Humane Gardener

If your habitat sparkles, congratulations! You’re doing something right. If it doesn’t light up with insects twinkling their way through the night, read on to learn how to welcome firefly friends.

Soon the Big Dipper fireflies will start writing their love letters across our back meadow, lighting up the tall grasses with their scrawling J-shaped serenades. This past week, the Spring Tree-Top Flashers have already been twinkling their way up the tulip trees around the edges, rising higher and higher as evening turns to deep night.

Wherever there is habitat, there are fireflies, so the presence of these luminescent animals is no longer confined to the backyard. For the past few years, after we stopped mowing all but a small strip of grass where neighbors walk their dogs, fireflies have taken up residence across our whole 2.23 acres, even flashing their courtship signals just feet from the road. They light up the path to the doorway, sparkle across the understory of the silver maple, and perch in the sea oats by the driveway.

Firefly populations are immeasurably higher on our side of the street than in the scalped field across from us. Situated between two crew-cut lawns, the field is an extra lot our neighbor doesn’t use but still mows from April through October. Few animals can use that exposed, flowerless land—not the fireflies or bumblebees or rabbits, except perhaps just to pass through quickly on their way to somewhere more welcoming.

Scientists aren’t sure what adult fireflies eat and have posited that most don’t eat anything in their last life stage, even though some adults have been found nectaring on milkweed. But a lack of pollination and seed dispersal services wouldn’t make these insects any less important than bees and birds. As larvae they feed largely on slugs and snails, offering a natural control of plant eaters. Fireflies are in turn food for orb weavers, jumping spiders and other invertebrates. Because of their reliance on rich habitat, their need for dark skies, and their sensitivity to pollution and pesticides, they’re also bioindicators of healthy ecosystems.

Firefly flashing by Terry Priest — Many firefly species around the world, including at least 18 in the U.S. and Canada, are at risk of extinction due to habitat loss, climate change, light pollution, poor water quality, invasive species and pesticides. (Photo by Terry Priest/frfly.com)

In my new book Wildscape: Trilling Chipmunks, Beckoning Blooms, Salty Butterflies, and Other Sensory Wonders of Nature, I explore the ways that our humancentric focus on arbitrary aesthetics privileges flat, monochrome barrenscapes of turfgrass over dynamic, layered, kaleidoscopic habitats that make a yard a home for so many wild animals. In creating these rigid, sensory-deprived sightscapes, our culture sacrifices the scentscape, soundscape, tastescape, and—perhaps most of all when it comes to fireflies, the touchscape: those rich, mixed layers of leaves, mosses, dead wood and grasses where they spend most of their lives.

What do fireflies need us to do to bring back all these critical habitat elements? More often than not, we don’t need to start doing anything new so much as stop committing acts of destruction. Stop mowing down their daytime refuges. Stop taking away their egg-laying sites. Stop spraying pesticides.

And if you live in any area where fireflies are endemic, you also don’t need to travel to see them. Many people head to the Smokies or even overseas for special firefly-viewing trips, and while I understand how enticing that might be, I regret that much of that time and money could be spent supporting fireflies in our own communities—so that we all may be surrounded by them, wherever we live, for generations to come. Here are 10 ways to welcome fireflies to your habitat:

1. Nurture the Mosses

Mossy firefly habitat — Some of the most underappreciated plants, mosses provide incredible habitat. Birds pluck them to line their nests, and fireflies lay eggs on them and pupate beneath them. (Photo by Nancy Lawson)

Most fireflies require moisture throughout their lives, and mossy areas can make a wonderful firefly nursery. In her book Fireflies, Glow-worms, and Lightning Bugs, Lynn Frierson Faust notes that last-instar larvae in the Photinus genus (which includes the Big Dipper firefly, Photinus pyralis) burrow several inches underground and pupate in a chamber underneath spongy moss. Photinus carolinus, the famous synchronous fireflies, are among the species that lay eggs on mosses.

