It’s mid June in the Great Smoky Mountains and the evening air is warm and damp from a late afternoon thunderstorm. Slowly, darkness creeps in and the lush emerald green forest takes on a blueish tint. It’s that quiet time of night when reality and dreams blend together. All of a sudden there’s a bright flash. Then another. And another! Soon the forest comes alive, pulsing with a natural rhythm. It’s firefly season, and all those bright yellow-green flashes are fireflies (Photinus carolinus), out looking for mates. It’s like a natural disco party, but the only music is the soothing sound of the rushing river.

It is quite dark indeed by the time the first fireflies start flashing, so in order to make a good photograph light collecting ability was critical. All of the firefly images in this post were made possible thanks to the fast glass (Zeiss Distagon 35mm f/1.4) I got for the trip from the great folks at I must say though, while that lens is a truly beautiful piece of equipment, it sure does weigh a lot (almost 2 lbs)!

In all of these firefly images each trajectory is typically just a few seconds long, but by using long exposures I was able to capture more of them in a single frame.

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Fireflies Smoky Mountains, Synchronous, Tennessee

Fairyland : Prints Available
Synchronous Fireflies (aka Lightning Bugs) light up the forest surrounding a stream late in the evening in the Great Smoky Mountains National Park in Tennessee.

The Tech: Canon 5D2, Zeiss Distagon 35 mm f/1.4, tripod
Exposure: iso 1600, f/1.4, 4 min
Notes: This is a single 4 min exposure, but I used an exposure from half an hour earlier taken at iso 100 and f/1.4 to reduce the noise (processed at the same luminosity as the original single exposure.)

This phenomenon, best seen in the area around Elkmont, Tennessee, has become so popular a sight among tourists that during the peak season over 1,000 people are brought in by busses nightly. This is just one of the many factors that contribute to the Great Smoky Mountains National Park being the most highly visited park in the national park system, getting over 9 million tourists annually. To avoid the crowds, my friend, Raghu, and I got permits to go backpacking for several days. Just a few miles into the forest we had the place nearly to ourselves. Aside from the bugs, of course.

Fireflies, aka “lightning bugs”, were no doubt a large part of many peoples childhood in the midwest, south, and northeast. As a west coaster, however, I never had the chance to run around empty fields chasing fireflies with insect nets and mason jars, making this experience even more surreal for me. The fireflies in the Smoky Mountains are particularly special, though, because every insect within eyeshot (and that can be quite a few!) synchronizes together, resulting in regular pulses of light once every second or so, interspersed with periods of darkness of 10-15 seconds. There are only a few locations in the world where fireflies synchronize together like this, and the Little River Valley of the Great Smoky Mountains is one of them. Even more impressive synchronized displays occur in Southeast Asia – someday perhaps I’ll get to see them, too!

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Camping with Fireflies, Smoky Mountains, Tennessee

Camping in Never Never Land : Prints Available
Backpacking in the Smoky Mountains can land you in the middle of a spectacular display of dancing fairies, aka Fireflies! The only source of illumination here was starlight and firefly light.

The Tech: Canon 5D2, Zeiss Distagon 35mm f/1.4, makeshift tripod
Exposure: iso 1600, f/1.4, 4min x4
Notes: This is a stack of 4x 4 minute exposures, to simulate a 16 minute continuous exposure, but without the excessive noise that would result in (yes, there is still quite some noise).

Why do fireflies flash? The answer to this question is complicated, in part because there are over 2,000 species in 100 genera, and although much progress has been made, this is still an area of active research. I will try to condense the contents of two review papers here, to give you a summary of our current understanding (further reading: Lewis & Cratsley, 2007; Buck, 1988).

Fireflies produce light in a part of their abdomen, called the lantern, through a chemical reaction involving luciferse and oxygen. This ability evolved in the early ancestors of fireflies in order to warn would-be predators of their toxicity, just as how many other poisonous animals sport bright orange and red colors as a warning sign. Over time, this ability has been co-opted for use in courtship (the story may be more complicated, as bioluminescence has evolved, and been lost, several times within the firefly family). In Photinus fireflies (eg. Photinus carolinus fireflies from the Smoky Mountains), perched females respond to the flashes of flying males (called rovers) in order to attract them. The females use the frequency of the males’ flashing to discriminate between species. Some species, including Photinus carolinus, form highly competitive mating clusters called “love knots”. As you might imagine, in such a cluster it could be difficult for one male to distinguish the flash of a female from all the other males around him. This is one of the many hypotheses for how synchronization of flashing may have evolved. If all the males flash together, then they each have a better chance of locating a female that flashes in response to them (for additional hypotheses, see: Buck, 1988). To protect their pairings from other intruders, males of some species will engage in prolonged copulations of up to 9 hours!

Bioluminescent courtship is only the first step. Recent observations, aided by laboratory induced courtship under infrared lighting (which makes observing their nocturnal behaviors possible), have unveiled an even more “romantic” aspect of the firefly mating ritual: nuptial gifts. Once a male and female have paired off, the male will give the female a “gift” consisting of a high protein sperm package that will help her produce more eggs. Since there is no way for the female to know whether she might encounter another male later that evening, or even during the next week, that can offer her a larger gift, she holds on to it. After mating with a number of males over the course of several days, she picks the best package.

(Above: movie showing the synchronous “wavelike” flashing behavior of the fireflies. You will see them all go dark for 10 seconds or so, and then start up again. The movie is mostly black, so watch closely… It was much more impressive to see in person!)

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Fireflies Long Exposure, Smoky Mountains, Tennessee

Fairy Fire : Prints Available
A long exposure (forty minutes) in the middle of the night reveals the spectacular trails of light created by the Synchronous Fireflies in Tennessee’s Great Smoky Mountains National Park.

