These caterpillars can be found feeding in colonies on the leaves of apple, pear, and some forest trees during July and August.
Damage can result in complete defoliation of small trees or of single branches on large trees.
The moth which emerges has a wingspread of about 2 inches and has gray front wings with brown markings and white hind wings with a small black spot along the rear edge. The moths fly to apple or related trees where females lay their eggs on the undersides of leaves in masses of 50 to 100. Control measures include removal by hand or other biological and chemical control methods.