Why Fireflies Are Disappearing And How to Bring Them Back
Published July 6th, 2026 · 8 min read · Nature + Conservation
It's one of those childhood memories that gets harder to explain the older you get.
You're outside after dark on a warm June night. The grass is still wet from the afternoon rain. And then, a light. Just one, low in the weeds. Then another, ten feet further. Then the whole field is blinking, slow and unhurried, a thousand tiny lanterns drifting up through the dark.
If you grew up in the Midwest, you know that feeling. And if you've noticed that the fields seem a little darker now, that you have to look harder to find that first light, you're not imagining it.
Firefly populations are in decline across North America and around the world. A 2024 study analyzing more than 24,000 citizen science surveys documented significant population drops linked to light pollution, habitat loss, and climate change. A 2020 survey of firefly researchers ranked the threats they were most concerned about: habitat loss, light pollution, pesticide use, water pollution, drought, and warming temperatures, in that order.
The good news is that fireflies are not lost yet. And some of the most effective things you can do to help them happen in your own backyard.
Here's what fireflies actually need, and why so much of the modern landscape is working against them.
The Secret Life Happening Below Your Feet
Most people think of fireflies as a summer thing, a June and July phenomenon that appears after dark and vanishes before breakfast. That's true of the adults. But fireflies spend the vast majority of their lives somewhere most people never think to look.
Underground.
Depending on the species, firefly larvae spend one to two years in the soil, in leaf litter, and along the moist margins of ponds and streams before they ever produce a single visible flash. During that time, they're active predators, hunting soft-bodied invertebrates like snails, slugs, earthworms, and grubs. They locate their prey, inject a paralyzing fluid, and feed. And here's the part that surprises most people: even at this stage, fireflies glow. Larval fireflies produce bioluminescence not as a mating signal but as a warning, a message to predators that they're chemically unpalatable.
This long underground phase is one of the most important things to understand about firefly conservation. When people think about protecting fireflies, they think about the adults they can see. But the real vulnerability is in the soil, in the conditions that the larvae need to survive for a year or two before they can emerge, pupate, and take their first flight.
How the Light Actually Works
The firefly's ability to produce light is one of the most beautiful chemical reactions in nature.
In an organ on the underside of the abdomen, the firefly combines a molecule called luciferin with an enzyme called luciferase, oxygen from the air, and chemical energy. The result is light, specifically, a "cold light" that produces almost no heat, making it one of the most energy-efficient light sources known to science. Different species produce light of slightly different wavelengths, ranging from green to yellow, which is one of the ways males and females of the same species recognize each other in the dark.
That recognition mechanism, the flash pattern, is at the heart of the firefly's vulnerability to artificial light.
The Three Things That Are Killing Fireflies
1. Light Pollution
Firefly courtship is built entirely around darkness. Male fireflies fly low over vegetation after dusk, producing species-specific flash patterns. Females rest in the grass and vegetation below, watching. When a female recognizes the pattern of her own species, she responds with her own flash. The male finds her. They mate. The cycle continues.
Artificial light disrupts this at every step.
Streetlights, porch lights, floodlights, the ambient glow of subdivisions and commercial districts, all of it washes out the darkness that fireflies need to see each other's signals. Males in lit areas flash less. Females respond less. Successful matings drop. And because firefly populations depend on reliable reproduction each summer to replenish the larvae that will emerge in future years, a few consecutive seasons of disrupted courtship can collapse a local population.
Research published in Frontiers in Ecology and Evolution demonstrated clear behavioral suppression in fireflies exposed to artificial light at night, reduced flash rates, altered timing, and reduced mating success. The effect is measurable even at relatively low light levels.
2. Pesticides: Including the Ones Aimed at Mosquitoes
Most people who spray their yards for mosquitoes aren't thinking about fireflies. But mosquito spray, whether applied by homeowners or by professional services, is a broad-spectrum insecticide. It doesn't distinguish between the mosquito resting on the fence and the firefly larva moving through the leaf litter two feet away.
The effect works at multiple levels. Adult fireflies caught in the spray zone are killed directly. Larvae in the treated soil absorb pesticide residue over their year or two underground. And critically, the soft-bodied invertebrates that firefly larvae feed on, the snails, slugs, and earthworms, are also eliminated, leaving the soil both toxic and empty of food.
