Our Museum Educator, Carolyn, saw these moth caterpillars during their earlier stages, with a bunch of their buddies in a silken tent on a host tree. Pat snapped a picture of an older one that had set out on its own. (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 present from mid to late summer …which means this newly emerged moth is right on time! After a successful mating, females lay oval shaped masses of 150 to 250 eggs that partially encircle twigs, branches and sometimes the main stems of small diameter trees and shrubs. The new generation overwinter as first instar larvae inside the eggs and emerge the following spring. They can be found from southwestern Canada and the western US to northern Mexico.
Photos are credited in clockwise order: Carolyn Taber on 7/14/20 in Clinton, MT. Carolyn Taber on 5/6/20 in Clinton, MT. Pat Little on 6/1/20 near Missoula, MT.