306 BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



The followiug five species have so many characters in common that a 

 short statement of the distinctive characters of each will be more to 

 the purpose than a long description. They were all taken near Webber 

 Lake, Sierra County, California, July 22-24, nearly in the same locality. 

 G. rejectus and sudator also occurred at Summit Station, Central Pacific 

 Eailroad, July 17. It is not improbable that several other species, belong- 

 ing in the same group, exist in the same localities, or else that the spe- 

 cies are subject to variation, as I have a few specimens left which I can- 

 not refer to any of my species. The characters which these species have 

 in common are : — 



Eace and front grayish- or brownish-pollinose, beset with black hairs ; 

 occiput and mentum with white hairs ; antennte black ; thorax grayish- 

 or brownish-pollinose on the whole surface, with more or less well- 

 marked darker stripes; scutellum densely grayish- pollinose, with a fringe 

 of black hairs on the hind margin, and sometimes some pile on its up- 

 per surface ; abdomen black, shining, with cross-bands of white pollen 

 on the hind margins, sometimes entire, often more or less interrupted, 

 sometimes so much as to leave white spots only on the extreme lateral 

 ends of the margin ; this is always the case on the first segment, with the 

 only exception of C. evidens, where the whole hind margin of the first 

 segment is whitish-pollinose. The abdomen is beset on the sides of the 

 segments nearer to the ba^e with soft white hair. Halteres with a 

 brownish stem and yellow knob ; legs black, with black pile ; some 

 white hairs on the under side of the femora, less numerous on the 

 anterior femora. Wings hyaline on the proximal half, slightly tinged 

 with grayish or brownish on the distal half (almost altogether hyaline in 

 C. nugator). The fan-like fringe of hairs in front of the halteres is white 

 in the first three, black in the last two, species. 



In identifying these species, it must be borne in mind that all the 

 specimens were taken at the same time and in the same locality, and 

 that specimens taken at another season or in other localities may differ 

 in the intensity of the coloring of the thoracic stripes or of the brown- 

 ish tinge of the wings ; the white abdominal cross-bands may be also 

 more subject to variation than I assumed them to be. Still, for each 

 of the species, some permanent distinctive character will remain, as tor 

 nugator the shape of the abdomen, the hyaline wings, the color of the 

 ungues; for sudator, the. breadth of the front and its whitish, hoary 

 pollen, etc. G. rejectus alone is doubtful to me, and may possibly be 

 only a varity of G. evidens. 



I. The fan-like fringe of hairs in front of the halteres is ivhite: 



II. Cyrtopogon evidens n. sp., $ 9 . — First abdominal segment 

 with an uninterrupted white cross-band on the posterior margin ; stripes 

 on the thorax very distinctly marked, brown ; the longitudinal dividing 

 line of the geminate stripe is very distinct ; the portion of the lateral 

 stripe anterior to the thoracic suture is large, conspicuous, of a rich 



