Buzz
Once doubted by scientists, the unique fireflies of the Smoky Mountains now captivate tourists worldwide, a phenomenon that was unrecognized just two decades ago.
At precisely 9:27 P.M., as twilight fades into night in the Great Smoky Mountains National Park, the mesmerizing display begins. During June, in Elkmont, Tennessee, thousands of fireflies synchronize their glow. Rather than random flickers, they pulse in unison for hours, creating a surreal, silent harmony. The trees appear adorned with rhythmic Christmas lights—bright for three seconds, dark for six, repeating endlessly for hours.
As a child, Lynn Faust would gather with her family on their cabin porch, spellbound by the silent, rhythmic glow. For generations, they cherished this natural wonder, though Faust never considered it extraordinary. “I thought all fireflies were the same and simply put on a lovely show in the Smokies,” she recalls.
Faust has always been captivated by the natural world. She pursued forensic anthropology in college with a minor in forestry. In her twenties, she spent three years traveling the globe, exploring remote islands accessible only by boat, documenting vanishing cultures, and diving into underwater photography. Now, at 60, she is a naturalist who authors scientific papers and field guides on fireflies. However, her fascination with these insects began only in the 1990s after reading an article by Cornell mathematician Steven Strogatz, who described the rare synchronization of Southeast Asian fireflies. Strogatz emphasized that such phenomena were absent in the Western Hemisphere.
Faust found this claim puzzling, as it clashed with her childhood memories of synchronized firefly displays. Delving deeper, she discovered over a century of anecdotal evidence describing North American fireflies flashing in unison, though scientists dismissed these accounts as myths or illusions. Faust was certain her Tennessee fireflies were as remarkable as their Asian counterparts, but proving it was the challenge.
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Fireflies, also known as lightning bugs, are nature’s enchanting illusionists, illuminating the world from within. These bioluminescent beetles produce light through a chemical reaction involving oxygen, calcium, and enzymes like luciferin. They flash for various reasons: communication, mating, or deterring predators. Despite their magical glow, fireflies are widespread, with around 2,000 species globally and over 125 in North America, where catching them is a cherished childhood tradition.
Over two decades ago, Faust reached out to Strogatz after reading his article. He introduced her to Jonathan Copeland, a biologist at Georgia Southern University studying firefly behavior in Malaysia and Indonesia. Copeland was initially doubtful of Faust’s claims, as previous reports of synchrony in North America had proven unreliable. “The prevailing belief was that they don’t synchronize here,” he recalls.
Despite his skepticism, Copeland humored Faust by asking her to illustrate her observations with a “musical score.” A former tuba player who once aspired to join the Boston Symphony, Copeland often applied musical principles to his study of nature. During grad school, he analyzed the rhythmic patterns of praying mantises and used a similar approach to evaluate firefly behavior. He believed that charting synchronic rhythms could distinguish genuine accounts from false ones. Faust, nervous but determined, put pencil to paper. “Viewing it scientifically is far different from casually enjoying it on a porch,” she admits. “I didn’t want to come across as foolish.”
When Faust’s note arrived, Copeland recognized the patterns as synchrony. Intrigued, he drove eight hours to Elkmont in June 1993. Arriving at dusk, he saw no fireflies and dozed off—only to wake surrounded by flashes of light. “It was undeniable!” he recalls. He rushed to a pay phone to call his colleague Andy Moiseff. “It was around midnight,” he says. “I told him, ‘Andy, you have to see this—they’re flashing in sync!’ Andy, ever the scientist, laughed and said, ‘Prove it.’” The following summer, Copeland, Faust, and Moiseff, a physiology professor at the University of Connecticut, embarked on proving it. Their collaboration was unconventional but powerful. Copeland, a neuroethologist, studied animal behavior; Faust, a skilled outdoorswoman, knew the area intimately; and Moiseff, a tech-savvy theorist, designed experiments to test their hypotheses.
The team transported lab equipment, microscopes, cameras, computers, and insect samples across the Smokies. Starting in Elkmont, they expanded their research to determine the phenomenon’s scope. They analyzed firefly flashes frame by frame in the lab. In the wild, the synchrony was unmistakable, but isolating fireflies in freezer bags disrupted their rhythm. Without visual cues, the insects no longer flashed in unison. By 1995, the team had gathered conclusive evidence.
“This discovery was groundbreaking in the firefly community,” says Copeland. While four synchronous species are known in Asia, they are smaller and less intense than Photinus carolinus. “Their flashes are weaker, but they compensate with numbers,” Copeland explains. Unlike carolinus, which fly through the woods, Asian fireflies typically remain stationary in riverside trees. “Our species is more complex,” Faust adds.
Confirming synchrony in Western Hemisphere fireflies was thrilling but raised new questions. Why did they flash this way, and how did it differ from their Asian counterparts or asynchronous relatives in North America? For the next two decades, Copeland, Moiseff, and Faust studied the fireflies each summer, striving to unravel their mysteries. But just as they neared breakthroughs, Elkmont underwent significant changes.
