On warm August evenings, people across the world step outside to watch fireflies. On our Alitaptap map, members recently logged Common Eastern Fireflies in Ann Arbor, Michigan, and Durham, North Carolina. Across the ocean, observers in Bismark, Germany, and Choulex, Switzerland, spotted European Glow-worms resting quietly in the dark grass. It is easy to think that fireflies belong only to the night sky.
That is only a small part of their story. Adult fireflies live for only a few short weeks. Before they ever fly or flash in the trees, fireflies spend one or two full years living on the ground. They hide inside wet soil, under rotting wood, and beneath fallen leaves.
Underground, a young firefly is called a larva. Firefly larvae look like tiny, flat armored bugs. They do not have wings, and they cannot fly. Instead, they crawl through damp dirt looking for food. They are active hunters. Their favorite meals are snails, slugs, and soft worms.
To eat a snail, a firefly larva bites it and injects a special liquid. That liquid turns the inside of the snail into a soft soup. Then, the larva drinks it up. A single firefly larva can eat dozens of snails before it grows up.
Without a safe place to live underground, a larva can never turn into an adult firefly. Today, many young fireflies face a big hidden danger right beneath our feet.
The Problem with Yard Bug Sprays
Many homeowners and lawn care companies want lawns to look like smooth green carpets. To get rid of unwanted bugs or weeds, people often spray chemical poisons on the grass. These sprays are called pesticides or insecticides.
Insecticides are made to kill insects. The big problem is that chemical sprays do not pick and choose which bugs to harm. They do not skip fireflies while only targeting mosquitoes or lawn grubs. When someone sprays a lawn with bug killer, the chemical poison sinks right into the top layer of dirt.
That top layer of dirt is the exact place where firefly larvae live and hunt.
When young fireflies come into contact with lawn poisons, they can die quickly. Even if a chemical spray does not kill a larva right away, it can ruin its food. Pesticides kill the snails, slugs, and worms in the yard. If a firefly larva eats a poisoned snail, the larva gets sick too. If all the snails in a yard die off, the young fireflies starve to death long before they ever grow wings.
Rain can also wash these chemical sprays off the grass. The poison travels into nearby flower beds, vegetable gardens, and small creeks. This means chemical sprays can harm fireflies far away from the spot where the poison was sprayed.
Clean Yards Can Cause Problems Too
Chemical bug sprays are not the only threat to young fireflies. Another problem comes from how people clean up their yards and gardens.
Firefly larvae must stay damp to survive. Their soft bodies dry out quickly if the soil gets too hot or dry. In nature, falling autumn leaves, decaying twigs, and tall grass act like a wet sponge over the dirt. Leaves trap rain and dew. They block hot sunlight and keep the ground cool and moist. This damp soil is a great home for snails, worms, and young fireflies.
When people rake up every single autumn leaf, scoop away all the wood chips, and cut grass super short every week, the ground changes. The hot summer sun shines directly on bare soil. The ground dries out and bakes hard like a clay brick.
Snails and slugs cannot live in hard, dry soil. They leave or die. Without moisture and leaf cover, firefly larvae lose both their food and their shelter. A yard that is scraped clean and mowed short becomes a desert for young fireflies.
What Our Map Shows Us
On Alitaptap, citizen scientists log firefly observations from many different countries. Their reports give us clear clues about where fireflies survive.
For instance, a spotter in Macapá, Brazil, recently logged Aspisoma lineatum near the damp Amazon basin. Another user spotted the same species in Asunción, Paraguay. These fireflies depend on moist soil and thick plants that keep ground moisture locked in.
In Wood County, Texas, an Alitaptap user spotted Pleotomus pallens. The females of this species do not fly. They stay close to the dirt, relying completely on healthy ground cover. In Nellore, India, an observer logged Abscondita anceyi. In Calenzano, Italy, a user found Lampyris fuscata fuscata.
In the United States, users recently reported Common Eastern Fireflies in places like Avondale, Pennsylvania; Urbana, Illinois; Wheeling, West Virginia; and even Brooklyn Bridge Park in New York City.
Notice what these places have in common? Even in big cities or busy towns, fireflies show up where there are patches of soft dirt, damp leaves, and shade. If those patches get sprayed with harsh bug killers or cleared down to bare earth, the fireflies disappear from the map.
Four Ways You Can Help Fireflies in Your Yard
You do not need special tools or lots of money to protect fireflies. Small changes in how you care for your lawn or garden can save hundreds of young fireflies. Here are four simple steps you and your family can take today.
First, stop using chemical bug sprays on your lawn. Skip chemical mosquito foggers and grub treatments. If mosquitoes are a problem, try using natural water treatments called mosquito dunks in standing water. These use harmless bacteria that target mosquito larvae without hurting fireflies or soil bugs.
Second, leave a wild patch of grass. You do not have to let your entire lawn grow wild. Choose a small area in a back corner or along a fence. Let the grass grow taller there. Avoid mowing that spot during the summer. Tall grass traps moisture in the dirt and gives adult fireflies a safe place to rest during the day.
Third, keep autumn leaves in your garden beds. When trees drop their leaves in the fall, do not put them all in plastic trash bags. Rake a layer of leaves into garden beds, under trees, or around shrubs. Leaving dead leaves creates a warm, damp winter blanket for firefly larvae. They sleep under those leaves all winter and wake up ready to hunt in the spring.
Fourth, plant native plants and keep soil moist. Native plants have deep roots that hold water in the ground. Adding a small rain garden or a patch of thick wood mulch helps soil stay damp even during dry summer weeks.
Track Your Firefly Sightings
Fixing up your yard is an awesome step, but you can also help by doing science. Whenever you see a firefly in your neighborhood, at a park, or near a creek, take note of where you are. Share your observation on Alitaptap or iNaturalist.
When you record your sightings, scientists can look at maps to see where fireflies are doing well. They can compare neighborhoods with heavy chemical sprays to neighborhoods with organic yards and leaf piles. Your sightings give researchers real evidence about what helps fireflies survive.
By skipping chemical sprays, leaving some leaves on the ground, and sharing what you see, you help keep fireflies glowing for years to come.