These three broods seem, therefore, to he closely allied in their 

 origin, and, curiously enough, occupy territory which divides the 

 two main sections of the great 17-year Brood X, which next follows 

 in regular succession. Brood XI, following X, is evidently an 

 extreme northeastern extension of the latter. 



Brood XII, immediately preceding XIII, is represented by a series 

 of colonies connecting the western Brood XIII with group 5. Brood 

 XIII is the principal representative of group G and represents a large 

 western group of the 17-year race of group 6, which comprises the 

 main western branch of the 17-year race, as group 5 clustered about 

 X is the principal representative of the eastern branch of the same 

 race. Brood XIV has a very wide range to the eastward of XIII, 

 and connects with the latter through the colonies in northern Illinois 

 and Indiana. Brood XV, following XIV, is limited to the Atlantic 

 seaboard with the exception of one doubtful colony in Indian Terri- 

 tory, 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 Brood XIX, and comprising Broods 

 XVIII, XIX, and XX; and (2) related to Brood XXIII, and com- 

 prising 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 exten- 

 sion. 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 verifi- 

 cation, no significant relationship can be pointed out. 



