"A Trill of a Lifetime"
(originally published in The Illinois Steward, Summer 2004)
text by Susan L. Post, photos by Michael R. Jeffords
"The emergence of periodical cicadas or 17-year locusts of the genus Magicicada has been observed in the eastern woodland areas of the United States since 1633 or 1634 when the Pilgrims of Plymouth Colony first encountered them. At this early date the cicadas came out of the ground in the spring and made the woods ring with their 'singing', according to Moreton. The colonists had never seen such insects but the Amerindians had, and predicted that pestilent fever would follow. The cicadas 'sang', mated, layed their eggs, and died, and as the hot summer wore on the fevers came, killing many of the colonists and Indians alike. In the autumn the pestilence abated, but it reappeared the following year. The Pilgrim 'flies' or 'locusts', however, were not seen again until 1651. They have since appeared as if regulated by clockworks every 17 years down to the last recorded emergence in 1974. Fortunately, the last correlation with pestilent fevers has not proven constant."
Frank Young and Gene Kritsky, 1987
Indiana Academy of Science
No other insects in North America excite as much curiosity and wonder as do periodical cicadas when they make their sudden appearance every 13 or 17 years. These cicadas are widely distributed in the United States east of the Rocky Mountains, but occur nowhere else on earth. There are seven species of periodical cicadas—four with 13-year life cycles and three with 17-year life cycles, distributed over several broods (see map below). The best way to identify individual species is by sound because each cicada song is species specific.
A periodical cicada emergence typically consists of three species, which are easily separated by size, coloration, and song. Some scientists feel that those emerging every 13 years consist of three different species than those emerging every 17 years. Other scientists feel that the same three species emerge every 13 or 17 years. The cicadas that emerge in the same geographical area in the same year are considered to be in the same brood. Sometimes the geographical areas of a brood are disjunct, but they are typically near each other.
In 1907, U.S. Government entomologist C.L. Marlatt published what was considered the most complete and definitive work on the periodical cicada. He gave each of the cicada broods a number. Marlatt’s number designations are still in use today, even though he originally thought there were 30 broods. At present only 15 broods are recognized (Broods I though X, XIII, and XIV are 17-year broods and Broods XIX, XXII, and XXIII are 13-year broods).
In 1975, Illinois Natural History Survey entomologist Lewis Stannard, Jr., published The Distribution of Periodical Cicadas in Illinois. In it he describes the five broods that occur in Illinois and he also mapped them.
Iowan Brood (Brood III)—The Iowan Brood has a 17-year cycle and most recently emerged in 1997. It has a disjunct population. The western counties correspond to a western spur of the northern part of the Illinoisan-age glacial plain. The small parts of DeWitt, Piatt, and Champaign counties are a disjunct population. Brood III also occurs in Iowa and Missouri and will emerge during 2014.
Great Southern Brood (Brood XIX)—The Great Southern Brood has a 13-year cycle and last emerged in 1998. Most of this brood is on the Illinoisan-age glacial plain. Brood XIX also occurs in Alabama, Arkansas, Georgia, Indiana, Kentucky, Louisiana, Maryland, Missouri, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee, Texas, and Virginia. They will emerge during 2011.
Great Eastern Brood (Brood X)—The Great Eastern Brood has a 17-year cycle and has emerged in 2004. This brood is found only in Vermilion, Edgar, and Clark counties and a small section of Champaign County and occupies an area that supports other relict eastern species such as American beech and tulip poplar. Brood X also occurs in Delaware, Georgia, Indiana, Kentucky, Maryland, Michigan, North Carolina, New Jersey, New York, Ohio, Pennsylvania, Tennessee, Virginia, and West Virginia. They will emerge again in 2021.
Northern Illinois Brood (Brood XIII)—The Northern Illinois Brood has a 17-year cycle and last emerged in 1990. Most of the region occupied by this brood lies within the Wisconsin-age glacial plain. Brood XIII also occurs in Iowa, Indiana, Michigan, and Wisconsin, and will emerge again during 2007.
