Seventeen-Year Cicadas Trivia Quiz

Answer: Eastern North America

Although cicadas are well-known around the world, most species are annuals, emerging every year with a life cycle of about two to five years. The seven species of the genus Magicicada are periodicals with much longer life cycles: thirteen years (four species) or seventeen years (three species)! What's more, individual populations of these species are synchronized: almost all the cicadas in the state of Virginia, for example, will emerge as adults at the same time.

Their huge numbers dominate night noises and conversations for weeks.

Answer: Yes. They move more slowly and are easier to catch.

Because of their vast numbers at their emergence, seventeen-year cicadas are thought to be less vulnerable to predators than their annual cousins. There are so many insects that even relatively slow and unflappable individuals will survive long enough to breed -- but annual cicada populations are small enough that long reaction times and ponderous movements are a virtually certain death sentence. Natural selection ensured that annual cicadas gradually became faster and more easily frightened, but the same pressures didn't apply to periodical cicadas.

Answer: Underground

Nearly all of a cicada's seventeen years are spent underground, at depths of about a foot (30 cm). During that time -- which lasts from just after hatching to a few weeks before mating and death -- the young insects (called "nymphs") drink the juices of roots, undergo five distinct life-cycle changes, and grow to a length of 1-2 inches (25-50 mm). They finally emerge almost at the same time, when the soil temperature rises above a certain threshold.

Periodical cicadas are small compared to some of their cousins; one Malaysian cicada species grows up to six inches (15 cm) in length!

Answer: Brood

Entomologists have assigned thirty numbers (always in Roman numerals) to the various Magicicada broods. Broods I-XVII refer to the seventeen-year species, and Broods XVIII-XXX refer to the thirteen-year varieties. Brood II always emerges a year after Brood I. Some of these numbers don't refer to actual broods: not every year sees a periodical cicada emergence! Those null numbers are included in the classification system, however, for consistency and ease of use.

In general, all the cicadas in a given area belong to the same brood, and cicadas of different broods can never mate with each other -- cruel fate ensures that they'll never even encounter one another. (The course of insect love never did run smooth.) Strangely, each brood will include cicadas from all the different cicada species with the right period, which further complicates finding a mate! Not all broods are the same size, either. The largest known brood is the Great Eastern Brood, Brood X, whose range extends from Lake Michigan to New York to North Carolina; their first 21st-century emergence was in 2004. The year this quiz was written, 2007, saw the emergence of Brood XIII in northern Illinois and other areas of the Midwest.

Answer: White

Though cicadas are black for almost all of their above-ground lives, they're a bright white immediately after molting; it takes them less than an hour to darken to their final color. They leave behind their golden-brown molted exoskeletons, affixed to tree trunks, stairs, and other wooden surfaces, preferring to point their heads toward the sky and their tails toward the ground.

The surprisingly rigid molts can last for months before decomposing.

Answer: By rubbing two ridged membranes (tymbals) together

Tymbals, found in the first segment of the abdomen, are common to almost all species of cicada (although in most cases, only the males possess them). The songs vary from alarms to courtship calls to summons to a chorus - a large group of male cicadas that sing together and attract females to mate. Cicadas hear these songs with hearing organs on their bellies.

Females do use wing flicks to communicate, generating a low sound in response to a male mating call. Once a male and a female find each other, they "sing" a duet, judging distance and direction by the timing of their signals until a rendezvous is achieved.

Answer: In living twigs

The female makes a large number (between six and twenty!) of V-shaped slits in tree bark, preferably the bark on new twigs. To make these incisions, she uses an organ called an ovipositor, which is also useful when it comes to the actual laying. She'll generally lay all her eggs relatively near each other, so it's possible that the siblings know each other -- but cicada family life is certainly not a simple matter!

Answer: They drop to the ground and burrow below the surface.

The eggs hatch about six to eight weeks after they were laid, by which time their parents have all gone off to that great chorus in the sky, their above-ground lives having lasted for only four to six weeks. The beginning of a nymph's life is a flurry of movement and digging, which must be tiring: it will spend the next seventeen years almost totally motionless underground.

Answer: No

Cicadas don't bite humans or sting them; there is no poison in their bodies, which is a good thing as they are treasured delicacies in many cultures. And unlike all too many other insects, they've never been charged with transmitting any disease dangerous to humans. At a mass emergence, their sheer numbers can overwhelm young and immature plants, but there's no evidence that fully developed plants suffer any long-term damage.

Cicada emergences are popular with children because they're such harmless animals; plus, they're loud, everywhere, and kind of cool-looking. I was five years old during one mass emergence, and I spent many afternoons building little twig-and-leaf houses that the cicadas could live in. None of them were particularly interested, but they were pretty good sports about it. As a curious aside, they all seemed to be named Clara, which I'm sure was totally unrelated to "The Nutcracker" ballet with which I was obsessed at the time.

Answer: New adult cicadas are vulnerable. Since they appear at intervals that are a prime number of years, predators with shorter lifespans can't "synch up."

Periodical cicadas are certainly preyed upon after a mass emergence; a variety of opportunistic predators (such as spiders, birds and snakes) feast on them with pleasure. But the cicadas' numbers are so overwhelming - densities of over a million cicadas per acre have been reported - that "predator satiation" occurs: predators eat until they're sated without appreciably denting the population.

There would be trouble, however, if a predator population managed to synchronize with the cicadas. Imagine that a species of spiders developed, so that millions emerged at the same time as their prey! Predator satiation would no longer be a winning strategy. It is thought that periodical cicadas once had a wider range of lifespans, but that shorter or non-prime life cycles allowed predators to synch up and eat the cicadas to extinction. This would explain why long-cycle cicadas have been so favored.

Thanks for taking this quiz. I hope you've enjoyed this introduction to some of nature's most fascinating insects!