Routine lawn pesticide applications, not just mosquito spraying but also grub control products and broad-spectrum insecticides used to prevent ant and beetle damage, have the same effect. Firefly larvae live in the soil. Chemicals applied to the soil reach them.
3. Habitat Loss and Lawn Culture
Firefly larvae need specific conditions: moist soil, organic matter, leaf litter to hide in, and the invertebrate prey that lives in undisturbed ground. Adult fireflies need tall vegetation, grass, wildflowers, shrubs, the edges of unmowed fields, to rest during the day, to display from after dark, and for females to watch from below.
The modern American lawn provides almost none of this.
A closely mowed, chemically maintained turf offers no leaf litter, no invertebrate community, no tall vegetation, and no moist shaded margins. From a firefly's perspective, a manicured suburban lawn is close to a biological desert.
Development compounds the problem at scale. When wetland margins, meadow edges, and woodland borders are cleared for construction, the habitat that firefly larvae have lived in for generations disappears. Unlike many species that can adapt to fragmented habitat, fireflies have limited dispersal ability, they don't travel far from where they emerged. Local population losses tend to be permanent.
What's Happening in the Midwest Right Now
Late June into July is peak firefly season across Minnesota, Wisconsin, Iowa, and the upper Midwest. The common eastern firefly (Photinus pyralis), the one most people grew up with, emerges on warm evenings when temperatures stay above 65 degrees Fahrenheit, typically from mid-June through July.
Fireflies are still present in rural areas, along forest edges, in fields with intact soil, and near water. The decline is sharpest in suburban and urban zones, the places where lawns, streetlights, and mosquito spray converge.
A 2025 study of suburban and rural firefly populations in Missouri found that suburban areas showed significantly lower firefly abundance than wild lands, with light pollution and pesticide use identified as the primary drivers. The species composition was also shifting, light-tolerant species were persisting while those requiring true darkness were declining.
Minnesota has more than two dozen firefly species, though most residents encounter only two or three. The species most affected by light pollution tend to be the ones that fly and flash the latest in the evening, when darkness should be deepest, and when artificial light does the most damage.
What a Firefly-Friendly Yard Actually Looks Like
The most encouraging part of the firefly story is that individual actions add up. Fireflies are locally rooted and habitat-sensitive, which means that positive changes in a single yard can support a local population in ways that genuinely matter.
- Let a section of your lawn go unmowed. Even a strip along the back fence or the property edge, a few feet of tall grass, clover, and wildflowers, provides the resting and display habitat adult fireflies need. You don't need a meadow. You need a margin.
- Leave the leaf litter. The impulse to rake every leaf every fall is one of the most firefly-hostile things a homeowner can do. Leaf litter is where larvae overwinter. Leave a layer under shrubs and along garden edges, and you're creating habitat for the next generation of fireflies.
- Turn off outdoor lights after 10 p.m. Or switch to motion-activated fixtures that stay dark when no one needs them. Red-spectrum bulbs, which are less disruptive to insect behavior than white or blue-white LEDs, are another option. The courtship window that matters most for fireflies is from roughly 8 p.m. to midnight in midsummer, that's the darkness that needs protecting.
- Reconsider mosquito spraying. This is the hardest ask, because mosquitoes are a genuine nuisance. But broad-spectrum insecticide applications around the yard are one of the most direct ways to reduce firefly populations. If mosquito control is a priority, targeted larviciding, treating standing water where mosquitoes breed, is far less damaging to beneficial insects than broadcast spraying.
- Add a water feature. Even a small garden pond or a shallow dish kept full of water provides the moist microhabitat that firefly larvae thrive near. You don't need a stream. You need a corner of the yard that stays damp.
At Abode Outside, 1% of every sale goes back to conservation and environmental causes, including the organizations working to protect the habitats and ecosystems that make nights like this possible. We make our knitwear to last, because lasting things leave less behind. That's the kind of outdoor life we're building toward.
There's a field somewhere, you probably remember exactly where, where the fireflies were thick enough on a July night that the whole edge of the tree line seemed to be breathing light.
That field still exists in places. It could exist in more places.
Fireflies don't ask for much: some darkness, some soil, some leaf litter, a little patience. The fact that we've made those things rare is a choice. And choices can be made differently.
