Why do fireflies glow?

Fireflies glow due to a chemical reaction in their light-producing organs, involving luciferin, luciferase, oxygen, and ATP. This bioluminescence is highly efficient, producing light without generating heat. Fireflies use their glow primarily to attract mates, with each species having its unique flashing pattern. In some cases, the light also serves as a warning to predators, signalling that the firefly is toxic or unpalatable. This natural light display is both a survival mechanism and a key part of their reproduction.