Firefly, or Lightning Bug, a beetle that produces light. The light is produced in special organs called photophores located on the underside of the abdomen. They consist of several layers of small reflector cells and a single layer of light-producing cells. The light-producing cells contain nerves, air tubes, and two types of chemicals— luciferin and the enzyme luciferase. When luciferin is activated by adenosine triphosphate (ATP) and luciferase, it combines with oxygen in the air tubes; this reaction produces energy in the form of a heatless, greenish-yellow to reddish-orange light. Fireflies produce light to attract mates. In most species, both sexes produce light.

FirefliesFireflies are beetles that produce light.

Most of the 2,000 known species of fireflies live in the tropics. About 60 species live in North America. The insects range in length from less than half an inch (12.7 mm) to more than an inch (25.4 mm).

Luciferin and luciferase, extracted from preserved photophores and purified, are used to detect ATP in a biochemical test. This test has applications in bacteriology, cancer research, oceanography, and space exploration.

Are Fireflies Flies, Bugs, or Beetles?

Fireflies are not really flies. Some people call them lightning bugs, but they are not bugs either. Fireflies are actually beetles.

The firefly is a flat, egg-shaped beetle 1/4 to 3/4 inches (5 to 20 millimeters) long. Its color is mostly brown or black. The firefly would be a rather ordinary beetle, except for one thing. At night, it can “light up.” You probably have seen fireflies whizzing around and flashing their lights on warm summer nights.

Some firefly larvae can glow, too. This is why people call them glowworms. Of course, they are not worms at all.

How Do Fireflies Make That “Cool” Light?

The firefly’s light is cool in more ways than one. Unlike natural and human-made light, it gives off no heat. The firefly’s light is produced by a complicated set of chemical reactions that take place in its abdomen. This complex process is called bioluminescence (by oh loo muh nehs uhns).

There are three layers to the organ that produces the firefly’s light. The innermost layer acts as a reflector. The middle layer contains the light cells. The outermost layer is clear and can be seen through.

Fireflies can control the light they produce. They send out light in a pattern of flashes. Scientists believe that fireflies do this by regulating the amount of oxygen they take into their bodies. Oxygen is the fuel that helps create the light.

What Do All Those Flashes Mean?

The male firefly flashes its light for a very important purpose. It wants to find a mate. When it gets dark, the male firefly flies through the night. It flashes its light like a signal. Each kind of firefly has its own signal.

The female firefly has short wings and often can’t fly. It perches itself on a bush or a rock and waits. When a male passes by with a signal the female recognizes, the female flashes back the same signal. The male lands and touches the female’s antennae. This is how fireflies smell each other. If the female smells right to him, the two fireflies will mate. Later the female lays her eggs.

Fireflies belong to the families Elateridae and Lampyridae of the beetle order, Coleoptera.