Nature’s Red-Eyed Rogues
Every 17 years here in the Chicago area we see the emergence of Brood XIII, the crazy, red-eyed, periodical cicada. While 2007 has been one of those years, 1989 was an even bigger year for hot cicada action. That year saw the regular annual cicadas, of course, plus the 17-year cicadas, plus the 13-year cicadas!
Now 17 years ago, when I was but a slip of a lass and had never heard of these cicada emergences, I had an internship at the Morton Arboretum, located in a suburb of Chicago called Lisle. My main focus was preparing tree mountings. (These are not as funny as they sound. It basically involves taking normal, representative parts of a tree — a leaf or seed, for instance — and mounting them on a piece of paper. Or it’s when you get all excited and jump into a tree. I did both of these at the Arboretum, but I only got college credit for one of them.). But I really wanted to work with any form of animal, the furrier the better. For some wonderful reason the Arboretum indulged me, allowing me to work on several different projects as long as I also finished my tree mountings.
At first everything was just randomly interesting: when I wasn’t wandering around the 1,700-acre grounds collecting representative parts of trees, I worked with the brilliant Dr. George Ware developing hybrid street elms that could withstand both Dutch elm disease and the elm leaf beetle. I also worked with a really cool hippy ecologist catching forest birds in a volleyball net and banding them and weighing them and talking about Karl Popper. I learned how to use a wood chipper and a soil analyzer (only for the forces of good, of course). All of this was just fantastic, and a happier summer I may not ever have spent.
But then one day, off duty, I saw my first periodical cicada. More properly, I saw approximately one kazillion periodical cicadas, in various stages of undress, on a tree in LaGrange, Illinois. My initial response was horror — I’m sure I made the chimpanzee fear grimace for several minutes. All these hideous, wet, noisy creatures! I knew immediately that if one of them moved, I would scream. That’s all there was to it.
But the soup du jour, which I’m pretty sure is French for “the main thing that I’m talking about,” is that the Arboretum put me to work on bugs. Hitherto, I had worked with an entomologist to determine what products keep aphids away. Suddenly, we turned to all things cicada, mostly whether they were wrecking the trees, and if so, what kind. Which, given my terror, meant I would be in the midst of a quandary. But as it happens, I rapidly lost my fear and began to find myself quite attached to these weird little creatures.
There was of course a fly in the ointment (hee hee): the entomologist was one middle-aged Dr. Miller, his first name lost to history, who had a propensity for calling my house at 10:00 and 11:00 o’clock at night to tell me things like he'd just gotten home from a business trip, or to discuss his laundry, and to generally hit on me in a futile, middle-aged entomologist sort of way. I think he was divorced.
Anyway, I didn't sleep with him, but he promised to carry out a periodical cicada experiment I developed, in Iowa, the very next year. As with so many creepy older guys, I didn't really keep up with him to see what happened. I'm sure the study was a rousing success, heralded with accolades and published in Nature and such and I'll somehow stumble across it some day:
“Excuse me ... but are you Denise Pace? The Denise Pace? Oh my god! I like totally read your study in Nature! You are as a god to me!”
And I'll say, “What study?”
And my fair groupie will say, “Why, I have a copy right here in my purse/wallet! I always carry it with me.”
One of the coolest lasting things about that summer is that I learned the word ovipositor, which I can toss around quite handily, and also that I kept the husk of a cicada, which wasn't difficult since they were in my clothes and hair every day. It would have been harder to not keep one. But I still have that little exoskeleton in a matchbox, which leads directly to my next sentence:
One of the coolest things about having a matchbox with a cicada husk in it is that one time my mother, who normally didn't do things like this, stumbled across it and was convinced it contained drugs. When she opened the matchbox and the cicada husk popped out, she scared the crap out of herself.
OK, so now you’re probably dying to hear about the 2007 emergence. Well, here’s the thing about 2007: I don’t live in the cicada zone any more, so I don’t really have any memories from this summer. I saw a bunch one day on a suburban sojourn, and my Dad took a picture of me with one, but really the whole thing was more like slumming. Still, I did manage to write this very informative piece, which I shall share with you now.
Things I Know About Periodical Cicadas
A Special Report with a Midwestern Viewpoint
I love cicadas. Not for eating, per se, but for learning about. For example, right off the bat I can tell you that their genus is Magicicada … How great is that? It’s like “magic cicada.”
