As night falls on Laguna Azul, an ecotourism lodge on the outskirts of the Mexican hamlet of Nanacamilpa, it looks like rain, and a group of eight tourists nervously watch the sky. Their guides look unconcerned. Cold rain makes for a miserable walk, but the fireflies love it.
A younger guide introduces himself in a strong voice as an older one looks on, leaning on a thick walking stick. The guide lists the basic rules of the tour: walk only on the path, no wandering, no music, no alcohol, no insect repellent, no lamps, and absolutely no cell phones. Any light, even that of a cell phone display, can distract the fireflies.
The walk follows sprawling farmland up a hill to the very edge of the forest. The guides pass fields of wheat, barley, fava beans, and corn before stopping for a moment. They explain that the corn fields to our right are a native corn that doesn’t require pesticides. The hybrid corn to our left, abutting the forest, requires regular spraying.
In the forest we see pines, oaks, and a fir called oyamel. The crowd bunches and murmurs. Several children look bored and start to squirm. Then it begins, slowly—a blink here, a flash there. When the dusk fades, the fireflies come out in earnest.
Individually they are yellow points of light wandering crooked paths, rhythmically blinking. As a whole they are a swirling mass of light, like fairies just out of reach. The guides asked for silence but no one listened, especially the kids, who are squealing and talking excitedly.
After about an hour the show hits its climax, with thousands of fireflies swirling and lighting up almost in unison. The younger guide motions to us, and we silently step away from the group. Away from the starstruck kids, the fireflies come even closer, zipping past our faces in a desperate search for mates. Then, as gradually as it started, the show ends and the swarm dwindles to a few flashing fireflies.
With a projected 100,000 visitors from mid-June to mid-August, Nanacamilpa and its fireflies are fast becoming a national treasure and a lucrative source of cash for a chronically poor region. It wasn’t always like this. Just five years ago there were no firefly tourists here, and indeed the fireflies themselves were unknown to science. The explosion of interest in the nocturnal light shows has thrilled some and worried others, as scientists scramble to understand these insects and authorities puzzle over how to protect the goose that lays the golden egg.
Though scientists are just now studying fireflies here in western Tlaxcala state, they are not new to locals. Everyone in town has a firefly-related story from their childhood—women getting upset about glowing spots on hanging laundry, or children catching them in glass jars to use as lanterns. And anyone who grew up here can tell you about using dead fireflies to write their names like neon lights on their shirts or color their pants so that their butts glowed yellow.
It’s not completely clear how firefly tourism started but there’s no shortage of people claiming credit. Some say it was a local historian, others say it was a businessman from nearby Puebla state, and still others say it was a biologist on vacation. Whoever had the idea, the first organized trips started in 2011 at a cooperatively owned tourism and logging company called Piedra Canteada. The trips drew just a handful of tourists, according to Juan José Morales Pérez, the current president of the business. He says local people took control of the 1,600-acre site first as squatters and then as legitimate owners after a legal battle against wealthy landowners in the 1990s. Afterward, it became a somewhat lucrative logging operation that earned around $50,000 a year for its members.
In 2012 the number of tourists rose to 4,000 as other operators started offering tours. That same year, a scientist at the National Autonomous University of Mexico (UNAM) published a paper describing the firefly species and naming it Macrolampis palaciosi (reclassified this year into the genus Photinus). It’s the only scientific paper published about the Nanacamilpa fireflies.
It didn’t take long for word to get out after the state launched a promotion campaign. The town saw 51,000 visitors in 2013 and 77,000 in 2015, though many locals were still puzzled by the lines of cars appearing in June and disappearing in August.
“One day some girls knocked on our door asking for directions on how to get to the firefly sanctuary. I told them there was no such thing here; we didn’t know anything about that,” says Mariela Morales, who now runs a restaurant catering to firefly tourists.
In 2013 there were food shortages in restaurants, few places to sleep, and fewer proper roads. Quickly, hotels began popping up in town and in the forest, while the number of registered tour operators jumped from four in 2012 to 33 today.
Nowadays no one talks about writing on their shirts with glowing firefly guts; they are far too valuable. Last year 91,000 visitors came to see the fireflies, and the state has actually stopped advertising it for fear of getting too many tourists. Tlaxcala’s secretary of tourism says fireflies are now the state’s second most important draw, behind cultural tourism, such as visiting ancient ruins. And these days Piedra Canteada makes twice as much on firefly tours in two months as it does all year with logging.
“One day we were a ghost town, and the next one we were the most visited town in the state,” says Nanacamilpa’s mayor, Víctor Hugo Sánchez Flores.
