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The Great Smoky Mountains' Incredible Firefly Light Show

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Today, the rare Smoky Mountain fireflies are a tourist attraction. Twenty years ago, science didn’t believe they existed.  

At exactly 9:27 P.M., when dusk slips into darkness in the Great Smoky Mountains National Park, the “light show” begins. It’s June, and for two weeks in Elkmont, Tennessee, the fireflies pool their efforts. Instead of scattershot blips of light in the summer sky, the fireflies—thousands of them—pulse this way for hours, together in eerie, quiet harmony. It’s as if the trees were strung up with Christmas lights: bright for three seconds, dark for six, and then bright again, over and over. It continues this way for hours.

As a child, Lynn Faust would huddle with her family on the cabin porch to watch the spectacle. They’d sit, mesmerized by the “drumbeat with no sound.” And though they’d appreciated the show for generations, Faust never thought the event was newsworthy. “I’d assumed there was only one kind of firefly and thought they did a nice show in the Smokies,” she says.

The natural world has long enchanted Faust. In college, she majored in forensic anthropology and minored in forestry. In her twenties, she circumnavigated the globe for three years, visiting islands you could only get to by boat, learning about cultures before they disappeared, pursuing underwater photography. Today, at 60, she’s a naturalist who writes scientific papers and field guides about fireflies. But she wasn’t always obsessed with the insect. In fact, her academic interest began only in the ’90s, when she read an article by Steven Strogatz, a Cornell mathematician, in which he marveled at a species of Southeast Asian firefly that synchronized its flashes. Highlighting how rare this phenomenon was, Strogatz noted that there were no synchronous fireflies in the Western Hemisphere.

This struck Faust as odd. It contradicted the light shows she had seen growing up. As she dug deeper, Faust found that while there had been more than 100 years of colloquial accounts of North American fireflies flashing in sync, scientists discounted those reports, attributing them to lore or optical illusion. Faust knew the truth: that her Tennessse fireflies were every bit as special as the species in Asia. But how could she prove it?

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Fireflies—or lightning bugs—may be the closest thing nature has to a magic trick: lighting the world from the inside out. Technically, they are bioluminescent beetles. Their glow comes from an internal chemical reaction that combines oxygen and calcium with a series of enzymes, including a key light-producing one called luciferin. The bugs flash for lots of reasons: to communicate, to attract mates, to scare off predators. But for creatures so striking, they’re also common. There are roughly 2,000 species worldwide and 125 or more in North America alone, where catching them is a childhood rite of passage.

More than 20 years ago, Faust wrote a letter to Strogatz after reading his article. He connected her with Jonathan Copeland, a biologist and professor at Georgia Southern University who was studying firefly behavior in Malaysia and Indonesia. Copeland was skeptical of Faust’s tale. Reports of synchrony had crossed his desk before but had never panned out. “The dogma said they do not synchronize in North America,” he says.

Still, he indulged Faust, asking her to describe what she’d witnessed by drawing a “musical score.” As a child, Copeland, a tuba player, dreamed of playing with the Boston Symphony. Ever since, music dominated his approach to the natural world. In grad school, he’d studied and documented the rhythmic lunge and strike patterns of praying mantises. He took a similar slant on firefly behavior and found that if people charted the synchronic rhythms they were witnessing, he could separate a bogus account from a real one. Putting pencil to paper, Faust was nervous. “To look at it scientifically is very different from sitting in your rocking chair with a blanket and enjoying it,” she says. “I didn’t want to sound like a complete idiot.”

When her note arrived, “it looked like synchrony on paper,” says Copeland. In June 1993, he was intrigued enough to make the eight-hour drive to Elkmont. He pulled into the cabin’s driveway as dusk fell, no trace of the insects to be seen, and promptly fell asleep—only to wake up to flashes of light all around him. “It was completely obvious—no doubt about it!” he remembers. He rushed to find a pay phone to call his colleague Andy Moiseff. “It must have been about midnight,” he says. “I said, ‘Andy, Andy, you’ve got to see this, they’re flashing synchronously!’ Andy laughed and said, ‘Prove it,’ like any good scientist.” The following summer, that’s exactly what Copeland, Faust, and Moiseff, a professor of physiology at the University of Connecticut, set out to do. It was an unlikely partnership, but the trio made a formidable team. Copeland is a neuroethologist—he studies the neural basis for animal behavior. Faust, an unflappable outdoorswoman and keen observer, knows the area and its wildlife like home. And Moiseff is a computer whiz, with a proclivity for dreaming up theories and building devices to test them.

