The firefly is capable of producing a "cold light", containing no ultra violet rays, due to a chemical reaction that occurs in specialized light-emitting organs.
This capability is called bioluminescence. It's primary function in adult fireflies is for finding a mate. Usually the ones flying around are males.
All fireflies glow as larvae. Firefly Larvae are predaceous and have been observed feeding mostly on earthworms, snails and slugs.
Observations of adults feeding on other prey items are practically non-existent. It's likely adults feed on plant nectar in order to sustain their energy requirements in the adult stage which can last several months or longer. There are more than 2000 species of firefly.
Ohio state firefly websiteWikipedia infoYoutube of a lightening bug on his back. Someone help him up already!
youtube fireflies in NYC