2. Respect the dead wood.

rotting log in firefly habitat — Underneath rotting wood, fireflies pupate. Provide these safe havens by lining paths with logs and branches around your habitat. (Cavity-nesting bees and woodpeckers will thank you too!) (Photo by Nancy Lawson)

Photinus fireflies can also be found pupating underneath logs and other rotting wood, writes Sara Lewis in Silent Sparks: The Wondrous World of Fireflies. Fireflies in another genus, Photuris—known as femme fatales because of the females’ habit of deceptively flashing to lure males of different species for the purposes of eating them—pupate on the soil surface or under logs too.

3. Love the slugs and snails.

Slug in firefly habitat — Slugs have my heart. These misunderstood animals are beautiful and fascinating to me, and they are quite tasty to firefly larvae. (Photo by Nancy Lawson)

Firefly larvae prey upon soft-bodied invertebrates, especially snails, slugs and earthworms. Despite their poor reputation, snails and slugs are wonderful creatures in their own right, and they play an important role in breaking down organic matter in the soil. In fact, after we traded hostas for native plants when we first moved to our home, we rarely saw slugs on the green leaves anymore; they’re happier in the rich leafy layer that we nurture at the ground level! Resist the urge to bait or harm these tiny creatures who are just doing their jobs like everyone else—and remember that a firefly will thank you for not stealing her meal.

4. Leave the leaves.

Toad in leaves — Fallen leaves keep the ground moist, nurturing toads and all the other animals who are sensitive to drying out—including vulnerable fireflies and their prey. (Photo by Nancy Lawson)

Fallen leaves aren’t just habitat for toads, birds, and bees — they’re another great firefly nesting site too. They also help the ground hold moisture, which is critical to most fireflies during all their life stages; larvae and flightless females could be especially prone to drying out. Lack of moisture can affect firefly food sources as well, since snails and slugs require wet areas too. “Some western firefly habitats have completely disappeared due to water table reductions,” write the authors of the 2021 paper “Evaluating firefly extinction risk: Initial red list assessments for North America.” Leaving fallen leaves under trees and shrubs and in gardens provides a moist refuge that’s denied by turfgrass lawns.

5. Nurture native plants, including native grasses.

Sea oats in firefly habitat — Firefly.org founder Ben Pfeiffer has found sea oats among the plants present in high-quality firefly habitats. (Photo by Nancy Lawson)

Firefly expert Ben Pfeiffer, the founder of Firefly.org, has noticed that a decline in riparian native plant communities in his home state of Texas has compromised firefly habitat. “One of the first things native plants do is they maintain soil moisture in the ground,” he says. “That’s really critical for fireflies that tend to use mud or some kind of substrate like that to lay eggs in.” A diverse, layered landscape with shrubs and tall grasses also provides perching spots for females to search for flashing males. On his website, Pfeiffer maintains a list of native plants that he’s observed in high-quality firefly habitat. Though he conducts his research far from my Maryland home, I was delighted to find among his recommendations two plants that are abundant in my habitat—late boneset (Eupatorium serotinum) and sea oats (Chasmanthium latifolium)—as well as cardinal flower (Lobelia cardinalis), wildrye (Elymus virginicus), Indiangrass (Sorghastrum nutans), switchgrass (Panicum virgatum) and other natives also present here.

6. Plant pines, other native evergreens, and dense hedgerows.

Hedgerow in the making — My neighbor’s pine trees kept our habitat dark at night for years. After he cut half of them down, we started a hedgegrow to block his security lights and create habitat. Included in the plantings are American hollies, Eastern red cedars, Virginia pines, loblolly pines, smooth sumacs (shown here), hazelnuts, chokeberries, chokecherries, river birches, witch hazels, bayberries, Virginia roses, elderberries and more. Filling in the gaps are mountain mints, wild bergamot, and many other native wildflowers. (Photo by Nancy Lawson)

Like fallen leaves, pine needles serve as egg-laying sites and provide habitat for firefly larvae. Native pines and other evergreens, such as the American hollies and Eastern red cedars endemic to my area, also help cast shade and block artificial lighting from neighbors. The Spring Tree-Top Flashers (Pyractomena borealis), a widespread Eastern species that uses tree canopy for flickering serenades, pupates in the bark of trees. Flashing across the deciduous forest canopy surrounding our habitat starting in May, they are often the first fireflies to emerge in spring, appearing about an hour after sunset each night.

