Larvae escaped from Trouvelot and the gypsy moth began its spread. Gypsy moth's spread across the United States has been slow because female gypsy moths are unable to fly. Gypsy moth is mainly dispersed by larvae crawling, 'ballooning' larvae being carried by the wind, or a variety of life stages being accidentally transported by humans. Gypsy moth goes through one generation per year. Egg mass hatch typically coincides with budbreak.
Gypsy moth spends four to six weeks in the larval stage.
The pupal stage of the life cycle lasts approximately two weeks. In the east, adults generally emerge in July. Adults mate soon after emergence. Egg masses, which contain 100-1000 eggs, are usually laid almost immediately after mating. The egg mass is the overwintering stage.