“Luciferins vary in chemical structure; the luciferin of luminescent bacteria, for example, is completely different from that of fireflies.” — From an article at Encyclopædia Britannica Online, 2012
“Light is produced by fireflies through a chemical reaction between luciferin and its enzyme counterpart, luciferase.” — From an article at photonics.com, June 20, 2012
“Luciferin” got its name from the Latin word “lucifer” (meaning “light-bearing”), which is also a source of the word that is sometimes used as a name of the devil. We won't go into how Lucifer came to be called by that name—suffice it to say he wasn't always associated with darkness—but we will look a bit more closely at the Latin word “lucifer.” It comes from Latin “luc-,” meaning “light,” plus “-fer,” meaning “bearing” or “producing.” Additional relatives include the nontechnical adjective “luciferous,” meaning “bringing light or insight,” and “luciferase,” the enzyme that catalyzes the oxidation of luciferin.
From Merriam-Webster Online at www.Merriam-Webster.com.