270 ERNEST A. BACK. 



species. The pulvilli of the four hind tarsi are brown, while in calli- 

 pedilus they are whitish. The wings are a little shorter. The abdomen 

 is slightly tapering from base to tip, instead of being nearly cylindrical, 

 as in callipedilus. A vestige of a spot of whitish bloom is generally 

 visible in the hind corner of the fourth segment. 



J. — Length 12-13 mm. — Black, polished; thoracic dorsum with a 

 slight brownish bloom, which is a little denser than in the male, but 

 much less dense than in the female of callipedilus. The hair on the 

 face is deep black; a little whitish pile on the lower part of the occi- 

 put and on the front coxas; pile on the legs black; their coloring the 

 same as in the male, only the front tibia? sometimes are reddish at the 

 base and along their front side; abdomen with small triangles of 

 whitish bloom on the posterior corners of segments 2—4, the largest 

 on the fourth segment. The shape of the abdomen is different from 

 that of the callipedilus ; gradually tapering from base to tip, instead 

 of slightly expanding about the middle." 



Type. — M. C. Z. Type series consist of two male and three 

 female specimens. 



Habitat. — Summit Station, Sierra Nevada, July 17, and 

 Webber Lake, July 23-24, Cal. ; both sexes found in each 

 locality. 



Cyrtopogon plausor. 



Cyrtopogon plausor Osten Sacken, West. Dipt. 



Cyrtopogon plausor Williston, Tr. Am. Ent. Soc, XI, 12, 1884. 



Cyrtopogon plausor Howard, Insect Book, 1902, PL XIX, fig. 26. 



Cyrtopogon plausor Jones, Trans. Am. Ent. Soc, XXXIII, 277, 

 1907. (Note.) 

 " % 9 . — Length 12-13 mm. — Very like callipedilus and cymbalista in 

 the ornamentation of the four anterior tarsi of the male, and at the 

 same time very different, even in those characters. 



% . — Pile on the face yellow, sometimes yellowish-white, black above 

 the mouth; lower part of the head posteriorly and front part of the 

 thorax with yellowish-white pile; thoracic dorsum, including even the 

 base of the scutellum, covered with a yellowish-brown pollen, except 

 at the four corners, which are black; three stripes on the dorsum are 

 less pruinose and therefore darker; the intermediate one geminate, 

 and abbreviated posteriorly; the lateral ones broad, abbreviated and 

 rounded anteriorly, converging toward each other posteriorly, in front 

 of the scutellum; abdomen black, polished, clothed on the sides with 

 dense yellowish pile, gradually diminishing in length toward the tip. 

 Legs black; tibias reddish, black at tip; front tibia? often altogether 

 black. Segments 2-5 of the front tibia? densely beset with silvery 

 white recumbent hairs along the outer and upper side only, and there- 



