Synchronous fireflies (Photinus carolinus) are one of at least 19 species of fireflies that live in Great Smoky Mountains National Park. They are one of only a couple species in North America whose individuals are known to synchronize their flashing light patterns.

When can you see synchronous fireflies?

Each year, from late May to early June, certain species of fireflies glow in unison as a part of their mating process. Males flash for several seconds and then go dark, and the females respond in kind. If you travel to one of these spots in early June, you can observe the natural phenomenon for yourself.

Why do fireflies flash in sync?

One explanation for this behavior is that synchronized flashing cuts down on visual clutter and helps the females clearly spot the males' patterns. The night skies over Elkmont get pretty crowded, with lots of males in the same place at the same time. "At their peak, the fireflies are very dense," said Moiseff.