Mature larvae loop strands of silk around a twig and become firmly attached. Feeding and development usually continue until August. As the larvae (Image 1) grow over the eight to ten week feeding period, they continue to enlarge the exterior of their bags with pieces of foliage, bits of bark, or other plant parts.

Upon hatching, young larvae crawl out of the bottom of the bag and start to feed and construct silken shelters over their bodies. Eggs start hatching from late May through early June. Females lay 500-1000 eggs in each bag during the previous fall. This pest overwinters as eggs inside the female's abdomen inside the bag she constructed. Lenhard - Louisiana State University UGA0795015b

Image 2 - Bagworm: male adult, bag, and pupal case. Lenhard - Louisiana State University UGA0795017b Image 1 - Bagworm: head of larva protruding. The adult male is sooty black and moth-like with transparent wings that are nearly devoid of scales. She never leaves the bag that she constructed as a larva. The adult female lacks eyes, wings, functional legs and mouthparts. Fully developed larvae are about 18 to 25 mm long.

Mature larvae are dull, dirty gray and splotched with darker markings toward the head. Young larvae hatching from the eggs are approximately two mm long, glossy black on the back and dull amber on the undersurface of their bodies. When the larva is mature, the bag may be 30 to 50 mm long. These materials are interwoven to disguise and add strength to the case. The bag is made of silk and bits of host foliage. This insect is most easily recognized by the case or bag that the caterpillar forms and suspends from ornamental plants on which it feeds. Their dispersal over wide areas occurs mainly through movement of infested nursery stock and ornamental plants, or by ballooning (wind dispersal) of small bagworm larvae during early June. The spread of the bagworm is slow since adult females are unable to fly. Infestations have recently been noticed north of Interstate 80 in the state. The bagworm is most common in southern regions of Pennsylvania. It also attacks certain deciduous trees such as black locust, honeylocust, and sycamore. The bagworm is a perennial insect pest of arborvitae, juniper, pine, spruce, and many other evergreen species (including Christmas trees).

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