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The firefly's light comes from a chemical reaction that takes place in special cells in its lower abdomen, called 'photocytes'. These cells contain two chemicals, luciferin and luciferase. When oxygen is sent to the photocytes, the oxygen, luciferin and luciferase combine with two other chemicals, magnesium and ATP. ATP (adenosine triphosphate) is a compound that all living plants and animals use as energy in their cells; your body turns most of the food you eat into ATP. When luciferin is combined with ATP and oxygen, the luciferin is transformed into a very-high-energy chemical. But it is unstable in its high-energy form, and when it reverts to its normal state, it gives off energy in the form of light, usually of a greenish-yellow color. Scientists call this process "bioluminescence", because it is the production of light (luminescence) by a biological process. |