It takes two years for the densely hairy caterpillars to complete development — transforming into the stunning moth that you see (take a peek at the hindwings too). The caterpillars are active during the short northern summer, feeding on various plants, but particularly hardwoods such as willows (Salix spp.), alders (Alnus spp.), and birches (Betula spp.), and are dormant under the snow for much of the rest of the year.  Their range extends from Newfoundland and Labrador to the tundra of Northwest Territories, Yukon, and Alaska, south in the east to Michigan (and in the Appalachians to North Carolina), and south in the Rockies to Arizona and New Mexico. Adults are on the wing from June to August in boreal mixed woods and parklands, moist shrubby arctic tundra, and mountains in the south. In our area, they are most common in late June and early July.
Photo by Laura Blue Palmer on 7/6/20 or 7/7/20 in Glacier National Park, MT.