The Science Behind The Glow

Scientists in the Department of Entomology at Purdue University in West Lafayette, Indiana, note that the magic of "cold" living-light production by fireflies has fascinated scientists for many years. Fireflies' living light is a chemical reaction, known as bioluminescence. Bio means "living" and luminescence means "light." Bioluminescence is the ability of living things to produce light by means of a chemical reaction. "Much of what we know about firefly flash chemistry was discovered by Bob Hillingsworth, Larry Murdock and associates at Purdue University in the Entomology Department in the 1980's" Provonsha explained.

In an article titled "Fireflies: Science Lesson in a Jar," Turpin explains that fireflies' light comes from a chemical reaction that takes place in special cells in their abdomen. The cells are called photocytes, which mean "light cells." Photocytes contain two chemicals essential for making the light: luciferin (a substrate) and luciferase (an enzyme). When a firefly pushes oxygen into the photocytes, the oxygen along with the luciferin and luciferase combine with two other chemicals, magnesium and adenosine triphosphate (ATP). ATP is a compound that all living plants and animals use as energy in their cells. When luciferin is combined with ATP, or the fuel and oxygen, which add even more fuel, the luciferin is transformed into a very high-energy chemical. Energy is given off in the form of light, and scientists refer to the process as bioluminescence because it's the production of light by a biological process. Bioluminescence is referred to as "cold light" because a firefly does not use any of its energy to create heat when it is making light. If the light was not cold, the firefly would burn up when the flash went off.