BROOD XVIII—TREDECIM—1919. 65 
Broods of the Thirteen- Year Race. 
Broop XVIII—Tredecim—1919. (Fig. 21.) 
This is an unimportant brood, most of the records representing 
scattering specimens rather than dense swarms. It was originally 
established by Professor Riley as Brood XVI on the testimony 
of Dr. G. B. Smith, who gives in his Register a record of its appear- 
ance in Cherokee County, Ga, in 1828, 184i, and 1854. Its appear- 
ance in the same locality was also recorded by Dr. J. G. Morris 
in 1867, and this seems to be the most important swarm of the brood. 
The records obtained since relate to scattering occurrences in three 
other States. 
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Fic. 21.—Map showing distribution of Brood XVIII, 1919. 
This brood immediately precedes in time of appearance the largest 
13-year brood known, namely, Brood XIX. The latter brood occu- 
pies the Mississippi Valley in the main, but with scattermg swarms 
extending well over the Southern States and into Virginia, and thus 
overlaps the territory covered by Brood XVIII, indicating very 
plainly the origin of the latter as accelerated swarms of Brood XIX. 
The localities for Brood XVIII as listed in Bulletin 14 are those 
given by Professor Riley in 1894.7 None of them was verified in 
a Annual Report, U. 8. Department of Agriculture, 1893, p. 204. (The records on 
which localities for this brood are based are given in an editorial note in Vol. V, Insect 
Life, pp. 298, 299.) 
31117—No. 71—07——5 
