LINVILLE, N.C. — The discovery of a special type of firefly on Grandfather Mountain has experts aglow with excitement.
The nonprofit nature park in Linville, N.C., is officially home to Photinus carolinus, the only species of firefly in North America whose individuals can synchronize their lighting display, meaning they can flash in unison.
Photinus carolinus famously resides in the Great Smoky Mountains National Park, where it is a major draw for visitors from late May through early June. During that time, hopeful spectators enter a lottery to win tickets to witness the phenomenon. And with only a limited number of tickets offered, the spectacle has grown ever more exclusive.
And now it’s grown a mile high.
The revelation of Photinus carolinus’ existence on Grandfather Mountain comes courtesy of Dr. Clyde Sorenson, an entomologist from N.C. State University. While hosting a workshop on the mountain, Sorenson was invited to stay the night in the park’s guest cottage near the Woods Walk & Picnic Area.
“I had the intention to see what kind of fireflies might be around at the high altitude,” Sorenson said.
Around 9:30 p.m., he saw a few fireflies flashing and knew right away that it was something special.
“As it got dark, the numbers steadily went up, and between 10 and 10:30 p.m., there were several hundred all around the guest cottage and Woods Walk, flashing synchronously,” Sorenson said. “I knew what to look for, and apart from the flash patterns, which are species-specific, there are neurological features that are distinct. They were doing what they were supposed to be doing, and when I looked at them in my hand, they had all the diagnostic features for that same species.”
Sorenson later confirmed his findings with East Tennessee naturalist Lynn Faust, a preeminent expert on the subject, who, among numerous other publications, wrote a field guide on fireflies, which Sorenson described as “one of the best resources to anyone who is interested in learning more about these critters.”
“You know, this is a really exciting discovery, and on Grandfather Mountain, one of the exciting things about visiting the park is that you never know what you’ll see or find,” said Jesse Pope, president and executive director of the Grandfather Mountain Stewardship Foundation, the nonprofit organization that owns and operates the Linville, N.C., nature park.
Sorenson is particularly excited because synchronous behavior is rare in fireflies.
“There’s only a handful of species all around the world that do this, and for a long time, this particular species, the phenomenon of seeing large numbers of them synchronizing has been associated tightly with just a couple geographical areas,” he said. “But the species goes all the way from New York to Georgia. Where they have been most widely known and recognized for so long is at Elkmont in the Great Smoky Mountains National Park. But that’s at 2,200 feet. Where I saw them (at Grandfather) was at 4,200 feet.”
What makes Grandfather Mountain such a unique location, Sorenson said, is its elevation range. Starting at a relatively low elevation of 3,000 feet, the mountain reaches up to nearly 6,000 feet. And while conducting a research survey near the Mile High Swinging Bridge, Grandfather Mountain’s director of education, Amy Renfranz, observed the same fireflies blinking synchronously.
“At the top of the mountain, they blinked in a slower cadence, because the temperature was colder,” Renfranz said. “Males were observed flying low to the ground, and females were perched along the ground. The groups of fireflies would totally sync light rhythms with each other.”
During one survey, Renfranz observed more than 1,000 fireflies from one overlook on the mountain.