For many regions across the world, the arrival of fireflies signifies the arrival of summer.

It has been accepted that the orb of light radiating from the abdomen of a firefly, or lightning bug, is bioluminescent. That means that the production and emission of the light are as the result of a living organism.

Recently, however, the chemical process that makes a firefly turn from an average beetle into a symbol of summer was discovered by Dr Bruce Branchini of the department of chemistry at Connecticut College in the USA.

The American Chemical Society reports that the key to the firefly’s bioluminescence lies in a molecule that is toxic to most animals. This molecule, superoxide, contains an extra electron and causes inflammation and cell damage in humans and most animals. Fortunately, we are protected against its effects by our biological systems.

Branchini has found that, in the firefly, this molecule reacts with luciferase, the class of oxidative enzymes used in bioluminescence, to make the abdomen of the firefly glow.

Watch the video above for more about the discovery.

Source: American Chemical Society and the Journal of the American Chemical Society via The Huffington Post.