THE LIGHT IS FADING in Miguel Lira y Ortega, a community outside of town and a relatively new player in the firefly business. Unlike Piedra Canteada, there are no cabanas here, and the locals are still trying to decide how firefly tourism fits into their community. We’re perched on a wooded ridgeline at the northern tip of a forest that spreads 35 miles south, to the hulking volcano of Popocatépetl. At more than 9,000 feet, the air is thin and fresh with the smell of pine. As dusk creeps into the valley, a chorus of juncos and mockingbirds is replaced by tree frogs. The ground is covered in hulking sacaton grasses, which look a little like giant shaggy green dogs.
The tranquility is broken only by the sound of frustrated scientists. “Have you found any females?” asks Tania López Palafox, a UNAM graduate student who has been studying the Nanacamilpa fireflies for two years. “Not yet,” comes the response from a fellow student who’s volunteered to help her. She and three friends are combing the sacaton plants, which for some reason the fireflies prefer, looking for females before darkness falls.
López is writing her doctoral thesis on the behavior and genetics of the Nanacamilpa fireflies, trying to understand the basics of their biology. She is analyzing their genetic diversity to study inbreeding and adaptation, which will help scientists choose which areas to prioritize for conservation. She’s also hoping to film their courtship and mating, hence the hurried hunt for females before dark. In theory it should be easy, since female P. palaciosi can’t fly. In practice, it’s tough to spot a firefly when it’s not glowing.
There are more questions than answers when it comes to these fireflies. Nothing is published on how long they live, how long they are underground as larvae, and what kinds of conditions they prefer. No one knows how light pollution affects them or if they are vulnerable to chemical pollution. In fact, other than their name and general description, not much of anything is known about the state’s second-most important attraction.
“We are just walking in the dark,” López says.
These are not just idle curiosities. Tour operators and a few policymakers in the region are hungry for guidance to help them protect this new source of income. And it’s not just here in Mexico. Firefly tourism has become important in Taiwan, Thailand, Japan, Malaysia, and parts of the eastern United States.
“Ecotourism is a really interesting double-edged sword, with some real challenges for preserving firefly populations but also some real opportunities,” says Sara Lewis, a firefly expert at Tufts University.
She says that in Taiwan, where visitors walk on raised boardwalks to protect the fireflies and follow a host of different rules, humans might actually be good for the insect. But she worries about areas in the United States where tourists wander freely and possibly crush females underfoot.
“They’re tolerant of firefly research, but they’re not encouraging it,” Lewis says of rangers and private land managers in the Smoky Mountains, where she often works. “They really have their hands full just trying to manage people who are coming to see the fireflies.”
Here in Mexico, she says it’s too early to tell which way the sword cuts but she’s never seen tourism grow quite so fast. Another big question about the fireflies is whether they are affected by pesticides, such as those used near Laguna Azul. Nanacamilpa potato farmers, for example, spray their fields 10 times a year to kill pests. Studies have suggested spraying can be detrimental to bees but the two studies—one in South Korea and one in Florida—that looked at the effects on fireflies had mixed results.
Rodolfo Campos and Tulio Méndez are researchers at the University of Chapingo, a school 20 miles to the west, in Texcoco, focused on agriculture, livestock, and forestry. They’ve been working here since 2014, when locals asked them for help managing firefly tourism.
They’ve found that fireflies here live for about a year, mostly underground as larvae, and that there are far more males than females, suggesting that females hold the key to conservation. But they haven’t published any of this research and are grossly underfunded. Last year they received less than $300 for fieldwork.
“We are hanging from our nails here.” Campos says.
Without solid science, locals tend to cobble together scraps of information they find online or hear through the grapevine. For instance, the town’s brand new firefly information center describes a femme fatale firefly—a female that kill its mate—despite the fact that those live thousands of miles away.
“The only things [scientists] have told us is to take care of the woods, that fireflies eat worms, that we should keep the conditions of humidity, and the name of the species. That’s it,” says Luis Flores, manager at an ecotourism lodge called Villas del Bosque Santa Clara.
Which brings us back to López and her ragtag team of firefly hunters. After two hours of searching, they have four females, which they bring to a makeshift lean-to just as night sets in. And with the dark come the fireflies. As before, they begin with just a few scattered flashes, mostly near the bunch grasses. Then, seemingly following some signal, they emerge en masse. In this lonely corner of the forest, without other tourists, the fireflies feel different, almost ominous. They cluster in one part of the valley and then another. After a few minutes they begin to blink in semi-unison, almost pulsing in one giant throbbing swarm all around us. Standing in the middle of them, it feels like being in some kind of living, breathing tide. The whole scene would be terrifying, were it not so beautiful.
