84 DIPTERA OP NORTH AMERICA. [PART III. 



those of Platystoma. They are, however, easily distinguished 

 from the latter by the narrower front, the much less turgid 

 occiput, the larger and flatter scutellum and the much broader 

 wings, with straight, very much diverging longitudinal veins. 



1. A. pertusus n. sp. % and £ .—(Tab. VIII, f. 1) Viridis, nitidus 



alae nigrae, guttis et fascia subapicali hyalinis. 



Green, shining ; wings black with hyaline dots and a hyaline crossband 

 before the tip. Long. corp. 0.13—0.14; long. al. 0.11—0.12. 



Dark metallic-green, shining. Head black; the front blackish- 

 brown, even, rather long, but only of a medium breadth, not 

 narrowed anteriorly ; the ocelli are closely approximated to each 

 other near the edge of the vertex; the small ocellar triangle and 

 the little stripes running down at the corners of the vertex are 

 of a shining blackish-green. Bristles of the vertex rather long, 

 directed backwards ; the bristle which is in front of them on each 

 side is short; the ocellar bristles are not distinct. Antennae 

 reaching down to the edge of the mouth, brownish-yellow; their 

 narrow third joint is blackish at the tip; often the greater part 

 of its outer side is brownish. Face excavated ; its lateral portions 

 very narrow; antennal foveae indistinct. The shining black 

 clypeus broad. Palpi broad, shining black, with a paler border 

 on the under side and at the tip; proboscis of moderate thick- 

 ness; mentum but little swollen. Eyes much hjgher than 

 broad; cheeks narrow; occiput but little turgid. Thorax very 

 delicately transversely aciculate. Scutellum large, flat, weakly 

 rugose, with four bristles. Abdomen more distinctly rugose. 

 Ovipositor black, considerably extensile. Feet black, brownish- 

 black in less mature specimens; the first joint of the front and 

 hind tarsi and the first three joints of the middle tarsi of a dirty 

 ochre-yellow. Halteres black, tegulae but little developed. Wings 

 rather broad, black, more grayish-black near the hind margin ; 

 immediately before their apex is a conspicuous, arcuated, hyaline 

 crossband ; before this band there is a moderate number of hyaline 

 dots of regular shape, which become more sparse towards the 

 anterior margin; five dots which are nearest to the crossband 

 form a row, parallel to the latter; the blackish-gray coloring near 

 the hind margin of the wings has no hyaline spots. The veins 

 are much more straight than in Platystoma and very diverging; 



