t 



114 DIPTERA OF NORTH AMERICA. [PART II. 



Mack. Front dull from being covered with an ochre-yellow dust. 

 Cilia of the lateral and inferior orbit whitish.. The upper side of 

 the thorax is covered with a grayish ochre-yellow dust, so as to 

 make the green ground color but little apparent ; up 1 on its middle 

 there are two brown longitudinal lines, which diverge a little behind 

 and' are very much shortened ; some portions of the usual lateral 

 stripes are also visible, and the single bristles are inserted upon 

 brownish-black spots. Scutellum dull, usually more brown than 

 the upper side of the thorax. Pleurae greenish-gray. Abdomen 

 green, covered with a rather thick whitish dust, which gives it a 

 somewhat checkered appearance ; viewed from another point, the 

 middle line and the posterior margins of the single segments ap- 

 pear almost black. Hypopygiurn black, with whitish dust ; the 

 lamellae are of moderate size, rounded oval, with short hairs, 

 which are black on the upper and apical margin, and whitish on 

 the lower margin. Coxae black, with yellow- whitish dust ; fore 

 coxas beset with extremely short, delicate and sparse hairs ; be- 

 sides, on the inner side of their basis there are a few stiif black 

 hairs, and towards the tip a few black bristles. Feet black ; fe- 

 mora and tibia? with a metallic-green lustre ; on the front side of 

 the hind femora there is a single black bristle, rather distant from 

 the tip ; very characteristic are the bristles on the upper side of 

 the hind tibiae, which have shorter bristles in the vicinity of the 

 basis and a longer one near the tip, otherwise of the usual shape ; 

 upon the middle, however, there is a row of three solitary remark- 

 ably flattened bristles. All the tarsi plain. Cilia of the tegulae 

 black. Wings narrow, towards the basis remarkably narrowed, 

 grayish-hyaline ; the second portion of the marginal cell more dis- 

 tinctly dusky, the posterior transverse vein with a somewhat 

 darker margin ; the costa distinctly thickened upon the middle of 

 its first segment. 



Hob. District of Columbia. (Osten-Sacken.) 



Gen. VII. QRTHOCHILE. 



The following are characters of the genus OrtliocMle : Probos- 

 cis slender, elongated and directed straight downwards. Palpi 

 likewise very elongated. The first joint of the antennae distinctly 

 hairy on the upper side, the second transverse, the third not elon- 

 gated. Arista dorsal, with an extremely short, almost impercepti- 



