In this century of rapid scientific discovery, there still exist natural phenomena with the power to inspire wonder and mystery. The cicada, an insect known since ancient times, is one such phenomenon. Because scientific
knowledge of the cicada contains many gaps, these mysterious insects can still stimulate our imagination or lead
us into confusion. At the present time, the cicada is many things to many people: it is a curiosity that should be approached scientifically; it is a source of superstition and dread; it is also little more than an annoying, seasonal inconvenience.
The cicada is a stout, black insect about an inch in length. Various species of this insect can be found all over North of the America. When the cicada is at rest, its large, transparent, veined wings are folded over the top of its body and extend about a quarter of an inch beyond it. Cicada wing veins are and information reddish orange in color, as are its eyes and legs. The front legs are sharp and crablike, allowing the animal to hold tight to the bark of trees. The species of American cicada most written about by scientists and most wondered about by the general public is known as the periodical cicada. Its scientific name is Magicicada septendecim. This species of cicada appears above ground only once every seventeen years.
What the cicada does underground for most of its seventeen-year life span was a mystery until fairly recently. In the early part of this century, a man named C.L. Marlett, who worked for the United States Department of Agriculture, decided to find out. He began burying cicada eggs in his backyard and digging them up periodically for observation. He soon found out that the cicada begins life as a tiny nymph about six hundredths of an inch in length. A nymph is an immature insect, before it has fully developed
wings or reproductive organs.
During their sixteen years and ten and one-half months underground, cicada nymphs are nestled against tree roots from which they gently suck the juices. Nourished by this root sap, they begin to grow. They shed their skin four times before they reach adult size.
Once matured, a cicada does not necessarily leave its underground nursery. All cicadas of the same generation in a region wait for a seventeenth spring before they come creeping forth from the ground as a group. The eeriness of this group effort has puzzled humans for centuries. People have responded to the mystery with a host of superstitions, educated guesses, and scientific theories.
One of the earliest explanations for the mass appearance of cicada populations after their long absence in an area was that the insects had come to foretell war. This idea stems from an observation of the adult cicada shortly after it appears above ground. It immediately sheds its skin for the last time and begins to darken in color. Near the outer edge of its front wings, a black mark appears that looks distinctly like the letter W. Some thought this W stood for war. In the past, people who saw a group of cicadas emerge from the ground like an invading army were filled with panic. The sight was especially frightening because literally millions of insects can appear within an area of a few square miles.
Later explanations for the mass appearance of cicadas stem from more scientific observations. Dr. L. L. Pechuman, a professor at the New York State College of Agriculture and Life Sciences at Cornell University, has suggested that coming above ground only once every seventeen years is an excellent way for a species to discourage its natural enemies. Perhaps the cicadas have evolved a special kind of biological time clock to protect them from predators.
James Heath, an insect physiologist at the University of Illinois, theorizes that the cicadas all emerge at around the same time in a certain year because the soil has reached a temperature of 64 degrees. Theories like this have still not been proved absolutely, but they do a lot to dispel the fear, awe, or confusion experienced by many people who witness millions of cicadas surfacing at once.
Once cicadas surface, they lose no time. At this point in This their life cycle, they have only 5 or 6 weeks of life remaining. They head quickly for the nearest tree or bush and climb onto it. Then, holding onto the bark with their clawlike front legs, they shed their skin for the last time and become large-winged adults. These adults will mate, and the females will then dig into the tender bark of small twigs to deposit their eggs.
The adult cicadas die shortly after the mating and egg- laying process has occurred. The eggs hatch a few weeks after being laid, thus yielding a new generation of nymphs. The nymphs fall to the ground from the trees and then crawl to the soil, renewing the 17-year cycle.
