Big Noise, Little Bug: The Cicadas are Coming!

April 11, 2013

As the East Coast prepares for the cicadas invasion due sometime in the next month, we dig in our vault to find some more information about this tiny, yet noisy bug. The following article is from Uncle John’s Fully Loaded Bathroom Reader.


Cicadas are the vuvuzelas of the insect world. (What are vuvuzelas? Those loud horns that nearly caused soccer fans’ brains to explode during the 2010 World Cup.) Vuvuzelas reach a decibel level of 60, but cicadas? These little bugs can reach a decibel level twice that loud.That’s as loud as a rock concert or a jet engine.


CicadasCicadas are bizarre, especially the “periodical cicadas” that live only in eastern North America. What’s odd about them is that they’re on either a 13- or a 17-year cycle. They emerge in “broods” of so many bugs it’s like some shock-and-awe insect invasion, make a lot of deafening noise, mate, lay eggs, and, within just a few weeks, die. Then they disappear again for an another exact number—13 or 17—of years. Entomologists are still trying to figure out what makes periodical cicadas tick. The main problem: those long cycles. It’s difficult for scientists to study an insect that shows up only once or twice in their careers. The name cicada is Latin for “tree cricket,” which is actually incorrect: cicadas are not crickets. And though one species is commonly called the “17-year locust,” they’re not locusts, either. Locusts are “eating machines” that can devour entire crops. Cicadas don’t eat leaves; they’re sapsuckers, like their closest relatives leafhoppers and spittlebugs. Cicadas have also been called “jar flies,” “harvest flies,” and “dust flies,” but their Australian nickname, “galang-galang,” which echoes the racket they make, may be the most fitting.


Periodical cicadas wait a long time for their 15 minutes of fame, spending the bulk of their lives hidden underground. Each cicada begins as one of about 600 eggs embedded into V-shaped slits that a female cicada makes into new growth at the tips of tree twigs. The female makes the grooves using the sharp proboscis (feeding tube) under her chin. (It’s the same tool cicadas stick into plant stems to suck out the sap, their main food.) The egg-laying process can cause the twig tips to turn brown but doesn’t harm adult trees. Saplings are a different story—too many cicada eggs can kill young trees. When cicada eggs hatch it’s kind of like a family riding the Drop Zone at an amusement park. After 6-10 weeks, baby cicadas emerge as “nymphs.” They look like the adults they’re going to become, except they’re smaller (about the size of an ant) and they can’t fly. That’s why a nymph’s intro to the cold cruel world is a sudden plummet from the tree to the ground below.


After crash landing, cicada nymphs burrow into the ground, digging down 1 to 9 feet where they settle in next to a juicy root. They leach off the root for their entire 13 (or 17) years underground. During that time, periodical cicadas don’t cocoon, they molt. Over and over. They eat, their bodies grow, and when they grow too big for their skin: pop! Their exoskeletons burst open, and a slightly bigger and more mature cicada emerges. This happens seven times before they become adults. In the spring of their 13th (or 17th) years, the cicada’s biological alarm clock sounds. As for the time of year, many experts think soil temperature triggers cicada nymphs to emerge. When it reaches a constant minimum of 64° F or 18° C, cicadas burrow to the surface for the first time since they dropped from the tree at hatching. If the ground is wet, “mud chimneys” appear on the ground as the nymphs tunnel upward. If the ground is dry, the emerging cicadas leave it pockmarked with round holes. As soon as they reach the surface, cicadas scurry off to attach themselves to a plant (trees are particular favorites) for one final molt—this one will make them full-fledged adults. The skin down the middle of their backs splits open and the adult cicadas climb out, stretch their wings and wait for them to dry, and then fly off, leaving their empty skins hanging on the tree. (These look so much like live cicadas that they act as decoys for predators.) After about six days of hiding in leaves while their new outer shells harden, it’s time to start singing.


