A dazzling firefly light show in the United States

I’ve been in Great Smoky Mountains National Park in Tennessee for less than an hour when I’m mistaken for a woodland fairy. Even though I’m here to witness the ethereal phenomenon of synchronous fireflies—Photinus carolinus, a species famed for its ability to flash in unison—the association is surprising. In fact, when I hear a stranger calling out from across the forest glen, it takes me a second to realize that she’s addressing me. She waves me over and asks: “Are you a magical creature?”

The woman gestures toward the two young children with her and says, “We saw you walk down to the river, and then you disappeared. I told the girls you must be magical. This whole place is magical.”

It does feel as if we’ve travelled through a portal to another realm. The woman is sitting on a porch stoop, but there’s no porch. And there’s a chimney nearby, but no house. To reach a trailhead in an area of the park known as Elkmont, we—along with hundreds of other visitors here for the fireflies’ light show, which generally occurs in a two-week period around early June—had to walk along an avenue of cabins, abandoned after the park was formed.

A Tufts University study of firefly tourism, released in 2021, found that, globally, one million people travel to witness firefly-related phenomena every year. The synchronous fireflies of Elkmont are some of the most famous in the world.

The firefly event in Great Smoky Mountains National Park, which straddles Tennessee and my home state of North Carolina, draws seekers from across the continent. The US National Park Service has a lottery for people to secure passes, but even so, the annual gathering isn’t a small one. In fact, the reason that I had dipped down to the river was to get a brief respite from the crowd.

A synchronous firefly in western North Carolina. Photo for The Washington Post by Travis Dove.

Along the trail designated for firefly viewing, people have been setting up folding chairs. Firefly habitat is so specific, so mercurial, that no one, not even rangers, can predict the best seats, so people find a spot that feels right to them. Finally, dusk comes.

When the first synchronous fireflies appear, sporadically flashing, they don’t seem to be much different from common species that illuminate backyards. But as their numbers grow to be thousands—each appearing to light the one next to it, like a candle being passed—the crowd stands.

For a while, the insects’ rhythm remains a bit discordant, like that of an orchestra warming up. Scientists have found that the more individual fireflies participate, the more in tune they get. Before long, there are so many that it’s clear they’re working in unison. The effect isn’t a lights-on-lights-off situation, as I’d expected; it’s more like watching a stadium wave, when members of a crowd successively lift their hands.

The insects are responding to each other’s light, working with their neighbours to find their role in the whole. From a distance, the activity appears as a shimmering current running through the forest from right to left: whoosh. Then darkness. Then, again, a whoosh of light.

The woman beside me calls out “Dun, dun, dun, dunnn,” mimicking the famous motif in Beethoven’s Symphony No 5. “It’s like they’re playing music,” she says.

Lynn Faust, a naturalist who used to spend summers in the now-defunct Elkmont community, grew up admiring the fireflies we’re watching. As an adult, she came across an article about synchronous fireflies in Asia, and she recognized similarities between what the scientists were reporting on there and what she’d seen as a child.

When she reached out, researchers were skeptical. They asked her to imagine the flashing lights as musical notes and record their rhythm on a blank piece of sheet music. Her efforts convinced firefly scientists that they should make the trip to the park, where they confirmed the existence of a previously unrecorded synchronous species.

Synchronous fireflies on a road on Grandfather Mountain. Photo for The Washington Post by Travis Dove.

Most people in attendance seem to be familiar with the concept of firefly flashes as a function of mating. The insects we’re seeing are males signalling to females, who stay close to the ground.

Scientists generally agree about the mating-related utility of fireflies’ bioluminescence, but they’ve long tussled over how, exactly, fireflies make light. It’s thought that illumination occurs when a firefly opens an air tube, allowing oxygen to ignite organic compounds in its body. This means, in a roundabout way, that when you see a firefly light up, you’re watching it take a breath.

Collectively, the crowd gasps and sighs as the fireflies flit through the forest. But despite the dazzle, I find my eyes wandering toward the infinitely dark ground. Because once I started researching fireflies, I came across this incredible fact: By the time we see a firefly in flight, it has potentially been living among us for up to two years in various life stages, dimly glowing on the ground. What we’re witnessing now is the grand finale of a long-term metamorphosis.

