1851.] 



273 



but darker, and the segments of the abdomen below are more narrowly bordered 

 with yellow. Note different from that of C. septej^decim, and more like that of 

 some of the gras'shoppers. Inhabits the neighborhood of Philadelphia, appearing 

 in the winged or perfect state at intervals of seventeen years. 



Note on the above species of Cicada, and on the Cicada septendecim, Linn. 



By John Cassin. 



There are two distinct and easily recognized species of Cicada which appear at 

 intervals of seventeen years, and both of which were observed in this neighbor- 

 hood, especially in the woods at Powelton, during the present year. I saw them 

 in Delaware county, Pennsylvania, in 1834, and their entire specific distinctness 

 I have insisted on through good and evil report for the last seventeen years. 



It was, therefore, highly gratifying to me to have an opportunity of calling the 

 attention of the gentlemen of this Academy to the smaller species which Professor 

 Fisher has done me the honor of naming as above, and particularly to its note. 

 This is quite different from the prolonged and loud scream of the larger species, 

 (which is C. septendecim, Linn.) and begins with an introductory clip, clip, quite 

 peculiar. No disposition to associate with each other exists between the two 

 species, and although I have seen both on the same tree, yet most frequently they 

 were entirely separated, and occupied different parts of the woods. In 1834, I 

 observed the smaller species in localities which were somewhat favorably situa- 

 ted for moisture, but during the present year it occurred in localities as varied as 

 those of the other and larger species. At Powelton it was very abundant in an 

 orchard of apple trees on the most elevated part of the estate, and also on trees 

 in the adjacent woods. 



That the smaller species preferred low grounds was the observation of Dr. 

 Hildreth, of Marietta, Ohio, who, in an article on the Cicada septendecim, in Sil- 

 liman's Journal, xviii. p. 47, (1830) has the following paragraph : " There ap- 

 peared to be two varieties of the Cicada, one smaller than the other ; there was 

 also a striking difference in their notes. The smaller variety was more common 

 in the bottom lands and the larger in the hills." 



The size and the peculiar note are the most striking characters of the smaller 

 species, otherwise it much resembles the larger. The consideration of its claims 

 to specific distinction involves the general problem of specific character, which is 

 difficult in theory, but practically is readily solved. An animal which constantly 

 perpetuates its kind, or in other words reproduces itself either exactly or within 

 a demonstrable range of variation, is a species. These two Cicadce do not asson 

 ciate together as varieties commonly do. Of the very numerous instances in 

 which the phenomenon introductory to propagation has been observed this year, 

 in the course of the particular attention paid to these insects by gentlemen of this 

 Academy, not one case occurred in which the male and female of the two insects 

 were seen together. They are distinct species. 



The appearance of the Cicada sfptendecim in various localities at different 

 periods, each terminating intervals of seventeen years, for instance in Ohio in 

 1846 and in Eastern Pennsylvania in 1851, is a matter of remarkable interest. 

 Many independent ranges or provinces are known to exist in the United States, 

 and they are now ascertained to be so numerous that this species probably appears 



