Synchronous fireflies illuminate the forests of Great Smoky Mountains National Park, Tennessee

© Floris van Breugel/Minden Picture

By the light of the fireflies

Every year between late May and mid-June, synchronous fireflies gather into a sparkling, rhythmic light show in the forests of Great Smoky Mountains National Park. As part of their two-week mating display, the female lightning bugs synchronize their flashes with nearby males so that every few seconds waves of light ripple through the woods. Of at least 19 species of fireflies that live in Great Smoky Mountains National Park, Photinus carolinus is the only species with synchronous light displays, but they can also be found in Allegheny National Forest in Pennsylvania and Congaree National Park in South Carolina. Other species of synchronous fireflies are particularly prevalent in Southeast Asia.

Not all firefly species flash light. But of those that do, each species has a characteristic flash pattern that helps the males and females recognize each other. In most species, like this one, the males fly and flash, while the females generally stay still and respond with a flash of their own. It's not clear why some species of fireflies flash synchronously, although some hypotheses involve diet, social interaction, and altitude. No matter why they do it, the flashing of lightning bugs is a magical sight to see—and we can all use a little magic sometimes.