55 



possible that certain swarms originated from a later-appearing brood 

 by retardation of individuals, and other swarms from an earlier brood 

 by acceleration in time of apx^earance of individuals. 



This same condition may be true of other of the more scattered 

 broods, but with the broods presenting a compact range a singleness of 

 origin is evident. 



Examination of the distribution of the broods in connection with 

 their sequence in time of appearance indicates, however, a certain 

 relationship between the different broods in point of origin, which may 

 be indicated as follows : 



THE RELATIONSHIP OF THE 17-YEAR BROODS. 



From the standpoint of distribution the broods of the 17-year race 

 maybe grouped as follows: (1) Broods I and 11; (2) Broods III and 

 IV; (3) Brood V; (I) Brood VI; (5) Broods VII, VIII, IX, X, and XI; 

 (6) Broods XII, XIII, XIV, and XV; (7) Broods XVI and XVII, the 

 last connecting again with Brood I. 



Taking up these broods in regular order: 



The main body of Brood I occupies territory immediately west of 

 the more important Brood II, and also presents a number of colonies 

 extending westward to Colorado. Broods I and II seem, therefore, 

 closely allied in point of origin. 



Brood III presents little, if any, relationship to Brood II in point of 

 location and distribution, but is closely allied to the following brood, 

 IV, and the latter is evidently a western and southern extension of III. 



Brood V presents little relationship with Brood IV in point of dis- 

 tribution and covers a very compact territory. 



Brood VI, being a widely scattered one, and occurring usually in 

 small numbers, does not seem to present any particular relationship 

 with any of the preceding or following broods. 



Brood VII is local in distribution and not very important, and is 

 divided into two sections by the territory occupied by the following 

 Brood VIII, with which it thus seems to be closely allied. Brood IX 

 is very distinctly a southern extension of Broods VII and VIII. These 

 three broods seem, therefore, to be 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 6 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 



