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Are Fireflies in Danger?

by Belinda Recio

The beauty of bioluminescence

Bioluminescence in the breaking ocean waves

I remember the first time I saw a firefly. The boy next door showed me a bug that he had caught in a jar. It struck me as an uninteresting beetle-like insect—until its tail started flashing a green light. And right then and there he had me (the firefly, not the boy) and my fascination with bioluminescence (light produced and emitted by living organisms) was sparked.

Fireflies—which are actually winged beetles belonging to the order Coleoptera—are the most familiar of earth’s bioluminescent life forms. They are widespread and live in temperate and tropical zones all over the world. But fireflies are not alone in their ability to produce their own light. Centipedes, millipedes, snails, fungi, fish, coral, jellyfish, octopi, squid, clams, plankton and other bioluminescent creatures glimmer and glow in an entire spectrum of colors, including red, orange, yellow, green, blue and violet.

Decades ago, certain parts of the world were so full of flashing fireflies that people could charge tourists to see the light displays. But today’s landscapes are not quite as bright with bioluminescence as they once were because the “lightning bugs” are disappearing. Scientists speculate that habitat loss and light pollution are to blame. Fireflies need open space, and as fields, forests, marshes and other firefly habitats are developed, or destroyed with pesticides, their populations decrease.

Photo credit: © bidgee / Wikimedia Commons / CC-BY-SA-3.0

Light pollution is another factor in firefly decline. Fireflies use their glowing tails to communicate with one another by flashing a kind of firefly code with their lights. According to Ben Pfeiffer, founder of firefly.org, fireflies use their language of light to attract mates, warn off predators and defend their territory. Scientists believe that light pollution interrupts all kinds of firefly communication, but especially the kind used for sexual selection. When mating flashing is interrupted—think of it as losing your Internet connection in the middle of an online dating exchange—fewer fireflies hook-up, which means fewer firefly larvae hatch in the next season.

Fireflies are important. Their larvae feed on snails, slugs and earthworms, which helps keep ecosystems in balance. Pfeiffer also explained that fireflies “are medically and scientifically useful: The two chemicals found in a firefly’s tail, luciferase and luciferin, light up in the presence of ATP [adenosine triphosphate]. Every animal has ATP in its cells in amounts that are more or less constant—or should be. In diseased cells, the amount of ATP may be abnormal. If the chemicals from fireflies are injected into diseased cells, they can detect changes in cells that can be used to study many diseases, from cancer to muscular dystrophy. But that’s not all they’re used for. Electronic detectors built with these chemicals have been fitted into spacecraft to detect life in outer space, as well as food spoilage and bacterial contamination on earth.”

But when it comes to fireflies, perhaps what’s most important is the magic they bring to a summer night. With their tiny sparks of dancing light, they re-enchant fields, forests, marshes and meadows, and remind us of the beauty and mystery of life.

Save the Fireflies

Here are a few simple things you can do to help bring fireflies back into your neighborhood. (Visit firefly.org/how-you-can-help for more information.)

• Turn off outside lights at night.

• Create water features in your landscape.

• Avoid use of pesticides, especially lawn chemicals.

• Use natural fertilizers.

• Don’t over-mow your lawn.

• Plant trees.

• Do NOT introduce earthworms to your yard.

• Try to get your neighbors to do these things.

You can also join Boston’s Museum of Science citizen science project, Firefly Watch. Learn more here: legacy.mos.org/fireflywatch/about_firefly_watch

Species of Light

If bioluminescence sparks your interest, consider traveling to one of these three glowing destinations where you can experience other forms of living light.

Jamaica’s Luminous Lagoon: Sparkling Dinoflagellates


Considered one of the best places in the world to observe marine bioluminescence, the lagoon sparkles at night when aquatic microorganisms called dinoflagellates are disturbed. Dip your hand in the lagoon, and the water lights up around you. Take a swim, and your body is surrounded by a glimmering glow. And watch fish swim by, haloed in an aura of light.

California’s Sierra Nevada Mountains: Luminous Millipedes

When hiking in the Sierra Nevada mountain range, watch for the only known glowing millipede, Motyxia. These cyanide-producing, light-emitting millipedes can be seen near the roots and branches of Sequoia trees or elsewhere on the forest floor. Look for a flat, orange millipede about two inches long, or search for an almond scent with your nose (the millipedes produce hydrogen cyanide, which smells like almonds). Note: Although the amount of cyanide produced by the millipedes is not fatal to humans, you should keep your distance and not handle them.

Alabama’s Dismals Canyon: Glowing Fly Larva


In Alabama’s Dismals Canyon there is a large population of flies (Orfelia fultoni) that glow in their larval stage. Known locally as “Dismalites,” the insects are related to the rare glowworms of Australia and New Zealand. These tiny larvae light up the rocky walls of the canyon like starry skies. The blue light produced by the “Dismalites” is one of the bluest lights created by bioluminescence. The best viewing times are May through September, although they can be seen in smaller numbers all year long.

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