As dusk falls on or about the 25th of May, suburban Chicago will unavoidably become part of a wriggly, crunchy, distinctly American phenomenon that has been recognized since Colonial times as among the deepest mysteries in nature`s realm.
For the last 17 years, the insects known as periodical cicadas have been biding their time underground by the millions, preparing for a grand night-The Great Emergence-that precedes their brief shot at sex and a month in the sun. This year`s sibilant class of 17-year cicadas (pronounced si-Kay-dahs)
will show up like gangbusters, predicts the University of Chicago`s Monte Lloyd, a professor of ecology and evolution who has been studying emergences around the nation since 1956, enjoys eating cicadas and is recognized as the senior biologist of these unique Methuselahs.
”You`ll probably find some cicadas in Chicago, but the small numbers will quickly succumb to common predators like birds,” Lloyd says. ”In the suburbs, however, the story will be entirely different. You`re going to find that you`re up to your ankles in these things in street gutters.”
The Chicago-area cicadas-which are classed by scientists as Brood XIII in the national ranking system-have not seen the light of day since the summer of the Senate Watergate hearings in 1973, when, as tiny helpless antlike nymphs, they wriggled free from birth nests carved by their mothers in the twigs of trees, tumbled to the ground and burrowed into the protective soil.
About a foot down, the white nymphs hollowed out football-shaped growing chambers in the dark and sank their stylet-beaks into the tender roots of grasses and trees. They have nursed silently ever since on watery xylem sap, seldom moving as seasons drifted by and governments rose and fell except to enlarge their dens as they slowly grew in length to an inch and a half. If Lloyd has figured them out correctly, it has taken the male cicadas until this year to grow big enough to make the proper sounds at the proper frequencies to attract the proper mates and produce more periodical cicadas. ”The story,”
he observes with some understatement, ”is more complicated than it might first appear.”
This month, however, after roughly 204 months, some secret but awesomely urgent hormonal signal will sweep across the northern Illinois landscape, all around Chicago from the southern suburbs to the Wisconsin border. After a warm rain, the solitary cicadas will respond in a perfect synchrony akin to the crack precision of the old Count Basie Band and begin to emerge together in the astonishingly tight span of just two hours.
Peppering suburban yards, woodlands, orchards, farms-and, particularly, undisturbed graveyards-with countless exit holes the size of quarters, cicada nymphs clad in hard black outer skins will scramble for the nearest upright objects, usually trees. Clinging desperately, they will split their skins down the middle of their backs, emerging as large, gossamer-winged adults and discarding the husks like broken armor. Soft and white at first, the insects will become tougher and darker as they dry, their stout bodies trimmed in orange. Emblazoned on their wings, the orange eerily takes the shape of the letter ”W.”
”People think the `W` means war,” Lloyd says. ”There`s a lot of folklore about these bugs. I was in southern Illinois years ago having a beer after a day of gathering cicadas. A woman asked me about the war thing. She said, `I haven`t found many with ”P`s” on their wings.` I told her I hadn`t either.”
The blunt-headed cicadas will bask in the sun, shifting positions to adjust their temperatures. They will stare out at the world with fiery red eyes, emanating stolid arrogance, that, it must be said, serves to mask a profound stupidity. The females of the species are voiceless and almost unbelievably coy. To attract them, the males make a clicking noise. They produce their sounds with hard plates, called tymbals, on either side of the thorax that buckle in and out-in precise rhythms-by lightning-fast muscular action, like squeezing a beer can. As soon as possible, the males will congregate as huge singing ensembles in trees and bushes, and their vibrating drums will fill the daytime spring air with the unearthly din of rasping, burring, coughing, crescendoing jackhammer choruses performed by the world`s loudest insects-their version of music strictly for lovers.
The life cycle of the 17-year cicada is the longest known of any insect, but when the bugs finally do emerge, they`ve got only a month to think sexy thoughts, sing lusty songs, mate like crazy, lay their eggs and die. So by the Fourth of July the Chicago area`s periodical cicadas will be history, although we`ll still be sweeping up their cast skins and corpses by the millions.
But then . . . quietly and unnoticed in the sultry heat of August . . . in numbers far too great to count, the minuscule progeny will venture out of their twig-nests, fall to the ground, scramble madly about in search of a crack in the dirt, turn tail-up and dig in for another long subterranean hiatus.
