Trail: Middle Creek Loop
Trailhead: Middle Creek
Distance: 3.5 miles
Elevation Gain: 282 ft.
Difficulty: Easy-Moderate

It’s June, and something magical is happening inside some of the shallow caves found within the Big South Fork National River & Recreation Area: glow worms are emerging.

Glow worms — the bioluminescent larvae of fungus gnats — are a relatively new phenomenon to this region, at least so far as being an attraction that catches people’s attention. For decades, they’ve been present in Pickett State Park’s Hazard Cave. In fact, they’re said to be found in greater abundance there than anywhere else outside New Zealand, where the deep caves come alive with glow worms and draw people from throughout the world who hope to witness the phenomenon. But the glow worms were not known to be present in the Big South Fork until much more recently.

BSF interpretive ranger Mary Grimm was the first to note the glow worms’ presence along the Middle Creek Loop Nature Trail. Their presence there, perhaps, shouldn’t have been too surprising. Middle Creek Loop is just a hop, skip and a jump from Pickett State Park — the trailhead, in fact, is just across the road from Pickett State Forest — and contains a greater concentration of rock shelters than just about any other hiking trail in  the national park.

But Grimm has since discovered glow worms inside a rock shelter along the Oscar Blevins Farm Loop near Bandy Creek, and suspects that they’re present inside other rock shelters, as well.

The biology that makes these gnat larvae glow is the same phenomenon that causes the common firefly to light up the summer night over the meadows and pasturelands of much of North America. There are only a few groups of insect larvae found throughout the world that glow through bioluminescence, including the larvae of some beetles and the some gnat larvae. 

In the case of the larvae of fungus gnats — like the ones found in the Big South Fork — the purpose of the glow is to attract tiny insects to the sticky webs that are spun by the predatory worms — although the worms primarily feed on fungal spores.

The species of glow worm found in the BSF — Orefelia fultoni — is the only bioluminescent species of flies found in North America, and it is restricted to the Cumberland Plateau and the southernmost Appalachians. While the larvae found here are distantly related to the celebrated Arachnocampa species found in New Zealand, their bioluminescent systems are very similar. The Cumberland Plateau glow worms are distinct in that they have the bluest light of any bioluminescent insect that has been studied by scientists.

In addition to damp, dark rock houses and caves, the glow worms can also be occasionally spotted in the moss that grows along stream banks.

The glow worms emerge each June, and are seen by turning off one’s flash light and allowing one’s eyes to adjust to the darkness, after which the tiny specks of blue light will begin to appear.

While the glow worms can be found in various locations along the Middle Creek Loop Trail this month, they’re most abundant in a deep rock house late in the hike, where wooden fencing has been erected by the National Park Service to protect the rare snakeroot plant from being unintentionally trampled by hikers.

Those who don’t want to hike after dark will find the Middle Creek Loop an incredible hike even during the daylight hours. It’s an easy, mostly level hike that leads hikers along and inside of an abundance of large rock shelters. There are numerous wet-weather waterfalls along the hike, as well.

For those who do want to hike after  dark and see the glow worms, the best way to experience the adventure will be a ranger-led hike on Saturday, June 15. The guided hike will depart from the Middle Creek Trailhead at 8:30 p.m. Saturday evening.

Middle Creek is a popular trailhead for backpackers who are beginning long-distance hikes through the Big South Fork. A connector trail links Middle Creek Loop to the Slave Falls Loop Trail and Sawmill Trailhead, which leads to many hiking possibilities spanning a multitude of trails that are all connected in some form or fashion.

Middle Creek Loop itself is a 3.5-mile trail that is best hiked in a clockwise direction, meaning that hikers will bear left when the trail forks a couple of hundred feet from Divide Road. The trail includes nearly 400 ft. of elevation gain, but spread out over 3.5 miles, it isn’t all that difficult. In fact, while the trail earns a moderate rating, it is actually a relatively easy hike that lends itself well to the inclusion of children and pets.

For the first nine-tenths of a mile, the trail sticks to the top of the ridge. The hike is uneventful, leading hikers through open hardwood forests that typify the tabletop plateau lands of the Big South Fork region. For much of that distance, the trail actually parallels Divide Road, although the road itself isn’t always in view from the trail.

Nearly a mile in, the trail turns right and descends beneath the bluff line. The nature of the hike changes quickly, as the trail follows the exposed sandstone walls, winding in and out of drainages for the better part of two miles.

Along the way, Middle Creek Loop passes by a series of large rock shelters, each of them seemingly more magnificant than the one before. Some can be explored; others are best left alone to avoid damaging the sensetive plant life that thrives in these sheltered areas.

One of the rock shelters actually includes a wooden fence to direct hikers’ steps and keep them away from the endangered Lucy Braun’s Snakeroot that grows inside. This rare plant is limited to the Cumberland Plateau, and there are thought to be fewer than 50 instances of it, many of them consisting of only a few plants. It is named for Dr. Emma Lucy Braun (1889-1971), the University of Cincinnati botanist who first described it in 1940.

Eventually, the trail begins a gradual ascent back to the top of the plateau, and follows an old log road back to the trailhead on Divide Road.

Getting There: Take S.R. 297 west from Oneida, through the Big South Fork gorge and into Fentress County. At the highway’s junction with S.R. 154, turn right and take 154 north for two miles before turning right again, onto Divide Road. Middle Creek Trailhead is located less than a half-mile ahead, on the right side of the gravel road.

Look For: If you’re hiking at night, look for the tiny blue specks of light inside the rock shelters. These are the glow worms that emerge in June. If you’re hiking at day, look for the endangered Lucy Braun’s snakeroot that grows inside some of the larger rock shelters.

Make It Better: Hike with a ranger Saturday night! The guided hike will depart from the trailhead at 8:30 p.m.

Be Careful For: The Middle Creek Loop is mostly free of hazards, but there is a small footbridge that can be slippery when wet, and at one point the trail climbs a boulder jumble. The trail is generally pet- and kid-friendly. If you’re hiking at night, be sure your flashlight is fully charged, and consider a spare set of batteries.

Remember To: Use the #20WeekHikingChallenge hashtag in your photos on social media, or email photos to, along with the names of all members of your hiking party, in order to log your miles.

Don’t Forget: Obey the Leave No Trace ethic by “taking only memories, leaving only footprints.” If you pack it in, please pack it out!

Go Big Points: While the Big South Fork NRRA’s Go Big 2019 Challenge is separate from the Twenty Week Hiking Challenge, you can earn points towards completing the Go Big Challenge while you participate in the hiking challenge. If you complete the Middle Creek hike, you will earn 4 points towards your Go Big Challenge (6 points if you hike with a ranger Saturday night). Also, keep a close eye out for the wildlife you encounter; if you see any of several birds, you can earn 3 points for each bird you see (blue heron, wild turkey, crow, pileated woodpecker, red-tailed hawk, indigo bunting). To log your Go Big points, download the challenge booklet at Participants who log at least 100 points will earn a challenge patch. Or, you can earn a medallion with 200 points (silver) or 300 points (gold).