Northern Prairie Wildlife Research Center
Wingspan 3.9 cm. Forewing is variable red-brown with darker and lighter wavy bands; the hindwing margin strongly dentate. This geometrid is common and widely distributed in wet conifer forests of western North America. Moths fly from late summer to spring, overwintering as adults. Caterpillars feed on the foliage of buckthorn (Rhamnus purshiana).
Similar species: Triphosa californiata is smaller, forewing is dark black-gray, widely distributed in western North America, caterpillars feed on coffeeberry (Rhamnus occidentalis); Hydria undulata (Geometridae) is smaller, forewing is densely covered with undulating pale lines, widely distributed, caterpillars are generalist feeders on the foliage of flowering trees and shrubs; Coryphista meadii (Geometridae) forewing with straight bands, widely distributed, caterpillars feed on berberis (Berberis).