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17 Noisy Facts About 17-Year Cicadas

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This summer, prepare for the return of Brood V.

No, that’s not the title of a B horror flick, but it does involve an army of insects rising from the earth Night of the Living Dead–style. Seventeen-year cicadas spend over 99 percent of their lives underground, only to crawl out by the billions on a warm spring night in their 17th year. Then, after dedicating a few weeks to repopulating the brood, their bodies fall back to the ground they emerged from.

Different cicada broods resurface on different years. Brood V was last seen in Ohio, West Virginia, and surrounding states in 1999, and now the offspring of that last batch are finally ready to emerge. Whether they’ll be in your neighborhood or not, these are 17 facts about the periodical bugs worth knowing.

1. THEY’RE ACTIVE THEIR WHOLE LIVES.

Just because we can’t see (or hear) cicadas when they’re a few feet under doesn’t mean they aren’t keeping busy. “They’re not hibernating ... they’re just slow-growing,” Louis Sorkin, an entomologist with the American Museum of Natural History, tells mental_floss. According to Sorkin, 17-year cicadas live underground as immature nymphs before reaching full adulthood above the surface. And because they’re still too young to procreate, one major activity occupies their time: eating.

2. THEIR DIET MAY EXPLAIN THEIR LONG LIFECYCLE.

A cicada nymph’s meal of choice is xylem, a type of sap they slurp from tree roots. The fluid is more than 90 percent water and very poor in nutrients. Some cicada experts believe that the insect’s lousy diet may be one of the reasons behind its drawn-out maturation process.

3. THEY USE TREES TO KEEP TRACK OF TIME.

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The cicada’s super-accurate timekeeping skills have been puzzling scientists for centuries. According to one paper published in 2000, they may be using more than just their biological clocks to count down the years. For the study, researchers transplanted 15-year-old 17-year cicada nymphs beneath a tree that had been manipulated to blossom twice in one season. After feeding on its roots, the insects emerged one year early. This suggests that cicadas use the influx of sugars and proteins from a blossoming tree’s roots to mark the passage of time underground.

4. MATH HELPS THEM AVOID PREDATORS.

Seventeen-year cicadas aren’t the only members of the periodical cicada genus. They share the title with 13-year cicadas, who, as their name suggests, live a similar lifecycle except it ends four years earlier. Thirteen and 17 may seem like arbitrary amounts of time to stay buried in the dirt, but the numbers share a mathematical property that may help keep the insects alive. Both 13 and 17 are decently large prime numbers, which means they aren’t divisible by any number smaller than themselves. This makes it next to impossible for predators to adapt to the cicadas’s emergences. Stephen Jay Gould wrote in his 1977 book Ever Since Darwin: Reflections in Natural History, “Consider a predator with a cycle of five years; if cicadas emerged every 15 years, each bloom would be hit by the predator. By cycling at a large prime number, cicadas minimize the number of coincidences.” That’s an impressive math trick for an arthropod.

5. THEY EVOLVED DURING THE LAST ICE AGE.

The prime number trick is just one of the reasons some cicadas live to be 17. Louis Sorkin tells us their long lifespan is likely a leftover adaptation from the last ice age. Periodical cicadas are believed to have evolved during the Pleistocene Epoch at a time when North America’s climate was fairly unpredictable. By staying underground for as long as possible, cicadas had a greater chance of avoiding a cold and deadly summer when it was finally time to come up.

6. THEY’RE TRIGGERED BY TEMPERATURE.

Chace Nelson, Flickr // CC BY-NC-ND 2.0

When it’s their year to emerge, 17-year cicadas wait until the soil 8 inches beneath the surface warms up to around 64 degrees. This specific temperature point is their signal to tunnel out of the earth and up the nearest vertical surface they can find, whether it’s a tree, fence post, or screen door. According to Sorkin, they’ll even climb up the leg of a person standing nearby.

