In June and July, oak webworms were found on red and bur oaks in central Minnesota. The webs of these caterpillars enlarge to three or four inches wide and nearly two feet long. Webs contain feeding caterpillars, excrement, and bits of leaves. Pupation and emergence of moths occurs in the webs. Overwintering eggs are attached to branches and trunks. Oak webworms are grayish green, and their heads and neck shields are black.