A REVISION OF THE GENUS LOCUSTA, L. 



141 



oi, anj^vay, do not help much towards a definite solution of the question whether 

 these two forms are really distinct or not. 



60 



5S 



a: 



a^ -s 





JCv<\o\.oX ^>v«3r>ox.t.«.o»\^ 



Fig. 3. Diagram showing range of variation of the femoral proportion in 358 specimens of 



Lociista migratoria, L. 



Characters drawn from the Genitalia. 



The late Dr. N. Adelung. of the Petrograd Zoological Museum, who tried long 

 ago to solve the problem of migratoria ancl danica, suggested to me, when I began 

 to work at it, that the anatomy of the genitalia, especially those of the males, might 

 give definite proof of the specific difference of these insects, which he himself believed 

 to be distinct. He even prepared some rough sketches of the male genitalia of 

 both forms, which, in his opinion, showed that they may be separated without much 

 difficulty by the shape of the penis. He gave up his work, but handed over to me 

 his sketches and photographs. After a careful examination of these, and a com- 

 parison with several good preparations, I am fully convinced that Dr. Adelung's 

 conclusion is not right ; since the seeming difference between the penis in migratoria 

 and danica in his preparations (so far as I know, he dissected only one specimen of 

 each form) depends entirely on the fact that he studied the whole genital apparatus 

 without dissecting it, and the somewhat different shapes shown in two of his 

 drawings are merely the result of covering tissues having been more completely 

 removed in one case than in the other. 



