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Larvae initially pale yellowish-green. As they mature, larvae darken to deep green or almost black with reddish brown to black head capsule and reach 15-21 mm in length. Pupae spindle-shaped, 9-17 mm in length, initially bright green and eventually turn brown or black. Adults brownish gray in colour with basal, middle, and outer brownish patches on forewings and fringe of hairs along posterior edges of hind wings. Wingspan of 25-35 mm (EPPO 2004, Cerezke 1992).

Pale green eggs are laid from June through July in large, flat masses on upper surface of aspen leaves. Larvae hatch 7-10 days after oviposition (EPPO 2004). First instar larvae congregate between flat surfaces of leaves they weave together. Although larvae skeletonize the foliage, their damage is not conspicuous at this time. In August, larvae find protected locations on the tree trunk to spin cocoons for hibernation, then molt and overwinter as second instar larvae. Larvae emerge in spring at time of bud break, climb the tree and begin mining expanding buds which can cause complete defoliation before buds open (Furniss & Carolin 1977, USDA 1979). Most of the defoliation occurs from late third instar until pupation when larvae roll leaves into shelters, feed, eat all but the larger leaf veins, and then pupate. Pupation occurs mainly in June and adults emerge 7-14 days later. One generation per year (EPPO 2004).