Hundreds of people have gathered on a dark mountain in Appalachia. There isn’t a flashlight shining among them. Fireflies drift overhead, but the real spectacle is closer to the ground—an embankment where, nestled in damp moss, glowworms shine like pinpricks of neon blue. “They’re just so bright!” someone exclaims.
These are Orfelia fultoni, the larval form of a fungus gnat, and they produce the bluest bioluminescence of any known insect on Earth, according to bioluminescence expert Vadim Viviani. Their glow—created by the chemical reaction of luciferin, luciferase, and oxygen—can rival that of fireflies. But while fireflies are familiar summer icons, Orfelia fultoni often go unnoticed. Many populations have been discovered by accident.
The larva of Orfelia fultoni, a fungus gnat found only in the eastern U.S., glows from both ends as it clings to a decaying log at Pickett CCC Memorial State Park.
That includes the one at North Carolina’s Grandfather Mountain, where staff first spotted the glowworms while surveying for synchronous fireflies in 2019. No one knows just how many glowworms live here—formal surveys haven’t been conducted—but this may be one of the densest populations in the world.
In 2022, Grandfather Mountain launched an annual after-hours event called Grandfather Glows to showcase the phenomenon. Most visitors come searching for the synchronous fireflies, made famous in the Great Smoky Mountains during the peak season from May to June. But many leave talking about the glowworms—tiny, translucent creatures that transform forest floors and streambanks into rivers of electric blue.
A species hiding in plain sight
Orfelia fultoni—sometimes referred to as foxfire flies or dismalites— are glowworms found only in the Appalachian region. Though related to Arachnocampa luminosa, the famed glowworms of New Zealand that draw more than a million tourists a year, Orfelia fultoni are far less well-known.
They are generally around 11 millimeters in length, with lanterns at both ends. These translucent creatures are known to produce gauzy webs, and it has been theorized that their light is intended to lure flying insects. When glowworms are concentrated, they turn roadsides and riverbanks into brilliant blue rivers that sparkle after sunset. But the species’ range—and even its presence—has often gone unrecognized.
The species was first described to science by B.B. Fulton, an entomologist who found glowworms in his western North Carolina yard and published his findings in 1941. Since then, populations have been documented from Massachusetts to Alabama, according to Gary Mullen, an entomologist who spent 30 years studying Orfelia fultoni during his tenure at Auburn University.. “They’re quite widespread in the mountains, but people don’t tend to walk around in the dark without flashlights on, so they don’t notice them,” he says.
Glowworms hide in foliage, and they shirk from light. Mullen has attempted to help film crews capture Orfelia fultoni’s likeness, but he says the glowworms are evasive in their natural habitat and challenging to rear in captivity. “If you disturb them, they’ll move into crevices,” Mullen says. “If you turn on a headlamp to see them, they’ll stop glowing. The smallest bit of temperature change or ambient light can affect them.”
Even trained naturalists have mistaken the species for something else. Until 2014, rangers at Anna Ruby Falls Recreation Area in Georgia assumed the mysterious springtime lights along their trails came from female blue ghost fireflies—another elusive, glowing insect. Only when a visiting scientist formally identified Orfelia fultoni did they realize what they had. A few repeat visitors have told Anna Falls employee Tracie Allen that, since learning how to identify Orfelia fultoni on night hikes, they’ve noticed small populations in their own neighborhoods.
“People are used to the idea of fireflies. But glowworms are like nothing people have ever seen before,” Allen says. “They kind of remind me of stars. Only, they’re on the ground. We could hold tours every night and still sell out.”
Why glowworms thrive in Appalachia
Even as scientists begin to understand how Orfelia fultoni produces its vibrant blue glow, much about the species remains a mystery. Its full range, reproductive habits, and ecological role are still under-researched, and no formal surveys have been conducted to estimate population size. Researchers also don’t yet know how vulnerable these glowworms might be to threats like habitat loss and light pollution.
What’s clear, though, is that glowworms thrive in darkness. In recent decades, Orfelia fultoni has been discovered in unexpected places across the Southeast—sometimes entirely by accident.
At Dismals Canyon, a privately owned slot canyon in northern Alabama, glowworms have long been an attraction. However, it was not until entomologist Gary Mullen identified them as Orfelia fultoni in 1995 that locals realized they were not members of the Arachnocampa genus, like the well-known glowworms of New Zealand. “People knew they had something, but no one realized it was Orfelia fultoni.
(See glowworms give a dazzling show at this national landmark.)
At Pickett CCC Memorial Park in Jamestown, Tennessee, Orfelia fultoni were found when a naturalist decided to camp under a rock overhang in the 1970s. Throughout the following decades, visitors wandered the park’s trails after dark to catch glimpses of the tiny blue lights. But, in recent years, demand has increased so much that administrators have decided to close trails at night to protect visitors and the habitat. In response, the park introduced guided night hikes to share the experience more safely.
Ranger Michael Hodge leads many of those hikes. When he guides visitors to a glowworm-rich spot where creek and stone meet, he instructs everyone to turn their lights off at the same time. It’s a practice that even his most night-nervous guests seem to enjoy. “As our eyes adjust,” he says, “the glowworms just sort of emerge from darkness.”
Hodge tracks sightings informally—Pickett lacks a dedicated research program—but he’s seen the insects flourish in the absence of artificial light. In 2015, he played a role in Pickett’s status as a Dark Sky Park, certified by DarkSky International. “I got interested in that program because I’m an amateur astronomer, but it helps the glowworms, too. They benefit from reduced light pollution, and we need the dark to see glowworms, just like stars.”
(Here’s why dark skies are actually good for your health.)
Hodge now hosts monthly stargazing programs, and he’s noticed a familiar reaction from visitors encountering either glowworms or the Milky Way for the first time. “You’ll hear gasps. You’ll hear people cheering. People realize that there’s nothing between them and the stars and the glowworms. It’s not on YouTube; it’s real. I think, on some level, people have those reactions because they experience a sudden awareness that there are still things out there for them to discover.”