Winter Moth - Life Cycle

The adult winter moths emerge from the ground in November or December, but only the male is able to fly. The female climbs to the base of a tree or building and attracts the male through the pheromone (sex scent) that she exudes. After mating the female lays a cluster of approximately 150 eggs under tree bark or in tree crevices, and her life is now over. In March or April the eggs hatch into a smooth green inchworm with a narrow white-stripe running lengthwise on each side of the body. The caterpillar spins a strand of silk, which, with the help of air currents, takes it into tree canopies in a dispersal method known as "ballooning.” Once there, the damage to the tree begins as the caterpillars work their way into the tree buds and leaves to feed. Winter moth caterpillars can also drop from trees to nearby ornamental shrubs such as roses. When feeding ends in mid-June the caterpillars migrate into the soil to pupate and emerge as moths.