114 DIPTERA OF NORTH AMERICA. [PART III. 



which is not described in the work itself. Wiedemann's collec- 

 tion proves that this species is identical with the present one. 



2. D. aemula n. sp. 9. — (Tab. VIII, f. 15.) Lutea. thoracis dorso 

 fasco, maculis nigris ante suturam qnatuor, pone sutnram nallis. 



Clay-yellow, dorsum of the thorax brown, with four brown spots before 

 the transverse sntnre and none beyond it. Long. corp. 0.25 ; cum 

 terebra 0.3t> ; long. al. 0.31. 



Very like the preceding in all plastic characters. Almost more 

 ochre-yellow than clay-yellow, the thoracic dorsum alone strongly 

 infuscated. The front, as in I), costalis, has on each side, near 

 the orbit, a shallow impression, clothed with white pollen ; below 

 it is a round, velvet-black spot, and immediately below the latter 

 again a spot of snow-white pollen, only the black spot is smaller 

 than in the preceding species; also the two snow-white transverse 

 spots on the upper part of the face are apparent, as in D. costalis. 

 On the thoracic dorsum there are not six, but only four rounded 

 oval velvet-black spots before the transverse suture, which corre- 

 spond to the outward ones of the preceding species ; there is no 

 trace of black spots on the other side of the suture. The scutel- 

 lum is convex and has four bristles ; the large first segment of 

 the flattened ovipositor is brownish-yellow, long, only moderately 

 attenuated towards its end. Feet of the same coloring with the 

 remainder of the body; the tarsi only moderately infuscated 

 towards their end. Halteres whitish-yellow. Wings of the same 

 shape as in I) costalis, only less long, especially their second 

 half less elongate, so that the small crossvein is somewhat uearer 

 the tip of the wing than in D costalis, and that the last section 

 of the longitudinal veins, ending in the apex of the wing, is 

 shorter ; otherwise the venation almost entirely agrees with that 

 of D. costalis. The surface of the wing is hyaline ; its posterior 

 half strongly tinged with a smoky-brownish. The brownish-black 

 design resembles that of the preceding species, differs, however, 

 from it by the dark border along the apex being much narrower; 

 the posterior limit of the border along the costa is also similar 

 to that in the preceding species, but not quite identical ; especially 

 where, in D. costalis. this limit crosses the second longitudinal 

 vein and leaves on the other side a hyaline segment of a circle ; 

 instead of the latter there is here only an indistinct paler dot and 

 between this and the costa no spot of a paler coloring ; the three 



