Gypsy moth defoliation in Virginia in 2000 Life history. The gypsy moth has one generation per year. Eggs hatch in early spring at about the time oak leaves are beginning to develop. This is the primary means of natural dispersal. As the larvae mature they undergo a series of growth stages called instars.
Mature larvae form a pupal stage, from which the adults emerge one to two weeks later.
A synthetic version of this sex pheromone is used as a lure in the common gypsy moth traps seen on the roadside during the summer. These eggs are the overwintering stage of the insect. It is usually the egg mass stage that is inadvertently moved by people on cars, trailers, campers, firewood, and outdoor equipment and furniture. They sometimes are confused with eastern tent caterpillar or fall webworm, but the gypsy moth does not form large silken webs and has entirely different behavior and seasonal development from these insects. The egg masses are buff colored and covered with hairs from the female's abdomen.