delaying the response to the temperature trigger by 5 to 10 days. The larvae, like the adults, can withstand below freezing temperatures at night. Larval dispersal is the dominant source of density-dependent larval mortality and likely regulates high density population dynamics of winter moth in New England. Larvae prefer Oak and Apple, but also feed on Maple, Birch, Hornbeam, Chestnut, Hazel, Quince, Beech, Larch, Poplar, Cherry, Pear, Rose, Raspberry, Blueberry, Willow, Elm, and other leafy trees and shrubs. Invasive Impact The winter moth is native to Europe, but invaded the northeast of the United States in the late 1990s. As of 2007, winter moths have spread to coastal Maine, eastern Massachusetts, Rhode Island, southeastern Connecticut, and eastern Long Island. The moths feed on a wide range of deciduous leaves, and some conifers. This has caused defoliation of the trees across the states in which the moths live. Between 2003 and 2015 winter moths caused defoliation of forests and shade trees from between 2,266 and 36,360 ha/yr in Massachusetts alone. Biological control In Europe, where winter moths are native, two parasitic species, a wasp (Agrypon flaveolatum) and a fly (Cyzenis albicans) prey on winter moth caterpillars. The wasps insert eggs into the larvae. The flies lay eggs on leaves, which the larvae ingest when eating the leaves. As a biological control, the wasp was introduced in Canada but is not being pursued in the United States because there is not sufficient evidence that the wasp would not lay eggs in larvae of other moth species. Introduction of C. albicans, which is species-specific to preying on winter moths, has proven successful in strongly reducing, although not entirely eliminating, winter moth infestation in Nova Scotia, Canada. Test introductions were begun in eastern Massachusetts in 2005. This proved successful, so more fly releases have taken place at sites from southeast Connecticut to coastal Maine. As moth densities can reach ten million larvae per acre, several years are needed before parasitism by the flies reaches 20-50%. Once this is achieved the winter moth density declines and leaf defoliation is reduced to levels not as harmful to the trees. The delay in establishment is likely the result of heavy mortality from predators and hyperparasitoids on the pupating C. albicans. Management of winter moth in Massachusetts using biological control with C. albicans is showing positive results. There are different ways to successfully control the winter moth population