7. THERE ARE 12 DIFFERENT BROODS.

Not every 17-year cicada emerges at the same time (if they did, the eastern half of the country couldn’t be blamed for taking a prolonged vacation every 17 summers). The insects are grouped into 12 distinct broods spanning from New York to Oklahoma (along with three broods of 13-year). When a brood procreates, their offspring are the ones who carry on that same brood 17 years later. Entomologist C.L. Marlatt was the first person to assign Roman numerals to the periodical cicadas in the late 19th century. Since then, a handful of the original broods have gone extinct.

8. THEY ARRIVE IN LARGE NUMBERS.

A single brood can contain billions of cicadas. When Brood V emerges this spring, their populations will be as dense as 1.5 million insects per square acre in some parts of the region. Simultaneously emerging in such great numbers is a survival strategy known as predator satiation. “[Predators] get completely full and engorge themselves,” Sorkin says. “They can’t catch everything, so you’ll have lots of [cicadas] doing fine and progressing to the next stage of their lives.” This ends up working out for cicadas as well as for the birds, rodents, and reptiles that get a surprise feast whenever they show up.

9. THEY’RE A TREAT FOR HUMANS, TOO.

Humans have a long history of dining on cicadas. Before European colonists arrived, indigenous North Americans enjoyed roasting them like peanuts. Today the bugs have become something of an unlikely food trend. Not only do they fit into the movement to utilize insects as a protein source, but they’re also gluten-free, low in carbs, and hyper-seasonal. When one Missouri ice cream shop introduced a batch of cicada-flavored ice cream in 2011, it sold out before hitting the display case. During the most recent summer of Brood II one chef served cicadas at his James Beard-nominated sushi restaurant in Connecticut. If you can’t find cicadas on the menu of your favorite local spot, catching them and cooking them at home is easy enough to do. Sorkin recommends grinding them up to make a flour, or even sautéing the critters with garlic and oil and eating them whole.

But if you want to put cicada on the menu, there are a couple of things to consider. Experts recommend that those with a shellfish allergy avoid the bugs, as should anyone who’s concerned about mercury in their diet: In 2004, researchers found cicadas could contain as much mercury as certain fish.

10. THEY LEAVE A LOT OF EXOSKELETONS BEHIND.

Before they can become adults, cicadas must get to a high-up spot to shed their immature skin. From the old exoskeleton a soft, new body unfurls, leaving behind the perfect shell of its nymphal self. Even though they’re harmless, the cicada skins can prove to be a nuisance for some. News stories from Brood II’s 1996 emergence reported shells piling up so high in some spots that people were using snow shovels to clear their driveways.

11. THEY’RE NOT LOCUSTS. 

While it’s true that 17-year cicadas do emerge in plague-like proportions, that doesn’t make them locusts. Sorkin says this misnomer was likely spread by European colonists who knew the bugs from the Bible. In reality, locusts are a type of grasshopper, and they tend to be much more destructive than relatively harmless cicadas.

12. THEIR SONGS CAN REACH 100 DECIBELS.

A cicada above ground has one job to do: make baby cicadas. To accomplish this task, an adult male will spend his last four to six weeks of life in furious song. There are three different species of 17-year cicadas and each one has a distinct mating call. The sounds are sometimes reminiscent of chirps, rattles, or high-pitched screams, and when males gather in trees to form a chorus, the noise can exceed 100 decibels. That’s about as loud as a car stereo playing at max volume. The song can be heard by females up to a mile away, and if she likes what she hears, she responds by flicking her wings.

13. THEY’RE ATTRACTED TO POWER TOOLS.

The deafening roar of a chorus of cicadas is often compared to the sound of heavy duty power equipment. The noises are so similar that confused females have been known to swarm around people using lawn mowers, leaf blowers, and other loud tools.