Unraveling the mysteries of how such unique biological communities survive has long happily occupied population ecologist Lloyd, 62, who comes across as a very pleasant man. Large bugs such as cicadas, aphids and leafhoppers belong to the order Homoptera, of which at least 30,000 species are known throughout the world. However, for some reason, perhaps a biological accident eons ago that set their slow clocks in motion, periodical cicadas are found only in the eastern part of North America. To Lloyd, they`re
”magnificent animals,” and after 34 years, he has grown rather fond of them. ”It`s too bad that people get so terrified of cicadas,” he says. ”The bugs may accidentally get tangled in your hair, but they won`t bite. I`ve handled thousands and never gotten bitten, even when I deserved it.
”Cicadas are attracted by noise, but they`re not good pitch-analyzers. So they`ll come and land on you and your lawn mower because they think you`re a super-cicada and they want to join your band. But they mean no harm. In fact, I think they`re a really good way to teach people about biology and the mechanisms of predation. Cicadas stay underground so long because they`re sucking mostly water; there`s not much nutrition in xylem. But this also serves as an adaptive strategy to flummox predators. Nobody`s going to wait around for you if you only show up every 17 years.”
When the cicadas finally do emerge, their spectacularly abundant numbers quickly satiate the predators-birds, wasps and the occasional scientist-that happen to be around to eat them, leaving millions free to perpetuate the species. Lloyd has a favorite photo that he often has published in scientific journals: It shows a cat too full to eat any more, laying fast asleep while all about, thousands of cicadas overrun a homeowner`s lawn.
These cicadas, Lloyd hastens to point out, should not be confused with the common variety known as dog-day cicadas (Tibicen), which breed in July and August and appear every year, contributing their buzzing chorus to the classic sounds of summer. These bugs look and behave differently. Unlike periodicals, dog-day cicadas are green and black, very hard to see and even harder to catch. ”They`re visual animals; they spot you as quickly as you notice them and flit away,” Lloyd notes. ”One of the great cicada biologists, R.H. Beamer, of the University of Kansas, used to hunt them with a rifle, using fine dust shot.”
Yet in their own way, annual cicadas are even more mysterious than periodical cicadas. ”They show up in relatively small numbers every year but actually are bigger bugs than periodical cicadas. To me, that means they take even longer to grow up, perhaps 20 or even 30 years. But they`re all mixed up underground-out-of-phase, not in synchrony. And the big evolution question is how did the others get to be periodical? There are about 1,500 cicada species around the world, but only the three in the U.S. have evolved this periodicity.”
Lloyd`s specialty keeps him busier than one might suppose, although the research is episodic and frenzied-he usually has only a month to find out what he wants to learn. On the average, about three out of every four years, somewhere east of the Great Plains, a synchronized brood of periodical cicadas can be found emerging. They are attuned by their genes to either a 13-year or 17-year cycle, and broods have been numbered in Roman numerals in chronological order-I through XVII for 17-year broods; XVIII through XXX for 13-year counterparts. A brood may cover several states or a mere county or two, but each has been tracked for more than a century, always adhering to a strict emergence schedule.
To complicate matters more, each brood is composed of three perfectly synchronized but distinct species, all lumped under the banner of periodical cicadas, or Magicicada (magical cicadas), as William T. Davis, a New England naturalist whimsically named them in 1925.
However, with some cicadas emerging every 17 years and others every 13 years, simple arithmetic dictates that once every 221 years, the two types will emerge in the same year. Should their ranges happen to overlap, there is no way to distinguish individuals.
Evidently, the cicadas can`t tell either. ”Nope. They don`t know who they are,” Lloyd says with a grin. When two such broods emerged in 1963 in southern Illinois and eastern Iowa, separated by 230 miles, Lloyd and his friend, the late Henry Dybas, curator of insects at the Field Museum, sped from brood to brood. They kidnapped virgin females and placed them in large cages with calling males. Random matings occurred, and young were hatched. The discovery was important because it is only during such chance co-emergences, every 221 years, that the genes of cicadas accidentally mingle-a happenstance that has led Lloyd to construct mathematical models showing why, as scientists have documented, the 13-year broods are gradually displacing the 17-year ones. Years later, Dr. JoAnn White, Lloyd`s wife and former student who shares his passion for the mysterious insects, showed that even different cicada species would interbreed if crowded into small cages where females were unable to rebuff advances from males of the wrong species.
Most people don`t know cicadas are edible, Lloyd says. In fact, most people don`t know anything about them. ”They taste,” he says, ”like a raw potato, with a touch of avocado. They`re good with Tabasco sauce.” In 1987, at Lloyd`s urging, the Cincinnati Zoo held a reception to coincide with the major emergence there and served cicadas as the main course. ”There can be more meat on the lawns of a suburban neighborhood,” Lloyd notes, ”than on a dairy cattle farm.”
