Gypsy moth egg masses overwinter on stones and trees. The eggs hatch from late April through early May and the young hairy larvae feed on foliage. The newly hatched larvae move by suspended silken threads, blown by the wind. In highly infested areas, these larvae come into contact with people and some people have allergic reactions to the hairs of the larvae. These larvae also decrease the beauty and attraction of campsites.
Mature larvae feed in the trees at night and seek shelter in crevices or under trash in the day.
Pupation takes place during late June and early July, with the pupal cases attached to tree bark, stones, buildings and other similar sites. The moths emerge in late June through mid-July. The male moths are dark buff and fly readily during the day while the females are white with black markings. The females do not fly and have thick abdomens. The larvae primarily affect deciduous forest trees by defoliation.