We live across the street from an historic church that also has the largest colony of bats in the central part of our state. Every night they come out to feed. Sometimes they stay for the night in crevices on our wrap around porch! They are harmless. If they get in your house, merely open a window and wait. The bat will definitely get out. They have incredible echolocation to help them "see" as they fly. Bats do have good eyesight also. Moth balls will do nothing. In the Fall, do a good inspection of the eaves of the home and patch up any small holes with screen. Bats need only 3/4 of an inch to get in! Good luck!!