346 DIPTERA OF NORTH AMERICA. [PART II. 



HygroceleuthuS and Dolichopus consists in the structure of the 

 head, which is higher and narrower in Hygroceleuthus, especially in the 

 males, and in the length of the face, which reaches farther down in Hygro- 

 celeuthus aud gives to the head a different profile. The genus Rhago- 

 neurus differs from Tachytrechus and Dolichopus by the feathered arista 

 of the antennae and the different structure of the male abdomen, which is 

 a little compressed laterally, as also by the fracture of the last segment of 

 the fourth longitudinal vein peculiar to it, and in which it is not equalled 

 by any of those species of Dolichopus which have the last segment of the 

 fourth longitudinal vein also fractured ; in the structure of the head Rha- 

 goneurus agrees with Dolichopus, in that of the hypopygiuin with Doli- 

 chopus and Tachytrechus.' 



1 Mr. Rondani has established the genus Rhageneura on those European 

 species of Dolichopus, the fourth longitudinal vein of which is broken. This 

 genus cannot be retained in this sense for several reasons. 1. Because 

 these species do not differ at all from the other species of the genus in the 

 other parts of their organization. 2. Because the fracture of the fourth 

 longitudinal vein of these species is very different in kind as well as in 

 degree. 3. Because this fracture in some species is sometimes present, 

 sometimes not. I have already stated above, on p. 19, that Dol. ziczac 

 Wied. requires the establishment of a new genus. At that time I knew 

 only this one species of the newly proposed genus, and considered therefore 

 its establishment as premature. Since then I have become acquainted 

 with several species, so that I feel prepared now to introduce this new 

 genus, and take occasion at the same time to furnish a description of the 

 typical species which I have figured. I propose for this new genus the 

 name of Rhageneura, introduced by Rondaui in a somewhat different sense, 

 modifying it only in the more correct Rhagoneurus. The characters of 

 this genus are : First joint of the antennae with bristles on the upper side ; 

 the arista of the antennae feathered or hairy; first joint of the hind tarsi 

 with a bristle ; fourth longitudinal vein twice broken at right angles, with 

 a considerable stump of a vein at each angle of the fracture ; abdomen of 

 the male a little compressed laterally ; hypopygium entirely disengaged, 

 as in Dolichopus. The figured species is the following : 

 Rhagoneurus pohjchromus nov. sp. and J . Viridis, thorace violaceo- 

 et cupreo-variegato, fronte violacea, antennis runs, pedibiis flavis, alis 

 cinereis, venis transversis non infuscatis. 

 ^ . Facie ochracea, hypopygii margine supero et apice flavis, lamellis 



parvis, albicantibus, teuuissime nigro-marginatis. 

 9 Facie albida. 



Green with violet and coppery spots on the thorax ; front violet ; an- 

 tennas red ; feet yellow ; wings gray ; the transverse veins without a 

 dark margin. 



1 . Face ochraceous ; upper margin and tip of the hypopygium yellow, 

 the small lamellae whitish, with a very narrow black margin. 



