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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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Animals
14 Fascinating Facts About Foxes
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Foxes live on every continent except Antarctica and thrive in cities, towns, and rural settings. But despite being all around us, they’re a bit of a mystery. Here’s more about this elusive animal.

1. Foxes Are Solitary.

Foxes are part of the Canidae family, which means they’re related to wolves, jackals, and dogs. They’re medium-sized, between 7 and 15 pounds, with pointy faces, lithe frames, and bushy tails. But unlike their relatives, foxes are not pack animals. When raising their young, they live in small families—called a “leash of foxes” or a “skulk of foxes”—in underground burrows. Otherwise, they hunt and sleep alone.

2. Foxes Have A Lot In Common With Cats.

Like the cat, the fox is most active after the sun goes down. In fact, it has vertically oriented pupils that allow it to see in dim light. It even hunts in a similar manner to a cat, by stalking and pouncing on its prey.

And that’s just the beginning of the similarities. Like the cat, the fox has sensitive whiskers and spines on its tongue. It walks on its toes, which accounts for its elegant, cat-like tread. And—get this—many foxes have retractable claws that allow them to climb rooftops or trees. Some foxes even sleep in trees—just like cats.

3. The Red Fox Is The Most Common Fox.

The red fox has the widest geographical range of any animal in the order Carnivora. While its natural habitat is a mixed landscape of scrub and woodland, its flexible diet allows it to adapt to many environments. As a result, its range is the entire Northern Hemisphere, from the Arctic Circle to North Africa to Central America to the Asiatic steppes. It’s also in Australia, where it’s considered an invasive species.

4. Foxes Use The Earth’s Magnetic Field.

Like a guided missile, the fox harnesses the earth’s magnetic field to hunt. Other animals, like birds, sharks, and turtles, have this “magnetic sense,” but the fox is the first one we’ve discovered that uses it to catch prey.

According to New Scientist, the fox can see the earth’s magnetic field as a “ring of shadow” on its eyes that darkens as it heads towards magnetic north. When the shadow and the sound the prey is making line up, it’s time to pounce. Here’s the fox in action:

5. Foxes Are Good Parents.

Foxes reproduce once a year. Litters range from one to 11 pups (the average is six), which are born blind and don’t open their eyes until nine days after birth. During that time, they stay with the vixen (female) in the den while the dog (male) brings them food. They live with their parents until they're seven months old. The vixen protects her pups with surprising loyalty. Recently, a fox pup was caught in a trap in England for two weeks, but survived because its mother brought it food every day.

6. The Smallest Fox Weighs Under 3 Pounds.

Roughly the size of a kitten, the fennec fox has elongated ears and a creamy coat. It lives in the Sahara Desert, where it sleeps during the day to protect it from the searing heat. Its ears not only allow it to hear prey, they also radiate body heat, which keeps the fox cool. Its paws are covered with fur so that the fox can walk on hot sand, like it’s wearing snowshoes.

7. Foxes Are Playful.

Foxes are known to be friendly and curious. They play among themselves as well as with other animals like cats and dogs. They love balls, which they frequently steal from golf courses.

Although foxes are wild animals, their relationship with humans goes way back. In 2011, researchers opened a grave in a 16,500-year-old cemetery in Jordan to find the remains of a man and his pet fox. This was 4000 years before the first-known human and dog were buried together.

8. You Can Buy A Pet Fox.

In the 1960s, a Soviet geneticist named Dmitry Belyaev bred thousands of foxes before achieving a domesticated fox. Unlike a tame fox, which has learned to tolerate humans, a domesticated fox is docile toward people from birth. Today, you can buy a pet fox for $9000, according to Fast Company. They’re reportedly curious and sweet-tempered, although inclined to dig in your furniture.

9. Arctic Foxes Don’t Shiver Until –70 degrees Celsius.

The arctic fox, which lives in the northernmost areas of the hemisphere, can handle cold better than most animals on earth. It doesn’t even get cold until –70 degrees Celsius. Its white coat also camouflages it against predators. As the seasons change, the coat changes too, turning brown or gray so the fox can blend in with the rocks and dirt of the tundra.

10. Fox Hunting Continues To Be Controversial.

Perhaps because of the fox’s ability to decimate a chicken coop, in the 16th century, fox hunting became a popular activity in Britain. In the 19th century, the upper classes turned fox hunting into a formalized sport where a pack of hounds and men on horseback chase a fox until it is killed. Today, whether to ban fox hunting continues to be a controversial subject in the UK. Currently, fox hunting with dogs is not allowed.

11. The Fox Appears Throughout Folklore.

Examples include: the nine-tail fox from various Asian cultures; the Reynard tales from medieval Europe; the sly trickster fox from Native American lore; and Aesop’s “The Fox and the Crow.” The Finnish believed a fox made the Northern Lights by running in the snow so that its tail swept sparks into the sky. From this, we get the phrase “fox fires.”

12. Bat-eared Foxes Listen For Insects.

The bat-eared fox is aptly named, not just because of its 5-inch ears, but because of what it uses those ears for—like the bat, it listens for insects. On a typical night, the fox walks along the African Savannah, listening, until it hears the scuttle of prey. Although the fox eats a variety of insects and lizards, most of its diet is made up of termites. In fact, the bat-eared fox often makes its home in termite mounds, which it usually cleans out of inhabitants before moving in.

13. Darwin Discovered A Fox Species.

During his voyage on the Beagle, Charles Darwin collected a fox that today is unimaginatively called Darwin’s Fox. This small gray fox is critically endangered and lives in just two spots in the world: One population is on Island of Chiloé in Chile, and the second is in a Chilean national park. The fox’s greatest threats are unleashed domestic dogs that carry diseases like rabies.

14. Foxes Sound Like This.

Foxes make 40 different sounds, some of which you can listen to here. The most startling is the scream:

Pleasant dreams!

All images courtesy of iStock unless otherwise stated.

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Big Questions
Why Do Cats Love Scratching Furniture?
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Allergy suffering aside, cat ownership has proven health benefits. A feline friend can aid in the grieving process, reduce anxiety, and offer companionship.

The con in the cat column? They have no reservations about turning your furniture into shredded pleather. No matter how expensive your living room set, these furry troublemakers will treat it with the respect accorded to a college futon. Do cats do this out of some kind of spite? Are they conspiring with Raymour & Flanigan to get you to keep updating home decor?

Neither. According to cat behaviorists, cats gravitate toward scratching furniture mostly because that love seat is in a really conspicuous area [PDF]. As a result, cats want to send a message to any other animal that may happen by: namely, that this plush seating belongs to the cat who marked it. Scratching provides both visual evidence (claw marks) as well as a scent marker. Cat paws have scent glands that can leave smells that are detectable to other cats and animals.

But it’s not just territorial: Cats also scratch to remove sloughed-off nail tips, allowing fresh nail growth to occur. And they can work out their knotted back muscles—cramped from sleeping 16 hours a day, no doubt—by kneading the soft foam of a sectional.

If you want to dissuade your cat from such behavior, purchasing a scratching post is a good start. Make sure it’s non-carpeted—their nails can get caught on the fibers—and tall enough to allow for a good stretch. Most importantly, put it near furniture so cats can mark their hangout in high-traffic areas. A good post might be a little more expensive, but will likely result in fewer trips to Ethan Allen.

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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