ARTHROPODA OF THE COMMANDER ISLANDS. 343 



lateral and posterior margins yellow. Abdomen brownish-black, the middle of the 

 venter and the genitalia yellow. Legs yellow, the apices of the tarsi brown. Wings 

 hyaline, costal cell yellowish brown, the stigma darker brown; auxiliary vein ending 

 in the first opposite the base of the second submarginal cell, and a short distance 

 before its tip connected with the costa by a cross vein; marginal crossvein scarcely 

 apparent; petiole of first submarginal cell slightly shorter than the hind crossvein, 

 base of second submarginal cell considerably proximal to the base of the first pos 

 terior, petiole of second posterior cell slightly longer than that cell, hind crossvein 

 at the middle of the discal cell. Halteres yellow, the apex of the knob brown. 

 Length, 10 mm. 



Type.— No. 4049, U. S. N. M. 



Bering Island. A single specimen, collected in July-August, 1897, by Mr. Barrett- 

 Hamilton. 



(8) Idioplasta? sp. 



A single specimen too much damaged for identification. 



Copper Island, August, 1897. Collected by Mr. Barrett- Hamilton. 



Family BIBIONID^. 



(9) Bibio fumidus, new species. 



Male. — Black, polished, the femora and tibiae reddish brown or blackish brown, 

 bases of the tibiee, of the hind femora, and of the first one or two joints of the tarsi 

 yellow; hairs of the head black or brown, those of the body pale yellow, of the legs 

 chiefly pale yellow. Wings pale brown, the stigma brownish black, first vein brown, 

 the others yellow, small crossvein slightly shorter than the first segment of the third 

 vein. Front femora greatly thickened, hind femora and tibiae greatly dilated on the 

 apical half, hind tarsi noticeably thickened. 



Female. — Differs from the male as follows : Thorax reddish brown, mottled with 

 dark brown, abdomen brownish yellow; coxae, femora, tibiae, and bases of the first two 

 tarsal joints yellow ; hairs of the head chiefly yellow. Length, 8 to 9 mm. 



Type.— No. 4050, U. S. N. M. 



Copper Island. Five males and one female, collected in August, 1897, by Mr. 

 Barrett- Hamilton. 



Family BMPIDID^. 



(10) Empis laniventris Esohsoholtz. EntomograpWen, I, 1822, p. 113. 



Five male specimens. Bering and Copper Islands, July-August, 1897. Collected 

 by Mr. Barrett-Hamilton. This species was originally described from Unalaska, Fox 

 Islands. 



(11) Taehydromia nubifera, new species. 



Male and female. — Black, the bases of the halteres yellow ; hairs and bristles black ; 

 head and thorax subopaque, gray pruinose. Third joint of antennae oval, only slightly 

 longer than the second. Wings grayish hyaline, the costal portion beyond the base 

 of the submarginal cell, extending from the costa to the fourth vein, brown, the limits 

 not sharply defined ; second basal cell slightly shorter than the first, anal cell wholly 

 wanting. Front femora only slightly thicker than the others. Length, 3 to 4 mm. 



Type.— No. 4051, U. S. N. M. 



Bering Island. One male and two females collected in July-August, 1897, by 

 Dr. L. Stejneger. 



