There are several species of caterpillars called sod webworms that can be highly destructive pests. Damage to grass is caused by the feeding of the larval or “worm” stage. The adult moth does not cause damage to turf, other plants or clothing. The damage caused by sod webworms may first appear in early spring. The damage shows up as small dead patches of grass among the normally growing grass. The summer generation may cause general turf thinning or even irregular dead patches in late June into early August. Sod webworms prefer sunny areas and the larvae are often found on south facing, steep slopes and banks, where it is hot and dry. Heavily shaded turf is seldom attacked by the larvae. The most severe damage usually shows up in July and August when the temperature is hot and the grass is not growing vigorously.