Identification Larvae enclosed in cone-shaped bags consume foliage. Insect seldom seen, except head of larva protruding from the bag. The larva is mottled brown to black and encloses itself in a bag spun from silkstrands. Bits of leaves and twigs from the host are incorporated in the bag during its creation. Adult males fly and are the only form occurring outside the bags.
Females develop inside the pupal case within the bag where the eggs are laid.
History Overwintering eggs begin hatching in early June. The tiny larva immediately begins to construct a tiny silken bag around itself and initiates feeding. Feeding and molting continues until August when pupation occurs. Adults are active in late August and September. Only males leave the bag to mate with females which remain in the bags to lay overwintering eggs.