Caterpillars in Maine are defoliators that strip and damage various tree species and non-floral shrubbery. Each caterpillar type feeds to support its needs toward metamorphosis, such as eventual moth transformation or egg-producing hibernation. It uses the specific parts of a tree's branch system or foliage for hosting and nutrition during its caterpillar stage. Several types of caterpillars annually feed in Maine's forests and open lands, and each type usually favors a particular tree species.
Non-Specific Hardwood Tenting Caterpillars
Eastern tent caterpillars and forest tent caterpillars build their tent-like webs close to a tree's trunk at branch intersections. They target wild fruit trees and most species of hardwood trees. These black-bodied caterpillars, with brown hair and either blue or white oval spots, are an active threat to budding trees every springtime in Maine. Fall webworms build large webbings at the end of branches, which encompass the foliage area they feed on and damage. Brown-bodied fall webworms covered in white hair are most active in late July and August.
Oak Tree Caterpillars
Hairy black gypsy moth caterpillars, with red or orange banding, have affected trees in Maine since 1869. The state's oak tree species suffer severe damage from this caterpillar's defoliating appetite. Oak tree caterpillars wander from tree to tree late July through August devouring foliage. Oakleaf caterpillars exhibit varied physical traits, including red or green colorings and spotted to lined features. They primarily feed on the white oak leaves and hatch on the leaves' undersides. They also feed on beech leaves throughout the summer months. Caterpillars drop to the ground to burrow when done feeding.
Cottonwood and Ornamental Poplar Caterpillars
Leafy foliage favored by the satin moth caterpillar grows on cottonwood, willow and poplar trees, which grow densely across eastern and central Maine. These small caterpillars are often grey or black with yellow hair and a white spotted pattern across the body. They slumber through the winter in cocoons until awakening in May to feed on foliage. Cocoons attach to any part of a tree, building, fence post or utility pole as these caterpillars feed and wander from tree to tree.
Birch Tree Caterpillars
European birch tree species, such as white, paper and gray, grow throughout Maine. The birch casebearer caterpillar and saddled prominent caterpillars feed on full growth leaves or new twig and leaf bud systems. The smooth-skinned brown birch casebearer constructs curved cases from which they feed. They prefer the joints of new twigs and branches sprouting from the host tree trunk and create tunneling holes or "mines" in the bark. Small brownish-bodied saddled prominent caterpillars, with spiny antler shaped hair, target Maine's yellow birch and oak tree foliage from May through June as the newly hatched feast on the underside of leaf structures.