The Synchronous Fireflies of Elkmont

“It’s starting.” “Look.” “It’s beautiful.” A chorus of soft murmurs came from the hundreds of now barely discernable gray figures scattered throughout the clearing. As the blue twilight faded toward darkness and dozens of blinking lights became hundreds – and then thousands – the din of conversation gradually faded into a quiet undercurrent of whispers and gasps of wonder.

It was not just the number of fireflies that inspired such awe and that brought so many spectators to this place. Rather, it was the unique way that the fireflies orchestrated their blinking. One moment, the forested slope above the clearing would be dark – cavernously dark. Then, suddenly, a few flashes would appear off to the right, and like a fuse, they seemed to set off a chain reaction. In a diffuse and unruly wave, thousands of flashes would appear from right to left across the field of vision, lighting up the entire forest in an eerie green light. It was as if the world’s largest chain of blinking Christmas lights had been turned on and then was suddenly unplugged again. The forest would return to that deep, cavernous dark for a few seconds… then… a few flashes occurred off to the right and the cycle would repeat itself.

Aside from the darkness, it was unnaturally quiet. Amid close to 700 people arrayed in lawn chairs, blankets, or just sitting in the grass, there was almost complete silence. Everyone spoke in the softest whispers, as if any noise might dispel the enchantment or disrupt the divine rhythm of the fireflies .

In addition to the air of wonder that suffused the crowd as the strange synchrony emerged out of random blinking, there was an unmistakable sense of relief. They weren’t going to be disappointed. In one moment of shared consciousness every person in the clearing knew without a doubt that they were witnessing one of the genuine wonders of nature.

Fireflies of the Far East… and Elkmont

It was this display of synchronous lighting by a rare species of firefly that drew the onlookers to the one known place in the western hemisphere where they could see it: a tiny cluster of abandoned cabins called Elkmont, just southwest of Gatlinburg, TN in the Great Smoky Mountains National Park.

While the existence of this phenomenon at Elkmont had been known only to a few until 10 or 15 years ago, synchronous fireflies have sparked wonder in visitors to Southeast Asia for centuries. Sir Francis Drake penned one of the early written accounts in 1577 after returning from an exploration of the East Indies:

Amongst these Trees, night by night, through the whole Land, did shew themselves an infinite swarme of fierie Wormes flying in the Ayre, whose bodies being no bigger than common English Flyes, make such a shew and light, as if every Twigge or Tree had beene a burning Candle.

Drake was describing the spectacle of seeing the firefly, Pteroptyx malaccae, in the mangrove forests of Malaysia and Thailand. In that species, the blinking is so perfectly synchronous that it convinced one early 20th century scientist that it was the blinking of his own eyes that caused the appearance of synchronous flashing.

The fireflies of Elkmont, Photinus carolinus, accomplish their synchronous flashing in a much different way. Whereas the Asian fireflies oscillate their flashing in a metronome-like manner – on-off-on-off in a regular sequence, Elkmont’s fireflies flash in a series of about six blinks and then pause for a while before starting again.

Synchronous fireflies were believed to be limited to a few Asian species, with at least one report from Africa, until Lynn Faust of Knoxville, Tenn., wrote a letter to scientists in the early 1990s to tell them about Elkmont’s fireflies. Neuroethologist Jonathan Copeland of Georgia Southern University, and Mathematician Steven Strogatz of Cornell University had studied synchronous flashing and their work had been featured in popular science magazines. As a result, both had been contacted by numerous crackpots and people in questionable mental states who had found “synchronicity” with lightning bugs in all sorts of places.

Yet, there was something more convincing in Lynn Faust’s reports from Elkmont. She wrote this to Strogatz:

These bugs ‘start up’ in mid June at around 10:00 pm nightly. They exhibit 6 seconds of total darkness then in perfect synchrony, 1000’s light up 6 rapid times in a 3 second period before all going dark for 6 more seconds… as far as we know, it is only in this small area that this particular type of group synchronized lightning bug exists. It is beautiful.

This letter was convincing enough for Strogatz to put her in touch with Copeland, who came to investigate the following June. He was delighted to confirm that synchronous fireflies did in fact exist in the Western Hemisphere, at least in this one small place.

The emerging science of “Sync”

Fireflies have since become the mascot of an emerging scientific field called “Synchrony” (shortened to “Sync” when book publishers have a say). Strogatz is a leading thinker in this new science and recently published a book entitled, “Sync: The Emerging Science of Spontaneous Order” (Hyperion). Adorning the cover of his book are, of course, fireflies.

To those who prefer a mystical explanation for the cosmic rhythm of the fireflies, Strogatz’s work can be summarized as an elegant, parsimonious and logically rigorous buzz-kill. He clearly has little patience for mysticism or any type of explanation beyond the naturalistic, although even he will talk about nature’s “eerie yearning” for order. But the bottom line is that he has top-notch mathematical proofs to back up his naturalistic viewpoint.

Those proofs boil down to this: any system will tend toward synchronous behavior if the individuals involved follow some sufficient set of “rules.” In the case of fireflies, those rules include:

1. Individual fireflies possess an internal timer or oscillator.
2. They can sense when their immediate neighbors are flashing.
3. They tend to advance their cycle in order to flash before their neighbors flash.

Strogatz shows that these conditions are sufficient to lead a whole forest of fireflies to flash in synchrony. As to why each of these rules exist, though, that is beyond the realm of mathematics and gets into biology. The important point to “Sync” thinkers is that similar sets of rules exist throughout nature, and natural systems, in a huge number of cases, tend toward synchrony. A few examples of “Sync” in nature include the synchronized timing of women’s menstrual cycles, the movement of electrical impulses between nerve cells, the onset of epileptic seizures, and the synchronous movements of flocks of birds and schools of fish.

Why, then, aren’t all fireflies synchronous? According to Strogatz, there are many possible answers. First, there needs to be a reason why fireflies “care” about what their neighbors are doing. If females pay more attention to males that flash first, there’s a reason to care – this is precisely what has been hypothesized for many synchronous fireflies. But if there’s no selection by females on when males flash, there may be no reason to adjust their oscillations to those of their neighbor’s. Also, many species may lack the ability to “see” what their neighbors are doing.

The spectators at Elkmont

Being certain that few of the spectators at Elkmont were worried about nerve cells, epilepsy, or the mathematics behind “Sync,” however, I set out to discover why so many had made the trip up to this remote (and exceedingly difficult to find) clearing.

At first, the answers were a little disappointing, and the respondents appeared puzzled as to why I was asking the question.
“My sister came up here last year and told me about it,” said Brenda Wulf of Knoxville.

“We called the ranger, found out it was in early to mid June, we made reservations [at the campground], and here we are,” added her companion, Tim Hatheway.
“It’s the one place other than Southeast Asia where you can see this,” said Byrum Bolum, one of a group that had come over from Gallatin, TN.

It’s nearby. It’s one of two places in the world where it occurs. Some variation on these themes was the universal reply from everyone I asked. What was most striking, though, was that nobody I spoke with lived more than a few hours away. And nobody had come there alone.

They were awed and impressed, but it would have taken a lot less to draw these folks up there. Apparently, it doesn’t take much to inspire East Tennesseeans to spend a beautiful evening outdoors in the Smoky Mountains together with their friends and their loved ones.

Suddenly, their answers didn’t seem disappointing at all.