32 DIPTEEA OF NORTH AMERICA. [PART II. 



base of the four anterior tarsi, yellow ; face white ; cilia of the inferior 

 orbit white ; cilia of the tegulse black ; hind femora of the male ciliated 

 with white. Long. corp. 0.15 0.16. Long. al. 0.17 0.18. 



In the color and even the structure of the body this species re- 

 sembles D. albiciliatus; but it is much smaller. Pace white, that 

 of the male rather narrow, that of the female proportionally rather 

 broad. Palpi blackish at the base, at the tip more yellowish and 

 with a somewhat whitish reflection. Antenna? black ; third joint 

 rather short, in the g somewhat larger than in the 9. Front 

 metallic green. Cilia of the inferior orbit black above, white on 

 the side and below. Coxas black, trochanters brownish-yellow. 

 The fore coxa? dusted on their fore side and beset with black hair. 

 Femora black, with brownish -yellow tip, the hind ones before the 

 tip with a bristle. The hairs of the femora are black, but there 

 are on the .under side of the four anterior femora of the male some 

 delicate and short white hairs. The under side of their hind 

 femora is ciliated with very long white hairs ; upon the under side 

 of the anterior femora of the female the hairs are closer than in the 

 male, and show a whitish appearance only in a certain direction, 

 whilst in another direction they appear rather blackish. Tibise 

 yellowish ; the hind tibiae are colored with black at the tip ; this 

 black coloring has but a moderate extent and is rather sharply 

 limited. Tarsi plain in both sexes; on the four anterior ones 

 the tip of the first joint and the four following joints are co- 

 lored black ; the hind tarsi are entirely black ; in the male their 

 first joint has more thorn-like bristles than in the female. Cilia 

 of the tegulse black, but mixed with minute white hairs, as it is 

 also the case with the related species, for instance with D. albici- 

 liatus. Wings grayish hyaline ; in the male the anterior margin 

 has at the tip of the first longitudinal vein a small knot-shaped 

 swelling. The white lamellae of the hypopygium are of a rounded- 

 ovate form, bordered with black, jagged on the upper and apical 

 margins and fringed with black bristles. 



Nab. Sitka. (Sahlberg.) 



Observation. Between the diagnosis of this species and that 

 of D. albiciliatus there is no difference with regard to the female 

 sex except in the size. Indeed the females of both species are 

 very much alike. In order to distinguish them it will be well to 

 bear in mind that the female of D. xanthocnemus is not only 



