Unlike the blinking yellow-ish light of the big dipper fireflies Kentuckians might see in their backyard, Appalachian blue-ghost fireflies leave their light on for several seconds, leaving a pale trail of blueish-green light behind them.
On a recent June evening, illuminated only by the nearly-full moon, Kelly Vowels and Bill Napper swung their nets to catch a few of the rare blue-ghost fireflies darting between the trees and across the trail in Bernheim Forest and Arboretum, a privately-owned 16,000 acre nature preserve and arboretum in Clermont, just a half-hour south of Louisville.
Vowels, Bernheim’s research coordinator, held up her net after catching one of the little beetles. It still shone its ghostly light as she shook out a plastic bag to hold him.
“He's really glowing,” Vowels said as he flashed from inside her net. “He’s a happy one.”
These fireflies glow a light bluish green color that appears neon green on camera. While little is known about the blue-ghost’s population or their broader habitat, they’ve become a tourist attraction in places like North Carolina and now Bernheim.
Napper, a volunteer who leads night tours through the forest, is helping collect specimens for a study out of the University of Georgia. Researchers are working to understand the genetics of Bernheim’s blue-ghosts to see if they’re genetically similar to those found from Georgia up through North Carolina and Tennessee.
“These are widely dispersed over a big area in the United States,” Napper said. “For all we know, there could be different species within what we all think is the same one.”
Since these and other fireflies are understudied, it's hard to say definitively whether they’re in decline, especially at Bernheim, but researchers say there are many threats to them. Like other firefly species, blue ghost fireflies are threatened by habitat degradation, light pollution, and climate change. Unlike some other fireflies, the blue ghost females never develop wings, instead sticking to the ground, meaning they’re also more vulnerable to ground disturbance.
The beetles also need heavy darkness for their mating rituals so their dim bluish glow can be seen by mates, which artificial lights can disturb. Bernheim too has struggled to limit light pollution from creeping in, and it's been encroaching further into the forest over the years, Napper said.
To be able to understand the impact of these likely disturbances, Vowels said they need to know what they’ve got in the forest already, which comes with its own logistical difficulties.
“That is one of the things I think a lot of people are trying to figure out is, how can we start monitoring,” Vowels said. “It's really hard to survey for a firefly because it's hard to count when you have a bunch of them lighting up or none lighting up.”
Vowels said fireflies are also important to the Appalachian ecosystem, serving as predator and prey alike. They are a food source for bats and other creatures and can help pollinate plants. In their larval stage, fireflies are also voracious predators.
“They like to eat everything,” Vowels said. “They'll eat snails and anything else that they can catch.”
Napper said he first fell in love with the blue-ghosts when he discovered them in Bernheim more than a decade ago. They’ve now officially confirmed 13 different firefly species in Bernheim and unofficially observed up to five more. Napper said he believes there could be even more species waiting to be discovered — he’s identified up to 39 potential species he believes could be scattered throughout the forest.
As he looked out over the sea of little blue green lights, Napper said they reminded him of something supernatural.
“Just little fairies lit up, flying through the forest, hovering two, three feet off the ground,” Napper said.
He said he was worried they wouldn’t see many blue-ghosts this year due to light pollution encroaching on their territory or torrential flooding washing them out, but this year the little creature still came out en force.
Last month, Napper captured Bernheim’s first-ever photo of a female blue-ghost with all her glow spots visible. They’re especially hard to find as they remain flowing dimly on the ground instead of whizzing through the trees.
Vowels said it’s remarkable that in a place founded in 1929 it’s still possible to find something new.
“I always try to encourage anybody who wants to be a biologist — study insects,” Vowels said. “You'll find lots and lots of things to learn. I'm still learning, and I will keep learning.”
Bernheim is hosting a few more opportunities to view the blue-ghosts and other firefly species until the end of June and the close of the blue-ghosts’ peak season.