Initially, the team worked in solitude. “Back then, it was just the three of us and the occasional fisherman,” Moiseff recalls. When Faust first told park officials about the firefly spectacle, they dismissed her claims. In 1992, her family lost their cabin when the government reclaimed the resort community’s leases. By then, Faust had observed that the fireflies’ synchronized behavior seemed confined to a specific area, not occurring even half a mile away. She theorized that the unique conditions near the cabins might explain the phenomenon. However, park officials suspected her claims were a ploy to retain her cabin.
In 1996, park administrators finally sent a ranger to investigate. “It was an amusing night,” Faust remembers. “We had an old computer on the porch and Christmas lights strung across the hill to test if we could influence the fireflies’ rhythm. The ranger kept asking, ‘Where are they?’ Then, suddenly, they appeared. He was stunned, repeating, ‘Oh, my God,’ multiple times.” The following night, 20 rangers joined to witness the spectacle.
By the early 2000s, the phenomenon gained widespread attention. Kent Cave, a park supervisory ranger, noted, “There were traffic accidents, road rage, and large crowds.” The Smoky Mountain fireflies had become a major tourist draw. In 2006, the park introduced a trolley service to manage the influx, restricting individual car access. “Visitors drove hours from places like Alabama or Lexington, only to find they couldn’t get in,” Cave explains.
Today, visitors must reserve parking spots online in advance. After predicting the peak firefly emergence, reservations open in late April and sell out within minutes. The event has become the park’s largest, attracting up to 12,000 attendees annually. However, as Cave notes, “The biggest challenge is predicting when these little creatures will flash.” Faust has developed a mathematical model to address this. “The pressure to predict the timing started 20 years ago,” she says. “While nature isn’t entirely predictable, my method provides a reliable estimate.”
Park entomologist Becky Nichols now uses Faust’s degree-day model to forecast the fireflies’ emergence. The formula, specific to Photinus carolinus, relies on temperature data collected from early March. “We use high and low temperatures in a formula to calculate the larvae’s growth,” Nichols explains. “Previously, we lacked accurate temperature data.” This issue has been resolved with tiny loggers placed on trees and the ground. Faust also uses her own data logger, and the two women compare results to ensure accurate predictions.
While the scientists are pleased that the public enjoys the light show, its popularity comes with mixed feelings. The site has become too crowded for research, forcing the team to relocate to other parts of the Appalachian Mountains. Copeland reflects, “We can’t conduct studies there anymore because it’s a tourist attraction, and we played a big role in making that happen.”
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Why do Photinus carolinus flash in unison? The exact reason remains unclear, Faust notes, but there are hypotheses. In a 2010 Science paper, Moiseff and Copeland proposed that synchrony helps female fireflies avoid confusion during mating. Using an electronic simulator with LEDs, they discovered that disorganized flashes—multiple lights at different times—disrupted female responses. Synchronized flashes, however, allowed clear communication between males and females. Faust agrees that carolinus synchrony is tied to mating behavior.
Moiseff, fascinated by the firefly’s brain and neural activity, questions how their eyes process information. Research suggests that under certain conditions, fireflies can pinpoint the source of a flash. This implies their brains might process information through distinct pathways, similar to primates and humans—an unexpected capability for insects. Moiseff continues to explore this: “How does a simple nervous system achieve this? What’s the underlying mechanism?”
Moiseff emphasizes that Photinus synchrony is significant not because it’s rare but because it shifts our understanding of how living organisms interact. With one confirmed case in the U.S., the discovery paved the way for finding others. In 1998, Copeland and Moiseff identified Photuris frontalis, a synchronous species along the Georgia and South Carolina coast. Additionally, Photinus pyralis exhibits “weak synchrony.” As Moiseff explains, “Once you find other species displaying this behavior, they’re no longer anomalies. Instead, they represent a solution to specific environmental challenges.”
In recent years, Moiseff and Copeland have focused their firefly research closer to home. “For the first decade, my spouse was incredibly supportive,” Copeland remarks about his work in Tennessee. “But eventually, she began questioning its importance.” As he retires from Georgia Southern this year, Copeland reflects on identifying Photinus synchrony as a career highlight. “Growing up as a suburban kid afraid of the dark, I never imagined I’d be alone in the woods with fireflies,” he says. “Serendipity—and a mindset that pulls you away from cable TV—plays a crucial role in scientific discovery.”
Faust remains deeply engaged with fireflies, currently compiling a field guide featuring her collection of over 60,000 photos. Her family cabin still stands in the same spot where she first witnessed the light show, though it’s no longer theirs—it now belongs to the park. Gone are the days of cozying up on the porch under blankets, eagerly awaiting the spectacle. Yet, one thing remains unchanged: Faust’s excitement every summer when Photinus carolinus returns. “The greatest joy is predicting the first night,” she says. “Seeing that first flash and thinking, ‘It’s happening again.’”
