OSTEN SACKEN ON WESTERN DIPTERA. 241 



I have one or two other well marked species, belonging to the same 

 group 5 one, from Fort Bridger, Wyo., is somewhat like A. lucifer, but 

 certainly different; the other, from South Park, Colorado, and Twin 

 Lake Creek, Colorado (W. L. Carpenter), is more like an A. tegminipennis, 

 but with a more hyaline latter half of the wings. 



Hemipenthes. 



This genus was established by Loew (Centur., viii,44) for the European 

 Anthrax morio, and for a species from British North America, of which 

 he described the female as H. seminigra. He does not say what pre- 

 vented him from identifying it with Anthrax morioides Say, which is 

 certainly a Hemipenthes. A well preserved male specimen from Montreal 

 agrees well with Say's and Wiedemann's descriptions ; the knob of the 

 halteres, however, is dark on one side, whitish-yellow on the other. It 

 does not have the strongly coarctate first posterior cell, which distin- 

 guishes H. seminigra, according to Mr. Loew's description. A number 

 of specimens from Spanish Peaks, Colorado, possess this character, and 

 therefore belong, I suppose, to H. seminigra. 



I have, moreover, a number of specimens from different parts of Cal- 

 ifornia (Yosemite and Webber Lake), which may likewise belong here. 

 The Hemipenthes occurring commonly in Marin County, California, in 

 May, seems to be a different species. The wings are more uniformly 

 black, and the pile and tomentum on the abdomen are different. 



Argyramceba. 



Contains a variety of forms, which have, as common characters, a 

 pencil of hairs at the end of the third antennal joint, and distinct, rather 

 large pulvilli. With a very insufficient material, I have attempted a 

 rough grouping of all the described species from the United States, in 

 which I have used some characters hitherto neglected. In using this 

 table, it must be remembered that I know only those species which are 

 marked with an asterisk (*), and that data about the others are drawn from 

 the descriptions. I have omitted Anthrax costata Say (Compl, Wr., i, 

 254), which may possibly be an Argyramceba. 



I. Large species ; third posterior cell bisected by a cross- vein : 



* simson Fab., Wied., i, 259 (syn. seripta Say, Compl. 



Wr., ii, 59). — Atlantic States. 

 delila Loew, Centur., viii, 45. — California. 



II. The male has the last abdominal segments clothed with silvery 



scales; the other segments in both sexes altogether 

 black : 

 (a) Wings black; posterior margin hyaline; the limit of the black 

 well defined : 



