FACTS ABOUT FIREFLIES

Interested in learning more about fireflies? Here are a few fascinating facts you may not know.

Fireflies talk to each other with light.

Fireflies emit light mostly to attract mates, although they also communicate for other reasons as well, such as to defend territory and warn predators away. In some firefly species, only one sex lights up. In most, however, both sexes glow; often the male will fly, while females will wait in trees, shrubs and grasses to spot an attractive male. If she finds one, she’ll signal it with a flash of her own.

Fireflies produce “cold light.”

Firefly lights are the most efficient lights in the world—100% of the energy is emitted as light. Compare that to an incandescent bulb, which emits 10% of its energy as light and the rest as heat, or a fluorescent bulb, which emits 90% of its energy as light. Because it produces no heat, scientists refer to firefly lights as “cold lights.”

In a firefly’s tail, you’ll find two chemicals: luciferase and luciferin. Luciferin is heat resistant, and it glows under the right conditions. Luciferase is an enzyme that triggers light emission. ATP, a chemical within the firefly’s body, converts to energy and initiates the glow. All living things, not just fireflies, contain ATP.

Firefly eggs glow.

Adult fireflies aren’t the only ones that glow. In some species, the larvae and even the eggs emit light. Firefly eggs have been observed to flash in response to stimulus such as gentle tapping or vibrations.

This is an image of a firefly larvae just emerging from the egg. Copyright © Terry Lynch

Fireflies eat other fireflies.

Fireflies are primarily carnivorous. Larvae usually eat snails and worms. Some species of fireflies feed on other fireflies—most notable is the genus photuris, which mimics female flashes of photinus, a closely related species, in order to attract and devour the males of that species. But adult fireflies have almost never been seen feeding on other species of bugs. Scientists aren’t sure what they eat. They may feed on plant pollen and nectar, or they may eat nothing.

Fireflies have short lifespans.

An adult firefly lives only long enough to mate and lay eggs—so they may not need to eat during their adult life stage. The larvae usually live for approximately one to two years, from mating season to mating season, before becoming adults and giving birth to the next generation.

Fireflies imitate each other.

Female photuris aren’t the only impostors among fireflies—the species is surprisingly devious when it comes to imitation. Sometimes male photuris imitate male photinus to attract females of their own species. She shows up looking for food, but instead he gets a mate.

Even more interesting, scientists believe some photinus males imitate photuris females giving off bad impressions of photinus male flashes, scaring off other photinus males and reducing competition.

Fireflies are found on almost every continent.

Fireflies love warm, humid areas. Because of this, they thrive in tropical regions as well as temperate zones—they come out in the summertime in these environments—on all continents except Antarctica. Fireflies thrive in forests, fields and marshes near lakes, rivers, ponds, streams and vernal pools. They need a moist environment to survive.

Some species of firefly larvae are generally aquatic—they even have gills—while others live almost entirely in trees.

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. 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.

Fireflies don’t make tasty prey.

When attacked, fireflies shed drops of blood in a process known as “reflex bleeding.” The blood contains chemicals that taste bitter and can be poisonous to some animals. Because of this, many animals learn to avoid eating fireflies. Pet owners should never feed fireflies to lizards, snakes and other reptilian pets.