38 Journal New York Entomological Society. fVoi. xx. 



Validity of the Species. 



As can be seen by reference to the original descriptions and to 

 the accounts of the species in the Monographs of the Diptera (v. 4; 

 pp. 188, 189), the species are very closely related. The color of C. 

 flavofcrrnginca is "ferruginous-yellow"; that of C. indivisa, 

 " yellow." In both species, '' pleurae spotted, abdomen banded with 

 brown." The size of the species is the same. The main difference, 

 however, and that on which the second species, indivisa, was sepa- 

 rated, is that flavofcrruginca has a supernumerary cross-vein in cell 

 R3 (second submarginal cell of Osten Sacken) while indivisa has 

 none. 



In the examination of 154 specimens, of both sexes, from the 

 localities mentioned above, it was found that the two species are not 

 distinct. Fifty, or about one third, were, on the basis of the super- 

 numerary cross-vein, clearly referable to flavofcrruginca; seventy-two, 

 or nearly one half, to indivisa, while the remaining thirty-two included 

 almost every possible intergradation between them. 



It is significant that of the seven specimens of flavofcrruginca 

 that Osten Sacken had before him at the time of the original publica- 

 tion, one possessed a supernumerary cross-vein in cell R^ in both wings. 

 As can be seen from the following data, the species indivisa must fall 

 as a synonym of the type flaz'ofcrrnginca. Mr. M. C. Van Duzee, of 

 Buffalo, N. Y., came, quite independently, to the same conclusion. 



A Study of the Wing by Fields. 



Subcostal field: The tendency of vein Sc„ to migrate backwards is 

 well-marked. In one extreme, Sc, equals Sc^ ; in the other extreme, 

 Scj is fully five times the length of Sc„. 



Radial field: Fig. i shows a normal indivisa wing possessing only 

 the radial cross-vein. Fig. 2 shows a normal flaz'oferruginea wing, 

 possessing, besides a radial cross-vein, the supernumerary cross-vein 

 in cell R„. The radial cross-vein is probably always present. In three 

 specimens, one a female in both wings, in the other two, males, in the 

 left and right wings respectively, there is a supernumerary cross-vein 

 beside the radial cross-vein (see Fig. 3). Cell R. : Many specimens 

 possess a supernumerary cross-vein in this cell. This occurs both in 

 the flavofcrruginca form (Fig. 4) and in the indivisa form. In the 

 former case this cross-vein varies greatly in its relative position to 



