Northern Prairie Wildlife Research Center
Wingspan 3.9 cm. Forewing is a pale green-white with two white lines. This geometrid is common and widely distributed in western North America. Moths fly in summer. Caterpillars are generalist feeders on foliage of flowering trees and shrubs, particularly, alder (Alnus), maple (Acer), cherry (Prunus), oak (Quercus), and willow (Salix).
Similar species: Cabera erythemaria (Geometridae) has three faint brown lines; Protitame matilda (Geometridae) forewing with a narrow black postmedian line. Both species are smaller than C. perlata, have white wings, widely distributed, caterpillars feed on foliage of willow (Salix).