14. THEY LAY THEIR EGGS IN TREE BRANCHES.

After the female cicada has mated, it’s time to lay her eggs. She uses a structure on her rear called an ovipositer to slice Y-shaped gashes on the tips of tree branches. Females can lay up to several dozen eggs in a single branch and as many as 400 eggs spread out over 40 to 50 sites. After incubating for several weeks, the newly-hatched cicada nymphs fall to the earth, where they will spend their next 17 years of life.

15. THEY’RE ONE OF THE OLDEST INSECTS.

With a lifespan of 17 years, cicadas are among the longest-living insects on earth. But queen termites have them beat: A colony's queen can live as long as 50 years.

16. THEY HAVE FIVE EYES.

Chrissy Wainwright, Flickr // CC BY-NC 2.0

An adult cicada is easily identified by the opaque pair of compound, usually crimson, eyes bubbling out from the sides of its head. But this isn’t the only set of eyes the creature owns. It also possesses a cluster of three smaller eyes hiding in plain sight on the top of its forehead. These eyes are called ocelli and are much simpler than its more prominent pair.

17. EVERY 221 YEARS, 13-YEAR AND 17-YEAR CICADAS CO-EMERGE.

The cycles of 17-year and 13-year cicada broods in the same region rarely coincide, which may be an evolutionary tactic to keep them from interbreeding. But you can mark your calendars now: the next co-emergence event is set to take place in Missouri in 2219.

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Scientific Reports, Fernando Ramirez Rozzi
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Stones, Bones, and Wrecks
Humans Might Have Practiced Brain Surgery on Cows 5000 Years Ago
Scientific Reports, Fernando Ramirez Rozzi
Scientific Reports, Fernando Ramirez Rozzi

In the 1970s, archaeologists discovered a site in France containing hundreds of cow skeletons dating back 5000 to 5400 years. The sheer number wasn't surprising—human agriculture in that part of the world was booming by 3000 BCE. What perplexed scientists was something uncovered there a few decades later: a cow skull bearing a thoughtfully drilled hole. Now, a team of researchers has released evidence that suggests the hole is an early example of animal brain surgery.

Fernando Ramírez Rozzi, a paleontologist with the French National Center for Scientific Research, and Alain Froment, an anthropologist at the Museum of Mankind in Paris, published their findings in the journal Nature Scientific Reports. After comparing the opening to the holes chiseled into the skulls of humans from the same era, they found the bones bore some striking similarities. They didn't show any signs of fracturing from blunt force trauma; rather, the hole in the cow skull, like those in the human skulls, seemed to have been carved out carefully using a tool made for exactly that purpose. That suggests that the hole is evidence of the earliest known veterinary surgery performed by humans.

Trepanation, or the practice of boring holes into human skulls, is one of the oldest forms of surgery. Experts are still unsure why ancient humans did this, but the level of care that went into the procedures suggests that the surgery was likely used to treat sick patients while they were still alive. Why a person would perform this same surgery on a cow, however, is harder to explain.

The authors present a few theories, the first being that these ancient brain surgeons were treating a sick cow the same way they might treat a sick human. If a cow was suffering from a neural disease like epilepsy, perhaps they though that cutting a hole in its head would relieve whatever was agitating the brain. The cow would have needed to be pretty special to warrant such an effort when there were hundreds of healthy cows living on the same plot of land, as evidenced by the skeletons it was found with.

Another possible explanation was that whoever operated on the cow did so as practice to prepare them for drilling into the heads of live humans one day. "Cranial surgery requires great manual dexterity and a complete knowledge of the anatomy of the brain and vessel distribution," the authors write in the study. "It is possible that the mastery of techniques in cranial surgery shown in the Mesolithic and Neolithic periods was acquired through experimentation on animals."

Either way, the bovine patient didn't live to see the results of the procedure: The bone around the hole hadn't healed at all, which suggests the cow either died during surgery or wasn't alive to begin with.

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Animals
15 Incredible Facts About Pigeons
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Though they're often described as "rats with wings" (a phrase popularized by the movie Stardust Memories), pigeons are actually pretty cool. From homing instincts to misleading rump feathers, here are 15 things you might not know about these avian adventurers.

