HARPSWELL, Maine — A new invasive pest that can damage hardwood and fruit trees has been discovered in Maine. The Maine Forest Service said a 400-acre area in Harpswell has been infested by winter moths: small, tan moths that lay eggs that develop into hungry caterpillars and cause leaves to look like Swiss cheese. Entomologist Charlene Donahue said it is the first time that a winter moth infestation has been detected in Maine. She said the moth has been seen in Eastern Massachusetts for the past 20 years, and probably came to Maine on landscape plants from the Bay State. The caterpillars have been known to weaken and kill a number of tree species — including oak, maple, elm, ash, birch, apple, cherry, and blueberry — by eating their leaves.