Photo by Drees. Full grown caterpillars within bags are up to 1 inch long before pupating in August or September. Seven to 10 days later, the pupae of male moths wriggle out of the bottom of the bag before the male emerges, leaving the empty pupal skin behind.
Adult males have short inch-long clear wings, hairy black bodies and feathery antennae emerge.
They fly and seek out a female to mate. Females do not develop into moths, but remain inside bags and resemble maggots, with no functional eyes, legs, mouthparts or antennae. Other bagworm species spend winter months as a partially-developed caterpillars that complete feeding and pupate in the spring. Adults emerge in the spring, although some emerge through October. Females produce a clutch of eggs in their bags before dropping to the ground to die.