Females lay fertilized eggs on the tree's bark or branches. The emerging caterpillars proceed to eat away at the leaves and soft plant tissue. In large numbers, annual substantial damage to the tree can kill it over time. After 30-40 days, the caterpillars form cocoons and will emerge as adults about two weeks later. An exception to that timeline is the generation of caterpillars pupating before winter comes. These caterpillars remain in their cocoons all season long, protecting them from the elements. They emerge as flying adults the next spring and will parent the first generation of that year.