When living creatures produce and emit light it’s called bioluminescence. The main reason fireflies glow is to find a mate, though they can also light up under other situations as a warning to others.
Why do fireflies glow? - Mystery Science
A glowing firefly energy transformation
Frontiers Behavioral responses of bioluminescent fireflies to artificial light at night
What makes fireflies glow?
About the Book The first-ever comprehensive firefly guide written for all those who want to know more about the amazing world of lightning bugs and
Fireflies, Glow-Worms, and Lightning Bugs - (Wormsloe Foundation Nature Books) by Lynn Frierson Faust (Paperback)
How do fireflies get their glow? We finally have some answers.
Why do fireflies shine in the night? - Quora
Science Behind Why Fireflies Glow
Unusual Labmates: Lighting up the lab
Fireflies
Blue Sky Science - Morgridge Institute for Research
Fireflies
How do fireflies get their glow? We finally have some answers.
Blue Sky Science
How a firefly's tail makes light