As the bagworm grows, leaf fragments are added to bags which often grow to 2 inches in length by the end of the summer. Larvae feed until late August or early September. Males emerge in September, usually leaving their pupal case extending from the bag, and mate with the wingless females through the bag entrance. Female moths deposit their eggs then die, never leaving the bag. Each female can produce 500 to 1000 eggs.
Adult males are small, grey moths with clear wings.
Approximately half the bags on a host plant will contain female bagworms, while the other half contain males. Damage Symptoms Bagworms feed on most coniferous plants and on many deciduous trees and shrubs. Common evergreen hosts include juniper, arborvitae, pine and spruce. Heavy infestations are capable of completely defoliating a tree or shrub, which may be severely stressed or even killed if control measures are not taken. Less severe injury will slow growth and stunt plants.