How Is The Light In Fireflies Produced?

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The light produced by fireflies (Photinus pyroles), or lightning bugs, is a heatless light called bioluminescence. Bioluminescence occurs in a number of species of bacteria, fungi, insects, some marine invertebrates (animals without spines) and fish. Bioluminescence in fireflies is caused by a chemical reaction in which the organic compound luciferin undergoes oxidation (the combination of a substance with oxygen) in the presence of the enzyme luciferase. The flash of light occurs when the oxidating chemicals jump to a high-energy state and then revert to their normal state.

The rate of flashing is controlled by the firefly's nervous system and takes place in special air-tube-containing cells called photocytes. The rhythmic flashing is most likely a mating signal. The flashing may also be a warning signal, designed to remind predators that the firefly has an unpleasant taste.

Air temperature also seems to be linked to the rate of flashing. The higher the temperature, the shorter the interval between flashes. For instance, a flash occurs every eight seconds at 65° Fahrenheit (18.3° Celsius) and every four seconds at 82° Fahrenheit (27.7° Celsius).

Sources: "Bioluminescence." Encyclopaedia Britannica CD 97; Duensing, Edward. Talking to Fireflies, Shrinking the Moon, p. 44; Farb, Peter. The Insects, p. 119; "Firefly." Encyclopaedia Britannica CD 97; Sutton, Caroline, and Duncan M. Anderson. How Do They Do That? pp. 206-7.

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