Fireflies put on a show at Great Smoky Mountains National Park

One of the greatest shows in the Smokies is going on right now.

Every year at this time, the fireflies at Elkmont blink in unison. It's part of their mating behavior.

The sight has become so popular that Park officials began managing the number of visitors to the trailhead. Visitors are now required to park at the Sugarlands Visitor Center and ride trolleys to Elkmont. The trolleys leave until the parking lot is full, which usually around seven in the evening.

For those riding the trolleys, it is recommended that visitors bring flashlights with red cellophane covers to reduce white light. Visitors can bring lawn chairs, and carry food and water in backpacks which can fit on their laps in the trolleys. It costs $1 per person.

The fireflies have become quite the attraction over the last couple of years, with around 1,000 people visiting the park every night to see the light display. The best place to view the fireflies is in an open area, where there are fewer trees. If you want to see fireflies, this coming Sunday is the last night that the trolleys run, and park officials only expect the behavior to last two more weeks at the most.