The common bagworm, Thyridopteryx ephemeraeformis (Haworth), is an interesting caterpillar. The most commonly observed form of this pest is the spindle-shaped silk bag camouflaged with bits of foliage, bark and other debris.

Completed bags range from 1-1/2 to 2-1/2 inches long. The larva within the bag is brown or tan, mottled with black, and the bee-like adult males have clear wings and fur-covered bodies. The females remain larva-like and do not emerge from the bag. The larva may stick its head and front legs out of the top of the bag to feed and move. When disturbed, the larva immediately pulls its head into the bag and holds the opening closed. Mature larvae may stay on their host plant or drag their bags some distance before firmly attaching the bag for transformation into the adult stage. 
The bagworm occurs in the eastern United States from New England to Nebraska and south through Texas. The larvae seem to prefer arborvitae and red cedar but many other conifers and deciduous trees are attacked. These include: pine, spruce, cypress, juniper, willow, black locust, sycamore, apple, maple, elm, poplar, oak, and birch.