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.

Example of a firefly larvae eggs glowing

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.

Image of Firefly Life Cycle

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