Gypsy moth larvae can feed and develop on more than 300 species of trees and woody shrubs. Oaks are their favourite host trees but aspen, apple and crabapple, basswood (linden), birch and willow trees are also highly suitable hosts. As the larvae grow, their list of host trees expands, sometimes including conifers such as white pine or spruces. A few tree species, including red maple and ash, are not suitable hosts for gypsy moths and typically sustain little or no defoliation, even during outbreaks.
Gypsy moth cocoons are often found in crevices of thick bark or on the underside of branches, but can also be present on outdoor items such as picnic tables, dog houses, planters and vehicle wheel wells or bumpers.
Adult gypsy moths are usually present from mid- or late June through mid- or late July, depending on location and weather. Adult gypsy moths do not feed and while gypsy moths may be present for two to three weeks in a local area, individual moths live only a few days.