BROOD XXIII—TREDECIM—1911. 7a 
Broop X XIII—Tredecim—1911. (Fig. 26.) 
This is Brood No. 5 of Fitch, Brood V also of Walsh-Riley, and 
Brood VII of Riley. There are two large 13-year broods, which 
honor Brood XXIII divides with Brood XIX. As indicated by Mr. 
Schwarz in Circular No. 30, both of these broods occupy the Missis- 
sippi Valley from northern Missouri and southern Illinois to Louisiana ; 
but while Brood XIX occurs also in many other localities, Brood 
XXIII is confined more strictly to the Mississippi Valley region. At 
the time of the recurrence of this brood in 1898 a very careful investi- 
gation was undertaken by the writer of its distribution. 
Several thousand replies were received in response to a circular 
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Fig. 26.—Map showing distribution of Brood XXIII, 1911. 
sent out, many of which were negative, the investigation being 
extended throughout all States in which there was any likelihood of 
the appearance of the Cicada, and necessarily covering many counties 
and districts where the Cicada was not suspected. Local investiga- 
tions were also undertaken by the official entomologists in several 
States, Professor Forbes adding four or five new counties for Illinois, 
Professor Garman adding six counties for Kentucky not previously 
reported, all in the eastern end of the State, and Professor Stedman 
adding one new county from Missouri. In ali three of these reports 
our own records were confirmed for nearly every county. The 
results of this canvass up to June 20 were recorded in Bulletin No. 14 