These creatures have been waiting for their turn to rise. And, finally, they’ve found it. When people begin leaving the park, the fireflies are still working like cells of a glowing, forest-sized lung.

There are more than 2,000 known species of fireflies in the world, and 19 of them reside within the Great Smoky Mountains National Park. Will Kuhn, director of science and research at Discover Life in America, a non-profit centred on biodiversity, believes there are more. “I don’t think we’ve found all the firefly species in the park,” he says.

There is a chance that we won’t know what we’ve got, even after it’s gone. Globally, firefly populations are under assault, and the largest threats to their well-being, according to the Tufts report, are habitat loss, pesticide use and light pollution.

When I meet Kuhn, he’s holding court with two dozen people who’ve signed up for a synchronous firefly viewing event hosted by his organization. Since the founding of Discover Life in America in 1998, the group has documented more than 10,000 animal and plant species in Great Smoky Mountains National Park—more than 1,000 of them were previously unknown to science.

We’re getting ready to travel down the mountain to Norton Creek, a private habitat outside of the park. Kuhn knows the area to be home to a large population of synchronous fireflies.

One of the women encircling Kuhn says that she’s excited because she has only “plain old fireflies” on her farm in Ohio. Kuhn says that her region is likely home to several species. The most common firefly in the United States is the big dipper, but there are 150 species with specific habitats and behaviours in North America. Each of the bioluminescent species’ flash patterns is as unique as a fingerprint.

Susan George, from San Antonio, Texas, is amazed that fireflies are tenacious enough to find homes in the city, in rare squares of land spared from asphalt and concrete. “Sometimes, when I’m sitting out in my yard, fireflies land right on me,” she says.

The woman from Ohio nods. “When they do that,” she says, “it feels like love.”

Unfortunately, when we finally make it to the waterway, the local population of synchronous fireflies fails to greet us. There are only a few partnered dots of light. It’s several degrees cooler here than it has been in the Elkmont region. The synchronous residents of Norton Creek apparently need a few more days to fully wake.

Just when it seems that spirits are irretrievably waning, someone spots a strange orb of light rising from the understory. It peers at us from across the creek, blue and unblinking.

I’ve been familiar with the term “blue ghost” for years, as it related to my home region’s firefly attraction. Synchronous fireflies and blue ghosts have slightly different mating seasons, but they often overlap. Currently, on Norton Creek, it seems to be the blue ghost firefly population that’s peaking.

The ghost moves toward us. And it isn’t flying, it’s floating.

Blue ghost fireflies (which appear as continuous lines) float below a synchronous species on Grandfather Mountain. Photo for The Washington Post by Travis Dove.

Soon there are carpets of light in and around the forest on all sides of us. These creatures are notable for their neon-bright colour and enduring flashes—which hold for up to 60 seconds at a time. Their traceable flight patterns make them look as though they’re intoxicated.

As group members wander off, I find myself walking alone. But with every step I take, more fireflies reveal themselves. Hundreds of them are swooping and swerving and serenading me—not as a visitor to this landscape, but as part of it.

By the time I hear voices on the road ahead, I’ve lost all sense of time and space. In dim moonlight, I can make out half a dozen silhouettes. Kuhn’s voice is hushed. “It’s amazing what happens when you let your eyes adjust to the dark—when you take the time to really look.”

For weeks after I return home from Tennessee, I find myself scanning meadows and creeks. And each night, I get the urge to go outside to check on the local firefly population.

I take to sitting beyond an old chicken coop, watching femme fatale fireflies winking from treetops and big dippers plunging through meadows. One night, I decide to explore the valley beyond my immediate environs.

After a little less than a kilometre, I slow my stride. I see a lone firefly blinking. Slowly, entire constellations of fireflies rise from the coal-black earth around me, twinkling with oxygen. I attempt to align with their rhythm: inhale, light; exhale, dark. We are breathing at this moment, in sync, on this complicated planet. And even the deepest parts of the mountain valley I’m standing in are pulsating with life, illuminated.

The Washington Post (September 7, 2021), Copyright © 2021 by The Washington Post. The text is excerpted from the original story.

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