DIPTERA. 330 



5 . Face a little wider ; wing with only a faint shadow of the apical spot. 

 Length 4*8 millim. 



Hab. Mexico, Atoyac in Vera Cruz (H. H. Smith). 

 Numerous males and females. 



7. Pelastoneurus punctipennis. (P. variegatus, Tab. VI. fig. 14, wing of s .) 

 Medeterus punctipennis, Say, Journ. Acad. Phil. vi. p. 292 x ; Complete Writings, ii. p. 362 2 . 



S . Face of medium width, the sides parallel, or a little divergent below ; suture well-marked ; ground-colour 

 entirely obscured by brown dust, which changes to whitish at the lower corners ; palpi long and pointed, 

 with whitish dust : proboscis very large and massive. Front opaque brown, darker in the middle. Antennae 

 black, rather large, the arista with short plumosity. Cilia of inferior orbit black. Thorax opaque brown, 

 with interrupted grey lines along the rows of inner dorsal bristles, and an interrupted median grey line, 

 all three being more distinct near the scutellum ; pleurae black, with thin grey dust ; halteres and tegula? 

 yellow, the latter with black hairs. Abdomen dull greyish-green, the incisures not prominently marked 

 with bands ; hypopygium small, short, black, with yellowish tip, the lamellae small, pointed, yellow. 

 Legs yellow, all the tarsi blackened from the extreme base, the tibiao, however, not black at the tip ; 

 middle and hind coxa? black at the base ; insertions of the tibial bristles marked by diffused brown spots. 

 Wings uniformly infuscated, with about twenty scattered roundish brown spots ; these are so distributed 

 as not to form distinct bands (see figure) ; last section of the fourth vein only gently bent towards the 

 third, gradually converging to the end, which is before the tip of the wing. 



Length 4-1 millim. 



Hab. Mexico 1 2 , Orizaba (II. II. Smith). 

 Five males. 



8. Pelastoneurus cognatus. 



Pelastoneurus cognatus, Loew, Mon. 1ST. Am. Dipt. ii. p. 109 ( ? ) '• 



cJ . Face rather narrow, with a distinct yellowish-brown stripe in the middle, the sides greyish-white ; antenna? 

 yellow, small, third joint a litte infuscated at the tip, arista with remarkably long plumosity. Front with 

 the ground-colour obscured by brownish-yellow dust, arranged somewhat in streaks. Cilia of lower orbit 

 white. Palpi black, with white dust. Thorax of a bronze colour, at the anterior end with the beginning 

 of a median line, and a blackish spot on the inner side of each humerus ; the velvety-black spot before 

 the root of the wing, while not divided, has a deep indentation on the upperside, and the anterior half 

 extends toward the middle of the dorsum ; the white spot in the sutural groove is small and rounded, 

 seated in the bottom of the groove (this is one of the best marks to distinguish the species in both sexes) ; 

 the large bristles of the dorsum arise from small black ish dots ; knob of halteres with a very slight infus- 

 cation ; tegula? yellow, with black cilia. Abdomen blackish-bronze, with small patches of white dust on 

 the sides of the segments. Hypopygium of medium size, black, with grey dust, the lamella? small, black, 

 with, small hairs (there seem to be a pair of small inner lamella?, of piceous colour) ; on the upper (ventral) 

 side of it the slender black organ usually considered to be the penis is much thicker than in related forms, 

 and has three or four hairs at its tip. Legs yellow ; middle and hind coxa? black nearly to the tips ; tarsi 

 but little infuscated ; fore coxa? not infuscated. Wings greyish, with a faint cloud on the cross-vein, and 

 another, even fainter, on the middle of the last section of the fourth vein, this section having a gradual 

 and even curvature. 



9. Easily distinguished from the corresponding sex of the other species of the genus by the small round 

 glittering white dot in the sutural groove, &c. 



Length 3-3'8 millim. 



Hab. North America, Connecticut 1 . — Mexico, Vera Cruz (H. II. Smith). 

 Three males and four females from Vera Cruz ; I also have a female, 4-8 millim. in 

 length, from Connecticut, collected by Dr. Williston. The male is now described for 



the first time. 



2x2 



