Fireflies are efficient sources of light, meaning that 70-90% of the energy (from the chemical reaction in their lanterns is emitted) as light, rather than heat. How much light does one firefly make? That's not an easy question to answer, and firefly researchers seem to focus more on the blink patterns and spectral distribution. The blink patterns can help identify an insect among the 2,000 species of fireflies. The blink patterns can also mark where the insects are in the courtship. For example, in some species a "flash"-y male flies past stationary females, and if a female is "turned on" she turns on her lantern and follows him.