1916.] NATURAL SCIENCES OF PHILADELPHIA. 199 



structural dimorphism, aside from the subject of macropterism and 

 brachypterism, is found in certain Dermaptera and in the Orthoptera 

 in certain groups of Phasmidse, very frequently in the Acrydiinae, 



in certain Truxalina 1 (Eritettix, Macncillia, etc.) and in species of 

 Gryllus. 



The final word on this very perplexing question can be said only 

 alter careful breeding experiments have been made. As far as 

 examination of dry material and field observations are concerned, 

 we feel that little additional information, except purely statistical 

 data, can be secured. We have had this problem in mind for over 

 ten years and have utilized every opportunity to secure data bearing 

 upon it, with the results here summarized. 



Schistocerca obscura (Fabricius). 



Delaware. Ortega, Duval County, IX, 6, 1913, 



Dover, (Macomber), 1 9 , [A. N. S. P.]. ( w - T - Davis), 19/ 



North Carolina. Georgia. 



Wrightsville, IX, 7, 1911, (R. & H.), Thompson's Mills, X, 1909, (H. A. 



5c^,59. Allard), 1 9 , [U. S. N. M.]. 



8»dh Carolina. JSt^l} f NS^/t^V^ 



Florence, IX, 6, 1911, (R. & H.), 2 *, **%$?' ^ *' 1913 ' ^ & H °' * *' 



v I, 9- t *■ vttt is ioiq ,T ^ ^ Savannah, VIII, 7, 1878, (Grote), 1 9 ; 

 Ashley Junction, Mil, 15, 1913, (R.), yni | 2 2, 1881, (Howard), 19, 



1 cf. [bothU. S. N. M.]. 



Florida. Tybee island, IX, 2, 1913, (R. & H.), 



Atlantic Beach, Mil, 24, 1911, (R. & 2 d\ 4 9. 



H.), 1 9 . Sandfly; IX, 3, 1911, (R. & H.), 1 9 . 



South Jacksonville, IX, 7 and 28, 1913, Cumberland Island, VIII, 31, 1911, 



(W. T. Davis), 1 tf, 19. (R. & H.), 5 <?, 119. 



The different form of the subgenital plate of the male is a constant 

 and readily perceived diagnostic character for this species when 

 compared with alutacea, to which it is closely related. The presence 

 of dark bars on the dorsal surface of the caudal femora, and the 

 general dark purplish or blackish color of the caudal tibiae, we find 

 to be variable, the former, however, being generally distinctly 

 indicated in striped specimens of both sexes of this species and 

 frequently absent or very faint in brownish individuals. In conse- 

 quence brown females, having the femora without dark bars on the 

 dorsal surface, are with difficulty separated from similarly colored 

 females of alutacea, the greater size of obscura being the best means 

 of discrimination in such cases, as no constant differential structural 

 features exist, as far as we can determine. We have before us one 

 striped male from Wrightsville, North Carolina, which has the usual 

 femoral bars practically absent, while of the "rubiginosa" type we have 