The three hauled lab equipment, microscopes, video cameras, computers, and insect specimens to sites throughout the Smokies. They started in Elkmont but quickly branched out to determine how widespread the phenomenon was. They hauled bugs back to the lab to do frame-by-frame analyses of the flashes. In the wild, “they were obviously in sync,” Copeland says. But when they repeated the test with individual fireflies in one-gallon freezer bags, the behavior changed. If an insect couldn’t see another, they no longer flashed synchronously. By 1995, the team had the data they needed.

“This was red-hot news in the firefly community,” says Copeland. There are four synchronous species of firefly known in Asia, and they are smaller than the team’s species, Photinus carolinus. “Their flash is wimpy in intensity, but what they lack in flash intensity, they make up in numbers,” Copeland says. They usually remain stationary in trees along the river, unlike carolinus, which fly around in the woods. “Ours are more complicated,” says Faust.

Proving synchrony existed in fireflies in the Western Hemisphere was exciting, but it raised questions about why they flashed this way. And how was that different from what their cohorts did in Asia or, for that matter, from the way their asynchronous relatives behaved in North America and even elsewhere in the park? For the next two decades, Copeland and Moiseff would study the fireflies with Faust each summer, determined to understand these magical creatures. But just as they were getting close, everything in Elkmont changed.

In the beginning, the team had the woods to themselves. “In the old days, there would be the three of us and the odd stranger who was fishing,” says Moiseff. In fact, when Faust first informed park officials about the light show, they didn’t believe her. In 1992, her family had to give up its cabin when the government took control of the resort community’s leases. By then, Faust had noticed that the firefly behavior seemed to be localized: The light show didn’t appear to be taking place even half a mile away from this settled location. She hypothesized that the synchronous behavior could be linked to the unusual conditions near the homes. But when she pointed it out, parks officials assumed her claims were a trumped-up attempt to keep her cabin.

Finally, in 1996, park administrators sent a ranger to the researchers’ campsite to investigate. “It was a funny night,” Faust recalls. “We had this ancient computer set up on the porch and Christmas lights strung across the hill to see if we could control the rhythm of the firefly flashes with the lights going off and on. He was like, ‘Where are they?’ And suddenly, there they were. The guy goes, ‘Oh, my God.’ He said that about six times,” says Faust. The next night they had 20 rangers watching.

By the early 2000s, word had spread. According to one of the park’s supervisory rangers, Kent Cave, “There were fender benders, road rage, crowds of people.” The Smoky Mountain fireflies had become a bona fide tourist attraction. In 2006, the park instituted a trolley service from a parking lot to the viewing area for peak nights, closing access to individual cars. “People were driving up. They might have driven five hours from Alabama or down from Lexington and couldn’t get in,” says Cave.

Today, tourists reserve parking spots in advance online. After the year’s peak firefly emergence has been predicted, reservations for the June viewings go live in late April. The spaces go in minutes. The light show has become the biggest of the park’s special events, with as many as 12,000 attendees in recent years. But as Cave puts it, “Our biggest headache is predicting when these little buggers are gonna flash.” There’s a system for that too. “The pressure of me telling people when to come see the fireflies began 20 years ago,” Faust says. “Like anything in nature, it’s not entirely predictable, but I’ve developed a mathematical way of figuring it out.”

Today, park entomologist Becky Nichols relies on Faust’s degree-day model to determine when the fireflies will emerge. The equation is specific to Photinus carolinus and relies on temperature data Faust and Nichols begin collecting in early March. “You take the high and the low temperatures and plug them into a formula to figure out the larvae’s accumulation of growth,” explains Nichols. “The issue in the past was that we didn’t have good temperature data.” Tiny temperature loggers fixed to trees for air temperature and to the ground for soil temperature have remedied that problem. Faust has her own data logger down the road as well, and the two women compare results as the numbers climb, hoping to come up with the same prediction independently.

Though they’re gratified that the public appreciates the light show, its popularity is bittersweet. The event is too crowded for the scientists to continue studying at the site, so they’ve decamped to other areas in the Appalachian Mountains. As Copeland says ruefully, “We can’t work there anymore because it’s a tourist attraction, and we’re largely responsible for that.”

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So why do Photinus carolinus flash together? No one has quite figured it out, Faust says. But there are theories. In a 2010 paper published in Science, Moiseff and Copeland suggest that synchrony keeps the female firefly from getting confused when searching for a mate. In an experiment using an electronic simulator with light-emitting diodes, they found that uncoordinated stimuli—too many lights coming from too many places at different times—inhibited the female firefly’s response. When flashes were coordinated, the females could clearly send their messages back to the males. Faust agree that synchrony in carolinus is related to mating.

