150 DIPTERA OF NORTH AMERICA. [PART II. 



The name of the genus (from ttsufys, provided with a large penis) 

 has reference to one of its most striking characters. 



Only one European species has as yet been made known. 



Gen. XXV. NEMATOPROCTUS. 



Character. Antennae short ; first joint without hair ; second 

 joint short, transverse ; third joint small, in the male not larger 

 than in the female, rounded ;. the rather long arista entirely dor- 

 sal. The face, much narrower in the male than in the female, 

 does not reach as far as the inferior corner of the eye. Palpi re- 

 posing upon the proboscis, those of the female much larger than 

 those of the male. Front of equal breadth. ^ The lower part of 

 the occiput distinctly bearded. Eyes very hairy, especially 

 towards the lower corner. Scutellum not hairy. The abdomen 

 of the male has six segments; the small rounded, and a little im- 

 bedded, hypopygium is at its tip ; the exterior appendages are long 

 and filiform, the interior appendages very short and usually not 

 distinctly perceptible. The female abdomen shows five segments. 

 Wings a little narrowed towards the basis, the first longitudinal 

 vein not elongated ; the posterior transverse vein distant from the 

 margin of the wing by more than its own length ; the last segment 

 of the fourth longitudinal vein very gently inflected and towards 

 the end parallel with the third. Feet rather strong ; pulvilli of 

 the fore tarsi not enlarged ; the first joint of the hind tarsi without 

 bristles. 



The species of Nematoproctus mostly resemble in their habitus 

 the species of Porphyrops ; they differ from them, however, by an 

 altogether different structure of the antenna? ; the third joint of 

 the male being also very short and the position of the arista com- 

 pletely dorsal. They are less closely related to the species of 

 Argyra, to which they were formerly reckoned, as the first joint of 

 the antenna? is without hairs, the third joint of the male is not en- 

 larged, but as small as that of the female, the arista not subapical 

 but entirely dorsal, the first longitudinal vein of the wings not 

 elongated, further, the exterior appendages of the hypopygium 

 have not the shape of short lamellce, but of long threads. The 

 species of Nematoproctus agree with the species of Leuoostola in 

 the glabrousness of the first joint of the antennae : otherwise they 



