Pupae may be found attached by silken thread to branches or trunks of trees, rocks, forest debris, buildings or fences. It is quite unlike the larger, light coloured, heavy-bodied female. Mating and egg laying occur near the pupation site. The eggs are laid in masses of 100 to 1000 and are covered with a mat of buff-coloured hairs from the female's body. Since female moths do not fly, natural spread can occur only in the caterpillar stage.
Young larvae are particularly light and buoyant because of their long hairs.
When disturbed, they spin down on a silken thread and are readily blown about by the wind, sometimes for considerable distances. Man also involuntarily helps the spread of this pest by transporting logs, trees, firewood, lumber or stones on which eggs have been laid. Recreational and other vehicles travelling in or from infested areas also carry eggs, larvae or pupae. There are several things that a homeowner can do to reduce gypsy moth around their property. Also, when the caterpillar stage is completed they will use these sheltered areas to pupate, after which the female moths will emerge and lay eggs close by.