Archived Outdoors

Synchronous fireflies draw thousands to the Smokies

coverIt’s a little after 7 p.m. when the first trolley shows up to Elkmont Campground. Green, red and yellow, the flashy Gatlinburg transit vehicle seems a bit out of place in the backwoods greenery of Great Smoky Mountains National Park, but so, too, do the crowds of people that pour out of it.  

People bearing fold-up chairs, blankets and cameras. People with North Face and Patagonia strapped to their backs, and people toting oversized purses and tote bags. Children, teenagers, parents, retirees. People who are always in and out of the National Parks, and people who have probably never set foot in one in their lives.

But by the time dusk descends, all 1,000 of those people will be seated along the edges of the trails stepping off from Elkmont. And all for a common purpose: to watch fireflies. 

Not just any fireflies, though. The Great Smoky Mountains are home to Photinus carolinus, the synchronous fireflies. Their dynamic lightshow airs for only two weeks out of every year, and it’s mostly a local channel. Mostly, it’s here at Elkmont. 

“It’s one of those awe factors of life,” said Danny Lynn, 55, as he and his wife Cheryl settled down to see the show for the second time in their lives. “It makes you go, ‘Wow.’”

“Put it on your bucket list,” Cheryl agreed. 

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Christmas in June

An air of excitement pervaded first-time viewers and repeat offenders alike as the sun set over the Smokies. The crowds erupting from the trolleys spread out, staking out their territory and setting up their chairs to face the woods, waiting.

Something great was about to occur, that much was obvious, but as someone with no experience in the synchronous firefly department, it was hard to know exactly what I was supposed to be getting excited for. 

Becky Nichols, park entomologist, did her best to explain. 

“As it gets dark and they can visually see each other a little better, they’ll really start to sync up with their flashes,” she said. 

It’s the males who do the syncing, blinking their lights in unison, five to eight times in a row at half-second intervals. At the height of the show, the entire forest blinks on and off at the same time, a sight reminiscent of Christmas lights in winter. 

“[The female] stays on the ground and flashes a little weak response,” Nichols explained. 

The famous firefly show is really a lighted mating ritual, Nichols said of the last hurrah of a life spent mostly underground, eating snails and earthworms. The fireflies spend most of their lives as larvae, devoting their three or four weeks of adult life to mating, laying eggs and dying. That scientific description put a few visitors off at first. 

“I couldn’t help but think, ‘We’re going to watch a billion fireflies have sex and die,’” said 70-year-old Richard Macko, who traveled from Orlando with his wife to watch the show with his brother and sister-in-law, who live in Knoxville.. 

No one knows for sure just what the relationship is between lights and mating. It could be male-on-male competition, a contest in which the dude with the brightest light wins. On the other hand, it could be collective action on the part of the males, a joint effort to make a flash big enough for the female to respond so that the males can find her. It’s the latter that’s the leading theory, Nichols said, but the verdict’s still not completely in. 


Primo habitat

Whatever the reason, the result is magnificent, a natural wonder that’s been drawing increasing waves of interest since word about the species’ existence began to spread in the 1990s. That’s when a Knoxville resident told a scientist about the “light show” she’d been enjoying at Elkmont for more than 40 years. The news came as a surprise to Georgia Southern University professor Jonathan Copeland, who had been traveling all the way to southeast Asia to study a different species of synchronous fireflies there. Turns out, a similar insect lives right here in the Smokies. 

Though Elkmont is unarguably the most popular place to view the fireflies, their range isn’t limited to that area. Photinus carolinus occur throughout the southern Appalachians, ranging from Tennessee as far north as southwestern Pennsylvania. 

That’s a sizable range, but they’re still not exactly common. They have a specific set of habitat requirements, and they’re sensitive to light pollution and trampling of the ground. The fireflies live mainly in the 2,000- to 5,000-foot elevation range, and they need moist soils, a comfortable temperature range and an open understory so that they can see each other’s displays. So their populations tend to exist in pockets, and Elkmont is a pocket that meets all of those qualifications with flying colors. 

“This is one of the best displays,” Nichols said. “Elkmont is pretty well-known for being primo habitat.”


A natural wonder

As the sun set and darkness descended, I had my doubts. The woods were quickly turning black, but no bugs lit them save a few evening fireflies, the kind I’d grown up watching every summer night. Where was this bucket list experience, this magical phenomenon of nature? 

Then … “Look, look!”

One of the preteens in the family sitting across the path from me had evidently seen something in the woods while I was turned the other way. Heads swiveled, including mine, and a few seconds later there it was — a cluster of flashing lights, bursting like a frazzled electrical circuit. This was the evening’s opening act.    

“You’ll see one, and it will go blink, blink, blink and shut down because it will have to recharge,” volunteer Glo Turner had explained to me earlier. “The bunches get bigger until the whole woods is on the same synchronization.”

