These days, with our greater appreciation for ecosystems, gardeners tend to have nicer things to say about insects than we did in the past. Maybe not all of them, and not all the time, but there’s more of an attitude of “try to find the good in everyone.”
One insect that’s never required any effort to appreciate is the firefly. It has always held a special place and been looked upon with admiration and amazement.
Glowworms, Lightning Bugs … Beetles?
Depending on where you live, fireflies may be better known as glowworms or lightning bugs—or by other names. We seem to call them everything except what they actually are, which is beetles.
And these beetles are known for giving off light. They do it through a chemical reaction inside their bodies, using a special light-emitting compound and an enzyme from a group that can produce bioluminescence. Combined with other elements, they create light—cold light—with very little heat. It’s far more efficient than even our best LEDs. Back in the 1800s, scientists were already studying fireflies to understand efficient light production—and we’re still trying to catch up.
Not All Fireflies Flash
All fireflies glow at some stage of their lifecycle, but the stages vary by species. For those that glow as adults, the light is mostly used to communicate for mating. Male fireflies fly around flashing their light hoping to attract a female. If she likes what she sees, she flashes back. And the patterns and timing of those flashes are specific to each firefly species.
But not everyone’s playing fair. Some females mimic the flashes of other species—not to mate, but to lure in a meal. The unsuspecting male responds, flies over, and finds out too late that he’s the prey.
Fireflies and Nostalgia
It’s that light that makes fireflies stand out. Many people have nostalgic memories of fireflies—chasing them with nets, putting them in jars. That may not have been a great experience for the fireflies, but it helped turn them into a flagship species for insect conservation, right up there with monarch butterflies.
There are also people who didn’t get to experience fireflies as kids and want to see them for the first time. Between increased urbanization and, probably, declining firefly numbers, they’ve become a rarer sight in many areas.
One Show Doesn’t Fit All
What you can expect to see—even if all goes well—depends a lot on where you live.
In much of Eastern North America, the firefly display is pretty random—one here, one there, flashing at different times. That can still be a beautiful show, especially in your backyard.
But in a few areas, you might see something completely different: thousands of fireflies flashing together in unison, creating a wave of light. These synchronous fireflies are a huge tourist draw at Great Smoky Mountains National Park in Tennessee. The star of that show is Photinus carolinus. But unless you live there or in a few other parts of the Appalachians, you likely won’t see them in your garden. There are other synchronous firefly species in North America, but the odds are you don’t have them where you live.
Southeast Asia is also known for its synchronous fireflies. In some places, they flash and go dark at exactly the same moment—like there’s a master on/off switch controlling them.
In much of Western North America, fireflies are active during the day—so no light shows at all. They rely on pheromones to communicate instead.
In Eastern North America, Ellychnia corrusca is active in winter and early spring. But it’s out during the daytime, so again, no glowing display. You may have had them in your garden and never noticed.
In the UK and much of Europe, the most common species is Lampyris noctiluca, better known as the common glowworm. Here, it’s the wingless adult females—still looking like grubs—that glow. The males can fly but barely glow. And similar glowworm species are common in parts of North America too, especially in the west.
Getting to Know the Firefly Lifecycle
So what you hope to see in your yard depends on your region and local species. But there are some common things you can do to attract and support them—and understanding their lifecycle helps.
Fireflies are members of the Lampyridae beetle family—currently around 2,400 species in over 140 genera, found on every continent except Antarctica. There’s a wide variety of appearances—at least as adults. The juveniles look very similar.
What they all share, though, is complete metamorphosis: egg, larva, pupa, and adult. This is significant when it comes to keeping them happy in your garden since you’re probably most interested in them as adults—maybe only interested in them as adults. But they have to get through three stages before they get there and they spend much more of their lives as larvae than as adults. For every day they spend as an adult they may have had two weeks as a grub in the ground. So, like gardeners, they care a lot about soil and what’s in the soil.
The adult stage is short—just a few weeks—but they may spend many months, even up to two years, as larvae in the soil. Most adults don’t even feed. They rely on energy reserves stored as larvae. So the fireflies you’re seeing this year likely started out as eggs a year or two ago, lived mostly underground as larvae, and are now flying around for a brief adult stage—just long enough to mate and lay eggs for the next generation.
That makes the larval stage especially important when it comes to firefly-friendly gardening.
Firefly Larvae: Glow-in-the-Dark Predators
All firefly larvae are bioluminescent. Many species glow in all life stages, but only the larvae always glow. In larvae, the glow appears to serve as a warning to predators—“Don’t eat me, you’ll regret it.” And in many cases, that’s true. It’s not a bluff. It doesn’t stop them all, but it improves the firefly’s odds, which is what counts in evolution.