Moiseff, who’s most interested in the firefly’s brain and nerve cells, wonders what it is about the insect’s eyes that helps it process information. Some data has shown that under the right circumstances, a firefly can determine where a flash is coming from. What this could suggest, he says, is that the insect’s brain might break information into different pathways for processing—something that primates and people do, but we don’t think of bugs doing. It’s a problem he’s still studying: “How does a simple nervous system accommodate that? What’s the mechanism?”

Moiseff also points out that Photinus’s synchrony is important not because the phenomenon is so rare but because it changes our perspective on the many ways in which living things interact. With just one proven case in the U.S., the gates opened wide for discovering others. In 1998, Copeland and Moiseff showed that a species on the Georgia and South Carolina coast, Photuris frontalis, was also synchronous. Additionally, the species Photinus pyralis, Copeland says, is “weakly synchronic.” Once you find other species doing this, “all of a sudden they’re not a freak of nature. Instead, they have a solution to a specific environmental need,” says Moiseff.

The last few years, Moiseff and Copeland have kept their firefly studies closer to home. “For the first 10 years, my spouse was very supportive,” says Copeland of his work in Tennessee. “Then she started asking questions about the significance.” He retires from his position at Georgia Southern this year, and, joking aside, considers identifying Photinus’s synchrony to be one of the highlights of his life. “I grew up as a suburban kid afraid of the dark, and I found myself [alone] in the woods with fireflies,” he says. “Serendipity—and a mind set that gets you away from cable TV—plays a role in science.”

Faust, for her part, is still involved with fireflies. She’s working on a field guide that will include images from her collection of more than 60,000 photos. And her family cabin still stands proudly in the same spot where she first saw the light show. But it isn’t quite the same. The cabin now belongs to the park, and she and her family no longer curl up on that porch under thick blankets, waiting for the pulsing spectacle to begin. One thing hasn’t changed, though: No matter how many times Faust has seen the show, Photinus carolinus’s return each summer is still a thrill. “The biggest kick is trying to predict the first night,” she says. “To see that first one and think, ‘Wow, that happened again.’”

This story originally appeared in an issue of mental_floss magazine. Subscribe here.

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Big Questions
Why Don't We Eat Turkey Tails?
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Turkey sandwiches. Turkey soup. Roasted turkey. This year, Americans will consume roughly 245 million birds, with 46 million being prepared and presented on Thanksgiving. What we don’t eat will be repurposed into leftovers.

But there’s one part of the turkey that virtually no family will have on their table: the tail.

Despite our country’s obsession with fattening, dissecting, and searing turkeys, we almost inevitably pass up the fat-infused rear portion. According to Michael Carolan, professor of sociology and associate dean for research at the College for Liberal Arts at Colorado State University, that may have something to do with how Americans have traditionally perceived turkeys. Consumption was rare prior to World War II. When the birds were readily available, there was no demand for the tail because it had never been offered in the first place.

"Tails did and do not fit into what has become our culinary fascination with white meat," Carolan tells Mental Floss. "But also from a marketing [and] processor standpoint, if the consumer was just going to throw the tail away, or will not miss it if it was omitted, [suppliers] saw an opportunity to make additional money."

Indeed, the fact that Americans didn't have a taste for tail didn't prevent the poultry industry from moving on. Tails were being routed to Pacific Island consumers in the 1950s. Rich in protein and fat—a turkey tail is really a gland that produces oil used for grooming—suppliers were able to make use of the unwanted portion. And once consumers were exposed to it, they couldn't get enough.

“By 2007,” according to Carolan, “the average Samoan was consuming more than 44 pounds of turkey tails every year.” Perhaps not coincidentally, Samoans also have alarmingly high obesity rates of 75 percent. In an effort to stave off contributing factors, importing tails to the Islands was banned from 2007 until 2013, when it was argued that doing so violated World Trade Organization rules.

With tradition going hand-in-hand with commerce, poultry suppliers don’t really have a reason to try and change domestic consumer appetites for the tails. In preparing his research into the missing treat, Carolan says he had to search high and low before finally finding a source of tails at a Whole Foods that was about to discard them. "[You] can't expect the food to be accepted if people can't even find the piece!"

