AMERICAN DIPTERA. 279 



consist entirely of black hairs; the long pile on the occiput is white; 

 in the vicinity of the vertex and on the greatest part of the posterior 

 orbit it is black. The pruinose design on the thoracic dorsum resem- 

 bles that of C. marginalis. It consists of three broad stripes covered 

 with dense brown bloom; the lateral ones are considerably abbre- 

 viated anteriorly; the intermediate one, seen from the front side, 

 appears entire; seen from the hind side, it appears bisected by a broad 

 black line; the region in front of the lateral stripes is covered with a 

 thin white bloom, of which there is also a trace in the intervals between 

 the middle stripe and the lateral ones. These intervals do not show 

 the polished surface of the broad lateral margin of the thoracic dorsum, 

 which is entirely free from bloom; the inner end of the thoracic suture, 

 on each side, shows a small spot of more dense whitish bloom. The 

 thoracic dorsum is beset with long black pile, which is rather scarce, 

 except on the polished black sides of the dorsum, where it is a little 

 more dense. Among this black pile there is a shorter and more delicate 

 white pubescence; it does not exist, however, on the polished black 

 portions of the dorsum. The polished black scutellum is rather densely 

 beset with long, exclusively black, pile. Pleurae with a thin grayish 

 bloom; their pubescence in front of the hal teres and of the roots of 

 the wings is altogether black; above the anterior coxae the stronger 

 hairs are black, the more delicate pile whitish. Segments 2-4 of the 

 polished black abdomen have on the posterior margin a very broad cross- 

 band of white bloom, which is even expanded in the middle; a similar 

 cross-band on the fifth segment is less broad, and a little interrupted 

 in the described specimen (perhaps in consequence of detrition). The 

 pile on the abdomen is rather long, but becomes gradually shorter to- 

 wards its end. On the first five segments it is chiefly white; however, 

 the side of the first three segments (exclusive of their posterior corners) 

 bear some black pile, which may show a trace of whitish reflection on 

 the tips of the single hairs only. This black pile reaches down to the 

 venter. From the sixth segment to the much developed hypopygium 

 the pile on the abdomen is altogether black. Coxae with whitish pile. 

 The black legs do not show any trace of lighter color; they have the 

 ordinary structure. The anterior tarsi are comparatively long, equaled 

 only by those of marginalis and montanus. The hairs on the legs are 

 long, chiefly whitish on the femora. At their tip, however, and on 

 the upper and hind side of the anterior femora, the hairs are more or 

 less exclusively black. On the under side of all the femora, especially 

 toward their base, the hairs have a pale yellowish tinge. The pubes- 

 cence of the anterior tibiae is chiefly black; but on their distal half 

 there is a good deal of white pile. On the posterior tibiae, the hairs 

 are prevailing white, although there are many black hairs near the 

 base, on the under side more than on the upper side. The hairs on 

 the tarsi are chiefly white, on the upper side the first three segments 



TRANS. AM. ENT. SOC, XXXV. JULY, 1909 



