How Do Fireflies Emit Light?

The Firefly

The firefly, also called a lightning bug, can be found on all continents except the Antarctica. In the United States and Canada alone, there are some 140 species of fireflies. Fireflies are a soft bodied beetle named for the fact that they emit a flashing or glowing light. One of the most common fireflies located east of the Rockies in North America, is the pyralis, which can be found hovering over lawns and meadows flashing a small yellow light. Not all species of adult fireflies emit light, although the larvae of all fireflies do, as do some of the eggs.

Purpose of the Glow

The unique illumination of the firefly is not a defense mechanism, but a means to attract a mate. Each species has a distinct flashing pattern to attract the opposite sex within their species. Both the female and male firefly use their luminous signaling to call out for a mate. The light they produce is virtually heatless, and referred to as bioluminescence.

The Firefly's Body

Adult fireflies possess a flat oblong shape, between a ¼ to ¾ inches in length. The firefly has two pairs of wings, with one used for flying and the second pair as a cover for the first. Not all female fireflies fly, and may be wingless or bear short wings. The firefly's photic organ, which enables it to emit light, is normally located below its abdomen.

How It Produces Light

Four components combine to create a chemical reaction which allows the firefly to produce light: Luciferin, Luciferase, Adenosine triphosphate (APT) and oxygen. Luciferin is a light-emitting pigment. Luciferase is an enzyme. APT is a high-energy molecule that stores energy. Oxygen is the element essential for plant and animal respiration. Luciferin and Luciferase are stored in the firefly's photic organ. When the firefly draws in oxygen, it finds its way to the stored Luciferin and Luciferase and causes them to oxidize. The Luciferase becomes activated, which generates light that glows through the firefly's abdomen.

Controlling the Light

Scientists can't agree on how a firefly turns its light off and on. One theory is the "Oxygen Control Theory." In the Oxygen Control Theory, the firefly controls the amount of oxygen that gets to the photic organ, which creates the chemical reaction. Another theory is the "Neural Activation Theory." In this theory the firefly controls the tracheal cells neurally, which sends a messenger molecule to the photic organ and controls the chemical reaction that creates the light.

Resources

• Bioluminescence: Fireflies and the Future