This use of firefly bioluminescence actually came first, and it was only later that some adult fireflies figured out how they could use it to their advantage in mating.
And firefly larvae aren’t just prey—they’re voracious predators themselves. Known for eating slugs and snails, they also go after earthworms and other soft-bodied creatures.
So for most of their lives, fireflies are living in the soil or in litter on top of it—glowing predators with big appetites. That’s the phase to focus on if you want to help them.
Are Fireflies in Decline?
Yes—probably.
Despite stories of firefly declines going back decades, actual data is limited. There have been some UK studies on shrinking glowworm numbers, but not much else. Some firefly species are listed as endangered, and while good data is scarce, many experts believe their numbers are down. Informed anecdotal evidence, you could call it. And for many people, it certainly feels like there are fewer fireflies than in the past.
Habitat loss and pesticide use are likely major factors, just as they are for insects in general.
And fireflies have a unique additional threat: artificial light. Nighttime used to be dark. Now it’s full of light from homes, offices, cars, billboards, street lights, and more. And even outside of urban areas you can get skyglow spilling over. This light pollution can disrupt mating, especially for nocturnal species that rely on darkness to flash their signals. How are they going to see those flashing signals properly?
So while we don’t have great data, it seems likely that declines are real.
How to Support Fireflies in Your Garden
1. Limit Artificial Light
Avoid having lights on in your garden at night, especially during firefly mating season. If you must have them, make them dim and focused—pointing downward. Timers or motion sensors can help reduce how long they’re on.
Even red lights, sometimes marketed as “firefly-friendly,” have been shown to inhibit firefly signaling. They’re less harmful, but not harmless. And red light has been shown to disorient other animals. Turning the lights off is still the best choice.
2. Make the Soil Firefly-Friendly
Maybe the biggest way way we can support fireflies in our garden is by providing the right habitat. When it comes to what we like in soil—where fireflies spend most of their lives—gardeners and fireflies have a lot in common. They want moist soil, which is exactly what we want too.
We’re not going to go water the garden and our yard in the hope of attracting fireflies, but we take care of our soil in ways that make a moist soil more likely. Applying organic matter like compost which helps retain water but not too much and also reduces soil compaction. Organic mulches also reduce evaporation from the soil and will add organic material over time.
“Leave the leaves” campaigns often mention fireflies—and with good reason. Leaf litter makes excellent larval habitat. You don’t need to leave all your leaves where they fall, but keeping some on the ground and using the rest to make leaf mold—which will also improve soil moisture when you apply it—can help.
3. Embrace a Bit of Mess
A tidy garden is less inviting to fireflies. Having a wilder corner, rotting logs, and decaying organic material gives them habitat. Shade helps retain moisture, so trees and tall plants can make a difference too. Shaded areas with leaf litter? Even better.
Mowing less often and with a higher blade supports insect biodiversity, including fireflies.
4. Disturb the Ground as Little as Possible
Since larvae live in the soil, disturbing it can disrupt their development. Avoiding unnecessary digging—and even walking—is good for the entire soil ecosystem.
5. Don’t Worry About Ponds
In North America and Europe, firefly larvae are mostly terrestrial. You don’t need a pond to support them. It’s different in Asia, where many fireflies have an aquatic larval stage—but not here. Natural ponds might help keep the surrounding soil moist, but lined garden ponds won’t make much of a difference.
6. Skip the Pesticides
This should be obvious. Pesticides can directly kill or weaken fireflies—or eliminate their prey. If you’re using pesticides, you can’t be surprised if you don’t have fireflies. If mosquitoes are a concern, Bacillus thuringiensis israelensis (Bti) is considered a less harmful option—as far as we know. But it hasn’t been tested on many firefly species. And this is just Bti. There are other Bt strains that do target beetles. Avoiding pesticides entirely is a safer bet. They all reduce insect diversity.
Final Thoughts
What you end up seeing will depend on the fireflies in your region. You may already have fireflies in your garden that you’ve never noticed because they don’t glow or don’t fly around. Unfortunately, Photinus carolinus from the Smoky Mountains isn’t going to show up just because your garden is amazing.
But with the right habitat, less light, and no pesticides, you’re doing what you can for your local fireflies.
And just to clear up one common point of confusion—those glowworms in New Zealand? The ones in the famous Waitomo caves? They aren’t fireflies. They’re fungus gnats—flies, not beetles. Yet another example of how common names can be misleading. Beetles are fireflies, and flies aren’t.
But they put on a great show too.