Northern Prairie Wildlife Research Center
Wingspan 4.1 cm. Forewing is white with fine, dentate black lines. This geometrid is common and widely distributed in western North America. Moths fly in spring. Caterpillars feed on the foliage of flowering trees and shrubs, such as alder (Alnus), willow (Salix), and snowberry (Symphoricarpos albus), and conifers, such as Douglas-fir (Pseudotsuga menziesii) and western hemlock (Tsuga heterophylla).
Similar species: many species in at least twelve genera of Geometridae, such as, Aethaloida packardaria, Anavitrinella pampinaria, and Biston betularia have similar colors and markings, however, E. crepuscularia is distinguished by the fine dentate marks along the black lines.