DIAPHORUS. .151 



the arista is likewise by no means always apical ; on the contrary, 

 it is even subapical in the majority of the species. 



The same happens to be the case with Diaphorus, where the 

 eyes of the males are contiguous upon the front in some of the 

 species only, while in others they are separated by the broad front ; 

 the arista likewise is not always distinctly dorsal, but in many 

 species subapical, and in some truly apical. Thus none of the 

 distinctive marks, which Meigen had established for these two 

 genera, holds good, except for Chrysotus, the wings divaricated 

 in repose, and the parallel wings for Diaphorus. As this charac- 

 ter can only be observed on living specimens, it is, even if proved 

 to be correct, entirely insufficient for a systematical distinction of 

 both genera. 



In order to escape this difficulty there are two different ways to 

 be followed : either the species, with the eyes of the males not 

 separated upon the front, must remain with Diaphorus, and those 

 the eyes of which, in the male, are contiguous below the antennae, 

 must go with Chrysotus, and a new genus must be established for 

 the species of Diaphorus and Chrysotus, the males of which have 

 the eyes distant above as well as below the antennae. The other 

 way to follow would be to discover characters for the distinction 

 of Chrysotus and Diaphorus better than those which Meigen had 

 chosen. 



The first of these two alternatives is liable to serious objections. 

 The establishment of three genera would disconnect the relation 

 naturally existing between the insects forming them, a relation 

 based upon their general habitus, and their distinction would con- 

 sist in a character pertaining merely to the male. Therefore 

 nothing remains but to try the other way. 



If we compare first the species of Chrysotus, in which the eyes 

 of the males are contiguous under the antennas, with those of Dia- 

 phorus, where the eyes are not separated on the front, we will 

 observe the following distinctions : The structure of the body of 

 the species of Diaphorus is more slender, the abdomen especially 

 is comparatively narrower, and more elongated; the hypopy- 

 gium of the male has on the hind side four bristles of rather 

 striking size ; the feet are longer, the pulvilli of the fore tarsi in 

 the male are not only enlarged, but considerably elongated (with 

 the exception of D. nigricans Meig.) ; the wings of Diapho- 