7. Ditch the mower, the “enemy” of the firefly.

Purpletop grass meadow — When we stopped mowing, native grasses such as purpletop and broomsedge began filling in the old field. Since then, beaked panicgrass, deertongue and nimblewill have shown up, and we’ve added switchgrass, Indiangrass, and many sedges. (Photo by Nancy Lawson)

Mowing is one of the worst things you can do for fireflies; as Pfeiffer put it so well when I interviewed him for my book, “The lawnmower is the one of the biggest enemies of the firefly.” Right up there on the bad-actor list, along with mowers, are the products used to maintain artificially green and lifeless landscapes. Lawn companies routinely apply broad-spectrum insecticides designed to kill all insects. They convince homeowners of the need to “control grubs,” and many people don’t even realize that “grubs” are beetle larvae—and beetle larvae are the babies of many different kinds of beetles, including fireflies, ladybugs, and others who play important roles in the ecosystem as pollinators, predators and prey. Commonly used herbicides, such as the systemic 2,4-D, can also harm fireflies; they’ve also been shown to be toxic to earthworms, which are part of the firefly food supply, and to beetles such as ladybugs.

8. Learn about firefly natural histories.

Firefly on burnweed — A firefly in the Photuris genus perches on a burnweed leaf. Photuris fireflies are known as femme fatales for their habit of luring male fireflies of other species to their doom. (Photo by Nancy Lawson)

The more you learn about your wild neighbors, the more you can begin to appreciate them, and studying their sparkling conversations is a natural way to start. Scientists have discovered that firefly bioluminescence first evolved among larvae as a way to warn predators of their toxicity. Only later did fireflies’ glowing talents develop into their more adult language of love—or rather, their many languages. Across the U.S. and Canada, there are more than 169 described species of fireflies, and of the many that produce light, each has its own flashy patterns. Females find males of their species by the timing of the flash, and males pay attention to females response times to figure out who’s who. Firefly flashing is also used for male competition, male rejection, female warning, and signals of alarm. Though many fireflies contain toxins, the femme fatale fireflies appear not to; that’s why they use their flashing mimicry skills to draw males of other species—it’s a way to acquire chemical defenses. Some male fireflies also “pseudo flash” to distract male competitors.

9. Let there be night.

Sunset and natural light in firefly habitat — Light pollution cuts short communication among fireflies the way a jackhammer disables our own ability to speak to one another. Considering the sensory lives of other beings can help us be more thoughtful in our actions. (Photo by Nancy Lawson)

You won’t see any of these spectacular firefly linguistics in your yard if you leave the lights on. Along with habitat loss and climate change, light pollution is among the top threats to firefly existence, with at least 18 species at risk of extinction in the U.S. and Canada. You can bring back the night by turning outdoor lights off when you’re not using them or using motion-detecting lights that only flash on when needed. Indoor lighting shining outwards also adds to the problem, but light-blocking curtains or blinds can mitigate or eliminate the glow. Even outdoor ambience lighting can be problematic; after I installed a string of tiny amber-colored lights inside our gazebo for dinner parties, I noticed a firefly flashing just outside the screens. Though amber lights are said to be less intrusive to other night insects, Lewis and her colleagues have found that they are actually even more disruptive to firefly communication. During firefly season I don’t turn those lights on at all anymore, opting instead for small candles on the table.

10. Spread the word with a Firefly Habitat sign.

“Why do you have fireflies in your yard and I don’t?” More than one wildlife gardener has encountered such questions from neighbors, often leading to enlightening conversations about the damaging effects of lawns, mowing, leaf removal, and pesticides. You can create even more opportunities for dialogue and education by posting a “Firefly Habitat” sign, available at Firefly.org.