He proved this in 1956 at what has become his major cicada laboratory-the Raccoon Grove forest preserve in Will County near Monee, about 33 miles south of Chicago. Joining Dybas and another colleague, the late Dwight Davis, Lloyd counted cicada emergence holes there that yielded between 1 and 2 million insects per acre. That represents a ton of cicadas, he estimates, a world-record biomass for any animal population. Average populations are about 10,000 bugs per acre, he guesses.
Ranging in color from orange to black, periodical cicadas, called ”17-year locusts” by everybody except scientists such as Lloyd, are not damaging insects. ” `Locusts` is a misnomer,” he says. ”Locusts are grasshoppers; they chew. Cicadas are bugs; they have beaks, and they suck. They`re very different animals.”
Voracious locusts may swarm in vast clouds and migrate for hundreds of miles, devouring wheat and corn. Periodical cicadas appear only in the hard forests and adjoining plains of the northeastern U.S. and don`t chew anything up. The males may migrate a bit to form their singing choruses-in fact, a male will sing only when it is stimulated by the calls of fellow choristers-but each cicada usually dies within a few hundred yards of its escape tunnel.
The only possible cicada damage occurs when females slit the tips of branches and twigs and lay their eggs. The ends of these small twigs sometimes turn brown and die (”flagging,” this is called), and cicadas can cause trouble in newly planted orchards or on unprotected new plantings of shade trees or shrubs. Lloyd advises homeowners to protect these trees and shrubs.
The locust confusion dates back to 1634 and the Cape Cod Pilgrims, who apparently were alarmed by the sudden emergence of what they imagined to be the biblical plague that tormented the ancient Egyptians. But the Pilgrims were actually spooked by Brood XIV, consisting of Magicicada septendecim, the largest American species, merely playing out its hand as periodical cicadas have been doing for 12,000 years.
The Egyptian imagery probably was heightened, Lloyd speculates, by the song of these septendecim cicadas. ”If you listen close, it seems as if they`re hissing Pha-a-a-a-a-a-roh!-with the sound dropping down at the end. We get them in the Chicago area. You can tell M. septendecim because the lower side of the abdomen is orange and they have a brown spot behind the eye. They sound like tree frogs early in the morning-a low, soft sound, not synchronized.
”We also get the smaller species called cassini (pronounced KASS-in-eye), for the American naturalist John Cassin, who described them in 1851, against the opinions of all his contemporaries. Nobody thought there could be two species that are perfectly synchronized to come out in 17 years and are out of phase in different parts of the country.
The song of cassini, as described by Lloyd: ”Tick-tick-tick-zzzzzzzzzz. Very fast. Like that. M. cassini don`t get going until about 10 in the morning. And unlike septendecim, they are in synchrony. They`ll all do it together.”
As if two periodical species weren`t enough, yet another, smaller, species, septendecula, was described in 1962 by Tom Moore and Richard Alexander at the University of Michigan, but only after the researchers devoted concentrated listening to a brood in Kentucky. They realized its song was different from the other cicadas.
”It sounds like zit-zit-zit-zit,” notes Lloyd. ”Much quieter. You really have to listen for it.” Septendecula may be found in southern Illinois in other years, but not in the Chicago region. The chorusing cicada songs are unmistakably different. In fact, trained ears can pick out the shrill call of a single cassini male from a chorus of hundreds of thousands of septendecim males. ”The converse is harder,” Lloyd says, ”because septendecim is much softer. But you can still do it.”
Why nature evolved not one but three types of periodical cicadas is the kind of knotty scientific question that can fill a career, especially when your study animals appear only periodically. Lloyd usually is out someplace digging up cicada nymphs in various stages of development so he can count them, or he`s transplanting nymphs in clusters, intentionally crowding them so that years later, he can see who wins. But the insects never have successfully been kept in the laboratory.
”They just die,” Lloyd says, the frustration evident in his voice.
”Everything I`ve tried in the lab has ended up in dismal failure. These things are so darned stupid that when you make them a big cage and build it around a tree, they`ll fly up into the mesh, sit and boil in the sun until they drop dead. They haven`t got the sense to fly a foot away to the protection of the tree. Outdoors, when it rains, vegetation protects them. But in captivity, raindrops will kill them. So put a roof over the cage if you want to keep cicadas.”
Luckily for him, cicada broods write their own history, so to speak, in the twigs of trees that bear their egg nests. The scars can be matched to a species for about a year after they depart and can provide other information for a decade. Populations can be estimated with reasonable precision.
