in Urbana, Champaign County, on a Liriodendron 

 tree, a non-native tree, planted there 8 years previ- 

 ously. Seventeen years earlier in 1953 when this 

 brood emerged, a straggler was also found in Urbana 

 by Dr. R. J. Dysart on August 12. Despite the scanty 

 records in Champaign County, it is possible that the 

 Great Eastern Brood occurred and still persists in 

 small numbers in the Big Grove of Urbana and that 

 eastern Champaign County should be included in the 

 list of counties inhabited by this brood. 



The 17-year Great Eastern Brood (Marlatt's X) 

 must have emerged in Illinois adjacent to and at 

 the same time as the 13-year Great Southern Brood 

 (Marlatt's XIX) in 1647 and 1868, and they should ap- 

 pear together again in 2089. Furthermore, the Great 

 Eastern Brood must have emerged adjacent to and 

 at the same time as the 13-year Lower Mississippi 

 River \'alley Brood (Marlatt's XXIII) along the border 

 of Clark and Crawford counties in 1664 and 1885, 

 and they should occur together again in 2106. 



According to Marlatt (1907) and as reinterpreted 

 by Dybas (1970), this brood has three main but 

 I almost certainly disjunct centers: a broad portion 

 of Indiana and western Ohio, a wide area pri- 

 marily bordering the Mason-Dixon line in Maryland 

 and Pennsylvania, and an area in the southern Ap- 

 palachians. 



I The Great Southern Brood (Marlatt's XIX) 



The Great Southern Brood has a 13-year cycle 

 ami emerged last in 1972. This brood emerges in 

 .iljundant numbers largely outside the limits of the 

 \\ isconsin moraine, except through the east-central 

 rc'^ion of the state, and outside the areas occupied 

 In the Great Eastern Brood (Marlatt's X) and the 

 Lower Mississippi River Valley Brood (Marlatt's 



j XXIII) (Fig. 3). An isolated colony of "extremely 

 heavy populations of cicadas" was reported to us by 



[k. R. BufRngton on May 18-20, 1972 along the Spoon 

 River near Truro, now called Williamsfield, in Knox 

 County. Along the upper Sangamon River in Cham- 

 paign County both the 1.3-year Great Southem Brood 

 and adventive or relict colonies of the 17-year lowan 

 Brood may occur together. In these woodlands in 



I western Champaign County, the Great Southern 



• Brood emerged in greater numbers in 1972 than did 

 the supposed lowan Brood in 1963. 



The 1972 INHS records show that the Great 

 Southem Brood started to emerge as adults as early as 

 May 14 in Pope County, on May 20 in Olney in 

 , Richland County, on May 2.3 at Fox Ridge State 

 I Park near Charleston in Coles County, and on May 

 ' 25 in Piatt County. Singing continued as late as 

 June 30 at Robert Allerton Park near Monticello in 

 ' Piatt County. 



Fig. 3. — Distribution of the Great Southern Brood 

 (Marlatt's XIX) of periotlical cicadas in Illinois. Black 

 dots indicate positive records of adult specimens, skins, holes 

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

 indicate negative records in areas carefully searched. 



In Illinois the 13-year Great Southern Brood prob- 

 ably emerged adjacent to and at the same time as the 

 17-year lowan Brood in 1725 and in 1946, and they 

 should emerge together again in 2167. In the Spring- 

 field area the Great Southem Brood probably emerged 

 at the same time as and adjacent to the 17-year 

 Northern Illinois Brood in 1582 and in 1803, and they 

 should emerge together again in 2024. The Great 

 Southern Brood probably emerged simultaneously 

 with the 17-year Great Eastern Brood in 1647 and 

 1868, and they should do so again in 2089. The 

 opportunity for this 13-year brood to interbreed w ith 

 these 17-year broods appears highly likely to occur 



