10 Fascinating Facts About Fireflies

Interesting Behaviors and Traits of Lampyridae


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Fireflies or lightning bugs are from the family Coleoptera:Lampyridae, and they may well be our most beloved insect, inspiring poets and scientists alike. Most importantly to remember, fireflies are neither flies nor bugs. Fireflies are actually beetles and there are 2,000 species on our planet.

Here are other interesting facts about fireflies.

The Flight of Fireflies

Like all other beetles, lightning bugs have hardened forewings called elytra, which meet in a straight line down the back when at rest. In flight, fireflies hold the elytra out for balance, and rely on their membranous hindwings for movement. These traits place fireflies squarely in the order Coleoptera.

Fireflies Are the World's Most Efficient Light Producers

An incandescent light bulb gives off 90 percent of its energy as heat and only 10 percent as light, which is something you know if you've ever touched one that's been turned on for a while. If fireflies produced that much heat when they lit up, they would incinerate themselves. Fireflies produce light through an efficient chemical reaction called chemiluminescence that allows them to glow without wasting heat energy. For fireflies, 100 percent of the energy goes into making light; and accomplishing that flashing increases the firefly metabolic rates an astonishingly low 37 percent above resting values.

Fireflies are bioluminescent, which means they are living creatures that can produce light. That trait is shared with only a handful of other terrestrial insects, such as click beetles and railroad worms. The light is used to attract prey and members of the opposite sex, and warn off predators. Lightning bugs taste bad to birds and other potential predators, so the warning signal is a memorable one to those that have sampled before.

Fireflies "Talk" to Each Other Using Light Signals

Fireflies don't put on those spectacular summer displays just to entertain us. You're actually eavesdropping on the firefly singles bar. Male fireflies cruising for mates flash a species-specific pattern to announce their availability to receptive females. An interested female will reply, helping the male locate her where she's perched, often on low vegetation.

Fireflies Are Bioluminescent Throughout Their Life Cycles

We don't often see fireflies before they reach adulthood, so you may not know that fireflies glow in all life stages. Bioluminescence begins with the egg and is present throughout the entire lifecycle. In fact, all firefly eggs, larvae, and pupae known to science are capable of producing light. Some firefly eggs emit a faint glow when disturbed.

The flashing part of fireflies is called a lantern, and the flashing is controlled by the firefly using neural stimulation and nitric oxide. The males often synchronize their flashes with one another during courtship, a capacity called entraining (responding to an external rhythm) once thought only possible in humans, but now recognized in several animals. Colors of firefly lights range widely among different species, from yellow-green to orange to turquoise to a bright poppy red.

Fireflies Spend Most Their Lives As Larva

The firefly begins life as a bioluminescent spherical egg. At the end of the summer, adult females lay about 100 eggs in soil or near the soil surface. The worm-like larva hatches out in three to four weeks and throughout the fall hunts prey using a hypodermic-like injection strategy similar to bees. Larvae spend the winter below ground in several types of earthen chambers. Some species spend more than two winters before pupating, in late spring, and they emerge as adults from their pupa after a period of 10 days to several weeks. Adult fireflies live only another two months, spending the summer mating and performing for us before laying eggs and dying.

Not All Adult Fireflies Flash

Fireflies are known for their blinking light signals, but not all fireflies flash. Some adult fireflies, most notably those that inhabit the western areas of North America, don't use light signals to communicate. Many people falsely believe that fireflies don't exist west of the Rockies since flashing populations are rarely seen there...but they do.

Firefly Larvae Feed on Snails

Firefly larvae are carnivorous predators, and their favorite food is escargot. Most firefly species inhabit moist, terrestrial environments, where they feed on snails or worms in the soil. But a few Asian species use gills to breathe underwater, where they eat aquatic snails or other mollusks. Some species are arboreal, and their larvae hunt tree snails.

Some Fireflies Are Cannibals

We don't know much about what adult fireflies eat. Most don't seem to feed at all, while some are believed to eat mites or pollen. We do know what Photuris fireflies eat, though—other fireflies. Photuris females enjoy munching on males of other genera.

These well-known Photuris femme fatales use a trick called aggressive mimicry to make meals of other fireflies. When a male firefly of another genus flashes its light signal, the female Photuris firefly replies with the male's flash pattern, suggesting she is a receptive mate of his own species. She continues luring him in, closer and closer, until he's within her reach. Then her meal begins.

Adult female Photuris fireflies are also kleptoparasitic and can be seen feeding on a silk-wrapped Photinus species firefly (occasionally even one of its own kind) hanging in a spider's web. Epic battles can occur between the spider and the firefly. Sometimes the firefly can hold off the spider long enough to consume the silk-wrapped prey, sometimes the spider cuts the web and her losses, sometimes the spider catches the firefly and the prey and gets them both wrapped up in silk.

Firefly Luciferase Is Used in Medical Research

Scientists have developed remarkable uses for firefly luciferase in the research lab. Luciferase is the enzyme that produces bioluminescence in fireflies. It has been used as markers to detect blood clots, to tag tuberculosis virus cells, and to monitor hydrogen peroxide levels in living organisms; hydrogen peroxide is believed to play a role in the progression of some diseases, like cancer and diabetes. Fortunately, scientists can now use a synthetic form of luciferase for most research, so the commercial harvest of fireflies has decreased.

Firefly populations are decreasing, and the search for luciferase is just one of the reasons. Climate change and modern construction have resulted in the loss of firefly habitats, and light pollution depresses the ability for fireflies to find mates and reproduce.

Some Fireflies Synchronize Their Flash Signals

Imagine thousands of fireflies lighting up at precisely the same time, over and over, from dusk to dark. This simultaneous bioluminescence, as it is called by scientists, occurs in just two places in the world: Southeast Asia and Great Smoky Mountains National Park, right here in the U.S. North America's lone synchronous species, Photinus carolinus, puts on its light show in late spring each year.

The most spectacular show is said to be the mass synchronous display of several Pteroptyx species in Southeast Asia. Masses of male fireflies congregate in groups (called leks) and in unison emit rhythmic courtship flashes. One hotspot for ecotourism is the Selangor River in Malaysia. Lek collective courting happens occasionally in American fireflies, but not for long periods.

In the American Southeast, male members of the blue ghost firefly (Phausis reticulate) glow steadily as they fly slowly over the forest floor searching for females from about 40 minutes after sunset until midnight. Both sexes emit a long-lasting, nearly continuous glow in the forested regions of Appalachia. Annual tours to see the blue ghosts can be joined at state forests in South and North Carolina between April and July.