106 PROCEEDINGS ENTOMOLOGICAL SOCIETY 



transverse rugosity interrupted down the middle. The frons widens rather 

 gradually toward the antennae. Wings, squamae and halteres paler than 

 in the male. 



Four males and two females: "Washington Territory;" Seattle, 

 Washington, May 22, 1897; Moscow, Idaho, June 2, 1908 (J. 

 M. Aldrich); Moscow Mountain, Idaho (J. M. Aldrich); Oregon, 

 (Koebele) ; Mono Lake, California, July 23, 1911 (J. M. Aldrich). 



The specimens, now in the National Collection, four from Colo- 

 rado and one from Washington Territory, which Williston re- 

 corded as nigrovittata Loew in his "Synopsis of North American 

 Syrphidae" do not fit the description that Loew gave for the 

 length of the third antennal joint. The four specimens he had 

 from Colorado now form part of the material of C. parva, a new 

 species described in this paper; his other specimen, from Wash- 

 ington Territory, except for a few minor points, fits the descrip- 

 tion of Bigot's C. sinuosa, which Williston had placed as a syn- 

 onym of C. stigmata. 



C. sinuosa may be recognized by its dark steel blue color, the 

 fulvous antennae, darkened squamae, halteres and wings, and the 

 microscopic pubescence on the body. The third antennal joint 

 varies somewhat in size in the male. In the Oregon specimen it 

 is a little longer than in the others, while in the specimen from 

 Moscow Mountain, Idaho, it is nearly as broad as long. 



Chrysogaster unicolor, new species. 



Medium sized, dark steel blue species; the entire dorsum of the abdomen 

 unicolorous with the thorax. 



Female: Frons shining, bluish black, with the transverse ridges more 

 broadly separated and the longitudinal, median dividing ridge broader 

 than in the other species of this group; pile short and pale. Antennae 

 elongate, first and second joints darkened, third reddish brown, darker 

 on the upper margin and about two and one-half times as long as broad; 

 arista darkened at the base, becoming lighter towards the tip. Face dark 

 steel blue., with a pollinose, whitish band extending across to the eyes 

 just below the antennae and below this broadly, faintly rugulose; a tubercle 

 or swelling on each side of the face below near the eyes. Thorax with mi- 

 croscopic pile; mesonotum with four blackish vittae, the outer ones very 

 faint. Abdomen entirely dark steel blue, the same as the thorax. Wings, 

 squamae and halteres darkened. Length: 7 mm.; wing 5.25 mm. 



Two females from Ormsby County, Nevada (type locality) , July 

 6 (C. F. Baker); Reno, Nevada (H. F. Wickham). 



Type: Cat. No. 20282 U. S. N. M. 



This is the only species of this group in which the disc of the 

 abdomen is not subopaque, but unicolorous with the mesonotum. 



