RELATIONSHIP OF SKVKNTKKX-VK AK HKOODS. 29 
folationshi]) IxMwcumi th(^ dillVroiil l)i'o()cls in point of ori^qn. wliidi 
may ho iiulicalcd as follows: 
I'lii: i;i:i. \ iioNsiiii" ok 'I'ln-. sk\'i:ntkkn-vkau ukoods. 
From tlio standpoint of disti-ibntion tlio broods of tlu^ 17-yoar rare 
mav be <;r()U})(Ml as follows: (1) Broods I and II; (2) Broods ill and 
IV-! (3) Brood V; (4) l^rood \1; (5) Broods VII, VIII, IX, X, and 
XI; (6) Broods XII, XIII, XIV, and XV; (7) Broods XM and 
XVII, the last connectin«2: a^j^ain with Ih'ood I. 
Takinir up those broods in re^ijidar order: 
The main l)ody of Brood I occupies territory innn(M]iately west of 
the more important and perhaps parent Brood Jl. and also presents 
a number of colonies exten(hn<2: westward to Kansas. Broods I and 
II seem, therefore, closely allied in point of origin. 
Brood III presents little, if any, relationship to Brood IT in ])()int 
of location and distribution, but is closely allied to the following 
brood, I\ , and the latter is evidently a retarded western and soutiiern 
extension of III. 
Brood A' presents little relationship witli Brood IV in point of dis- 
tribution and covers a very compact territory. 
Brood \1, being a widely scattered one, and occurring usually in 
small numbers, does not seem to present any particular relationshij:) 
with any of the preceding or following broods unless the explanation 
suggested by Professor Castle be accepted. 
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 IT-A^ear Brood X, which next follows 
in r(^gular succession, and is perhaps the oldest or parent brood of 
the 17-year race. Brood XI, following X, is evidently an extreme 
northeastern extension of the latter. 
Brood XII is roj)rosented l)y a series of very d()ul)tful records, 
\\liicli. if \"ali(lato(l in future rc^turn periods, will connect the western 
covered by Brood VI he for the most part just outside the area covered by Brood V 
and on opposite sides of the latter. 
This interpretation by Professor C'aslh^ may ho in ])ari con-cd ; Imt in view 
of the wide range of this l)rood and the very scattering nature and separation of 
the individual swarms, it' seems to me more pro])a1)l(' to account for it as a develop- 
ment of scattering broods originating for the most )):iri iiidiixiulciitl y by means of 
retardation or acceleration from other broods, and none ol ilu; colonics developing 
enough to fill and hold any very large definite territory. In other words, most of the 
colonies are probably of late origin rather than the remnants of an old, extensive, 
worn-out brood. 
