40 THE PERIODICAL CICADA. 
Brood XVI.— Tredecim— 1906. (Fig. 11.) 
This brood was originally established by Professor Eiley on the testi- 
mony of Dr. G. B. Smith, who gives in his register a record of its 
appearance in Cherokee County, Ga., in 1828, 1841, and 1854. Dr. J. 
G. Morris records its appearance in the same locality also in 1807. 
The records obtained since the latter date have extended its range 
so that it is now known from four States, occurring, however, in scat- 
tered localities, which may indicate an incompleteness of the records 
rather than the nonexistence of the brood in intervening districts. 
This brood immediately precedes in time of appearance the largest 
13 year brood known, namely, Brood XVIII, which next appears in 
1907. Brood XVIII occupies the Mississippi Valley as well as the South- 
eastern States, and lies immediately west of the territory occupied by 
Brood XVI, the relationship between the two being similar to that 
between Broods VI and VII, namely, of occupying adjoining territory 
and being separated in time of appearance by but one year. 
The localities for Brood XVI, as listed by Professor Riley in 1894, ] are 
given below. 2 None of them were verified in 1893, but an additional 
and very doubtful locality — Montgomery County, Ala. — was reported. 
It is very desirable to have confirmation of all the localities mentioned, 
and a careful study should be made to determine more accurately the 
range of the brood. 
The distribution, by States and counties, is as follows: 
Alabama. — Lowndes, Montgomery (?). 
Georgia. — Cohh, Cherokee. 
Tennessee. — Lincoln . 
North Carolina. — Lincoln, Moore. 
Brood XVIIL— Tredecim— 1907. (Fig. 12.) 
This is the largest of the 13-year broods, and also the best recorded 
perhaps, from the standpoint of distribution, of all the broods. It is 
Fitch's Brood No. 3, in part, and Brood XIII of Walsh-Riley. Its 
existence has been known since 1803. Its limits were most carefully 
studied by Walsh and Riley in 1868, particularly for the Missouri and 
Illinois localities. As has elsewhere been explained (p. 27), it seems 
probable that some of the northern counties, at least of Illinois and 
Missouri, listed for this brood belong to the 17-year Brood XXII, which 
appeared with Brood XVIII in the year mentioned. Some additional 
data were obtained in 1881 and published in Bulletin No. 8 of this 
Division, and the records were brought down to 1891 in the circular 
issued by Professor Riley in that year. The later records, mostly in 
reply to the circular just mentioned, considerably modify and extend 
'Ann. Rept. Dept, Agric. 1893, p. 204. 
2 The records on which the localities for this hrood are haBed are given in an edi- 
torial note in Vol. V, Insect Life, pp. 298-299. 
