In Brief
The process by which fireflies produce their distinctive glow is actually very complicated. Scientists have known in broad strokes how it works, but now they're starting to figure out the intermediate details.

Fireflies (or “lightning bugs,” as we sometimes call them) are seemingly magical creatures that put on dazzling displays of light. They appear in the largest numbers around sunset, but their greenish glow makes them unmistakable when the Sun completely disappears from the sky. Where does this glow come from? And how does it manifest itself?

Credit: Getty Images
Credit: Getty Images

In most cases, organisms with the capacity to render light through biological processes do so using something called chemiluminescence. The specifics aren’t the same for all bioluminescent creatures, but the bottom line is this: bioluminescence normally involves luciferin and luciferase (the former produces the light, while the latter is the catalyst for the reaction).

With fireflies, the answer doesn’t appear to be that simple. In a new video, the American Chemical Society explains:

“About 60 years ago, scientists figured out in broad strokes the cascade of reactions that allows fireflies to produce light. It starts with a chemical called luciferin, which interacts with the energy-transporting molecule adenosine triphosphate, or ATP. The product of that reaction then combines with oxygen, and this in turn releases light. Intermediate steps, however, have not been fully fleshed out. Bruce R. Branchini and colleagues wanted to explore potential mechanisms.

The researchers experimented with the enzyme luciferase, which boosts the initial reaction between luciferin and ATP, under varying conditions. In contrast to the commonly accepted model, the resulting data suggest that the transfer of a single electron to oxygen occurs during one of the final steps to spur light production. Other studies of bioluminescence have pointed to the same mechanism, raising the possibility that it could be a unifying feature of the natural phenomenon.”

Watch: “Experimental Support for a Mechanism in Firefly Bioluminescence”