REMARKS ON THE GENERIC CHARACTERS. 355 



from the usual transverse form, as, on the inside, it reaches a little over 

 the third joint; the arista is dorsal; the sixth longitudinal vein runs as 

 far as the margin of the wing ; the course of the last segment of the fourth 

 longitudinal vein varies in the different species, nevertheless it always 

 shows a distinct convergency towards the third longitudinal vein ; the 

 first joint of the hind tarsi is always considerably shorter than the second. 

 The color of all the species is either entirely yellow, or reddish-yellow, or 

 partly so. 



The genus Psilopus (44), closing the series, has the last segment of 

 the fourth longitudinal vein provided with a posterior branch ; this cha- 

 racter is not wanting in any of the American, European, or African species 

 that are known to me ; in some South Asiatic species, however, it is repre- 

 sented only by a fold of the wing, which sometimes is very indistinct. 

 Besides, the species of Psilopus are very easily recognized by the slender- 

 ness of the whole body and especially of the feet, by the very broad, more 

 or less excavated front, by the small antennae, provided with a long, thin, 

 dorsal or subapical, rarely almost entirely apical arista, and by the entirely 

 disengaged hypopygium. In the living state they keep the wings divari- 

 cated, which gives them an entirely different aspect from all other genera. 

 The males have their feet variously adorned, and in some species they are 

 distinguished by a structure of the wings peculiar to them. 



