302 DIPTERA OF NORTH AMERICA. [PART IV. 



especially towards the scutellura, have also the othei" black marks 

 smaller iu extent and paler in coloring, often pale brown, and the 

 sternum is black on the sides only, yellow in the middle). A well- 

 marked groove extends from the scutellum along the middle of 

 the intermediate stripe, and is interrupted long before reaching 

 the collare ; the intervals between the intermediate and the lateral 

 stripes are rugoso-punctate. Halteres pale, knob dusky. Feet 

 brownish-yellow ; tip of the femora, of the tibiae, and of the two 

 first tarsal joints, infuscated ; two or three last tarsal joints 

 brown. Abdomen brownish, last segments darker, venter paler ; 

 genitals brownish-yellow. Wings (Tab. I, fig. 1) tinged with 

 brownish-cinereous ; stigma elliptical, brownish ; submarginal cell 

 longer than the first posterior ; discal cell of variable, generally 

 of moderate size, nearly quadrangular ; four posterior cells ; 

 position of the great cross-vein variable, sometimes a little before, 

 sometimes a little beyond the inner end of the discal cell ; the 

 small cross-vein is usually wanting, that is, the inner end of the 

 submarginal cell is more or less contiguous to the «inner end of 

 the discal cell ; the extent of this contiguity is variable in differ- 

 ent specimens ; sometimes the small cross-vein is present, but 

 then it is short (among twenty-one specimens which I have com- 

 pared, only four had the cross-vein) ; the fifth longitudinal vein is 

 incurved at its tip. 



Hab. Washington, D. C. ; Xew York ; White Mountains, N. H. ; 

 Illinois (LeBaron) ; New Jersey (Cresson). Not rare in May 

 and June. 



The aculeus of the male forceps is very often projecting in the 

 dry specimens of this species. It consists, as observed on p. 

 292, of three horny, slender styles, connate at the basis, separated 

 and somewhat club-shaped at the tip. 



The resemblance between this species and the European 01 

 glabrata M. is complete, as far as their coloring is concerned ; 

 and it is therefore the more remarkable that they should differ so 

 much in some structural details. The antennae of the male C. 

 glabrata are much shorter ; if extended backwards, they would 

 not extend much beyond the roots of the wings ; the joints are 

 short subcylindrical, attenuated at the basis. The wings are 

 distinctly longer, and the submarginal cell is not in contact with 

 the discal cell, so that the small cross-vein is present. The 



