In summer, a few may breed in the cooler, mountainous sections of the state, but most go farther north. Its fur is yellowish brown, darker on the back. Pipistrelles take wing early in the evening and make short, elliptical flights at treetop level. In summer, they inhabit open woods near water, rock or cliff crevices, buildings, and caves. They sleep soundly, often dangling in the same spot for months completely covered with water condensation.
Pipistrelles eat flies, grain moths, and other insects.
Pipistrelles live 10-15 years. They are found throughout Pennsylvania, except in the southeastern corner. The fur is dark brown, and the face, ears, and flight membranes are blackish. Big brown bats fly at dusk, and generally use the same feeding grounds each night. They fly in a nearly straight course 20-30 feet in the air, often emitting an audible chatter.