DIFFERENT FORMS OF THE SPECIES. i 
described by Harris and Fitch, occurs in the greatest numbers, both in 
the 17- and 13-year broods. it will measure, on an average, 14 inches 
from the head to the tip of the closed wings, and almost always expands 
over 3 inches. The whole under side of the abdomen is of a dull 
orange-brown color, and, in the male more especially, tour or five of the 
segments are edged with the same color on the back. 
The other form (Fig. 1 6, ventral view of male) is not, on an average, 
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 described 
in 1851, by Dr. J. C. Fisher, in the ‘“ Proceedings of the Philadelphia 
Academy of Natural Sciences,” vol. V, pp. 272-273, as a new species of 
Cicada, hitherto confounded with septendecim, and was named Cicada 
cassinii. His description was followed by a note from Mr. John Cassin, 
in which the latter states that the two forms show no disposition to 
associate together, and produce very different cries. The fact of the 
very great difference in the song of the males has been fully confirmed 
by the observations of M. C. Hill, of northeastern Ohio, who likewise 
found that the small form 1s very much less numerous than the large one. 
The truest test of the specific distinction of these two forms lies in 
the comparative shape of the male genitalia, and the accompanying 
figures (c, d, e, and f, in Fig. 1), from drawings made in 1868 by Dr. H. A. 
Hagen, of Cambridge, Mass., show the male genital hooks of both. 
That of septendecim is represented on the outside at c, on the inside at 
d; and that of cassinii on the outside at e, and on the inside at /. 
By these figures it will be seen that there are sufficient differences to 
separate the two forms as distinct; but while the hooks of the large 
kind (septendecim) are quite constant in their appearances, those of the 
smaller kind (cassinii) are variable, and in some few specimens are in- 
distinguishable from those of the large kind. This circumstance, coup- 
led with the fact that the small kind regularly occurs with both the 
17- and 13-yéar broods, would indicate it to be a dimorphic form of 
the larger, and only entitled to varietal rank. 
The large form has been observed to make its appearance from eight 
to ten days earlier than the small form (cassinii), and there is not a 
single specimen of the latter, among a number of the 13-year brood 
(tredecim) that I captured in May, 1868, though I took a few specimens 
afterward. 
THE SEASON OF THEIR APPEARANCE AND DISAPPEARANCE. 
The season of their appearance and disappearance differs somewhat 
with the latitude, though not so materially as one might suppose. 
County, Pennsylvania, accompanied with the following: ‘‘I am justified, I think, in 
concluding these are two distinct species. They are different in size and coloration, 
produce entirely different stridulation, do not cohabit indiscriminately,” &c. 
3. The correspondent to the Department of Agriculture (July [1868] Rept.) from 
Hematite, Mo., says: ‘‘ 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.” 
