American Cicada or Locust. 49 



parting t/^ +Aa:y-i-Bx^ -{-Cij-\-'Dx-{-E = into its simple factors 

 and we have 



{y+a'x+b'){y-{-&x+d')=y' +Axy+Bx^- -i-Cy+Dx+E, (B). 

 Comparing the factors of (B) and any two of (A), for example the first 

 and second, and we have a'— a, b'=b, &=^c and d'=d, and (B) be- 

 comes a factor of (A), independently of x and y, for there are but 

 four independent co-efficients in (B) ; the co-efficients in (B) being 

 known in functions of those in F{xy), we have then f'v dy'^ -\-dx^ . 



Art. V. — JVoiices and Observations on the American Cicada, or 

 Locust; by Dr. S. P. Hildreth. 



Cicada, Septemdecem of Lin. Tettigonia, Septemdecera of Fabr. 

 Head black, eyes brick red, tl^iorax and back black or very dark 

 brown, the latter edged with orange ; wings transparent, immaculate, 

 lower margins of. a rich orange ; abdomen dark brown, the rings of 

 a dark yellow or of dun color ; opercula, oval ; legs and breast, same 

 color as that of the rings. 



No part of natural history more abounds in wonderful and extra- 

 ordinary productions, than that portion of it embraced in the study of 

 Entomology. Whether we consider the number and variety of in- 

 sects, or the curious changes they undergo in the progress of their 

 existence, we are led to admire not only their elegant forms and 

 beautiful colors, but also the harmony and order which attends all 

 the operations of nature. Amongst this numerous class, none ex- 

 cites the wonder and admiration of man, more than the cicada sep- 

 temdecera. The regularity with which they return at the expira- 

 tion of seventeen years, their simultaneous appearance over avast 

 extent of country, and the countless myriads of their numbers, equal- 

 ly arrest our attention. They have made their appearance at Mari- 

 etta, Ohio, at three different periods, since its first settlement, viz. : 

 in the year 1795 ; again in 1812 5 and now in 1829. With us they 

 have commenced their ascent from the earth the last of May and 

 first days of June ; and disappear the beginning of July, two or three 

 days earlier or later according to the temperature of the season. 



The month of May this season was very warm, and the cicadas 

 made their appearance rather earlier than heretofore. By the 15th 

 of this month, they had risen so near to the surface of the earth, 



