AMERICAN DIPTERA. 193 



8. Decidedly black species, with or without red on abdomen; the 



latter not obscured by grayish bloom 9. 



More reddish species, or if black, with ground color of abdomen 

 obscured by a bloom 10. 



9. Abdomen reddish-yellow, the base, venter, last two segments of 



female and genitalia of male, black seacidinus. 



Wholly black, abdomen polished black nitens. 



10. Southeastern species; reddish-yellow, abdomen quite slender, sub- 



polished; wings broad, uniformly brownish or blackish. 



subulatus. 

 Western species 11. 



1 1 . Abdomen unusually slender, wings longer and narrower. 



longulus. 

 Abdomen less elongate, wings shorter and usually broader. 



consanguineus, latipennis, pumilus, tenebrosus. 



12. Length about 15 mm.; black, but wholly and densely grayish- 



white pruinose; wings hyaline cinerascens. 



Length 20-23 mm.; species not grayish-white in appearance 13. 



13. Chamois-leather yellow species', abdomen proportionately long and 



slender, without black fascia? helvolus. 



Abdomen less elongate, yellowish-gray pruinose, in greased spec- 

 imens the segments showing black with posterior margins 

 and venter brick-red picticornis. 



Stenopogon gratus. 



Stenopogon gratus Loew, Cent., X, 31, 1872. 

 Stenopogon univittatns Loew, Berl. Ent. Zeit., 1874, 358. 



rf' ?. — Length 20 mm. — Black; bloom of thorax dull yellowish- 

 brown; mystax, pile and bristles of whole body pale, except on the 

 front, along the median line of the thoracic dorsum, and on the hypo- 

 pygium where the clothing is black; abdomen polished, slightly grayish 

 pruinose on the sides, and along the median line marked with more or 

 less broad reddish-yellow vitta extending from the second segment to 

 the tip; legs yellowish, the front and hind femora, except their apices, 

 a spot on the middle femora and the apical half of the hind tibiae 

 black; wings slightly tinged with black, the basal third, excepting the 

 edge of the costa, in the male, milky white; mesopleurae and hypo- 

 pleurae wholly bare, the sternopleurae with a tuft of long fine hair. 



Black; head grayish pruinose, clothed everywhere with sordid white 

 bristles and pile, the beard very fine and dense; hair along frontal 

 orbits, on ocellar tubercle, and on basal segments of antennae black; 

 on the latter sometimes yellow. Palpi black with pale hair. Antennae 

 black, base of third segment sometimes slightly yellowish; the style 

 about one-half as long as the third segment. Thorax dull yellowish- 

 brown pruinose, the three usual stripes showing only very faintly; 

 the pile and bristles on the lateral margins, posterior callosities, scutel- 



TRANS. AM. ENT. SOC, XXXV. (25) JUNE, 1909. 



