o> 
CHRONOLOGICAL ACCOUNT OF DIFFERENT BROODS. 17 
From the foregoing, the importance of knowing beforehand when to 
expect them becomes apparent, and the following chronological state- 
ment will not only prove of scientific interest but of practical value. 
CHRONOLOGICAL HISTORY OF THE PERIODICAL CICADA, WITH DATES 
OF THE FUTURE APPEARANCE OF ALL WELL-ASCERTAINED BROODS 
THROUGHOUT THE COUNTRY. 
As the facts in reference to the existence of a 13-year brood, re- 
corded by Dr. D. L. Phares, in the Woodville (Miss.) Republican, and 
already referred to, were unknown to naturalists generally,and had 
remained unnoticed and unrecorded in natural history publications, it 
is only since the year 1863 that a number of these 13-year Broods 
have been fully established. [n that year I published the account of 
twenty-two distinct broods, including all the information that I could 
obtain at the time both as to 17-year and 13-year Broods. The mass of 
material from which the generalizations were made would have been 
tedious and voluminous, if given in detail, and was necessarily omitted. 
The following chronology includes such additional data as I have been 
able to obtain in the intervening seventeen years. 
Sut little increase in our knowledge as to the distribution of the dif- 
ferent broods has been made, so that the chronology remains essentially 
the same. I have collected during that time, from correspondents and 
otherwise, numerous additional facts, but most of them, and among them 
the most trusiworthy, relate to broods that were already well known; 
while of the smaller broods, and especially of those which are in need 
of confirmation, the additional data are extremely scanty. It should 
not be inferred, however, that those broods which have not been con- 
firmed, are necessarily invalid; because the additional data have been 
obtained chiefly when I have made some effort in that direction, while 
some years, owing to absence from the country or other causes, I have 
neglected to make inquiry. 
I shall therefore be very glad to receive from correspondents as full 
information, and from as many localities as possible, not only anent 
the two broods occurring this year, but any of the other broods men- 
tioned in this chronology. 
The passages in small type are in each case quoted from the work of 
1868, with the exception of the headings, in which the two dates given 
are made to include the last and the next future appearance of the dif- 
ferent broods. 
While the discovery of the 13-year broods dispelled much of the fog 
in which this chronology had hitherto been wrapped, it at the same 
time rendered a complete and lucid exposition of that chronology ex- 
tremely difficult. The northern boundary line of the 13-year broods is 
about latitude 38°, but in Illinois one of them ascends between twe and 
15936—Bul., 8——2 
