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Fireflies: How Lightning Bugs Light Up and Their Contribution to Medical Research

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Fireflies (or lightning bugs) are not flies at all. They are actually beetles belonging to the order Coleoptera and the family Lampyridae. Fireflies are generally found in warm, humid areas, with the greatest number of different species found in tropical Asia and in Central and South America.

Adult fireflies eat plant nectar and do not feed on prey, except for some species of which the females practice "agressive mimicry": a female firefly pretends to be the female of another species in order to attract the male and eat it. Firefly larvae are also predatory, eating earthworms, snails and slugs.

How Fireflies Light Up

Most fireflies (not all) are bioluminescent - they have the ability to produce light. The cells that produce light are located in the abdomen of the firefly and are called photocytes. These cells contain luciferin and luciferase, two chemicals used in the production of light. Luciferase is an enzyme, which acts on the substrate luciferin in the presence of ATP (adenosine triphosphate) and oxygen, resulting in light. 

Some species of fireflies can turn their light on and off. It is thought that the larvae and adult fireflies glow to protect themselves as a warning to potential predators that they taste bad. This practice is called an aposematic display.

Secondly, adult fireflies have been observed to use a series of flashes or a continuous glow when trying to attract a mate. A full 100% of a firefly's glow is given off as pure light, while only 10% of a light bulb's glow is pure light, the rest ending up as heat.

The Role of Fireflies in Medical Research

The investigation of the firefly's ability to luminesce has led to some exciting research. One interesting area is "glowing mice,"  which are used in cancer research.

Also, the Ohio State University Fact Sheet gives some idea of how luciferin and luciferase from fireflies are being used in medical research. The two chemicals are helping in the investigation of cancer, heart disease, muscular dystrophy, urology, antibiotic testing, wastewater treatment, environmental protection, and the search for life in outer space. The article states that so far it is not possible to synthesize either chemical in the laboratory and that the sole source of luciferin and luciferase is fireflies.

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