OSTEN SACKEN ON WESTERN DIPTERA. 281 



brown longitudinal streak, on the lower side sparsely beset with rather 

 thin spines ; hind tibice straight, long, and slender, sparsely beset with 

 spines on the inner side as far as the knee ; at the tip, a circle of longer 

 spines. Wings uniformly tinged with a diluted brownish ; veins palo 

 yellow; halteres yellow. Abdomen of the same ground-color as the 

 thorax, but with black cross-bands ; the first segment quite black, ex- 

 cept the hind margin, the second black on the anterior half; segments 

 three to six have basal black cross-bands, triangularly expanded in the 

 middle ; they become narrower on each consecutive segment, so that 

 the cross- baud of the sixth segment is only a narrow anterior border ; 

 the hind margin of the segments is paler, more straw-yellow ; on the 

 second segment, it has on each side a brown, transverse callosity ; the 

 seventh and eighth segments are a little darker than the i^receding 

 ones, and are densely beset with black bristles ; the spines of the last 

 segment are ferruginous, obtuse. 



"A single female from California, in the Berlin Museum." 



I took two females on the sands of Lone Mouutain, San Francisco, 

 June 29, 1876. The coloring of the antennse is variable ; in one of my 

 specimens, the whole club is black; in the other, it answers Dr. Ger- 

 staecker's description ; in both of my specimens, the knob of the hal- 

 teres is brown, and not yellow. 



Leptomidas tenuipes Loew, Centur., x, 20.— California. 



Midas ventralis Gerstaecker, 1. c, 102 (syn. M. rujiventris Loew, 

 Centur., vii,|22). — California. 



I do not know these species. 



Ehaphiomidas no v. gen. 



Closely allied to Mitrodetus Gerstaecker (Stett. Ent. Zeit., 1868, 76), 

 as there are three cells intervening between the forked cell and the 

 margin of the wing, and as the structure of the proboscis is the same, 

 long and linear, directed forward, with very narrow lips at the end; 

 differing, however, from that genus in the structure of the antennte ; 

 in some minor characters of the venation, among them the structurerof 

 the second submarginal or forked cell, which is petiolate at the prox- 

 imal end only, and not at both ends; and in the presence of two distinct 

 ocelli. 



Vertex somewhat excavated on each side of the tubercle ; the latter 

 broad and flat, bearing two large ocelli on its sides (a character, as far 

 as I am aware, unique among the true Midaidcc). 



Antennce a little longer than the vertical diameter of the head from 

 the top of the eyes to the lower oral edge, inserted rather low, a short 

 distance above the mouth ; the first two joints form an almost cylindri- 

 cal body, somewhat constricted about two-thirds of its length where the 

 second joint begins ; third joint about once and three-quarters of the 

 two first taken together, in the shajie of a rabbit's ear, with a ring-like 

 expansion at the basis. 