Whenever I hear cicadas, I think, “Boy, it’s hot out.” This is because they usually come out every summer when it’s really hot out, like late July or August. Cicadas have a lot of similar characteristics to the locusts of the Bible, but they are not actually the same animal. Locusts are members of the grasshopper family.
Here is the life cycle of a typical cicada in America:
Early July: start crawling out of the ground
Mid-July: shed exoskeleton and dry
Late July: do it
Late August: die
[Intermezzo: eggs hatch, cicadlings crawl deep under ground, nourish selves on sap from
tree roots until…]
Early July: start crawling out of the ground
However, there are actually three types of periodical cicadas. Those that come out every year are called the annual ones. These are they guys who I associate with heat and duress. But somewhere along the line there was a mutation that caused the “intermezzo” period to last for almost 17 years instead of almost one, which is how the 17-year cicadas came about. And then there was a mutation in the 17-year cicadas that caused the “intermezzo” period to change from almost 17 years to almost 13 years. So now we have three different species that do not interbreed. This is an example of evolution.
Different areas of the country experience the cycles of 17-year and 13-year cicadas at different times. For example, this year was the emergence of the 17-year cicada in the Chicago area. The group is officially called Northern Illinois Brood XIII. There are 14 broods of 17-year cicadas and three broods of 13-year cicadas. Brood XIII is one of the largest emergences of cicadas anywhere in the country!
So … what’s on your calendar for the next few decades? In 2011 the Great Southern Brood, a 13-year emergence, is due in the southeast. (You’ll notice the South always includes “Great” in their naming conventions, which reminds me of a story I once heard. It seems that around the Civil War, when a lot of states started outlawing sodomy, one state did not put such a law on the books: Arkansas. Why? Well, the lawmakers felt that the people of the Great State of Arkansas oughtn’t to read such filth, and they ultimately decided the people of the Great State of Arkansas wouldn’t be performing sodomy with one another anyway. And so while it was indeed a law, it wasn’t published in the state code until like the 1960s, so that people wouldn’t read about it.)
So, let’s see, the Great Southern cicadas tend to come out in April because it’s so much warmer, and be dead by May, whereas in Northern states they emerge later in the summer. In 2014 there’s a 17-year emergence due in Iowa, and in 2015 out come the 13-year Lower Mississippi Valley Brood. There’s also a Great Eastern Brood, but I don’t want to get into any old stories about that.
Another key tidbit about periodical cicadas is that they only come out where they were before. This is because of how they reproduce. The female has some equipment called an ovipositor, which is kind of like, oh, let’s just say it’s like a sharp straw (although I think of it as a girly penis). She uses this strong, pointy, hollow device to cut little slits in smaller tree branches, and then lays her eggs, via the straw, into the slits. The weight of the developing eggs coupled with the perforation in the tree branch means that the branch soon drops to the ground. Then the little cicadlings (or nymphs, more properly) burrow down, down, down to the tree roots and stay there for one to 17 years, depending on what kind of cicada they are.
This is also why trees are generally safe from cicadas: the tree must be mature enough to nurture the nymphs, so younger trees are usually out. The branches must be of a sufficient circumference to get slits, but the branches must also be thin enough to break due to the perforation and the eggs. So trees that fit the requirements can usually survive a couple of broken branches. But it’s also true that some trees are like that hot guy at the bar — good enough to lay an egg in, as it were, but not strong enough to nurture it. This is all part of the mystery of the cicada.
Now I have to do a preamble: It is usually older growth areas that are dug up for developments — you wouldn’t build a house and right away knock it down and build another one, right? So when dirt and trees and grass are cleared to make way for, say, a skyscraper, all the little cicada nymphs are dug up too. That means they are no longer there to emerge in one or 13 or 17 years. So in 1989 in the Chicago area, there was a lot of discussion as to whether the 17-year cicadas would emerge at all, since there had been such a boom of development in the intervening years. We also wondered about the 13-year cicadas, since it was the rare and magical year when the 13- and the 17-year cicada emergences converged. But it turned out to be OK — there were a lot of cicadas.
Here’s an idea of how many cicadas there are sometimes: in 1956, the Field Museum counted “nymphal holes” of Brood XIII, which are not at all what many of you think they are. “Nymphal holes” are the tunnels in the ground made by the nymphs as they climb to the surface from the nourishing tree roots. The study counted 311 holes in a square yard, which equals 1.5 million cicadas an acre. A Chicago city block is 3.5 acres. That’s how many cicadas there were in 1956 in the Northern Illinois Brood of 17-year cicadas. A more normal-sized emergence is 27 nymphal holes a square yard, or 133,000 per acre.
