The Forest That Flashes in Perfect Unison

If you head into the Great Smoky Mountains National Park during a very specific two-week window of the year, you will not just see a few fireflies buzzing around in the dark. Instead, the entire forest will go dark and light up in unison.

The Science Of The Sync

Fireflies come in over 2,000 different species across the world. However, only a few of these species can synchronize their flashing lights. The species of fireflies that reside in the Smoky Mountains exhibits a specific flashing pattern and is called Photinus carolinus.

These fireflies use their flashing light as part of their mating ritual. The male fireflies will flutter to the ground where the females reside. In the pitch-black forest, it can be incredibly hard for the females to spot the males. To avoid this issue, the male fireflies will flash their lights five to eight times in rapid succession. Then the entire forest drops into pitch-black for about eight seconds, allowing the males to spot the flashing females.

Creating Cold Light

Fireflies produce bioluminescence. This chemical reaction involves mixing oxygen with the chemicals in their abdomens, luciferin and luciferase. Incandescent lightbulbs waste most of their energy as heat. In contrast, fireflies produce a “cold light” as nearly 100% of their energy is used to produce the light. If they released heat alongside their light, they would not be able to survive the chemical reaction.

Catching The Light Show

Fireflies live for only three to four weeks as adults. The synchronized light display only happens during late May or June. To protect the fireflies and their ecosystem and food sources, the National Park Service limits access to the main area where the show occurs in Elkmont.

People have to enter a lottery system each spring to receive a parking pass. If lucky enough to go, people have to cover their flashlights in red cellophane to avoid disorienting the fireflies. Standard flashlights will make fireflies stop flashing. This biological wonder only survives in the complete darkness of the Smoky Mountains.