Deep in the Great Smoky Mountains in a deserted Tennessee logging community known as Elkmont, male fireflies hover along mountainsides and open fields. At dusk, you notice a light blinking here and there. Then as more fireflies join in, their lights blink together in unison. By 10 p.m., whole glades and hillsides flash like massive strings of Christmas lights blinking in unison.
It’s an experience that inspires nothing short of awe.
“It’s very magical; it’s unbelievable when you see it,” said Wanda DeWaard, a Tennessee field researcher and educator who leads hikes into the Elkmont area during the brief spring mating season of synchronous fireflies.
Scientists aren’t sure why fireflies coordinate these brilliant light shows, but the spectacle seems to center around mating. In order to attract mates, different species of fireflies produce different light patterns. Some give off a steady bluish-green glow, others a series of bright yellow Morse Code blinks, and still others a tiny, double-blink beacon in the soil. It’s the Photinus carolinus — the synchronous firefly — that attracts big crowds to Elkmont in late May and early June.
During this three-week window, trolleys carry visitors from the Sugarlands Visitors Center (near Gatlinburg, Tenn.) up to Elkmont. Folks start arriving with blankets, chairs and flashlights by early evening, but the show doesn’t start until after 9:30 p.m. when it becomes pitch black under the canopy of trees.
Fireflies, or lightning bugs as they are also called, are technically beetles. Contrary to their name, not all fireflies light up at night (some cruise around by day) and not all have wings (some females remain ground-bound). Generally the males outnumber the females and appear to have larger bodies. When it comes to signaling with their abdomen lanterns, fireflies use different colors and frequencies depending on the species.
The male Photinus fireflies at Elkmont blink about four to eight times in the air, then wait about six seconds for the females on the ground to return a double-blink response. Once the male locates a female, he lands and mates on the ground.
An adult female will produce about 50 to 80 eggs at a time and lay them in the ground (even the eggs glow). After about three weeks, the eggs hatch and the little glow-worms will live in the soil for about two years before they undergo a metamorphosis, sprout wings and develop a shell over their backs.
The synchronous firefly show, which researchers have identified as a rare form of simultaneous bioluminescence, exists in high-elevation wetland areas in Southern Appalachian forests as well as in China and Thailand.
While Elkmont has become a popular — and sometimes crowded — spot to see synchronous fireflies turn on their love light, other similar glow-in-the-dark shows have been reported in Cades Cove, Joyce Kilmer-Slickrock Wilderness Area, Hot Springs, and Greenbrier, according to DeWaard.
Generally, synchronous fireflies have been reported in wetland areas in high altitudes above 2,000 feet, DeWaard explained, though recent sightings claim they exist in lower altitudes and other regions previously not thought to be “normal” firefly habitats — coastal Georgia, for example.
For some reason, Elkmont seems to have just the right climate to produce a natural, glow-in-the-dark theme park with white, green, blue and yellow colors of firefly lights. In the soil, you can also find fungi gnat larvae, glow-worms and railroad worms (named for their bioluminescent “tracks” on their bodies).
“Once your eyes adjust to the dark, you see all kinds of glowy things,” DeWaard said.
According to the Web site of the Great Smoky Mountains National Park, about 20 species of fireflies have been found in the park. (Some 126 species of fireflies exist throughout North America.) About eight species in the Park don’t produce light; they cruise around during the day. The other 12 have powers of illumination and various blinking patterns.
Jonathan Copeland, a Georgia Southern University research scientist who studies fireflies, initially thought the synchronous firefly only existed in places like China and Thailand, where he had witnessed these natural light shows first hand. But then he discovered similar firefly synchronicity at Elkmont after a former cabin owner named Lynn Faust wrote to him explaining what she and her family had seen while living there for years.
According to DeWaard, Copeland arrived at Elkmont, skeptical of what he might find, and fell asleep in the woods after dusk. When he awoke, the synchronous fireflies were doing their thing. It took three years of research to confirm that these fireflies were indeed synchronous. That was a decade ago, and Copeland, along with researchers like DeWaard, are continuing to learn more about these fascinating insects.
In addition to the Photinus carolinus, other species at Elkmont include the eerie “blue ghost” (Phausis reticulata), known for its prolonged bluish or greenish ghostly glow that can last 30-40 seconds.
Some firefly species have apparently developed the ability to use their blinker as a way to prey on other fireflies. Scientists have found about three species of Photuris fireflies that emit a series of single bright white flashes to mimic the flash response of females of the Photinus species. Apparently, the female Photuris lures the male Photinus. The latter thinks he’s honing in on a female, only to be captured and eaten.
DeWaard speculates that the fireflies’ bioluminescence could also be a way of protecting against prey — it’s a signal as if to say, “Stay back, you don’t want to eat me.” And it could work vice versa — firefly larvae may use their illumination to draw curious slugs that are then caught, immobilized and sucked dry.
With the recent popularity of synchronous fireflies in the Elkmont area, more and more people have come to see the nightly shows. According to Acting Chief Ranger Rick Brown, that’s meant 300-400 cars in the area on peak nights. So, the park service is now enforcing a no-parking rule June 8-19 at the Little River Trailhead at Elkmont. Rather than have a string of cars clogging up the sides of the road at the Little River Trailhead, park managers have teamed up with the City of Gatlinburg to offer trolleys as a way of shuttling scores of visitors back and forth from the nearby Sugarlands Visitor Center and the Laurel Falls Trailhead. A $1 fee covers a round-trip ride to and from the Little River Trailhead. The last pick-up going to Elkmont is at 9 p.m. The last rides back are at 11 p.m.
While the firefly shows have helped promote the Park’s reputation as a treasure of biodiversity, researchers like DeWaard and Copeland are concerned that extra lights will disrupt firefly beacons and human feet may trample on breeding fireflies. As a precaution, park rangers alert visitors not to capture fireflies and pass out red cellophane to put over flashlights. Red light, apparently, does not disturb the fireflies’ signaling.
Other areas in the Great Smokies region are also being studied for synchronous fireflies, but that can be tough when there’s such a short window of opportunity in the year and the blinking doesn’t begin until around 10 p.m.
“It’s just a matter of getting out and looking,” DeWaard said. “There’s so much we don’t know.”
As scientists continue to unravel the mysteries of synchronous fireflies, DeWaard is content to stop and stare at this unique light show. It’s living proof that humans still feel the need to experience the wonders of nature.