the two species hybridize. Distribution Native to Northern and Central Europe: In the South, its range extends to Northern Italy; in the East to the Caucasus and Asia Minor; in the North to the Baltic. The genetic populations of winter moth in Europe are a result of recolonization following the last glacial period. As an invasive species, this moth is found in Nova Scotia, coastal New England (Massachusetts, Maine, Rhode Island, Connecticut, and New York) and also the Pacific northwest (mainly Vancouver Island). In New England, expansion inland and north appears to be curtailed by cold winter temperatures, so for example, coastal Maine but not inland. Locally milder winters, as part of global climate change, may be allowing expansion of afflicted territory. A study conducted in Massachusetts documented that winter moth defoliation reduced the annual trunk diameter growth rate of oak trees by an average of 47% while not significantly impacting growth rates of the less defoliated maple trees. Life cycle Winter moth larvae (caterpillars) emerge in early spring from egg masses laid near leaf buds after a series of days in which the daytime high temperatures reach into the 50s Fahrenheit. Recently hatched larvae feed on expanding leaf buds, often after having burrowed inside the bud, and later on foliage, for approximately six weeks. In addition to feeding on the tree where they hatched, young larvae will also product silk strands to 'balloon' (be wind-blown) to other trees. By mid-May the larvae, green in color and about an inch long, descend to the ground. Very little mortality due to disease has been noted in winter moth larvae in North America. Pupation occurs in the soil in late May. Adults emerge from the soil in mid-late November. The female winter moths are flightless but release a sex pheromone to attract males. After mating, the female lays between 150-350 tiny eggs in bark crevices, on branches, in lichen, and under bark scales. With such a long pupal period, winter moth is vulnerable to numerous pupal predators and parasitoids. Research conducted in the Netherlands indicated that as climate warming is causing spring temperatures to become warmer sooner, some of the winter moth eggs were hatching before tree leaf buds - first food for the caterpillars - had begun to open. Early hatchlings starved. Late hatchlings survived. Because hatch timing is genetically controlled, the moths are evolving to resynchronize with bud opening by