Festival of the Cicadas

By Craig Vetter

Brace yourself for the biggest party in 17 years.

“I do not at all know what to think of your extraordinary case of the Cicadas.”

—Charles Darwin, in a letter to Benjamin Walsh of Rock Island, Illinois, October 31, 1868

A massive subterranean invasion is about to unearth itself and engulf northern Illinois, northern Indiana along the Lake Michigan shoreline, and parts of Michigan and Wisconsin. It has lain quiet underground, growing, gathering energy since 1990, since the father of our current president was president. It is the emergence of the 17-year periodical cicada, and when the tidal upwelling of these large winged insects digs itself into the light sometime in May or June, it will be in uncountable numbers: 5 billion of them, scientists estimate—the very rough equivalent of Earth’s total human population in just a few hundred square miles. It is one of the most unique and mysterious phenomena in the natural world, and nothing can stop it.

The good news is that they do almost no harm. They don’t sting or bite. Nor do they eat crops, as do the grasshopper locusts with which they are often confused. They just want to dance, to mate. And they bring their own music, a monstrous rattling chorus that, in wooded areas, will require you to yell at whomever you are face to face with if you want to be heard. Their party only lasts a couple of weeks, long enough for them to leave a nymph hoard that will burrow into the ground, then feed quietly on root sap for another 17 years. In 2024, these offspring will encounter each other as adult teenagers and go about the fundamental business of life: to make more life.

An Extraordinary Event

Photos from top: Michael Redmer, Casey Galvin, Dave Jagodzinski, Bill Beatty/AKM Images, Inc.

In Chicago Wilderness, the 17-year cicada is actually three species — Magicicada septendecim, Magicicada cassini, and Magicicada septendecula — each with distinctive behaviors and calling signals, and subtler differences in shape and color.

Those who study them tend to anticipate their appearance with the kind of excitement astronomers evince for the arrival of a reappearing comet. “It’s a great event,” says Steve Swanson, director of The Grove National Historic Landmark in Glenview, Illinois. “As a naturalist, it’s the kind of thing that only comes around maybe four times in your career. In fact, I’ve charted it back to the year 1 A.D. and there have only been 125 emergences over that time. It’s extraordinary, really.”

The Grove is the former home of Robert Kennicott, Illinois’ first naturalist and founder of the Chicago Academy of Sciences. It’s 123 wooded acres operated by the Glenview Park District, which runs environmental programs, a nature center, an archive building, and a wetland greenhouse along with other exhibits.

Swanson has been collecting and studying periodical cicadas since he was a boy. At 54, he has only been alive for three previous appearances of these prehistoric insects, and aware of them for only two. “I have cicada fossils,” he says. “Estimates are that the species has been around for 125 million years.”

All periodical cicadas that emerge in a single year (including the 13-year cicadas which occur more in southern states) are known collectively as a single brood and are designated by Roman numerals. The tide about to wash over us is Brood XIII. Like much about their origins and evolution, researchers don’t know exactly how long they have been in this swath of the Midwest, although their inclusion in Native American legend suggests an ancient local history.

Their presence at The Grove, however, is well documented. Robert Kennicott began collecting them and sending specimens to the Smithsonian and to entomologists around the world in the 1850s. And when Donald Culross Peattie, one of America’s premier naturalist writers who spent periods of his life at The Grove, witnessed the 1922 emergence there, he made a thoughtful and compelling 11-day journal of the event which was included in a book called An Almanac for Moderns, published in 1935. On June 6, he wrote:

They came very secretly, in the night perhaps; or it may have been that for several days they had been assembling, emerging like bad, buried deeds, out of the earth. I realize now that for several days I had been seeing strange, transparent shards of insects upon the pavement, and on the steps down through the grass. But only today when the children came in bright-eyed with excitement, and interrupting each other with a tale of enormous bugs everywhere, did I suspect of what they spoke.... I went to explore the grounds…I bagged a dozen and went into the city with them. Delightful old Dr. Howard was at his desk. He opened the box and one of my captives crawled out upon his hand. “Why man,” he cried, “it’s the 17-year cicada!” He seemed surprisingly pleased. “An old entomologist can never tell,” he explained, “whether he will live to hear them again.”

The Big Sleep

The cicada sheds its skin, embarking on a brief but eventful adulthood.

Photo: Kitty Kohout/Root Resources

Not much is known about their long, dark slumber, or exactly why the 17-year cycle developed. Scientists speculate that it is most likely a strategy to avoid predators. By emerging only every 17 years, the cicadas ensure that they will not synchronize with the life cycles of any single predator. In fact, the cycle of the 13- and 17-year periodical cicadas has fascinated mathematicians who wonder whether it is coincidence that they occur only in prime-numbered years.

As the ground warms toward 64 degrees Fahrenheit in the spring of the 17th year, the nymphs begin to dig tunnels about a half-inch in diameter. Then, like something out of “Night of the Living Dead,” the billions emerge in one evening. By morning they have begun to shed their skins; their exoskeletons harden within hours, and they are up and flying to the branches on which they will mate. At maturity, these cicadas have black bodies, red eyes, and orange wing veins. (Compare this to the dark eyes and green body markings of the annual cicadas, which come out every August.) For the next two weeks, the males, which are the singers, raise a din that sounds to human ears like a billion maracas but is actually made of five distinct songs: an alarm call, a calling song, and three courting calls.

This kind of singing, of course, leads to mating. The adults meet briefly, then the female flies off. For the males, it’s over. As Peattie put it in his journal, “Nature is now prepared to let the males all go to the devil, and die by bird and wasp and mold.”

The female lands on the outer twigs of a deciduous tree, cuts a Y-shaped slit, and lays her eggs, up to 600 each. The eggs hatch several weeks later, and the nymphs drop to the ground, dig down one to ten feet, and attach to tree roots on which they will feed for the duration of their lives.

Good Eats

An opossum enjoying a rare cicada treat.

Photo: Peter Dring

But predators don’t necessarily wait for the females to lay their eggs. As soon as the cicadas emerge, many animals gorge on them, including foxes, skunks, raccoons, squirrels, chipmunks, dogs, cats, birds, snakes, spiders, and other opportunistic feeders — even humans. (For cicada recipes, events, and other fun cicada links. But the cicadas, having all emerged at once, are so numerous that predators can’t possibly eat enough to put a dent in the population. It’s a survival strategy called “predator satiation.”

The greatest infestation of our brood will be in city and suburban areas with a high density of mature trees, especially along a band that includes Evanston, Oak Park, and Hinsdale. “We have a lot of them here at The Grove,” says Swanson. “Downtown Glenview has many, and the area around Brookfield and the zoo is just loaded.”

As for how to prepare for cicadas, Swanson says not much is needed. They land on people, but don’t bite, and “the only harm they do to trees is to very young ones. The chemical companies come out with all kinds of stuff to kill them, but there’s just no need to do that. I’d say all you need to prepare for is a truly great event, and enjoy it.”

One way Swanson enjoys them? “I’ve eaten them,” he says, “and they have an earthy, potato-like taste. You need to pick them just after they molt and before the exoskeleton has hardened. Then you blanch them in hot water right away, and you can use them in many different ways. You can sauté them, we’ve had them on pizza, and this year we’re going to substitute them for shrimp in a pasta.”

And while you dine on the unlucky, the nymphs of others will be underground in uncountable numbers, quietly counting the years. As Peattie put it: “There, at last, they are free from their enemies, and they enter upon the seventeen-year torpor that is their real and normal life, that existence in a state of nothingness for which all that hubbub and horror and coupling was intended.”

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News of the Wild,CW, Fall 2003