24 THE PERIODICAL CICADA. 
on which they are established, and revising, supplementing, and bring- 
ing down to date all the facts which have been accumulated bearing 
on this subject. The carrying out of this plan was prevented by a long 
illness of Mr. Schwarz, and in place therefore of this more elaborate 
revision, I have prepared a brief description of the different broods, 
merely summarizing the distribution by States and counties, and 
omitting the voluminous historical and chronological records on which 
this distribution rests. The data for these summaries is based on the 
rather full accounts given in Bulletin Xo. 8 of this Division, supple- 
mented, however, by the local studies made by entomologists and 
others in various States, and particularly the rather voluminous records, 
collated and classified by Mr. Schwarz, obtained by the Department, 
chiefly in answer to circulars sent out from time to time. The data 
relative to Broods VI and XV, last appearing in 1897, and VII and 
XVII of the present year, is taken from circulars published by Mr. 
Schwarz in 1897 and 1898, with such additions to the 1897 broods as 
the records of that year made necessary. 
It is sincerely to be regretted that Mr. Schwarz was unable to prepare 
the data of all the broods and to give their very interesting chrono- 
logical history. His long familiarity with the subject would have 
enabled him to form a much more critical and correct judgment of the 
value of the records bearing on distribution than could the writer, and 
it is hoped that in a future edition of this bulletin this section may be 
replaced by matter prepared by Mr. Schwarz, as originally planned. 
The numbering of the broods, as noted elsewhere, is that given by 
Professor Riley in 1868, and was based on the sequence of their appear- 
ance after that date. This numbering has been generally adopted and 
it would be very unwise to alter it for purposes of temporary conven- 
ience. Brood III is nonexistent, having been originally founded on a 
record since proven to have been an error. 
' Of the broods as now accepted, sixteen were separated in the Walsh- 
Eiley paper of December, 1868 (Am. Ent. Vol. I, pp. 68-70). These 
broods were afterwards renumbered by Professor Eiley, as elsewhere 
explained (p. 21), and six additional broods added. The Walsh-Riley 
Broods I to XVI, inclusive, as now numbered are as follows : I, III, V, VI, 
VII, VIII, IX, XII, XIII, XIV, XV,XVII, XVIII,XX, XXI, and XXII. 
Of Riley's additions, Broods II, IV, X, XI, and XVI, and also XIX for 
the most part, are based on Dr. Smith's register, 1 as the notes in the 
First Missouri Report, and in Bulletin Xo. 8 of this Division indicate. 
The nine broods listed by Dr. Fitch in 1855 2 compared with the broods 
as now numbered are as follows : 
Brood 1 equals XII, 2 equals XX, 3 equals VIII and XVIII, 4 equals 
XXII, 5 equals VII and XV, 6 equals V, 7 equals XVII, 8 equals XX, 
and 9 equals I. 
1 See Appendix C. 
2 First Report, pp. 39-40. 
