Forewings gray heavily suffused with black. Hind wings of males are white and are gray in females. (2)
Specimen identified by DNA analysis:
Larvae:
Larva has orange scoli or tubercles covered with short hair tufts or spines. The color is black [or dark red/brown] with a broad white lateral band. It is illustrated by Miller & Hammond (2003).
Range
South-central British Columbia southward and westward thru western Montana, Idaho, western Nevada. Southern extent in California is the Sierra Nevada in Tulare County and to Santa Clara County along the West Coast. (3)
Males of A. perdita are easily identified by the mottled black forewings and pure white hindwings. Females can be confused with Acronicta impressa but are larger, blacker, and have less distinct lines and spots than in this species. (4)
Acronicta othello replaces perdita south of the Coastal Ranges and the Sierra Nevada in southern California. (3)