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The light grey translucent wings are transected by two to three black lines (reduced on the hindwing), with rust-coloured scales along the forewing costa and in a faint stripe along the abdomen. The male antennae are prominently pectinate and the body is thickly scaled. Females are wingless. Slightly smaller with a more uniform colour than L. ursaria.

This intriguing moth usually flies before the last patches of snow have melted, when the first willows start to bloom (although adults do no feed). Adults are most active during the hour before sunset, possibly in response to the cold nights of early spring. The males very rarely appear at lights, likely because the flight finishes before full darkness sets in. The caterpillar is one of the most ornate of geometrid caterpillars, being grey with fine black and orange markings and a white and orange lateral stripe. The larvae develop slowly, occasionally not pupating until early October (Prentice 1963). The pupa overwinters (Criddle 1919, McGuffin 1977, Handfield 1999, Wagner et al. 2001).

A variety of deciduous shrubs; most larval collections have been from willow, but also from buffalo berry (Shepherdia canadensis), white birch (Betula papyrifera), alder (Alnus sp.) trembling aspen (Populus tremuloides), and chokecherry (Prunus virginiana) (Prentice 1963).