Fireflies produce light due to -
Bioluminescence is light produced by a chemical reaction within an organism.
It requires a combination of 4 different ingredients. The light is produced through a chemical reaction involving Luciferin (which is the substrate), Luciferase (the enzyme), ATP and oxygen.
The basic reaction sequence is: The luciferase catalyzes the oxidation of luciferin into oxyluciferin. In the process, light is emitted.
NADH
GTP
ATP
Phosphocreatinine