As you can see, unlike many caterpillars that venture out on their own to feed, these guys like company and spend a large part of their caterpillar life with a bunch of friends in a silken tent. The Western Tent Caterpillar can be found from southwestern Canada and the western US to northern Mexico. On years where their population is high, the caterpillars can completely defoliate their host tree. When the caterpillars reach their later stages of development, they will break up the group, heading off individually to continue feeding and eventually pupate. In Montana, the adult moths are usually found from mid to late summer. 

Size: When first hatched, larvae are about 1/8 inch (3 mm) long; mature larvae are about 2 inches (4.5-5.1 cm) long

Photos by: Kim Murray on 5/28/22 near Florence, MT