178 DIPT ERA OF NORTH AMERICA. [PART 111^ 



1. C. nigern. sp. . Modice nitens, niger, halteribus concoloribus, 

 coxis pedibusque luteis, alis cinereis, adversus costam et apicem nigris. 



Moderately shilling, black, with, the halteres of the same color ; coxae and 

 feet dark- yellow ; wings gray, tinged with black along the anterior 

 margin and towards the apex. Long. corp. $ 0.15 ; $ cum terebri 

 0.21; long. al. $ 0.11; ? 0.13. 



Black, moderately shining, beset with short, unconspicuous, 

 black hairs. The bristles on the sides of the vertex of medium 

 length. Antennae deep black; third joint comparatively long, 

 of equal breadth, rounded at the end ; the bare arista of medium 

 length, perceptibly stouter towards the basis; the parts of the 

 mouth comparatively small and rather hidden. Abdomen long 

 and narrow, of almost equal breadth. The first segment of the 

 ovipositor, at the basis, has the same breadth as the posterior 

 margin of the last abdominal segment ; it is but little narrowed 

 towards its end; it is clothed with a black pubescence which, 

 although by no means long, is nevertheless rather conspicuous ; 

 in some specimens its sides are turned upwards, so that it appears 

 narrower towards its end than it really is; the second and third 

 joints of the ovipositor are generally retracted within the first, 

 which might produce the impression that the species is a new 

 form of Micropezidse ; when they are projecting, both prove to 

 be comparatively rather broad and the third ends in a short, but 

 sharp point. Coxae and feet are of a dark yellow color ; the tarsi 

 are infuscated towards the tip ; the hind femora with some stiff 

 bristles of moderate length on their under side, which, however, 

 do not resemble spines. Halteres blackish. Wings gray with 

 black veins ; the apex of the wings blackened and the costa with 

 a black border, beginning at the tip of the costal cell. 

 ffab. Texas (Belfrage). 



Gen. II. RICHARDIA ROB. DESV. 



Charact. Front of most species rather broad ; ocelli not far from the edge 

 of the vertex ; the anterior one more distant from the posterior ones 

 than these from each other ; in the males of several species the head 

 is very much expanded transversely, as in the species of Achias, 



Arista pubescent, or short-feathery. 



Mesothoracic and prothoracic bristles present, although weak. 



Scutellum with four bristles ; metathorax steep. 



Abdomen narrow, still more narrowed towards the basis. 



Front femora only moderately incrassated; the intermediate ones not 



