Fireflies

The firefly uses chemiluminescence to produce light and attract a mate. The reaction occurs inside the living organism and is known as bioluminescence. They produce light via a chemical reaction consisting of Luciferin (a substrate) combined with Luciferase (an enzyme), ATP (adenosine triphosphate) and oxygen. When these components are added, light is produced. McElroy (1951) described the reaction as: