The Distribution of Periodical Cicadas in Illinois 



Lewis J. Stannard, Jr. 



For decades, entomologists ha\e relied upon 

 Marlatt's (1907) compilation of the distrilnition of 

 the broods of the periodical cicada to forecast emer- 

 gences of these insects. Such forecasts are especially 

 important to persons concerned with protecting trees 

 and shrubs. Unfortunately, as will be shown in this 

 report, many of Marlatts records are in error. In 

 their place, a more accurate picture of cicada distribu- 

 tion in Illinois, as observed over the past 10 years, is 

 gi\en here. Additional surveillance of periodical ci- 

 cadas could be continued profitably to pinpoint exact 

 boundaries of their ranges in some of the central 

 counties of our state, to determine the rates of their 

 dispersal to new areas or extirpation from original 

 areas, and to obtain information on the possibility of 

 introgressive hybridization between broods. 



To orchardists, nurserymen, and horticulturists, 

 periodical cicadas are more than mere curious and 

 interesting insects. Even though they occur infre- 

 quently (once every 13 or 17 years), they may dam- 

 age more than 95 percent of the terminal shoots 

 of young fruit trees (Hamilton 1962) or ruin the 

 shapes of specimen trees or choice shrubs. When one 

 considers that as many as 20,000 cicadas may emerge 

 from beneadi one apple tree, it is easy to understand 

 ho\\- so many twigs can be destroyed during the 

 cicadas' egg-laying process (Hamilton 1962). Trees 

 whose terminal shoots are killed by cicadas usually 

 reco\er by epicormic branching, according to my 

 obser\ations, but fruit production in orchards can be 

 severely curtailed, causing substantial economic loss. 



This report is presented primarily as an aid to 

 fruit growers in making accurate predictions of emer- 

 gences of periodical cicadas and as a contribution to 

 our basic knowledge of these unusual insects. 



ACKNOWLEDGMENTS 



I wish to express my appreciation to the staff of 

 the Illinois Natural History Survey, extension ento- 

 mologists of the University of Illinois, county exten- 

 sion advisers of the state of Illinois, and the many 

 persons in our state who have helped to collect speci- 

 mens and have shared their observations on the dis- 

 tribution of cicadas o\'er the past 10 years. Without 

 their assistance the state could not have been covered 

 thoroughly in the approximately 3 weeks of the par- 



This paper Is published by authority of the State of Illinois. 

 IRS Ch. 127, Par. 58.12, and Is a contribution from the Section 

 of Faunistic Surveys and Insect Identification of the Illinois 

 Natural History Survey, where Dr. Stannard Is a Taxonomlst. 



ticular years when these insects exist above ground 

 as adults. 



My particular thanks are extended to Drs. Thomas 

 E. Moore and Henry S. Dybas for their advice, 

 suggestions, and many favors, especially to Dr. Dybas 

 for rexiewing the manuscript. I am further obliged 

 to Mr. Wilmer D. Zehr, who photographed the 

 specimen appearing on the cover; to Mr. Lloyd 

 Le Mere, who prepared the maps; to Mrs. Bernice 

 Sweeney, who typed the manuscript; and to Mr. 

 Robert M. Zewadski, who edited it for publication. 



THE ILLINOIS BROODS 



With the exception of woods in certain areas that 

 are predominantly sandy (in extreme northeastern 

 Lake County, in eastern Iroquois and Kankakee 

 counties, and in areas in Lee, Ogle, Mason, and a 

 few other counties) almost every wooded .section 

 of Illinois is inhabited by a brood of periodical 

 cicadas. Of the five Illinois broods, three have 17-year 

 life cycles and two have 13-year life cycles. A report 

 of their distributions, based mostly on data gathered 

 o\'er the 10 years from 1963 to 1973, is presented 

 here. Documentary notes for this report and the 

 specimens are kept in the collections of the Illinois 

 Natural History Survey (INHS). The research for this 

 report was essentially completed in 1973, and the 

 report was submitted for publication in December 

 1973. 



HISTORICAL RECORDS 



One of the first entomologists to record Illinois 

 broods of periodical cicadas was Asa Fitch in 1856. 

 Fitch thought, as did everyone at that time, that all 

 cicada broods in the USA had life cycles of 17 years' 

 duration. The first brood he mentioned as being from 

 Illinois ("Southern Illinois") was the 13-year C'.reat 

 Southern Brood (Marlatt's XIX), which emerged in 

 1855 simultaneously with an adjacent eastern brood 

 (Marlatt's XIV). Fitch lumped these togctiicr as 

 his "third" brood, later analyzed by Walsh & Riley 

 (1868). The other Illinois brood mentioned by Fitch 

 was the 17-year Northern Illinois Brood (\Iarlatt"s 

 XIII) as his "sixth" USA brood. He stated tliat this 

 brood extended across northern Illinois, ranging as 

 far south as Peoria, in 1854. 



Shortly after the appearance of Fitch's work. Cyrus 

 Thomas, the "father" of the Illinois Natural Histor)' 

 Sun'cy, learned of records of a third brood of cicadas 



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