AMERICAN DIPTERA. 215 



halteres, white; elsewhere on the dorsum and. scutellum, black. Hal- 

 teres yellowish. Abdomen wholly black, thinly whitish pruinose, at 

 the base and on the sides more densely so; aside from the short white 

 bristles on the lateral margins of segment 1, with microscopic black 

 hairs above, and similar white ones on the sides. Hypopygium black, 

 with black pile. Legs black with short black hair and longer, but pro- 

 portionately short black bristles; the middle almost wholly, and the 

 hind femora in part, with short white hair; claws wholly black, pulvilli 

 blackish. Wings uniformly blackish with white veins; the first pos- 

 terior cell closed before the margin and with a short peduncle. 



9 • — The type female differs from the male, to which it is very similar, 

 in the pale yellowish color of the bloom of the head, thorax and coxa;; 

 in the reddish color of the tergum of the abdomen covering the third, 

 fourth and fifth segments except on the sides, and the sixth segment 

 toward the base; and in that the last four segments of the abdomen 

 are not pruinose, but polished. 



Type. — M. C. Z. Single male and female type. 



Habitat. — Dallas (type) and Victoria (June 5), Texas. 



In Note 100 of his " Catalogue of the Diptera of North 

 America," Osten Sacken says, "The Mus. Comp. Zool. pos- 

 sesses a number of specimens of a Microstylum which are of 

 the same size as M. morosum, but which Dr. Loew, to whom 

 I communicated a specimen, considers a different species and 

 calls M. pollens. It is less intensely black than morosum, 

 antennas and legs are often quite reddish-brown, the bristles 

 of the sides of the thoracic dorsum are yellowish-white, etc. 

 As I had no opportunity to make a thorough comparative 

 study of both species, I merely draw the attention of col- 

 lectors to it." On the strength of this note, Prof. Aldrich, in 

 his recent catalogue, raises "pollens" to a specific rank with 

 the note " Osten Sacken's reference was not intended as a 

 description, but I think the data and the availability of the 

 types make it valid." 



The specimens thus referred to are five females collected at 

 Dallas, Texas, the type locality for morosum. I do not con- 

 sider morosum and these five specimens which Loew calls 

 " pollons," in litt., as distinct species, for the study of con- 

 siderable material at the M. C. Z., the National Museum and 

 the Am. Ent. Soc. shows that even the typical morosum is 

 inclined to vary as to the color of antennas, etc., and even 



TRAXS. AM. ENT. SOC., XXXV. JUNE, 1909. 



