116 



DIPTERA OF NORTH AMERICA. 



[part IV. 



Gen. IX. mCRAIVOPTYCHA. 



One submarginal cell ; four posterior cells ; a discal cell ; the first longi- 

 tudinal vein very long, its tip is not very far back of the tip of the wing ; 

 the submarginal and the posterior cells also elongated ; a distinct fold, 

 originating from about the middle oj" the sixth longitudinal vein, runs along the 

 middle of the anal cell towards the posterior margin (Tab. I, fig. 8). Wings 

 elongated, strongly iridescent ; veins pubescent. Feet long, pilose ; tibise 

 without spurs at the tip ; erupodia distinct ; ungues smooth. Antennae 

 16-jointed, of moderate length. The forceps of the male consists of the 

 usual basal pieces, with claw-shaped or hook-shaped horny appendages 

 (Tab. Ill, fig. 12, one-half of the forceps of D. sobrina ; Tab. Ill, fig. 11, 

 forceps of D. nigripes). 



Rostrum short, epistoma transverse, stout ; lips rather fleshy ; 

 palpi short, second joint short, stout, the third a little longer, the 

 fourth not much longer than the third. Eyes glabrous, front 

 rather broad ; on the under side of the head, the eyes are con- 

 tiguous. The antennae, when bent backwards, reach the root of 

 the wings in the male ; they are a little shorter in the female ; 

 second joint stout ; four or five basal joints of the flagellum short 

 cylindrical; the following ones. more elongated, slightly incras- 

 sated at the basis ; verticils moderately long. Collare moderately 

 developed, the head closely applied to it ; thoracic suture deeply 

 marked. Feet long, rather stout, pilose ; empodia large and 

 distinct ; no spurs ; the usual excision exists on the under side 

 between the two last tarsal joints in the male. The appendages 

 of the male forceps of D. sohrina are double on each side ; a 

 horny, pointed, unguiform piece, and a more lamelliform, coria- 

 ceous, curved piece, with a brush of short hairs at the tip ; 

 the forceps of D. nigrvpes (Tab. Ill, fig. 11) has a somewhat 

 similar structure ; only the horny appendages are longer and 

 form a double curve (for more details, compare the explana- 

 tion of the plates at the end of this volume). Upper valves of the 

 ovipositor are of moderate length, arcuated, somewhat flattened, 

 and rather blunt at the tip. The wings (Tab. I, fig. 8, wing of 

 D. sohrina) are elongated and comparatively narrow ; the aux- 

 iliary vein reaches considerably beyond the origin of the praefurca, 

 and ends in the costa a short distance beyond the inner end of 

 the submarginal cell ; the subcostal cross-vein is close by its tip ; 

 the first Isngitudinal vein runs very far towards the apex of the 

 wing; its tip is nearer to this apex than to the tip of the aux- 



