20 



FIRST ANNUAL REPORT OF 



the 17 fear brood. Mr. Walsh informs me that Charles Darwin, Prof. 

 Asa Gray, and Dr. Hooker all agree in the belief that the 17-year and 

 the 13-year forms ought not to be ranked as distinct species, unless 

 other differences besides the period of development could be discover- 

 ed, the mere rarity of variability in such a point not being sufficient. 



TWO DISTINCT FORMS. 



It is not a little singular, also, that two distinct forms occur in 

 both broods — a large one and a small one — the former by far more 

 numerous than the latter. This fact has been observed in past years, 

 and was noticed the present year by independent observers in differ- 

 ent parts of the country.f Indeed, it was observed by Dr. Hildreth, 

 of Marietta, Ohio, as far back as 1830 (vide Silliman 7 s Journal XVIII, 

 p. 47). The true Cicada septemdecim of Linnreus (Fig. 6 J., ventral 

 view of male), as described by Harris and Fitch, occurs in the great- 

 est numbers, both in the 17 and 13-year broods. It will measure, on an 

 average, one and a half inches from the head to tip of the closed 

 wings, and almost always expands over three inches. The whole 

 under side of the abdomen is of a dull orange-brown color, and in 



[Fig 6.] 



the male more especially, four or five of the segments are edged -with 

 the same color on the back. 



The other form (Fig. 6 B, ventral view of male) is not, on an aver- 

 age, much more than two-thirds as large, and usually lacks entirely the 

 dull orange abdominal marks, though there is sometimes a faint trace of 

 them on the edges of the segments beneath. This small form was describ- 

 ed in 1851, by Dr. J. C. Fisher, in the Proceedings of the " Philadelphia 

 Academy of Natural Sciences," Vol. V, pp. 272-3, as a new species of 



f 1. Mr. V. T. Chambers, in the August number of the "American Naturalist," p. 332,. 

 is said to point out gome variation in color from those described by Dr. Fitch. 



2. Mr. S. S. Rathvon favored me with specimens of both species from Lancaster county, 

 Pa., accompanied with the following: "I am justified, I think, in concluding these are two dis- 

 tinct species. They are different in size and coloration, produce entirely different stridulation, 

 do not cohabit indiscriminately," etc. 



3. The correspondent to the Department of Agriculture (July Rep.) from JJematHe, Mo., 

 rays : "There are two species, one (both male and female) about twice the size of the other, 

 and differing greatly, also, in their cries and actions." 



