Forest Pests: Insects, Diseases & Other Damage Agents

Evergreen Bagworm (Thyridopteryx ephemeraeformis)

Maier, C.T., C.R. Lemmon, J.M. Fengler, D.F. Schweitzer, and R.C. Reardon. 2004. Caterpillars on the Foliage of Conifers in the Northeastern United States. FHTET-2004-1. Morgantown, WV: USDA Forest Service, Forest Health Technology Enterprise Team; 151 p.

Description. Easily identified by its large case constructed of silk and embedded with pieces of its food plant. Dark purplish brown body with lighter areas on head, thorax, and anal plate. Light gray head and thoracic dorsum marked with dark brown to black, amount of dark color increases from T1 to T3; brown (non-sclerotized) band on anterior margin of T1 to T3 and A1, most visible when head and thorax extended out of case. Dark brown anal plate with light gray usually at hind margin. Up to 35 mm.

Food. Many trees and shrubs, including especially eastern red-cedar and northern white-cedar (arborvitae).

Life Cycle. One generation. Egg overwinters in case of female. Mature caterpillar present in August and September.

Comments. This caterpillar is a well-known pest of arborvitae, junipers, and other plants in landscaped settings. It may cause severe damage or browning of foliage that can kill the tree. The female moth, which lacks many adult characteristics, lays eggs in her case and dies there. The evergreen bagworm rarely is found north of coastal areas in southern New England.

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