Northern Prairie Wildlife Research Center
Wingspan 10.3 cm. Forewing is variable rose-red, purple-red or dark red-brown with a large white, comma-shaped reniform spot, white basal and postmedian lines, and a round black subapical spot; hindwing is similar with an extremely elongate reniform spot. This saturniid is common and widely distributed in the Pacific Northwest. Moths fly in spring. Caterpillars are generalist feeders on the foliage of flowering trees and shrubs, particularly snowbrush (Ceanothus velutinus) and bitterbrush (Purshia tridentata) and the foliage of some conifers, sometimes found on Douglas-fir (Pseudotsuga menziesii).
Similar species: Hyalophora gloveri hindwing with a short reniform spot and broader basal and postmedian lines, occurs in the Southwest, Great Basin and Rocky Mountains. Hybrid populations of H. euryalus and H. gloveri occur in the northern Rocky Mountains.