brood numbers to each year of the lo-j^ear period, making a total 

 enumeration of the broods of both races of XXX. As already 

 indicated, six of the numbers given to the 13-5^ear race have had no 

 brood assigned to them, although records have been secured which 

 seem to indicate the existence of scattering broods filling some of 

 the gaps, as will be noted in the records given further on. 



It does not necessarily follow, in fact it is quite unlikely, that Brood 

 I, as here designated, is the original or oldest brood of the 17-year 

 race. Undoubtedly some of the 17-year broods, perhaps half or 

 more of them, originated by retardation of individuals, and perha})S 

 half by acceleration of individuals; so that the original brood, if it 

 still exists, is more likelj" to be one of the intermediate ones. Brood 

 X, being the largest of the 17-year broods, perhaps has best claim 

 to this distinction. 



For the same reasons an intermediate brood in the i;]-year series 

 is doubtless the original brood of the 13-year race, and this title may 

 possiblj' belong to Brood XIX which has the widest range of all the 

 broods of the 13-year race. The fewer number of broods in this race 

 would seem to indicate that it is of later origin than the 17-year 

 race, and this belief is further justified by the fact of its occupying, 

 in the main, a territor}^ of later geographical formation. 



The following table, beginning with 1893, when the initial broods 

 of both the 17-year and the 13-year series appeared in conjunction, 

 illustrates the new nomenclature suggested, and in parallel col- 

 umns also are given the corresponding nomencdatures proposed by 

 Professor Riley, by Walsh and Riley, by Fitch, and the year records 

 in Dr. Smith's regfister : * 



Nomenclatare of the broods of the periodical Cicada. 



*In Bui. 14, Div. Ent., U. S. Dept. of Agr., the Riley nninhers given in col- 

 ninn 3 were employed, and should be corrected to the later enumeration indi- 

 cated in column 1. 



