200 DIPTERA OP NORTH AMERICA. [PART II. 



Wings with black veins, hyaline, in the female with but few irre- 

 gular gray spots upon the apical half, in the male moreover near 

 the tip with a few grayish-black longitudinal stripes, and on 

 the tip itself with a black spot, containing near the end of the 

 fourth longitudinal vein anteriorly a round drop, which, -the light 

 falling through it, has a snow-white reflection ; on the anterior 

 margin of this drop, in the black, there is always a small paler 

 spot. The outline of the wings in the male differs considerably 

 from that of the female, being not only narrower, but also sinuated 

 on their whole posterior margin in a peculiar manner. The ex- 

 terior appendages of the short black hypopygium are two very 

 long threads, which reach back almost as far as the basis of the 

 abdomen, and which are beset on their whole length with very 

 long pale hairs. 



Hab. Middle States. (Osten-Sacken.) 



Gen. XXXVI. SCELLUS. 



Character. First joint of the antennae comparatively narrow, 

 bare ; the second short ; the third rounded, elongated only in a 

 hitherto undescribed European species, not excised on the edge. 

 Arista dorsal, apparently bare, distinctly two-jointed. The front 

 on the vertex but little deepened, a little narrower anteriorly. 

 The eyes much higher than broad, encased below by the linear 

 cheeks. Face of middling breadth, very long, reaching somewhat 

 below the lower corner of the eye ; its lowest sharply-edged part 

 is separated from the narrowly-margined eyes by an incision, 

 which turns away from the eyes on its upper end. Palpi recum- 

 bent, of middling and about equal size in both sexes. Proboscis 

 stout. Upper side of the thorax upon its middle with but 

 short bristles. Scutellum flat, with two bristles. Abdomen with- 

 out .bristles and only with scattered and very short hairs. The 

 abdomen of the male has five segments ; the first four are normally 

 developed, while the fifth is usually shortened, often also of a 

 different color ; the following segment is formed by the short, 

 half-imbedded hypopygium. At its lower end there are two 

 small, dark lamellae, directed obliquely downwards, which lie so 

 close together as to present the shap6 of a stout, dentiform pro- 

 jection ; besides these, the comparatively thick penis, bent down- 

 ward and curved, may be seen, but no other appendages. Between 



