Northern Prairie Wildlife Research Center
Wingspan 3.5 cm. Forewing is pale gray-cream with narrow wavy black lines and a brown patch bordered by two black tooth-like marks in the subapical area. This geometrid is common and widely distributed in western North America. Moths fly in midsummer. Caterpillars are generalist feeders on the foliage of flowering trees and shrubs, such as alder (Alnus), and huckleberry (Vaccinium).
Similar species: numerous species exhibit similar shades of gray, brown, and white colors with fine wavy black lines such as Aethaloida packardaria, Anavitrinella pampinaria, Biston betularia, and Ectropis crepuscularia, however, I. emasculata is distinguished by the subapical brown patch with black markings.