1. THEY MIGHT BE THE FIRST DOMESTICATED BIRD.

The common city pigeon (Columba livia), also known as the rock pigeon, might be the first bird humankind ever domesticated. You can see them in art dating back as far as 4500 BCE in modern Iraq, and they've been a valuable source of food for thousands of years.

2. THEY WON OVER CHARLES DARWIN—AND NIKOLA TESLA.

Pigeon-breeding was a common hobby in Victorian England for everyone from well-off businessmen to average Joes, leading to some fantastically weird birds. Few hobbyists had more enthusiasm for the breeding process than Charles Darwin, who owned a diverse flock, joined London pigeon clubs, and hobnobbed with famous breeders. Darwin's passion for the birds influenced his 1868 book The Variation of Animals and Plants Under Domestication, which has not one but two chapters about pigeons (dogs and cats share a single chapter).

Nikola Tesla was another great mind who enjoyed pigeons. He used to care for injured wild pigeons in his New York City hotel room. Hands down, Tesla's favorite was a white female—about whom he once said, "I loved that pigeon, I loved her as a man loves a woman and she loved me. When she was ill, I knew and understood; she came to my room and I stayed beside her for days. I nursed her back to health. That pigeon was the joy of my life. If she needed me, nothing else mattered. As long as I had her, there was a purpose in my life." Reportedly, he was inconsolable after she died.

3. THEY UNDERSTAND SPACE AND TIME.

In a 2017 Current Biology study, researchers showed captive pigeons a series of digital lines on a computer screen for either two or eight seconds. Some lines were short, measuring about 2.3 inches across; others were four times longer. The pigeons were trained to evaluate either the length of the line or how long it was displayed. They found that the more time a line was displayed, the longer in length the pigeon judged it to be. The reverse was true too: If the pigeons encountered a longer line, they thought it existed in time for a greater duration. Pigeons, the scientists concluded, understand the concepts of both time and space; the researchers noted "similar results have been found with humans and other primates."

It's thought that humans process those concepts with a brain region called the parietal cortex; pigeon brains lack that cortex, so they must have a different way of judging space and time.

4. THEY CAN FIND THEIR WAY BACK TO THE NEST FROM 1300 MILES AWAY.

A pigeon flying in front of trees.
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The birds can do this even if they've been transported in isolation—with no visual, olfactory, or magnetic clues—while scientists rotate their cages so they don't know what direction they're traveling in. How they do this is a mystery, but people have been exploiting the pigeon's navigational skills since at least 3000 BCE, when ancient peoples would set caged pigeons free and follow them to nearby land.

Their navigational skills also make pigeons great long-distance messengers. Sports fans in ancient Greece are said to have used trained pigeons to carry the results of the Ancient Olympics. Further east, Genghis Khan stayed in touch with his allies and enemies alike through a pigeon-based postal network.

5. THEY SAVED THOUSANDS OF HUMAN LIVES DURING WORLD WARS I AND II.

Pigeons' homing talents continued to shape history during the 20th century. In both World Wars, rival nations had huge flocks of pigeon messengers. (America alone had 200,000 at its disposal in WWII.) By delivering critical updates, the avians saved thousands of human lives. One racing bird named Cher Ami completed a mission that led to the rescue of 194 stranded U.S. soldiers on October 4, 1918.

6. TWO PIGEONS ALMOST DISTRACTED FROM THE DISCOVERY OF EVIDENCE OF THE BIG BANG.

In 1964, scientists in Holmdel, New Jersey, heard hissing noises from their antenna that would later prove to be signals from the Big Bang. But when they first heard the sound, they thought it might be, among other things, the poop of two pigeons that were living in the antenna. "We took the pigeons, put them in a box, and mailed them as far away as we could in the company mail to a guy who fancied pigeons," one of the scientists later recalled. "He looked at them and said these are junk pigeons and let them go and before long they were right back." But the scientists were able to clean out the antenna and determine that they had not been the cause of the noise. The trap used to catch the birds (before they had to later be, uh, permanently removed) is on view at the Smithsonian Air & Space Museum.