Here is my woeful aside: there are no 13-year or 17-year cicadas in Chicago proper. They were either never here, because Chicago’s built on a swamp, or they disappeared a long time ago due to the building of the city. There are lots of cicadas in the suburbs though! Particularly the older ones — at Brookfield Zoo this year the animals went crazy with cicada delight, since almost everything eats cicadas. I saw a photograph of a tiny little tamarin monkey, one of the kinds that fits in your hand, eating a cicada just like you or I might eat an ear of Illinois sweet corn. And I hear the sloths have torn up their exhibit digging for the plump, clumsy, and delicious 17-year cicada.
I must confess: I stole that phrase entirely from a documentary I saw about locusts (no relation!). The documentary was showing how in the Middle East, they too have periodical insects, including … the seven-year locust! These are the guys who everybody thought was the plague from God in the Bible. But they weren’t. What the periodical locusts do is join together in ever greater swarms and fly through the land devouring everything. The modern film footage showed a “before” shot of a field of grain. Then the sky turned black with locusts. The cameraman filmed the blackened field for over an hour before the entire swarm had passed, leaving only beige desolation. But then they showed happier times: every animal and person in the desert was just grabbing locusts out of the air and eating them like manna! And the voice-over described the locust as “plump, clumsy, and delicious.” And then a friend of mine who was watching the documentary with me (and who might also write for this magazine) said, “Oh … that should be the heading of my personal ad!”
Anywho, cicadas don’t swarm. They pretty much hang out where they came out of the ground as nymphs. This has led to some cicada hilarity, what with the shortage of trees. It seems that in this emergence, a lot of people noticed “defective” cicadas — their heads were shaped funny, or they had a little divot in their side, stuff like that. People began wondering whether it was chemicals or pesticides, but no! It’s way funnier than that. See, when cicadas tunnel out of their nymph holes, they climb up whatever’s vertical and handy, usually the tree what brung them. Then they pump fluid into their thorax, which splits their exoskeleton, and out they pop, about an inch and a half of glory. The exoskeletons are all those husks that you find everywhere that look like mini-cicadas. After they’re free of the exoskeleton, the cicadas have to dry out for a couple of hours until they harden into their final size and shape.
Well, it seems that so many cicadas have emerged and there are so few trees around in people’s yards that it’s a little crowded. And while all these new wet cicadas are hanging around drying, they keep bumping into each other and bingo … permanent dings. Just like little automobiles at the supermarket.
There is one big question left: for an animal that’s so group-oriented, it is clear that the cicada’s survival is dependent on everybody coming out all at once. So why the 13- and 17-year variations? It is believed that by having a more or less erratic cycle (since most everything else seems to be annual), these species of cicadas happen to avoid certain disasters, such as droughts or floods or surges in the predator population. They would also avoid having a predator evolve to eat only them, except that everything eats cicadas, so that kind of backfired. I read a little blurb in The Economist magazine that said that the key to it all is that 13 and 17 are prime numbers. While prime numbers occur surprisingly frequently in nature (don’t get me started on the Fibonacci sequence!), I don’t buy it. In fact, in the same small, unattributed article The Economist reports that we Illinoisans call cicadas “locusts” and that we eat them. I say The Economist is rife with yellow journalism.
It could have just as easily been a nine-year variation. Ain’t nine a goodly span? And the same force of evolution, to produce viable offspring, applies to insects and to mammals. What forces would exert prime numbers on insects, but not on mammals? Ain’t they all wanting to survive? Five and seven and 11 are divisible by only themselves and one … and ain’t they prime numbers? (You probably couldn’t tell, but I was typing that all just like Sojourner Truth.) Anyway, the real lesson is: Don’t get your deep biology from paragraph-long articles in some soft-science rag like The Economist. There’s probably something to the prime numbers, but I think it’s more in the “Look! Another prime number!” sense, not that viability is restricted to prime numbers.So I guess that’s about everything I know about cicadas. If you enjoyed learning about cicadas, and would like to learn more, here is an independent study question that I have not yet explored: How come some cicadas are half-eaten and are still hopping around alive? WTF?
Copyright 2007, Denise Pace
Photo © Jack Pace, Virginia Pace & Phil Pace
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