NORTH AMERICAN DIPTERA. 12") 



Described froni one specimen; Bi'ookings, S. Dak. (J. M. Aldricli.j 



€iIyKTO€iL.OSSA n. gen. 



Rather small, shining black species, with abdominal segments sil- 

 very at base. Belongs in Phytoina\ Head irregnlarly quadrilateral 

 in profile ; front rather prominent, a little more than one-halt width 

 of head in $ , slightly wider before, face about one-half width of 

 head; frontal bristles in two rows on each si<le, the inner row de- 

 scending obliquely nearly to or a little below third antennal joint ; 

 two inner vertical bristles strongest, posterior three or four of each 

 row directed backward, a little stronger than anterior ones, which 

 are directed more or less inward, particularly those of inner rows; 

 posterior ones of outer rows directed also outward, and those of inner 

 rows inward ; two to five orbital bristles in $ directed forward, 

 often one of them is weaker, and may be directed either forward or 

 backward. Face a little receding, epistoma somewhat ])rominent ; 

 facial depression more or less triangular, in the mean from three- 

 fifths to two-thirds width of face, widest below, n)oderately deep, but 

 divided into two furrows by a well developed median carina ; facial 

 ridges ciliate to within short distance of base of third antennal joint, 

 a little constricted below ; sides of face wide above, very narrow 

 below, bare ; cheeks narrow, bare except some bristles on or near 

 lower border ; vibrissfc moderately strong, inserted on a line with 

 oral margin, but somewhat removed from its sides. Eyes bare, de- 

 scending a little short of vibrissie. Antennte fully as long as face, 

 second joint slightly or hardly elongate; third joint four to six 

 times as long as second, noticeably swollen toward tip, the posterior 

 apical corner more rounded than anterior ; arista much shorter than 

 third antennal joint, bare, thickened throughout, apex sharpened, 

 distinctly o-jointed, and usually geniculate, second joint very long, 

 from one-half to two-thirds as long as last joint, distinctly curved or 

 bowed. Proboscis about twice as long as hight of head, the apical 

 three-fourths or more below geniculation extremely fine and bristle- 

 like, flattened, basal j)()rti()n of latter slightly or considerably elon- 

 gate bulbous, tip usually curved forward or upward, sometinies cleft, 

 no labella ; palpi well developed, more or less slender and filiform, 

 or thickened at tip. Thorax narrower than head ; scutellum with a 

 weak apical pair of macrochsetse, a strong subapical pair exceeding 

 middle of second abdominal segment, and two shorter lateral pairs. 

 Abdomen hardly broader than thorax, somewhat elongate oval. 



TR.\NS. AM. ENT. SOC. XIX. M.\Y. 1892. 



