8 



Fulton County, to June 28 in De Witt County. Sing- 

 ing was heard until June 28, also in De Witt County, 

 and flagging (wilted branches that were girdled in 

 the egg-laying process) was noticed on the same date 

 in that county. 



Apparently this brood is disjunct in Illinois, the 

 western counties which it inhabits being Brown, 

 Fulton, Henderson, Knox, McDonough, Schuyler, and 

 Warren, and the eastern counties being Champaign. 

 De Witt, and Piatt. Intei-vening counties, particularly 

 Logan and Mason, did not seem to have populations 

 of these cicadas. In the western counties mentioned 

 and De Witt County large numbers of cicadas 

 emerged, whereas Champaign and Piatt counties had 

 only limited emergences. 



This brood must have emerged simultaneously, in 

 1946, in some instances in adjacent areas or even in 

 the same woods, with the Great Southern Brood 

 (Marlatt's XIX), and these broods will again emerge 

 simultaneously in 2167. Unfortunately, we have no 

 records of the 1946 emergences in the INHS collection. 

 Both broods may occupy the same woods in Cham- 

 paign County if our records are correctly interpreted. 

 Woods along the Spoon River, Knox County, should 

 be carefully observed in the future to determine 

 whether some of the woods harboring the lowan 

 Brood also support populations of the Great Southern 

 Brood. 



In 1963 Clarence E. White, an INHS entomologist, 

 collected specimens and reported a large emergence 

 in woods at the junction of Illinois 150 and the Spoon 

 River. In 1972 Kent R. Buffington reported in a letter 

 a large emergence in woods north of that area along 

 the Spoon River near Truro, or Williamsfield, as that 

 town is now called. The 1963 population could be 

 assigned to the lowan Brood and that of 1972 to the 

 Great Southern Brood unless the 1972 emergence 

 was made up of an unusually high number of strag- 

 glers of the 1973 Northern Illinois Brood that is 

 known to have colonics nearby. 



The Lower Mississippi River Valley Brood 

 (Marlatt's XXIII) 



The Lower Mississippi River Valley Brood has 

 a 13-year cycle and last emerged in 1963, the year of 

 the lowan Brood's most recent emergence. Records 

 in 1963 (Fig. 1) were obtained from late May until 

 the middle of June. In Illinois this brood is also 

 disjunct, being confined to Alexander, Jackson, Perry. 

 Pulaski, and Union counties in the southwest and 

 to Crawford, Jasper, Lawrence, and Wabash counties 

 in the southeast. Several Illinois counties harboring 

 no cicadas of this brood intervene between these 

 populations, but the distribution of this brood prob- 

 abh' continues to the south in Kentuckv and Missouri. 



A wide gap exists between the locations of this brood 

 and those of the lowan Brood within the state. 



The Great Eastern Brood (Marlatt's X) 



The Great Eastern Brood has a 17-year cycle and j 

 most recently emerged in 1970. Although reported I 

 to be well distributed along the eastern border of ^ 

 Illinois and even in southern Illinois (Marlatt 1907), ' 

 in 1970 this brood was found in only a few counties 

 (Vermilion, Edgar, and Clark) despite careful searches ■ 

 elsewhere (Fig. 2). Adults were found from May 21 

 at Kickapoo State Park, \'ermilion County, until June 

 30, when a small chorus was heard b\' Dr. R. W. 

 Larimore at nearb\' Fairmount. A shed skin was found ■ 



Fig. 2. — Distribution of the Groat Kasteru Brood (M . 

 latfs X) of periodical cicadas in Illinois. Black d. 

 indicate positive records of adult specitnens. skins, ho', 

 in the ground, flagging tree branches, or singing. CircU 

 iiuiicale negative records in areas carefully searched. 



