This is our most widespread silkmoth in the US. It is also one of our largest, with a wingspan of up to 6 inches. Like our other giant silkmoths, males have smaller bodies but much larger and more feathery antennae than do females (a male is pictured here). The species is widespread in North America. Here in western MT they can be found mostly in May and June. Larvae feed on leaves of broad-leaved trees and shrubs, including chokecherry, birch, maple, willow, and members of the rose family.
Photo by Brady S. on 6/3/20 in Missoula, MT