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Strongly sexually dimorphic. Males are smaller (wingspan about 5 cm) with narrow, somewhat pointed forewings that are grey with darker grey mottling. The hindwings are thinly scaled, with a black basal area, a thin black terminal line and a large bright yellow-orange splotch at the anal angle. Females are much larger (6-7.5 cm wingspan), dirty white with a mesh-like overlay of fine dark lines and wider dark lines that fill in some of the spaces, especially in the median area, and give it a blotchy appearance. The hindwings are similar, but the overlay is less distinct and lacks the wider lines and blotchy appearance. Both sexes have narrowly bipectinate antennae. Males may be mistaken for a small sphinx moth, but can be recognized by their bipectinate antennae. Females can be separated from the similar Acossus populi by the blotchy grey on the forewings, and from A. centerensis by the grey hindwings.

The larvae are borers, and live in galleries they create in the trunks and stems of hardwood trees, where they feed on the cambium area. On the prairies, the larvae take up to 3-4 years to complete development. They are 5-7.5 cm long at maturity, greenish white with brown heads and thoracic shields or pinkish with brown spots and reddish brown heads and shields. Pupation occurs in the tunnels during the spring of their final year. Their galleries can weaken trees, making them more vulnerable to wind damage and drought. They can be a pest in shelterbelt and ornamental plantings on the prairies, but they are not abundant enough to be of much concern in Alberta. Adults are usually collected at light.