The Lampyridae are a family of elateroid beetles with more than 2,000 described species, many of which are light-emitting. They are soft-bodied beetles commonly called fireflies, lightning bugs, or glowworms for their conspicuous production of light, mainly during twilight, to attract mates. Light production in the Lampyridae is thought to have originated as an honest warning signal that the larvae were distasteful; this was co-opted as a mating signal in the adults. In a further development, female fireflies of the genus Photuris mimic the flash pattern of Photinus species to trap their males as prey.
Firefly
Photuris female by flash photography (above); by her own light (below)
Lamprohiza female by her own light
Fireflies in the woods near Nuremberg, Germany, 30-second exposure
Bioluminescence is the production and emission of light by living organisms. It is a form of chemiluminescence. Bioluminescence occurs widely in marine vertebrates and invertebrates, as well as in some fungi, microorganisms including some bioluminescent bacteria, and terrestrial arthropods such as fireflies. In some animals, the light is bacteriogenic, produced by symbiotic bacteria such as those from the genus Vibrio; in others, it is autogenic, produced by the animals themselves.
Flying and glowing firefly, Photinus pyralis
Female glowworm, Lampyris noctiluca
Osamu Shimomura isolated the photoprotein aequorin and its cofactor coelenterazine from the crystal jelly Aequorea victoria in 1961.
Mycena chlorophos, a bioluminescent mushroom