7. YOU CAN TRAIN THEM TO BE ART SNOBS …

Japanese psychologist Shigeru Watanabe and two colleagues earned an Ig Nobel Prize in 1995 for training pigeons, in a lab setting, to recognize the paintings of Claude Monet and Pablo Picasso and to distinguish between the painters. The pigeons were even able to use their knowledge of impressionism and cubism to identify paintings of other artists in those movements. Later, Watanabe taught other pigeons to distinguish watercolor images from pastels. And in a 2009 experiment, captive pigeons he'd borrowed were shown almost two dozen paintings made by students at a Tokyo elementary school, and were taught which ones were considered "good" and which ones were considered "bad." He then presented them with 10 new paintings and the avian critics managed to correctly guess which ones had earned bad grades from the school's teacher and a panel of adults. Watanabe's findings indicate that wild pigeons naturally categorize things on the basis of color, texture, and general appearance.

8. … AND TO DISTINGUISH WRITTEN WORDS.

In a 2016 study, scientists showed that pigeons can differentiate between strings of letters and actual words. Four of the birds built up a vocabulary of between 26 and 58 written English words, and though the birds couldn't actually read them, they could identify visual patterns and therefore tell them apart. The birds could even identify words they hadn't seen before.

9. FLUFFY PIGEON FEET MIGHT ACTUALLY BE PARTIAL WINGS.

A white pigeon with curly feathers and fluffy feet.
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A few pigeon breeds have fuzzy legs—which hobbyists call "muffs"—rather than scaly ones. According to a 2016 study, the DNA of these fluffy-footed pigeons leads their hind legs to take on some forelimb characteristics, making muffed pigeon legs look distinctly wing-like; they're also big-boned. Not only do they have feathers, but the hindlimbs are somewhat big-boned, too. According to biologist Mike Shapiro, who led the study, "pigeons' fancy feathered feet are partially wings."

10. SOME PIGEONS DISTRACT FALCONS WITH WHITE RUMP FEATHERS.

In a life-or-death situation, a pigeon's survival could depend upon its color pattern: Research has shown that wild falcons rarely go after pigeons that have a white patch of feathers just above the tail, and when the predators do target these birds, the attacks are rarely successful.

To figure out why this is, Ph.D. student Alberto Palleroni and a team tagged 5235 pigeons in the vicinity of Davis, California. Then, they monitored 1485 falcon-on-pigeon attacks over a seven-year span. The researchers found that although white-rumped pigeons comprised 20 to 25 percent of the area's pigeon population, they represented less than 2 percent of all the observed pigeons that were killed by falcons; the vast majority of the victims had blue rumps. Palleroni and his team rounded up 756 white- and blue-rumped pigeons and swapped their rump feathers by clipping and pasting white feathers on blue rumps, and vice versa. The falcons had a much easier time spotting and catching the newly blue-rumped pigeons, while the pigeons that received the white feathers saw predation rates plummet.

Close observation revealed that the white patches distract birds of prey. In the wild, falcons dive-bomb other winged animals from above at high speeds. Some pigeons respond by rolling away in midair, and on a spiraling bird, white rump feathers can be eye-catching, which means that a patch of them may divert a hungry raptor's focus long enough to make the carnivore miscalculate and zip right past its intended victim.

11. DODOS WERE RELATED TO TODAY'S PIGEONS.

Two blue and green Nicobar pigeons.
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Though most of this list focuses on the rock pigeon, there are 308 living species of pigeons and doves. Together, they make up an order of birds known as the columbiformes. The extinct dodo belonged to this group as well.

