By Jenell Talley
The faint glow coming from the wooded terrain just beyond a cluster of Tennessee cabins called Elkmont looks like common lightning bugs at first glance. But on closer inspection, you can see that these are no ordinary fireflies. The little creatures are simultaneously flashing in perfect unison over and over again. These tiny points of light are a highly concentrated group of synchronized fireflies, a far cry from those you might find at backyard barbecues along the Eastern Seaboard each summer.
Synchrony, concurrent repetitive group flashing, is rare. There are only two known synchronized firefly species in the United States: Photinus carolinus and Phoruis frontalis, and only the males are synchronous. The former is found at Elkmont in Great Smoky Mountains National Park, at Congaree Swamp National Park in South Carolina, in high elevation areas-at least 2,000 feet-in parts of the Carolinas, and in parts of the Appalachian Mountain range, from Virginia to Georgia. The P. frontalis species mostly is found along coastal plain areas, primarily in Georgia.
The species' mating systems and their physiological controls are similar, and they both flash in 20-degree centigrade, 5.6-second cycles, but they have very distinct flash patterns. According to Jonathan Copeland, a biology professor at Georgia Southern University and one of the world's foremost authorities on fireflies, about ten to 20 P. carolinus in a given area at Great Smoky Mountains flash in sync from about 9 to 11 p.m., from June 1 to around June 21. They flash about five times, pause for about ten seconds, and repeat the cycle. In Georgia, from May 10 to about May 28, about two to six frontalis flash continuously for one cycle, never pausing or breaking rhythm. "When you see them, it's completely obvious that they're synchronous," Copeland says.
Synchronized fireflies are small, luminescent beetles that belong to the family Lampyridae, the Latin word for "torchbearer," family. Both synchronized species have two pairs of wings, one of which creates the tough outer pair that protects the more delicate under wings and the body. The under wings are used for flying, the outer wings for balance during flight. Carolinus has black wing covers and a blackish body with red splotches around the neck. Frontalis is a brownish black. All fireflies have three main body parts: the head, abdomen, and thorax. The lantern, the organ that creates the flash, is in the abdomen.
The fireflies typically generate a yellowish-green light or a greenish-yellow light. Generally, those with a yellowish light appear in early evening. Those that flash a pale green light appear after dark. The males at Great Smoky Mountains, for example, flash a pale green light at dusk. "Sometimes the colors seem to change as you are watching them," says Copeland, "but that's probably just your visual system."
Synchronous flashing is a modern-day phenomenon. Scientists once believed that the phenomena did not occur outside of Southeast Asia. But in the early 1990s, an amateur naturalist named Lynn Faust saw what she thought were synchronized fireflies while at Elkmont in Great Smoky Mountains. After reading a newspaper article about synchrony, Faust wrote to a scientific mathematician who suggested she contact Copeland about her finding.
In 1995, Copeland and fellow scientist Andy Moiseff confirmed that Faust had in fact spotted synchronizers at the park. They collected a video of the flashing insects in a frame-by-frame motion, then repeated the process with trapped insects to prove that fireflies were "flashing rhythmically and at precisely the same time."
Although scientists have been able to demonstrate that the fireflies do in fact synchronize, explaining why has been much more difficult. Scientists believe that the synchronous flashing is linked to mating, but little, if any, conclusive evidence has been made available. Copeland and Moiseff are collecting three years of experimental data to prove the theory.
Copeland is able, however, to reveal a little more on the hows of synchrony: "The firefly has a pacemaker in his brain [telling it to] flash, and this can be accelerated or retarded…. The firefly sees a flash and, say, speeds up; the other firefly sees a flash and, say, slows down. They speed up and slow down each other, and in doing so become synchronized."
In other words, the stimulus from the preceding cycle determines the behavior of the subsequent cycle. In this way, fireflies differ from, say, a school of fish or a flock of birds. "[Fireflies'] signals get added together and some sort of decision is made. Birds and fish are driven by reflexes, whereas fireflies' flash is driven by a preceding set of signals that get interpreted in their brains," Copeland says.
Elkmont's species has attracted considerable attention over the past few years from both scientists and the public. Many visitors to Great Smoky Mountains National Park like to watch the synchronizers light up, and scientists, now more than ever, are convinced that further study of the insects will benefit the human population.
Copeland agrees. "You might gain insight that might be useful to humans, like heartbeat, control of menstruation, [and] release of insulin from the pancreas," he says. "Synchrony is a very unique type of biological timing, and fireflies do it better than any animals. The human body is full of biological rhythms that affect our health. The more we know about biological systems, the more we can gauge."
