Bags of early stage larvae are small, conical, and inconspicuous. During this period, the bag is usually held upright. Molting takes place within the bag, and bags are enlarged as larvae grow. Larvae become fully grown by about August. The pupal period lasts about three weeks, and adults are generally present by the end of August or early September.
Females emerge from the pupal case but remain in the larval bag.
Male pupae wiggle part way out of the bag through the lower opening. Mating with the female inside the larval bag is accomplished through the opening at the lower end of the case. Oviposition generally occurs in September. The number of eggs per female varies, but most lay 400-1000 eggs. Following oviposition, the female drops from the bag and dies.