Flightless and (somewhat) docile, dodos once inhabited Mauritius, an island near Madagascar. The species had no natural predators, but when human sailors arrived with rats, dogs, cats, and pigs, it began to die out, and before the 17th century came to a close, the dodo had vanished altogether. DNA testing has confirmed that pigeons are closely related to the dodo, and the vibrant Nicobar pigeon (above) is its nearest genetic relative. A multi-colored bird with iridescent feathers, this near-threatened creature is found on small islands in the South Pacific and off Asia. Unlike the dodo, it can fly.

12. AT ONE POINT, MORE THAN ONE-QUARTER OF ALL THE BIRDS LIVING IN THE U.S. MAY HAVE BEEN PASSENGER PIGEONS.

Wild/feral rock pigeons reside in all 50 states, which makes it easy to forget that they're invasive birds. Originally native to Eurasia and northern Africa, the species was (most likely) introduced to North America by French settlers in 1606. At the time, a different kind of columbiform—this one indigenous—was already thriving there: the passenger pigeon (Ectopistes migratorius). As many as 5 billion of them were living in America when England, Spain, and France first started colonizing, and they may have once represented anywhere from 25 to 40 percent of the total U.S. bird population. But by the early 20th century, they had become a rare sight, thanks to overhunting, habitat loss, and a possible genetic diversity issue. The last known passenger pigeon—a captive female named Martha—died on September 1, 1914.

13. THEY'RE REALLY GOOD AT MULTITASKING.

According to one study, they're more efficient multitaskers than people are. Scientists at Ruhr-Universitat Bochum put together a test group of 15 humans and 12 pigeons and trained all of them to complete two simple jobs (like pressing a keyboard once a light bulb came on). They were also put in situations wherein they'd need to stop working on one job and switch over to another. In some trials, the participants had to make the change immediately. During these test runs, humans and pigeons switched between jobs at the same speed.

But in other trials, the test subjects were allowed to complete one assignment and then had to wait 300 milliseconds before moving on to the next job. Interestingly, in these runs, the pigeons were quicker to get started on that second task after the period ended. In the avian brain, nerve cells are more densely packed, which might enable our feathered friends to process information faster than we can under the right circumstances.

14. PIGEONS PRODUCE FAKE "MILK."

Only mammals produce genuine milk, but pigeons and doves (along with some other species of birds) feed their young with something similar—a whitish liquid filled with nutrients, fats, antioxidants, and healthy proteins called "crop milk." Both male and female pigeons create the milk in the crop, a section of the esophagus designed to store food temporarily. As is the case with mammal milk, the creation of crop milk is regulated by the hormone prolactin. Newly-hatched pigeons drink crop milk until they're weaned off it after four weeks or so. (And if you've ever asked yourself, "Where are all the baby pigeons?" we have the answer for you right here.)

15. ONE STUDY SUGGESTS THAT, GIVEN THE RIGHT CONDITIONS, THEY'RE AS GOOD AT IDENTIFYING CANCER AS DOCTORS.

We've already established that pigeons are excellent at differentiating between artists and words, but a 2015 study revealed they can also distinguish between malignant and benign growths in the right conditions. Researchers at University of California Davis Medical Center put 16 pigeons in a room with magnified biopsies of potential breast cancers. If the pigeons correctly identified them as either benign or malignant, they got a treat, According to Scientific American.

"Once trained, the pigeons' average diagnostic accuracy reached an impressive 85 percent. But when a "flock sourcing" approach was taken, in which the most common answer among all subjects was used, group accuracy climbed to a staggering 99 percent, or what would be expected from a pathologist. The pigeons were also able to apply their knowledge to novel images, showing the findings weren't simply a result of rote memorization."

Mammograms proved to be more of a challenge, however; the birds could memorize signs of cancer in the images they were trained on but could not identify the signs in new images.

No matter how impressive their results, "I don't anticipate that pigeons, no matter how good they become at pathology or radiology, will be playing a role in actual patient care—certainly for the foreseeable future," study co-author Richard M. Levenson told Scientific American. "There are just too many regulatory barriers—at least in the West."

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