THE CLASSIFICATION OF THE BROODS. PAS) 
It is possible to conceive also of conditions which would result in 
the acceleration or retardation in the development of an entire brood 
or broods of the Cicada, such as variation in climatic conditions, 
geological changes, or changed conditions of the topography of the 
country, including the character of the vegetation. 
In this or other ways, at any rate, the Cicada has become broken 
up into a large number of distinct broods, often covering different 
territory, but not necessarily so doing, each, however, maintaining 
its regular time of appearance. 
The sight but constant tendency to variation which has brought 
into existence the broods now so well marked, continued indefinitely, 
would so break up and scatter the present broods as to ultimately 
obscure them altogether, and the overlapping of districts and the 
variation in time of appearance would lead to a rather general occur- 
rence every year of the periodical Cicada throughout its range, the 
long period for development, however, still persisting. Anticipating 
such an outcome from the intermixture and overlapping merely of 
different broods, Doctor Smith (Smith MS.) rather mournfully says: 
“Tn those times, if these sayings of mine should be thought of, they 
will be ridiculed as a superstitious legend of the olden times.”’ 
THE CLASSIFICATION OF THE Broops. 
In the first edition of this bulletin the numerical designation of the 
broods of the two races suggested by Professor Riley was followed. 
This numbering has, however, objectionable features and obscures 
the relations of the broods of each race to each other. To overcome 
these objections a new system of numbering was proposed by the 
writer,” which has since been generally adopted. The reasons for 
making this change and the numerical designations proposed are here 
reproduced with little change from the publication cited. 
The earlier writers, viz, Prof. Nat. Potter, Dr. William T. Harris, 
and Dr. G. B. Smith, classified the broods solely according to the 
years of their appearance. The unpublished register left by Doctor 
Smith includes every important brood now known classified accord- 
ing to race, and gives the localities for one additional brood, the 
existence of which seems not to have been confirmed. Though 
lacking any special designation for the broods, Doctor Smith’s classi- 
fication is as complete and accurate as that published by Doctor 
Riley and since followed by all later writers.’ Dr. Asa Fitch was the 
first to introduce a numbering system for the different broods, enu- 
merating nine altogether, but his data were very limited and he was 
not aware of the thirteen-year southern period, and there necessarily 
resulted no little confusion of the broods of the two races. The 
@Bull. 18, n.s., Div. Ent., U. 8. Dept. Agric., pp. 52-58, 1898. 
+b See Appendix. 
