280 AMERICAN DIPTERA. 



HIATU^i gen. nov. (Plate VI, figs. 1, 2, 3, 4). 



Long and slender flies ; head longer than high; front as wide as 

 the eye and parallel, protruding at antennce, face not distinctly cari- 

 nate ; eyes nearly round; cheeks very narrow; mouth very large, 

 drawn upwards in front, and protruding as far forwards as the front ; 

 thorax with three dorso-centrals behind the suture ; first vein bristly 

 at end; hind femora much thickened. 



Head as long or longer than high, broader than high, wider than 

 the thorax. Eyes large and nearly round. Front as broad as eyes, 

 projecting at the antennae, not concave, smooth ; orbits parallel as 

 far as antennae, then narrowing; besides the usual vertical bristles are 

 two transfrontals, otherwise bearing scattered minute hairs. Face 

 short, excavated in profile; antennal fovese shallow ; carina acute; 

 sides of face very narrow, overhanging the depression, the ridge 

 minutely bristly on lower portion. Cheeks very narrow, about one- 

 eighth to one-tenth height of eye, giving the head in profile, a flat 

 appearance. Occiput con vexed, about one-eighth length of head. 

 Mouth very large, one-half width of head, drawn upwards in front; 

 margin bare, excepting towards the occiput. Clypeus small. Pro- 

 boscis short, thick. Palpi filiform, thickened at tip. Antennae 

 nearly as long as face ; second joint very short ; third joint rounded 

 at apex, front corner obtuse, not sharply pointed, front edge flat, 

 not concave ; arista bare, distinctly thickened at base. 



Thorax dusted whitish, elongate, nearly twice as long as wide, 

 bearing bristles as follows : three post dorso-centrals, two post alars, 

 one humeral, two nolapleurals, a distinct mesopleural, one propleural, 

 very small, a series of three to five small bristles on the prothorax 

 before the prostigma. Scutellum with four marginal bristles. 



Abdomen, of male, hardly longer than the thorax, broadest at 

 first and second segments; the first segment nearly twice as long as 

 the second ; the fourth as long as the first ; the fifth somewhat swol- 

 len and retracted ; o^ female, longer than thorax, otherwise as male ; 

 first segment of the ovipositor flat, as broad as the fifth segment; 

 second as long as first. 



Legs long ; femora thickened, especially of the hind leg ; promi- 

 nent bristles as follows : anterior femora with a few extensors, a 

 series of minute lateral flexors; middle tibia with a few apical 

 flexors ; hind femora with one median lateral extensor. 



Wings one and one half times as long as the thorax ; costa and 