Opinions remain divided concerning the amount of harm done by cicadas to trees and to bushes. The Pilgrims who is came to the New World assumed that cicadas were locusts. An army of locusts can destroy acres of greenery in record time by biting and chewing leaves and stems. To the present day, the Pilgrim misidentification of cicadas has stuck, and many people still refer to cicadas as seventeen-year locusts. Millions of plant lovers use the name as an excuse to fear and detest cicadas. In reality, cicadas can only suck-not bite-tender plant tissue; and adult cicadas eat little if at all during their five to six weeks above ground. According to Jane E. Brody, who writes science articles for The New York Times, the only harm done to trees by cicadas occurs during egg-laying. This egg-laying leads only to a kind of natural pruning and an injury that all but the young trees can easily withstand. However, Richard Maffei, author of Insects in Your Garden, strongly disagrees. He maintains that leaves on twigs and branches so punctured usually turn brown, but hang on as an eyesore for weeks before the branch breaks and falls to the ground.
Few disagree with the opinion that the skins shed by cicadas aboveground are an unsightly form of natural litter. A book by Peter Farb called Insects speaks disapprovingly of the junk yard of skins shed by a swarm of cicadas in an Indiana orchard in 1953. Jane E. Brody describes a time in the Northeast in 1970 when passersby had to skip like schoolchildren’ to avoid crunching the piles of cicada bodies beneath their feet. This litter is added to by birds who eat the cicadas, spitting out their wings in the process. For people with sidewalks to sweep and yards to clean, such animal remains can be a real nuisance. This is especially true in the
case of cicadas, as 20,000 to 40,000 can appear beneath a single tree.
As cicada invaders appear, they are also likely to leave their traces in lawns, flower beds, and fields. Cicada nymphs burrowing out of the soil in search of a tree can leave a hole as large as one-half inch across. Such honeycombing of the soil can be very dismaying to those who take pride in a well-kept lawn. During a 1987 appearance of cicadas in the Washington, D.C., area, the United States Agricultural Research Service was plagued by telephone calls from distraught people who wanted to know why their lawns suddenly had holes.
Of all the phenomena related to cicadas, their song, or-as some call it-their racket, has aroused the most comment. Attached to the underside of a cicada’s abdomen is a pair of large drumheads. These drumheads are operated by powerful muscles that set them vibrating. The loud, shrill sound produced has been compared to the creaking of an unoiled door hinge, a jet about to land, or the sound of a car motor about to break down. Of course, the cicada sound with which humans are familiar is actually made by thousands of cicadas singing together, and it has a hypnotic, droning effect.
Only male cicadas are equipped to sing. The noise attracts females, who eventually mate with their serenaders. Scientists are beginning to suspect that a very loud noise, produced by a giant chorus of male cicadas, is necessary for successful mating. Accordingly, small groups of cicadas, which cannot produce enough noise, tend not to mate and do not produce a new generation.
The human reactions to cicada music range from fascinated disbelief to annoyance to panic. The Guiness Book of World Records lists male cicadas as the world’s loudest insects maintaining that their abdominal drums vibrate at a rate of 7,400 pulses per minute. The noise produced has been described by the United States Department of Agriculture as sounding something like Tsh-ee-EEEE-e-ou! Motorists driving through a town populated with lovesick cicadas may stop their cars and open the hood to find out what is wrong with the engine. People who sleep during the day-the time when cicadas sing-often have to resort to earplugs. Finally, most people realize that there is no remedy other than to put up with this sound for five or six weeks. After all, it only occurs in a particular area once every seventeen years.
All in all, the cicada is a creature little understood by most humans. Throughout the centuries it has been misnamed or mistakenly feared. Legend has attributed terrible powers to it. The cicada has been called everything from a plague to an omen of war to a backyard nuisance. Perhaps, in years to come, as scientists discover more about this infrequent visitor, it will lose some of its mystery. Only then, in the human mind, will it join the familiar ranks of such warm-weather insects as the mosquito and the butterfly.
Brody, Jane E. After 17 Years, Cicadas Prepare for Their Roaring Return. The New York Times, May 12, 1985, pp. C1, C3.
Cicadas. The Encyclopaedia Britannica, vol. 3, 1980 ed.
Farb, Peter, and the Editors of Time-Life Books. The Insects. New York, New York: Time-Life Books, Inc., 1970.
The Living World. The Guiness Book of World Records. New York, New York: Sterling Publishing Company, Inc., 1987.
Maffei, Richard. Insects in Your Garden. New York, New York: Dalton, 1984.