Northern Prairie Wildlife Research Center
Females are wingless. The male wingspan is 3.4 cm. Forewing is elongate and gray with dark lines. This geometrid is common and distributed throughout the Pacific West. Moths fly in late fall and winter. Caterpillars are generalist feeders on the foliage of flowering trees and shrubs, particularly ash (Fraxinus), cherry (Prunus), and oak (Quercus).
Similar species: Operophtera bruceata is smaller with less elongate wings; Epirrita autumnata wings are gray-white with wavy dark lines; species of Venusia, such as Venusia pearsalli are smaller and fly in spring and summer.