What Makes Fireflies Glow?

A chemical reaction inside a firefly’s abdomen helps them glow. These light displays allow these insects to communicate, find mates, and ward off predators.

Aug 23, 2023byColt Dodd
what makes fireflies glow

Summer isn’t complete without fireflies lighting up the backyard. But how do these creatures emit such dazzling displays? Without getting too technical, a chemical reaction inside fireflies’ abdomens makes them glow. Per North Carolina State University, special organs in the bugs’ stomach release a chemical called luciferases, along with oxygen and a substance called ATP.

When combined, these chemicals emit light, which fireflies use to communicate with others and attract mates. Here, one can learn more about these bioluminescent beetles and their habits.

How Fireflies Glow

firefly on a leaf
Image Credit: Wikimedia Commons

Scientists suspect that initially, fireflies started glowing as a way to ward off predators. However, with evolution, they eventually started using light displays to attract mates. The University of Utah notes that both male and female fireflies glow, and each firefly species also has its own communication pattern––its own “language,” so to speak.

As noted, fireflies glow when they combine chemicals in their abdomens. These chemicals are:

  • Oxygen, the air we breathe
  • APT or the “currency” cells use to accomplish tasks
  • Luciferases, or an enzyme that produces light

A firefly can create light patterns by regulating how much oxygen flows to their abdomens.

Why Do Fireflies Glow?

firefly glowing on the floor
Image Credit: Wikimedia Commons

As previously mentioned, fireflies primarily glow to attract mates. However, other reasons for their displays include:

  • Warding off predators. Predators are generally turned off by the idea of eating a glowing meal. To an insect eater, seeing a firefly is as good as seeing a billboard that reads: “Go away.”
  • Communicating with other fireflies. Fireflies may flash light when they’re in danger or otherwise feel threatened. While they don’t live in colonies, they do congregate during certain times of the year, and there’s safety in numbers.
  • Recognizing familiar species. Fireflies want to spend time with their own species. Flashing a light pattern allows fireflies to stick together.

Fireflies Couldn’t Exist Without Their Glowing Abilities

Insects have existed for close to 500 million years. In that time, they’ve adapted to their ever-changing environments––and they’ve gotten pretty good at it, seeing that fireflies exist on every continent (except Antarctica). Without their glowing abilities, they would be unable to fit into their very small ecological niche.

Without the ability to emit light, fireflies would have problems:

  • Mating. If fireflies couldn’t find mates, they couldn’t propagate the species, leading to extinction.
  • Communicating. As noted, fireflies don’t live in colonies, but they still prefer to remain in groups. They may flash light at different speeds to warn others of a threat.
  • Avoiding predators. A firefly’s light wards off predators, extending their short, short time on Earth.
  • Attracting prey. Fireflies eat other bugs. They may flash their lights or emit a dim glow that encourages smaller insects to come closer––and into their jaws.

Do Other Insects Glow?

firefly not glowing on a leaf
Image Credit: Wikimedia Commons

There are many bugs that illuminate when the sun sets. These creatures include:

  • Glowing click beetles. Often mistaken for fireflies, these critters have two lights on their heads. They do not control how brightly they light up; they’re either lit up or not.
  • Railroad worms. Railroad worms look like trains traveling on a dark path. They have both yellow and red lights––with yellow lights across their bodies and a red light on their heads. The worm turns on the light when it feels threatened.
  • Firefly-mimicking longhorn beetles. These are perfect imitators of fireflies, even featuring the same color display. Even seasoned bug enthusiasts get tricked by these guys.

There are other glowing animals across the planet, including octopuses, jellyfish, and squid.

Where Can One Find Fireflies?

lightning bug up close on a leaf
Image Credit: Wikimedia Commons

For centuries, people have captured fireflies and put them in well-ventilated mason jars. But what’s the secret to catching these winged lightbulbs? Some tips include:

Be in the Right Place at the Right Time

Fireflies live on every continent, but they’re plentiful in humid areas, like Florida and parts of Asia. Many fireflies also mature from their larval stages in the summer, coming out mostly at dusk.

Remaining in Dark Locations

If there’s a porch light or another light source, fireflies likely won’t be easy to find. After all, why shine a light when there’s one on the wall? They’re generally attracted to dark areas. While in the dark, one may try flashing a flashlight, then waiting for the bugs to respond with a message of their own.

Capturing the Flies Using a Net

Nets are ideal for catching winged insects because they reduce wind resistance, catching bugs by surprise. One should get a net with small holes, less than an inch across. That’s because fireflies themselves seldom get longer than an inch.

Putting Them in a Well-Ventilated Jar

Like every animal, fireflies need air to breathe. So, once the fireflies are in the net, put them in a jar with holes poked in the lid. One should also put a damp coffee filter at the bottom, as fireflies do best in humid conditions.

Facts About Fireflies

a firefly up close white background
Image Credit: Wikimedia Commons

Here’s a fun fact about fireflies: they’re not actually flies. Instead, they’re beetles, belonging to the Lampyridae family.Some other facts about these glowing grubs include:

Fireflies Have No Problem Resorting to Cannibalism

According to the National Wildlife Federation, fireflies sometimes eat each other! For instance, a hungry firefly may shine its light, imitating the pattern of a similar species. Then, once in range of an unsuspecting firefly, they strike and chow down. In addition to eating each other, fireflies also thrive on diets of slugs, snails, worms, and pollen. Some do not eat once they pass the larval stage.

Fireflies Spend Most of Their Lives Underground

Most people only see fireflies on warm summer nights. In reality, these bugs spend most of their lives buried underground during their larval stage. Once they mature, they live less than two months.

Fireflies Are a Good Omen

Don’t worry––fireflies are nothing to be afraid of. In fact, they’re generally an omen of good things to come. Some believe that they’re also a reminder to see the light in others.

Colt Dodd
byColt Dodd

Colt Dodd is a sighthound enthusiast with three years of freelance writing experience. He has an Italian greyhound/Shetland sheepdog mix named Homer. In his spare time, he enjoys going to dog parks and writing fiction.