On a clear night in August, you might step outside and look up at the sky. If you live in a big city, you might only see three or four bright stars. But if you visit a quiet park far from city streets, hundreds of stars appear in the dark.
The same thing happens on the ground with fireflies. When bright electric lights shine across a lawn, quiet yellow flashes fade away. The fireflies are still trying to shine, but their signals get swallowed up by light.
Scientists call this extra light in the dark light pollution. It happens when lamps, streetlights, and porch lights spill light where it is not needed. Light pollution makes it hard for astronomers to see distant stars. It also makes it hard for fireflies to find each other and raise their young.
The good news is that light pollution is an easy problem to fix. By changing how we light our homes and gardens, we can bring back the stars and help fireflies at the same time.
How Fireflies Use Light to Talk
Fireflies do not flash just to look pretty. Their flashes are a language. A male firefly flies over grass and blinks out a pattern. Each species has its own special code. One species might give two short flashes every three seconds. Another species might make a long glowing swoop shaped like the letter J.
Female fireflies sit on grass blades or leaves near the ground. They watch the air for the right pattern. When a female sees a male of her own species, she flashes back from her perch.
This conversation only works if the night is dark. A firefly flash is gentle. It is about as bright as a single tiny drop of light. If a porch light or streetlight shines right on the grass, the female cannot see the male's flying pattern. The male cannot see her small answer from the ground.
When fireflies cannot see each other, they cannot mate. Over a few years, the number of fireflies in that yard drops. Dark skies give these insects a quiet place to speak their glowing language.
What Is a Lumen?
To fix light pollution, it helps to understand how light is measured. When you buy a bulb, the box lists a number followed by the word lumens.
A lumen is a unit that measures how much total light a bulb puts out. You can think of lumens like measuring water in a cup. A small splash of water is like a low-lumen light. A giant bucket of water poured all at once is like a high-lumen light.
Years ago, people looked at watts to guess how bright a bulb was. But watts only tell you how much electricity a bulb uses. Lumens tell you how bright the light actually is.
A flashlight for reading in a tent might put out 50 lumens. That is plenty of light for your eyes up close. An old streetlamp might put out 5,000 lumens. That is a massive wave of light.
Many outdoor porch lights are much brighter than they need to be. A light bulb with 800 or 1,000 lumens can flood an entire yard with glare. That high brightness blinds fireflies near the grass.
For a sidewalk or porch, a bulb with 200 to 400 lumens is usually plenty. It gives enough light for people to walk safely without blinding night animals.
Shielded Fixtures Keep Light Where It Belongs
Brightness is only half of the story. Where the light goes is just as important.
Have you ever seen a bare light bulb hanging over a doorway? Light shoots out in every direction. It goes up toward the sky. It shines sideways into your neighbor's window. It hits the trees and grass nearby.
When light shoots straight up into the air, it bounces off dust particles and clouds. This creates a soft, foggy glow over whole cities. Astronomers call this glow skyglow. Skyglow hides the stars.
When light shoots sideways, it floods the grass where fireflies live.
The solution is a shielded fixture. A shield is a solid cover over the top and sides of a light fixture. It works like a brim on a baseball cap. The shield forces all the light to point straight down toward the ground.
A fully shielded light illuminates the steps where you walk. But it keeps the sky dark above and keeps the surrounding grass dark below.
When you use a shielded fixture, you do not waste energy lighting up the sky. You put the light only where your feet need it.
The Color of Night Lights
The color of an outdoor light also matters to nocturnal wildlife.
Bright white and blue lights feel like harsh daytime sun. Blue light spreads out easily in the air and confuses night creatures. Many insects, including fireflies, are drawn toward bright white or blue lights like a trap. They fly around the bulb until they get tired or eaten by spiders.
Warm light looks very different. Warm light has amber, yellow, or soft red tones. It looks more like a campfire or a sunset.
Fireflies do not react as strongly to warm yellow or amber light. Warm light does not wash out their flashes as badly as harsh white light does.
When choosing outdoor lights, look for bulbs labeled warm white or amber. Keeping lights at 2,700 Kelvin or lower gives a warm color that is gentler on eyes, stars, and fireflies.
What Citizen Science Map Shows Us Right Now
On Alitaptap, people around the world share where they see fireflies. Right now, in late August 2026, members are recording observations from many different places.
In North Carolina, volunteers reported Common Eastern Fireflies along Lewis Street in Durham, near Western Boulevard in Raleigh, and on Princeton Drive in Chapel Hill. Others logged Winter Fireflies in Mars Hill, North Carolina, and up in Cumberland, Rhode Island.
Over in Europe, observers logged European Glow-worms in Saint-Avé, France, and in Kylmälä, Finland. Unlike flashing fireflies, female European Glow-worms do not fly. They sit in the grass and glow with a steady green light. Bright artificial lights easily hide their gentle steady glow.
In Taiwan, spotters recorded species like Pyrocoelia praetexta in Pingtung County and Rimmed Window Fireflies in Chiayi County. Down in Brazil, a spotter found Aspisoma lineatum in Ipatinga.
When we look at this global map, one pattern stands out. Most firefly sightings happen in parks, backyards with tall grass, or edges of woods where the night stays dark. In places filled with bright unshielded streetlights, people log far fewer sightings.
Easy Ways You Can Help Fireflies Tonight
You do not need to turn off every light in your neighborhood to make a real difference. Small choices around your house add up quickly.
First, look at your porch and yard lights. Are they shining straight into the trees or up at the sky? You can ask an adult to tilt the fixtures down or add simple shields over the bulbs.
Second, check the brightness of your outdoor bulbs. Swapping an 800-lumen bulb for a 300-lumen warm amber bulb saves energy and keeps the yard dark enough for fireflies.
Third, use lights only when you actually need them. Adding a motion sensor means the light turns on when someone walks up, then turns off automatically. Timers can also turn decorative lights off late at night when everyone is asleep.
Fourth, close your curtains or blinds at night. Indoor light spilling through windows adds to outdoor light pollution without you realizing it.
When you protect dark skies, you give fireflies room to shine. You also get to look up on a clear August night and see the Milky Way stretching across the sky. Dark skies protect the world above us and the world right at our feet.