How do fireflies produce light?

Fireflies, which belong to the order Coleoptera, produce light through a chemical process known as bioluminescence. This reaction occurs within specialized cells called photocytes located in light-producing organs on the underside of the insect's abdomen.123

The process involves the oxidation of an organic molecule called luciferin, which is catalyzed by the enzyme luciferase in the presence of oxygen and ATP. This reaction creates an unstable, excited-state intermediate called oxyluciferin; as this compound returns to a lower energy state, it releases energy in the form of light.12

Because nearly 100 percent of the energy is emitted as light with almost no heat, it is referred to as "cold light". The light production is under nervous control, and the organs are supplied with air via tracheae to provide the necessary oxygen. Fireflies use these rhythmic, species-specific flashes primarily for communication and mating.123