88 DIPTERA OP NORTH AMERICA. [PART II. 



Observation. If the coloring of the tarsi should not prove con- 

 stant, the distinction from G. parvicornis would be rather diffi- 

 cult. It would then be necessary to observe that the feet of the 

 present species are decidedly somewhat more clumsy and covered 

 with coarser hair, and that the row of bristles on the upper side 

 of the fore tibia? consists of somewhat longer bristles. The con- 

 formity of both species in the structure of the antennas and of the 

 appendages of the hypopygium is striking. G. laevigatus cannot 

 be confounded with any other species, 



11. G. frequens LOEW. and 9. Obscure viridis vel aeneo-viridis, 

 antenuis nigris, facie et fronte ex albo cinereis, pedibus flavis, latnellis 

 hypopygii nigris. 



Dark-green or bronze-green ; antennae black ; face and front whitish-gray ; 

 feet yellow; lamellse of the hypopygium black. Long. corp. 0.12. 

 Long. al. 0.120.15. 



SYN. Gymnopternus frequens LOEW, Neue Beitr. VIII, 32, 10. 



Blackish-green, recently developed specimens rather bluish- 

 green, more aged specimens darker bronze-green. Face and front 

 covered with a whitish-gray dust. Antennas black, the third joint 

 quite small ; arista with a short but distinct pubescence. Cilia of 

 the inferior orbit black ; upon the surface of the scutellum there 

 are, besides the two bristles, several short hairs. Coxae and feet 

 yellow ; middle coxae almost on their whole outside blackish, or 

 at least brownish ; the fore coxae show only at the extreme basis 

 traces of a brownish tinge, such as is often also perceived on the 

 hind coxa?. The usual row of bristles on the upper side of the 

 fore tibiae is distinct and dense. The hind tarsi become, from the 

 tip of the first joint, more and more brown, their tip is black- 

 brown. The fore and middle tarsi are infuscated in a similar 

 manner, but less dark. Cilia of the tegula? black. Wings tinged 

 with blackish-gray, the third and fourth longitudinal veins with a 

 slight trace of convergency. The lamella? of the hypopygium 

 black, quite rounded at the end, fringed with black hairs ; the in- 

 terior appendages not bristly. 



Hob. Middle States. (Osten-Sacken.) 



Observation. G. frequens is, among the kindred species, the 

 only one whose males have black lamellce, and thus is easy to 

 recognize. Female specimens occur which have the dust upon 

 face and front much whiter ; in other respects they a,re like the 



