SPECIES: Thyridopteryx ephermeraeformis

CHARACTERISTICS: Dangling two-inch bags made of silk mixed with bits of leaves and twigs. Bagworms are larvae of moths; male adults are black with clear wings, while females are wingless and stay in cocoon. One generation produced per year; larvae hatch in mid-May and begin to feed on leaves and make bags that they carry along as they feed. Mature larvae pupate in late August inside bags; adults appear in 7-10 days to lay eggs and then die. Each bag can contain 1,000 eggs; in spring caterpillars hatch and feed.

PLANTS ATTACKED: Juniper, arborvitae, eastern red cedar, elm, pine, honey locust, maple and spruce, 128 plant species total.

DAMAGE: Deciduous trees not as vulnerable because they make new leaves. Silken bands attaching bags to trees can girdle and kill young branches.

CONTROLS: When you see them, handpick and destroy bags to minimize further damage. Next year, spray plants with biological control Bt or bacillus thuringiensis May 1-June 1. Grow pollen- and nectar-making plants to attract predators of bagworms. In mid- to late-May, when bags are about 1/2-inch-long, mist foliage with diazinon, orthene, rotenone or malathion, according to directions, to chemically kill destructive larvae.