54 



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 perhaps half by 

 acceleration of individuals; so that the origiual brood, if it still exists, 

 is more likely 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 13-year series is 

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

 sibly 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 territory of later geological formation. 



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

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

 trates the new nomenclature suggested, and in parallel columns also 

 are given the corresponding nomenclatures proposed by Professor 

 Biley, by Walsh and Riley, by Fitch, and the year records in Dr. 

 Smith's register : 



Nomenclature of the broods of the periodical Cicada. 





Broods of the 17-year race. 



Broods of the 13-year race. 



Tear. 



Proposed 

 enumer- 

 ation. 



Riley 

 num- 

 bers. 



Walsh- 

 Riley 

 num- 

 bers. 



Fitch 

 num- 

 bers. 



Smith 

 register. 



Proposed 

 enumer- 

 ation. 



Riley 

 num- 

 bers. 



Walsh- 1 -p., , 



Eil *y nu^ 



num- f"^- 



bers. .j bers - 



Smith 

 register. 



1893 



I XT 







1842 

 1843 

 1844 

 1845 

 1846 

 1847 

 1848 

 1849 

 1850 

 1851 

 1852 

 1853 

 1854 

 1855 



XVIII 



XIX 



XX 



XXI 



XXII 



xxin 

 xxrv 



XXV 

 XXVI 



xxvn 



XXVIII 



XXIX 



XXX 



XVIII 



XIX 



XX 



XXI 



XVI 



XVIII 



II 



IV 



VI 



VII 







1854 



1894 



1895 



II 



III 



IV 



V 



VI 



VII 



VIII 



IX 



X 



XI 



XII 



XIII 



XIV 



XV 



XVI 



XII 



xni 



XIV 



XV 



XVH 



XIX 



XX 



XXI 



XXII 



I 

 "'v' 



VIII 







viii 



IX 



X 



XI 



XII 



1 

 7 



xin 



3 



1842-1855 

 1843 



1896 







1844 



1897 



1898 



1899 



IV 

 V 



5" 



1845 

 1846-1859 



1900 



xrv 



XV 

 XVI 



i 



ii 

 iii 



VI 



2-8 

 5 

 4 

 9 



6* 



3 











1901.. 



X 







1849 



1902 









1903 











1904 











1905 











1906 



XVI 

 XVIII 



II 



IV 







1854 



1907 



XIII 



3 



1842-1855 



1908... 



IX 



VTT 







1843 



1909... 



XVII 















1844 

















THE RELATIONSHIP OF THE DIFFERENT BROODS. 



As a rule the relationship of the broods in point of distribution 

 agrees with their kinship as indicated by their sequence in time of 

 appearance. The relationship indicated by the latter, viz, their 

 sequence in time, is doubtless untrustworthy as indicating origin, in 

 some instances, on account of the uncertainty arising from the action 

 of the principle of retardation on the one hand and acceleration on the 

 other in the forming of new broods. 



In the case of a widely scattered brood, like Brood VI, it is quite 