Cicadas have a pair of stiff hollow membranes called tymbals located on the sides of their abdomens just behind their wings. When they flex the large muscles attached to the tymbals, the tymbals buckle inward. This buckling makes a vibrating click that’s amplified by an air chamber in the insect’s abdomen. As the muscle relaxes, the tymbal sounds again. Repeating this action quickly and repeatedly can sound like anything from a motorbike to the vuvuzela-infested soccer stadium. The specific sound depends on the species of cicada. “Choruses” of male cicadas congregate in high tree branches, hoping to get lucky with a receptive female. The louder a cicada sings, the better its chance of attracting a mate. There are a lot of competitors: As many as 1.5 million cicadas can emerge in a single acre, but many of those are females whose biological clocks are ticking away the last few weeks of their lives. Females don’t call. When they hear the singer of their dreams, they signal their interest with an alluring flick of their wings.


Every species has its own song. Differences in tymbal size between species create different tones, which combine with the speed of clicking and the length of the call to make up each species’ distinctive call. And like moms and elementary school teachers, cicadas have “selective hearing.” Each cicada species clearly hears its call while remaining virtually deaf to the calls of other species. Result: A dozen cicada species could be buzzing their tymbals off in a single forest, and each cicada would be able to pick out the call of its own species above the din. But cicadas are often fooled by machines: Because they can only hear one narrow range of frequency, odds are good that some undertone or overtone of machine noise will match it. The sounds of lawnmowers, weed whackers, and other chugging two-cylinder machinery can sound quite attractive to a female cicada. (“He’s playing our song.”)


Although cicadas are Johnny One-Note when it comes to pitch, they can modulate it a bit. Once a male attracts a female with its “calling song,” it switches to a softer, more romantic “courtship song.” Cicadas also have a “distress call” that they use when caught by a predator: They click erratically like a tiny engine revving and stopping as it runs out of gas. How loud a chorus gets depends on the concentration of cicadas in a given area. The noise can be as loud as 88–120 decibels (from a blender to a jet engine). Brood XIX, a 13-year brood also known as the Great Southern Brood, was scheduled to emerge in May 2011. Spurred on by horror movielike headlines, people from Virginia to Oklahoma started to worry about whether the “deafening” insects that were about to cover their trees could actually make them deaf. Biology professor Johannes Schul offered reassurance: “It won’t damage anyone’s hearing, and won’t have any adverse health effects aside from stressing a few people out.” Don Griffith, a 70-year-old retired Georgia school superintendent experienced that stress first-hand during Brood XIX: “It sounds like a million little wooden boxes rattling with a million marbles. They’ll land on your collar. They’ll land on your head. It causes you to think maybe you’re at war with them.” Despite Griffith’s periodical cicada paranoia, those masses of insects really are fighting for something: survival.


Many animal species hang out in herds, schools, or flocks. Why? Because there’s safety in numbers. Cicadas take this to an absurd length, coming out en masse, but not every year. Scientists theorize that if broods emerged every year, predator populations would be so well fed they’d increase. Every year, more and more predators would be standing around with their tongues hanging out, waiting for the cicadas to show up. Cicadas survive by going into hiding for so long that few individual predators live long enough to see the tasty bugs more than once in their lives. Brood X, also known as the Great Eastern Brood, is on a 17-year cycle and last showed up in 2004. This brood’s turf stretches from the Chesapeake Bay to the edge of the Great Plains. Scientists say the 2004 emergence was probably “the largest insect outbreak on Earth.” How large? It produced an estimated one trillion cicadas. Scientists call this natural strategy “predator satiation.” Predators that happen to be around gorged themselves until they can’t eat another insect. After a few days, predators get sick of eating cicadas and leave them alone. “If you walked outside and found the world swarming with Hershey Kisses, eventually you’d get so sick of Hershey Kisses that you’d never ever want to eat them again,” said biologist and editor-in-chief of American Entomologist, Gene Kritsky. Most cicadas survive and go on to sing, mate, and lay eggs (if they’re female) for about two weeks.


