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Why do lightning bugs glow in the dark?

Do you mean "why" or "how"?

They glow in the dark as part of a communication system they use to find mates. The female waits and flashes at flying males. The males flash back and try to find the right species females. The temporal and spatial pattern of the light flashes confer species specificity - usually. Biology is a case in exceptions. There is one species of firefly whose females flash in many different ways to attract other species males. When the wrong species male arrives, he is eaten! Gives new meaning to not believing everything you see.

As to how they glow: they use two chemicals called luciferin and luciferase. The luciferase is an enzyme, a protein catalyst which is not consumed in its reaction with luciferin. The luciferin changes chemically and gives off light. Whenever an electron drops an energy level (a quantum leap) in a molecule, it gives off a photon of light.

Jim Murray

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