THE STATE ENTOMOLOGIST. 31 



all surprising that errors were committed by former writers on the 

 subject. In the following chronology cf this insects periodical visits, 

 everything heretofore published has been revised as far as possible. 

 The mass of facts from which the generalizations are made would be 

 tedious if given in detail, and are therefore for the most part omitted. 

 This chronology could not, of course, be made complete from a single 

 season's researches,^and it may even contain errors, but it will remain 

 as a foundation lor luture work, and before another seventeen years 

 shall have passed away, we may hope to have this part of the history 

 of our curious Cicadas completed and perfected. 



While the discovery of the thirteen 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 extremely difficult. The northern boundary line of the 

 thirteen year broods is about latitude 37°, but in Illinois one of them 

 ascends between two and three degrees above this line, while the 

 seventeen year broods descend below it in several places, the two 

 broods sometimes occupying the Carolina. Thus the two broods some- 

 times occupy the same territory ; while two broods of the same kind, 

 appearing in different years may also overlap one another, as in the 

 instance given in the account of brood XXII in Virginia, where the 

 "locusts" appear every eighth and ninth year. In order to make the 

 subject as clear as possible, and to facilitate references, I have num- 

 bered the different broods of this insect in accordance with the date 

 of their future appearance from and after the present year. 



BROOD I.— Septemdecim— 1852, 1869. 



In the year 1869, and at intervals of seventeen years thereafter, 

 they will, in all probability, appear in the valley of the Connecticut 

 river. According to Dr. Asa Fitch (N. Y. Rep. I, p. 40), they appeared 

 there in ISIS and 1835, and according to Dr. Smith they occurred in 

 Franklin, Bristol and Hampshire counties, Massachusetts, in 1767, '84, 

 1801, '18, '35 and '52. 



BROOD II.— Tredecim— 1866, 1869. 



In the year 1869, being the same as the preceding, they will in all 

 probability appear in Georgia, in Habersham, Rabun? Muscogee, 

 Jasper, Greene, Washington and adjacent counties, having appeared 

 there in 1843 and 1856, according to Dr. Smith. 



BROOD III.— Septemdeclm~- 1853, 1S70. 



In the year 1870, and at intervals of seventeen years thereafter, 

 they will in all probability appear in what is known as the "Kreitz 

 Creek Valley" in York county, Pa., and possibly in Vinton county, 

 Ohio, and Jo. Daviess county, Ills. Mr. S. S. Rathvon, of Lancaster, 

 Pa., speaking of this brood, says : "Lancaster county is bounded on 

 the southwest by the Susquehanna river, dividing it from the county 



