Every June, the largest gathering of fireflies illuminates Elkmont Ghost Town in Tennessee’s Smoky Mountains National Park. It’s a mating ritual in which the males fireflies flash their beacons, then shut off their lights to await a feminine reply.
They require total darkness to mate. Thus the Nation Park Service has limited the use of lights and the number of people who can be in the region during the firefly mating season.

A still shot from "Elkmont Symphony" by Harun Mehmedinovic.