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Fireflies: Magical Insects

Arkansas Natural Heritage Commission - Wednesday, August 05, 2015

I have fond memories as a child watching intermittent flashes of brightness in the darkening summer sky. My excitement and anticipation building throughout the hot, miserable daylight hours, until twilight finally arrived, a lifetime later (or so it seemed to me). A blink here, a blink there, as I watched the tiny creatures flash, then go dark; flash, then go dark. 

If you were lucky and fast, you could catch one or two in a jar. Then everyone ran to you to peek inside the jar, to see the marvelous creature that created this tiny light. 

As a parent, I have even stronger memories of chasing fireflies with my children. Waiting with them as my children sat impatiently in their pajamas, staying up late to chase fireflies, and peeking out the windows to see if they could glimpse the little flashes of light. And then, witnessing their squeals of delight as they ran here and there, trying to catch just one.



What is a firefly?

A firefly, also called a lightning bug, is a member of the beetle family Lampyridae. They are nocturnal insects with wings, and have an organ that produces their “light”. There are approximately 2,000 different species of firefly, and they are found all over the world, on every continent except Antarctica.


Fireflies create the light within specialized cells in their abdomen. The cells contain a pigment called luciferin that makes an enzyme, luciferase. In a chemical reaction, luciferin combines with oxygen and luciferase to create a light. Fireflies are able to control the beginning and end of this chemical reaction, thus turning their light on and off, unlike other bioluminescent creatures which glow constantly. 

The light that fireflies emit is called “cold light” because it does not emit heat as part of the process or a result of the process. Their lights are considered the most efficient lights in the world, because 100 percent of the energy is emitted as light. In contrast, an incandescent bulb emits 10 percent of its energy as light and the rest as heat.

Why do fireflies light up?

Larvae light up as a warning to predators that they are not palatable. Adults light up to attract mates and prey, and communicate with other fireflies while defending territory or warning predators away.

The adult’s pattern of flashing light is unique to each species. However, not all firefly species have bioluminescent adults. Instead, some use pheromones to locate mates.

How do fireflies learn to light up?

Fireflies are born knowing how to glow. In some species, the larvae and the eggs emit light, and because of this the larvae have been nicknamed “glow worms”. Firefly eggs have been observed flashing in response to a stimulus, including tapping and vibration.

Why should I care about fireflies?

Researchers have discovered the genetic information in a firefly’s DNA that is responsible for making luciferase (an enzyme that combines to create the firefly’s light). This gene could be implanted into the cells of other animals to “light up” specific cells. This would be useful in identifying cancer cells and tracking the effectiveness of cancer treatments, as well as studying and tracking changes in cells that lead to many other diseases. 

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