56 



the latter through the colonies in northern Illinois and Indiana. Brood 

 XV, following XIV, is limited to the Atlantic seaboard with the excep- 

 tion of one doubtful colony in Indian Territory, and connects directly 

 with the eastern colonies of XIV. 



Brood XVI is based on somewhat doubtful records, the Colorado 

 locality perhaps being due to confusion with some other species, and 

 the other records needing confirmation. Brood XVII is intermediate 

 between Brood XVI and Brood I, its western colonies connected with 

 the former and the eastern colonies with the latter. 



THE RELATIONSHIP OF THE 13- YEAR BROODS. 



The broods of the 13-year race break up into the following natural 

 groups : (1) Related closely to BroodXIX, and comprising Broods XVIII, 

 XIX, and XX; and (2) related to Brood XXIII, and comprising Broods 

 XXI, XXII, XXIII, and our new Brood XXIV. 



The first of these broods, Brood XVIII, is a rather insignificant one 

 and is undoubtedly an eastern extension or offshoot of the great 13-year 

 Brood XIX, which succeeds it. Brood XX is undoubtedly a section of 

 Brood XIX retarded one year, just as Brood XVI is an accelerated 

 swarm of the same. Both represent eastern extensions of the parent 

 brood. 



Brood XXI, separated from Brood XIX by two years, seems to bear 

 little relationship to the latter, and a more logical arrangement consists 

 in connecting it with Brood XXIII through Brood XXII, of which last- 

 it may be considered as an eastern and northern extension. Brood 

 XXII is a very marked instance of the formation of a new brood by an 

 acceleration in time of the appearance of a portion of a larger and 

 older brood. Its relationship with Brood XXIII is very marked and 

 can not be questioned. Brood XXIII, the main representative of this 

 group, is followed by the new Brood XXIV, which is evidently a 

 retarded swarm of the preceding brood. 



Of the new Broods XXIX and XXX, both of which need verification, 

 no significant relationship can be pointed out. 



Brood XXIX is very doubtful, and the records are possibly based on 

 confusion with the 17-year race. 



NEW BROODS, 17-YEAR RACE. 



Brood XII, 1904. — If his records are correct, this brood is the one 

 referred to by Dr. (x. B. Smith as occurring in 1853 in Vinton County, 

 Ohio, and Jo Daviess County, 111. Its recurrence seems not to have 

 been recorded either in 1870 or 1887, and Smith's records are therefore 

 open to question. 



Mr. J. R. Burke, Milton, Cabell County, W. Va., writing under date 

 of May 22, 1897, says: "The Cicada is not due here until 1904; its last 

 visit was in 1887." 