Eventually, the bunch of fireflies lighting up the hemlock across the path lost their limelight, because independent bunches started up in all different corners of the forest. The initial excitement over, the crowd settled into a mostly reverent quiet as the show took off.

Before long, it was just like Turner had said — a whole forest full of fireflies flashing their lights on exactly the same schedule. The moon rose, illuminating the sky against the highest branches of trees, and the fireflies carried on, fairy-like, exposing the contour of the ground beneath them. 

“It’s so spectacular,” said Knoxville resident Debra Simmons. “It’s really hard to put into words how spectacular it is.”

Maybe it’s the darkness, maybe it’s the woods or maybe it’s just the awe of the sight itself, but the firefly show is one that gives an illusion of solitude. The National Park Service counted 972 people at the trailhead that night, the majority of those people settling within half a mile of the trailhead, but as darkness descended and the woods lit up, their existence disappeared. For Simmons, it’s a feeling that harkens back to the early days, before every inch of the world was mapped out and traveling to the other side of a mountain could reveal a previously undiscovered wonder. 

“I can’t imagine if you were like Laura Ingalls Wilder and you woke up at night and not knowing what it was,” Simmons said. 


The most popular insect in town

More and more, though, people do know what it is. The firefly phenomenon has taken off in popularity over the past decade or so, traveling by word of mouth ever since scientists started studying it and growing by leaps and bounds with the proliferation of the Internet and social media. 

“For me even, it was still word of mouth at that point,” said Caitlin Worth, public affairs specialist for GSMNP, who first heard of the fireflies as a high school student in Tennessee during the early 2000s. “But we certainly started getting that local media interest at that time, and that definitely caused a little more commotion down there. Today one of the reasons it’s as popular as it is, is because of how much it’s shared in social media circles.”

In fact, the popularity eventually became so extreme that the park had to do something about it. 

“It just got to the point where there were too many cars trying to park,” Nichols said. “People were parking at odd places and getting stuck when the rains came.”

They were setting their blankets in the woods, trampling the understory and likely killing the flightless females resting there. They were filling the forest with light, and the sheer numbers in themselves created a safety hazard. What if a lightning storm leapt up? What if a tornado warning appeared? There would be no way to get all those people to safety. 

So, in 2006 the park did its first-ever dedicated firefly event. Basically, that amounted to mandatory parking at Sugarlands Visitor Center rather than in the campground and transit by trolley up to Elkmont. 

“Ten years ago when I first started volunteering, it was a table with four or five of us standing around handing out the firefly brochures and telling people to keep their lights covered,” said Rick Turner, who volunteers with his wife Glo. 

That system helped somewhat with the crowd control, but it still had its issues. The Sugarlands parking lot filled up quickly, sometimes as early as noon, so people who arrived at a more reasonable time would get turned away. Often, they’d driven for hours to get there. 

“It was certainly work-intensive for our staff to get out and work in the hot from 3 or 2 o’clock all night long, but we honestly also felt sorry for the visitors,” Worth said. 

So in 2011, the park piloted its reservation system. It allots a set amount of parking passes and sells them for a nominal fee, $1.50 per car with a $1 fee per person to ride the trolley. They don’t last long. 

“It’s like trying to get tickets to a rock concert,” said Gabe Summe, 47, of Covington, Kentucky. “I’ve never seen anything sell out so fast in my life.”

To prevent ticket scalping, the park service has a one-person-one-parking-pass limit, but that means that families who want to go together have to ramp up their coordination. Summe traveled to Elkmont with her three sisters, a niece and a brother-in-law, seven people using two cars. 

“We called each other and sat on the phone and didn’t do anything at work until we bought them,” Summe said. 

Though the park service holds back 85 tickets for sale the week before the event, the bulk of them are gone within minutes. 

The new system limits visitation, for sure. The year before the reservation system went into effect, 12,400 people visited the campground over the eight-day viewing period, even with one of those days cancelled for rain. By comparison, the event now averages 6,000 to 8,000 people, depending on weather. This year, 7,523 people came. 

“The numbers have drastically changed due to the reservation system, and in some respect we think that is for the better, because there is really not a good reason to take 2,000 people into the woods to see those fireflies at night each night,” Worth said. “It’s really, really detrimental to the resource.”

Not to mention, the show’s spectacularity is sort of inversely proportional to the number of people you’re sharing it with. Being in the woods with 2,000 other people is a lot different than being with 1,000 other people, so limiting numbers means that people who do get to see the show have a better experience. It also means that park service employees are better able to answer questions, make sure visitors have their lights covered with the red cellophane provided — this confuses the fireflies less than white light and reduces distraction to fellow spectators — and keep everyone as safe as possible. 