What eats cicadas? Just about any animal that isn’t a vegetarian: birds, foxes, wolves, dogs, cats, opossums, pigs, squirrels, frogs, lizards, fish, other insects…and people. Since pre-history humans have been eating cicadas either fresh off the tree, stir fried, deepfried, or roasted over fires. “They’re high in protein, low in fat, no carbs,” Kritsky told National Geographic News during the 2004 outbreak. “They’re actually quite nutritious.” (Female cicadas, by the way, have a reputation for being meatier and more succulent.) If being eaten after 13 or 17 years stuck underground seems unfair, it may be preferable to two other fates. First, the cicada’s most virulent enemy, Massospora cicadina. It’s a fungal disease to which these insects are particularly susceptible. Spores can infect cicadas when they’re still underground, resulting in malformed bodies and wings. Cicadas can also be infected as they emerge. If that happens, the infected individual’s abdomen swells up and breaks off, exposing a white, chalky mass of spores. This sterilizes the cicada but does not kill it; infected cicadas pass the fungus on to others as they try to mate, infecting them, too.


Frankly, if we were cicadas, our least preferred predator would be the second one: the giant (2″ long) cicada killer wasp (Sphecius speciosis). Instead of administering a quick death, the cicada killer queen swoops down and lands on an unsuspecting cicada. She administers a paralyzing sting, straddles the cicada, grasps it with her legs, and flies it to her underground nest, where she rolls the unlucky cicada into a cell, and lays an egg on it (if the egg is female, the wasp may provide two or three cicadas). Finally, she seals the cell to create a sort of climate-controlled incubator. Two to three days later, the egg hatches and the larva emerges to discover a juicy birthday breakfast. What makes this such a horrible death is that the cicada killer’s paralyzing sting keeps the cicada alive so that the larvae can dine on living flesh for 10-14 days, until only the cicada’s outer shell remains.


So, how does our cicada story end? With the entire brood dying off in a peaceful mass death like some insect Jonestown, leaving no survivors. (And predators wondering if that all-you-can-eat buffet was just some crazy dream.) From start to finish—from the time the first cicada nymph digs tunnels up until the final die-off—a brood’s above-ground life lasts about 4–6 weeks. “They come and go so quickly,” said University of Georgia entomologist Dr. Nancy C. Hinkle. But, at least we know one thing. “They’ll be back…”


• There are at least 2,500 species of cicadas. Africa has about 450, Australia 200, North America at least 105, and the British Isles 1.

• Some tropical species grow to as long as 6 inches. Some desert species can sweat to cool themselves. (Very rare among insects.) Some cold-weather cicadas can raise their body temperatures at will by more than 70°. (Very rare among not just insects, but most living things.)

• With two large red compound eyes on the sides of the head and three small ocelli (simple eyes) in a triangle on the front of the head, periodical cicadas have excellent vision.

• In India, one cicada species is called the “World Cup Cicada.” It emerges in synch with the FIFA soccer tournament, held every four years from mid-June to mid-July. (Who needs vuvuzelas?)

• In China, cicada “flowers” (shells left behind after molting) are collected and used in traditional medicine. They’re a common ingredient in formulas used to cure fevers, sore throats, blurry vision, spasms, and skin irritations.

• Because of its extended life cycle, the 17-year cicada is the world’s longest-living insect.

• Most periodical cicadas have red eyes, but a small percentage have blue or white eyes. During the 2011 emergence of Brood XIX, which covers 15 states, word spread that researchers were paying $3,000 for specimens of blue-eyed cicadas, but according to Vanderbilt University biology professor Patrick Abbot, that was “a recurrent myth.”

• Scientists say its tough to understand the purpose of an insect as bizarre as the periodical cicada, but they do play positive roles: They are a food source for a wide variety of species. Their tunnels aerate the soil and aid tree growth. The twig damage caused by female egg-laying “prunes” trees and stimulates future growth.

• Periodical cicada nymphs that burrowed underground during the Clinton Administration will still be emerging until the year 2017.

• Because of the clearing of hardwood forests, several broods of periodical cicadas are now extinct.

• In 2004 University of Maryland grad-student Jenna Jadin put together a brochure called “Cicada-Licious: Cooking and Enjoying Periodical Cicada.” Recipes include El Chirper Tacos, Cicada Dumplings, Cica-Delicious Pizza, Banana Cicada Bread, and Cicada-Rhubarb Pie. (The brochure can be found online.)