Unless the meat industry mounts a major campaign to shift American tastes, Thanksgiving will once again be filled with turkeys missing one of their juicier body parts.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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Animals
10 Juicy Facts About Sea Apples

They're both gorgeous and grotesque. Sea apples, a type of marine invertebrate, have dazzling purple, yellow, and blue color schemes streaking across their bodies. But some of their habits are rather R-rated. Here’s what you should know about these weird little creatures.

1. THEY’RE SEA CUCUMBERS.

The world’s oceans are home to more than 1200 species of sea cucumber. Like sand dollars and starfish, sea cucumbers are echinoderms: brainless, spineless marine animals with skin-covered shells and a complex network of internal hydraulics that enables them to get around. Sea cucumbers can thrive in a range of oceanic habitats, from Arctic depths to tropical reefs. They're a fascinating group with colorful popular names, like the “burnt hot dog sea cucumber” (Holothuria edulis) and the sea pig (Scotoplanes globosa), a scavenger that’s been described as a “living vacuum cleaner.”

2. THEY'RE NATIVE TO THE WESTERN PACIFIC OCEAN.

Sea apples have oval-shaped bodies and belong to the genus Pseudocolochirus and genus Paracacumaria. The animals are indigenous to the western Pacific, where they can be found shuffling across the ocean floor in shallow, coastal waters. Many different types are kept in captivity, but two species, Pseudocolochirus violaceus and Pseudocolochirus axiologus, have proven especially popular with aquarium hobbyists. Both species reside along the coastlines of Australia and Southeast Asia.

3. THEY EAT WITH MUCUS-COVERED TENTACLES.

Sea cucumbers, the ocean's sanitation crew, eat by swallowing plankton, algae, and sandy detritus at one end of their bodies and then expelling clean, fresh sand out their other end. Sea apples use a different technique. A ring of mucus-covered tentacles around a sea apple's mouth snares floating bits of food, popping each bit into its mouth one at a time. In the process, the tentacles are covered with a fresh coat of sticky mucus, and the whole cycle repeats.

4. THEY’RE ACTIVE AT NIGHT.

Sea apples' waving appendages can look delicious to predatory fish, so the echinoderms minimize the risk of attracting unwanted attention by doing most of their feeding at night. When those tentacles aren’t in use, they’re retracted into the body.

5. THE MOVE ON TUBULAR FEET.

The rows of yellow protuberances running along the sides of this specimen are its feet. They allow sea apples to latch onto rocks and other hard surfaces while feeding. And if one of these feet gets severed, it can grow back.

6. SOME FISH HANG OUT IN SEA APPLES' BUTTS.

Sea apples are poisonous, but a few marine freeloaders capitalize on this very quality. Some small fish have evolved to live inside the invertebrates' digestive tracts, mooching off the sea apples' meals and using their bodies for shelter. In a gross twist of evolution, fish gain entry through the back door, an orifice called the cloaca. In addition expelling waste, the cloaca absorbs fresh oxygen, meaning that sea apples/cucumbers essentially breathe through their anuses.

7. WHEN THREATENED, SEA APPLES CAN EXPAND.

Most full-grown adult sea apples are around 3 to 8 inches long, but they can make themselves look twice as big if they need to escape a threat. By pulling extra water into their bodies, some can grow to the size of a volleyball, according to Advanced Aquarist. After puffing up, they can float on the current and away from danger. Some aquarists might mistake the robust display as a sign of optimum health, but it's usually a reaction to stress.

8. THEY CAN EXPEL THEIR OWN GUTS.

Sea apples use their vibrant appearance to broadcast that they’re packing a dangerous toxin. But to really scare off predators, they puke up some of their own innards. When an attacker gets too close, sea apples can expel various organs through their orifices, and some simultaneously unleash a cloud of the poison holothurin. In an aquarium, the holothurin doesn’t disperse as widely as it would in the sea, and it's been known to wipe out entire fish tanks.

9. SEA APPLES LAY TOXIC EGGS.

These invertebrates reproduce sexually; females release eggs that are later fertilized by clouds of sperm emitted by the males. As many saltwater aquarium keepers know all too well, sea apple eggs are not suitable fish snacks—because they’re poisonous. Scientists have observed that, in Pseudocolochirus violaceus at least, the eggs develop into small, barrel-shaped larvae within two weeks of fertilization.

10. THEY'RE NOT EASILY CONFUSED WITH THIS TREE SPECIES.

Syzgium grande is a coastal tree native to Southeast Asia whose informal name is "sea apple." When fully grown, they can stand more than 140 feet tall. Once a year, it produces attractive clusters of fuzzy white flowers and round green fruits, perhaps prompting its comparison to an apple tree.

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