How and why do fireflies light up?

Fireflies are beetle insects from Lampyridae family in the order Coleoptera with over 2,000 described species. They are soft-bodied beetles that are commonly called fireflies or lightning bugs for their conspicuous use of bioluminescence during twilight to attract mates or prey.

Fireflies produce a "cold light", with no infrared or ultraviolet frequencies. This chemically produced light from the lower abdomen may be yellow, green, or pale red, with wavelengths from 510 to 670 nanometers. Some species such as the dimly glowing "blue ghost" of the Eastern US are commonly thought to emit blue light (<490 nanometers), though this is a false perception of their truly green emission light due to the Purkinje effect.

Fireflies are found in temperate and tropical climates. Many are found in marshes or in wet, wooded areas where their larvae have abundant sources of food. Some species are called "glowworms" in Eurasia and elsewhere. While all known fireflies glow, only some adults produce light and the location of the light organ varies between species and sexes of the same species. The form of the insect which emits light varies from species to species.

Fireflies have a large amount of variation in their general appearance, with differences in color, shape, size, and features such as antennae. Adults can differ drastically in size depending on the species, with the largest being up to an inch long. Although the females of some species are similar in appearance to males, larviform females are found in many firefly species. These females can often be distinguished from the larvae only because the adults have compound eyes, although the latter are much smaller than those of their males and often highly regressed. The most commonly known fireflies are nocturnal, although numerous species are diurnal. Most diurnal species are not luminescent; however, some species that remain in shadow areas may produce light.

WHY DO FIREFLIES LIGHT UP?

The reason is so simple, they do light up in order to attract mates or prey.

HOW DO FIREFLIES LIGHT UP?

Fireflies produce a chemical reaction inside their bodies that allows them to light up. This type of light production is called bioluminescence. The method by which fireflies produce light is perhaps the best known example of bioluminescence. When oxygen combines with calcium, adenosine triphosphate (ATP) and the chemical luciferin in the presence of luciferase, a bioluminescent enzyme, light is produced.

Unlike a light bulb, which produces a lot of heat in addition to light, a firefly's light is cold light, without a lot of energy being lost as heat. This is necessary because if a firefly's light-producing organ got as hot as a light bulb, the firefly would not survive the experience.

A firefly controls the beginning and end of the chemical reaction, and thus the start and stop of its light emission, by adding oxygen to the other chemicals needed to produce light. This happens in the insect's light organ.

Photo: A firefly insect, a white part of an abdomen is the Light organ

When oxygen is available, the light organ lights up, and when it is not available, the light goes out. Insects do not have lungs, but instead transport oxygen from outside the body to the interior cells within through a complex series of successively smaller tubes known as tracheoles. For a long time it was a mystery as to how some firefly species manage such a high flash rate, considering the relatively slow speed of the muscles that control oxygen transport.

Various research show that nitric oxide gas plays a critical role in firefly flash control. In short, when the firefly light is off," no nitric oxide is being produced. In this situation, oxygen that enters the light organ is bound to the surface of the cell's energy-producing organelles, called the mitrochondria, and is thereby not available for transport further within the light organ.

Photo: Fireflies glows at night

The presence of nitric oxide, which binds to the mitochondria, allows oxygen to flow into the light organ where it combines with the other chemicals needed to produce the bioluminescent reaction. Because nitric oxide breaks down very quickly, as soon as the chemical is no longer being produced, the oxygen molecules are again trapped by the mitochondria and are not available for the production of light.

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Posted by: Lusubilo A. Mwaijengo