Lower Mississippi River Valley Brood (Brood XXIII)—The Lower Mississippi River Valley Brood has a 13-year cycle and last emerged in 2002. This brood corresponds to where the baldcypress meets its northern distribution limit. Brood XXIII also occurs in Arkansas, Indiana, Kentucky, Louisiana, Missouri, Mississippi, and Tennessee, and will emerge during 2015.
After years of living in underground tunnels, thousands of periodical cicadas emerge from the earth, as if by a predetermined signal, shed their nymphal skins, and spread out through the nearby trees and bushes. Up to 40,000 can emerge from a under a single tree!
The cicada's precise but prolonged time schedule revolves around survival for the masses. When a large population of juicy insects appears on the scene, predators make the most of the situation, but simply cannot eat all the insects. Thus, a significant number of cicadas live to reproduce. Long-lived predators may actually remember the feast and return to the scene in subsequent years. Short-lived predators, being well fed from the cicada banquet, reproduce successfully and often leave a larger population to await next year’s emergence. However, "next year" doesn’t happen for at least 13 years, so the periodical cicada is able to outlast and escape most of its enemies.
From morning till night the males fill the air with their loud, droning song. The song is like the familiar sound of the common dog-day cicada so typical of summer evenings, only it is louder and heard at the end of spring. The males are the only ones singing.
During 2004, Brood X emerged. This brood has the greatest range and concentration of insects of any of the
17-year cicadas. Their deafening drone perked up woods from Mississippi to Long Island and from the Great Lakes
to Georgia.
Periodical cicadas spend 13 or 17 years buried 18 to 24 inches deep in the soil of wooded and forested areas feeding on sap from tree roots. They dig their way out of the soil during late May and June and climb up tree trunks, posts, and poles to molt into adults. The adult insect is about 1.5 inches long with a black body, red legs, and red eyes. They have piercing and sucking mouthparts and will feed on a variety of woody vegetation. Each adult may live five or six weeks. They will mate and the female will pump her egg into slits of small twigs and shrubs, using her sickle-like ovipositor. This will cause some twig dieback, called flagging, but has no long-term consequences to the tree. The eggs will hatch after six to seven weeks and the newly hatched nymphs (about the size of an ant) fall to the ground and burrow until they find a suitable tree root, where they settle down to feed and wait. The nymphs will undergo five molts in their 13 or 17 years.
Perhaps Aldo Leopold described the phenomenon best when he talked about the passenger pigeon: "They traveled the countryside, this traveling blast of life." Like Leopold’s pigeons, the cicadas will also disappear, but unlike the long-lost pigeon, these denizens of eastern forests will return. If you are an eager periodical cicada watcher, do not despair while waiting for the next emergence in 17 years. Several broods of both 13- and 17-year cicadas are found in Illinois and their emergences are staggered. Thus, every few years, if you are up for a little travel, a periodical cicada viewing opportunity presents itself, and as an entomologist from Iowa once stated, "It's a trill of a lifetime!"
Emergence
A cicada emergence is something to behold. I had the opportunity to experience just such an emergence during Memorial Day, 1998. My husband and I were camping at a beautiful place called Pounds Hollow in southern Illinois. The trees around the campground were littered with the shells of cicadas; the ground was covered with tiny holes from which they left their terrestrial homes and began an arboreal existence. At night, as we were sitting around the campfire, they began coming out of the ground in droves. They crawled up any upright object, including our legs, to molt from their last instar into adulthood. They also began falling from the trees as they lost their footing and pummeled us like dive-bombers. As we slept in our tent, we could hear them crawling up the sides. After they reached a suitable place under our rain fly, we could hear them cracking open. They emerged as white, ghostly aliens and slowly unshriveled into eerie black creatures with demon-red eyes. In the morning as I began taking down the tent, I removed the rain fly and a gaggle of them escaped into the trees. The air was filled with an ominous humming which could be heard for miles around. The entire forest sounded like a huge machine or like the hum of buildings in a city.
Brandi Sangunett, master’s student, Department of Natural Resources and Environmental Sciences, University of Illinois