López, meanwhile, is struggling to get video of mating fireflies. Several males have attached themselves to her rain jacket as she quickly narrates what she sees into a recorder. Her flashlights are tinted blue (a color she says doesn’t distract the insects) but the red LED lights on her camera have attracted the amorous attentions of male fireflies.
“Is it recording?” she says in a hushed voice as two fireflies eye each other on a clear plastic dish in a pool of blue light. Then, frustrated, she glances at her camera’s LCD. “I think they are responding to the screen.”
WHILE SOME SEE THE DEARTH of firefly information as a problem, others see an opportunity for pretty incredible citizen science. At first glance, Emmanuel Mendoza Domínguez doesn’t look much like an entomologist. With his tight jeans, white cowboy hat, and puffy, wool-lined leather jacket, he looks like a quintessential Mexican vaquero. But Mendoza is a passionate amateur biologist and one of the most talented naturalists in town.
“He was faster catching fireflies with his hat than we were with our entomologic nets,” Campos says.
Mendoza works as a corn farmer but long ago realized there was more money in breeding hardier corn varietals and selling them to his neighbors. He’s read countless scientific texts on fireflies and talks about prominent experts like they are rock stars. Taciturn by nature, he keeps his answers short and respectful until the conversation turns to the natural world.
“I’ve always been interested in nature,” he says. “I’ve been creating my own hybrid corn, adapting it to the conditions of my region. Weather here is very cold I need a corn with a shorter cycle.”
When he’s not breeding DIY corn, he wanders the forest. His phone is filled with photos of horned lizards, snakes, and bugs he has found while hiking. A few years ago, Mendoza noticed an odd firefly and mentioned it to one of Campos’s students, who didn’t take much note of it at the time. It was later confirmed to be a new species.
But that isn’t all Mendoza has discovered. While walking with his girlfriend one evening, he says he noticed something odd. One of the blinking females was actually a bulbous tan spider. “No, that can’t be,” he said to her, “there are no glowing spiders.” So he took some photos. Sure enough, it seemed to be luring the fireflies to its web with the blinking light in order to trap its dinner. Mendoza says he even captured a couple of the spiders and experimented with blinking LED lights until he got them to respond. The discovery has yet to be confirmed by scientists, but if true, it would be the world’s first known bioluminescent spider.
Mendoza worries constantly about the effect tourism might be having on the fireflies. When he was a kid, he says the fireflies were more plentiful, lighting up entire trees like they were on fire and even coming into town. Today they stay in the forest and, while still plentiful, don’t light up trees like they once did. He also notices communities that don’t use pesticides or offer tourism have far more fireflies.
“None of the money goes to the fireflies. They are the stars of our show yet everything is for us and nothing is for them,” he says. “The environmental impact is going to be catastrophic for them.”
It’s hard to know for sure. Even in the United States there isn’t enough data to construct meaningful management guidelines. Lewis says all you can do is limit logging and try to keep tourists from stepping on the females. In the end, we may just have to wait and see.
Watching fireflies during mating season is part biology lesson, part light show, and part spiritual experience. Standing on a trail above Santa Clara the night before we left Nanacamilpa, it’s hard not to be impressed as the valley below fills with tiny blinking lights, flitting about looking for other blinking lights. It’s like someone glitter-bombed an entire hillside. But equally impressive are the tourists. Unlike the first night, everyone is dead silent. A young girl sitting on her father’s shoulders whispers into his ear. He answers briefly and then hushes her. No one checks their cell phones or wanders off. It’s pitch black—there’s literally nothing to see except the fireflies.
These tourists are just a few of the thousands of people this summer who will trudge through the frigid rain and mud, up steep trails without flashlights or phones, all to see a swarm of bugs. It’s hard to see how a line of silent night hikers could be damaging to the ecosystem. And perhaps the attention will help preserve the forest and curb pesticides use in the region. But one thing is clear, the townspeople nearby will never be the same.
Five years ago Nanacamilpa was another forgettable town in Tlaxcala with a few tourist cabins and delicious pulque. Today it’s the firefly capital of Mexico. And it’s not alone, Puebla state next door and the city of Amecameca to the south now offer their own firefly tours.
Certainly one silent cluster of hikers whispering in the dark won’t harm the ecosystem. But a thousand? A hundred thousand? A million? Only time will tell.
Erik Vance, a freelance writer based in Mexico City, is a frequent contributor to National Geographic magazine and author of Suggestible You , a National Geographic book. Sally Ríos Kuri is a translator and science writer in Mexico City. Kirsten Luce is a freelance photographer who has been documenting issues along the U.S.-Mexico border for a decade. Follow her on Instagram.