwintering egg masses on tree trunks, rock outcroppings, fences, sides of buildings and woodpiles. Destroy the eggs by scraping the fuzzy buff colored egg masses into a container of kerosene or rubbing alcohol.