The Tech: Canon 5D2, Zeiss Distagon 35mm f/1.4, tripod
Exposure: iso 1600, f/1.4, 10min x2 + 20min
Notes: This was a bit of an experiment. I ended up stacking two 10 minute and one 20 minute exposures for a total of 40 min of continuous exposure. In hindsight, I could have used a lower iso without much loss in firefly light (fortunately noise reduction is easy when the background is pure black).

What do these magical little creatures look like? I contemplated keeping their true appearance a mystery, but, since thousands of images are only a google search away, here is a quick snap.


A firefly (Photinus carolinus), perched on a leaf. Although difficult to see here, the light patch on the underside of the animals' abdomen is its lantern, responsible for producing the bioluminescent flashes.

Why are the Smoky Mountains “smoky”? The Smoky Mountains initially got their name from the water vapor that so frequently hangs over the mountains, resulting in a thick blue hazy layer. This phenomenon inspired the Cherokee name for the area, Sha-co-na-qe, meaning “place of blue smoke”. Unfortunately, much of the haze we see today is due to man made pollution, which collects in and around the national park. Still, a large percentage of the “smoke” is natural water vapor, thanks to the 85 inches of rain the mountains receive annually. Although that pales in comparison with the 150 inches that the Olympic Rainforest receives, we did get our fair share of torrential downpours on our trip. I did my Dutch heritage proud, and built an effective drainage system around our tent pad which kept us from floating in a pool. It was so warm and wet that there was even haze inside the tent! Fortunately, fireflies seem to get excited by humid rain, and it was the nights just after such downpours that they were particularly active.

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Smoky Mountains Vista, Pisgah National Forest, North Carolina

Smoky Mountains : Prints Available
The moist hazy rolling hills that give the Smoky Mountains their name. This particular vista is from Pisgah National Forest in North Carolina.

The Tech: Canon 5D2, 70-200mm, handheld

Raghu, working on dinner while it's pouring rain outside - note the humidity in the tent!

Fireflies weren’t the only insects around. In fact, I can’t remember ever having seen so many in one place. To our surprise, however, we only encountered three mosquitoes – they are rare thanks to the lack of standing water. As a graduate student currently focused on understanding how insects, in particular the fruit fly, uses odor and visual information to find food, I was particularly impressed with the quantity of Drosophiladae that took a liking to my stinky socks.

Honeybees, moths, spiders, and all sorts of insects crawling all over our tent in the morning.

Apparently my stinky socks are incredibly delicious... if you were to ask these flies, that is.

Tips for photographing fireflies:

1. Avoid the tourists – get a permit to go backpacking.
2. Second week of June is best in a typical year, for the Smoky Mountains fireflies.
2. If you don’t own any, rent some fast (f/1.4) glass from I found a 35mm f/1.4 to be perfect.
3. Try some long exposures, anywhere from a few minutes to half an hour – consider the amount of noise you will accumulate, especially at high iso, though.
4. Careful timing and exposure planning will let you capture the landscape and fireflies together, but you only get one good chance on any given night (before it gets too dark)!

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Fireflies in Forest, Smoky Mountains, Tennessee

Pixie Hollow : Prints Available
Synchronous Fireflies illuminate the lush forests of Tennesse’s Smoky Mountains National Park.

The Tech: Canon 5D2, Zeiss Distagon 35mm f/1.4, tripod
Exposure: iso 400, f/1.4, 15 minutes
Notes: a single exposure with minimal processing... timed just right!

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14 Comments to “Forest Fairies – Synchronous Fireflies of the Great Smoky Mountains”

  1. Sandra says:

    Amazing stuff Floris!!! Just my taste of images … dreamlike. 🙂

  2. Thanks Sandra! You should definitely make it out to photograph fireflies sometime, you’d love it!

  3. Great stuff Floris, you really have a way of working with these low-light glowing phenomena! I’d been idly wondering if anyone out there was doing firefly work like this. I wish these guys lived out west!

  4. Zhou says:

    Fairy Fire, what a great image!

  5. Richard Wong says:

    Incredible Floris. I have never seen anything like this. Your post explaining the scientific aspects is great as well.

  6. Henrik says:

    Wow again!
    I love especially the last one – mystic as a really good landscape shot should be!

  7. Wonderful photos Floris. Always enjoy a post that outlines the biology behind things as well.

  8. Jon Reid says:

    What a great set of images! I’ve never seen anything like this before. It is rare to see unusual images these days.

  9. Lois says:

    Wonderful photos and commentary. Your pictures are always beautiful and I love that I always learn something. A few years ago I tried to photograph fireflies in Kentucky and managed to show a few spots of light, but nothing like this! I’d never heard of synchronous fireflies before.

  10. Such an awesome series of images, Floris. I keep finding myself drawn to the first frame “Fairyland”, combining all the elements fireflies represent to me. A quiet stream, an open deciduous forest with plenty of ground cover and the beginning of the night. “Fairy Fire” is super intriguing as well.

    It will still be about two weeks for them to peak around here and if I come home with one frame at least half as nice, I’m a happy camper. Literally. 🙂

  11. Ed Rosack says:

    Wonderful images and blog post! Very inspiring – I wish I lived closer.

  12. Thanks folks for all the kind words, I really appreciate it!

  13. jr forster says:

    great job Floris! Fairyland is my favorite – it’s so 3D. thanks for all the information along with the beauty. i can only imagine how much time and energy you put into each your projects.

  14. Theo Bosboom says:

    Beautiful, creative and very well executed, congrats Floris!