Why Are Our Fireflies Synchronized?

During late May and early June, thousands of eager observers from around the world travel to the Elkmont area of Great Smoky Mountains National Park to observe the phenomenon of synchronized fireflies flashing in the night. The synchronized flashing was first scientifically documented in the Smokies in the 1960s and has since been identified in places like Congaree National Park in South Carolina and Allegheny National Forest in Pennsylvania.

But the Elkmont area still draws the biggest crowds. In fact, access to the area during firefly season is now managed by the National Park Service with a free lottery system.

Most of the world’s hundreds of species of fireflies use their flashes to attract suitable mates. Generally, during breeding season, females wait patiently on the ground for males to fly over them and flash their flashers. If the females recognize the flashes (by flash length, flash intervals, and flash numbers) as coming from a male of their own species, they will respond with their own specific Morse-code-like sequence of flashes. Conversely, when the males recognize the correct flash response from a female, they respond with more flashes specific to their species. Once both male and female have confirmed that they are flirting with members of the same species, mating occurs.

Why then do the males of the Smokies species of firefly, (Photinus Carolinus) synchronize their courtship flashing? Research shows that female P. Carolinus respond to synchronized flashing better than non-synchronized flashing. So if you’re a guy firefly trying to attract a gal, synchronizing your flashes with the other fellows in the vicinity is the best way to get the attention of the gals. Or as park biologist Dr. Becky Nichols puts it, “The purpose of synchrony would be to preserve species and sexual recognition in a visually cluttered environment.”