“It’s a little scary to take 500 people and drop them off in the dark,” Worth admitted. 

Some of the people who jump online to claim tickets are avid outdoorsmen, people quite familiar with hiking, camping and appreciating ecology. Others, like Knoxville resident Melody Stooksbury and her daughter Katelyn, 6, would usually categorize bugs and insects as “icky.” 

But for the Stooksbury family, fireflies are different. Katelyn was excited to see a sight reminiscent of “Tinker Bell in Disney Hollow,” while Melody termed the outing a “girly bug adventure.” 


Plenty still to know

For some, the firefly show is just a bucket list item that trumps any previous ambivalence to natural wonder. 

“I’ve never been a big outdoors person, but I feel the older I get, the more I want to see things like this,” said Chris Andrews, 51, who heard about the fireflies from her son. “I just really want to see these lightning bugs. Why are they all lighting at the same time? How do they know? I want to be awed.”

And that, maybe, is the better part of the wonder that is the synchronous firefly show. A lot is known about the species — that the lights last for approximately two weeks in late May and early June, that the larvae are carnivorous with some fierce-looking mandibles, that the intervals between flashes are so precise you can set your watch by them. The park service has figured out how to predict peak display by monitoring temperature, moisture and larval development, and they’ve got enough years of observation under their belts to say that the park’s firefly population looks to be stable.

But a lot is unknown. 

To Andrews’ two questions, at least, there’s no solid answer. The leading theory right now, Nichols said, seems to be that the female needs to see the collective brightness of the males’ flash in order to respond, and that’s why the males flash in unison. But the truth could be different. And as to how the males know how to sync up, how they know the exact interval at which they’re expected to flash, that’s unknown. 

Some research teams have popped up to the park over the years to try and answer some of those questions, professors from the University of Connecticut and Georgia Southern University looking into how fireflies process visual information and how that results in a synchronous display. So, though the question is getting some attention, there’s still not really an answer to it. 

“It’s still kind of a mystery. There’s unanswered questions in there,” Nichols said. 

Their life cycle, and where it occurs, are not even exactly certain. In the park, the larvae live for about one year before pupating, but in the northern extent of the firefly’s range that duration could be as long as two years. It’s hard to say. Then, they pupate and emerge as adults incapable of eating anything at all. They live for three to four weeks to mate and lay eggs, and then they die. 

No one even knows, exactly, where all Photinus carolinus lives. Though Elkmont holds probably the highest density of synchronous fireflies, Nichols isn’t as sure as she used to be that the Smokies have the only high-density population. 

“Generally, I used to say that, but now I know a researcher who’s working in the Allegheny Mountains [in Pennsylvania],” Nichols said, and that researcher has found some pretty impressive displays even that far north. 

Once darkness descended on Elkmont, though, nobody was thinking too hard about the whys, wheres and hows. It was all about the show. Even Macko’s reservations disappeared after a few hours spent watching an entire forest blink on and off at the whim of a million tiny insects. 

“It was great,” he said. “I wish my grandchildren were here to see it.”

“We’ve heard about it for years,” his sister-in-law Mary Macko, 55, said as she got in line to board the last trolley out. “Just to see it, it’s hard to put it into words. It’s beautiful.” 



Did you know?

• Great Smoky Mountains National Park is home to 19 species of firefly, six of which do not flash. There are 125 species of firefly in the U.S. and Canada, mostly in the eastern and southern regions. 

• Fireflies make light using bioluminescence, a technique that many insects and marine creatures use. Fireflies have a chemical in their abdomen called luciferin, which is broken down by the enzyme luciferase. The reaction produces light, but barely any heat. 

• Synchronous fireflies start flashing at about 9:45 p.m. and stop around midnight. 

• Southeast Asia and Japan are the only other places where synchronous fireflies exist, but these are different species with different behaviors. 

• Firefly larvae are predacious, eating organisms such as snails and earthworms. Eggs hatch after three or four weeks, and the insect stays in the larval stage for one to two years, after which they pupate and hatch as adults. The duration of each stage depends on factors such as temperature and food availability. 

Source: Great Smoky Mountains National Park



Firefly round two

The display season for synchronous fireflies is over, but the evening fireflies, Photinus pyralis, are just getting started. A twilight firefly tour, 7:30 to 9:30 p.m. June 28 at Pink Beds Picnic Area next to Cradle of Forestry on U.S. Highway 276, will give all ages a chance to learn more about these light-up insects and to do some exploring. This naturalist-led program will include a discussion on firefly life cycle and biology and then a slow-paced walk to look for them in the surrounding forest. $6 adults; $3 kids, free for Federal Recreation Pass and Golden Age Passport holders. Bring a flashlight. Devin Gentry, This email address is being protected from spambots. You need JavaScript enabled to view it.. 

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