A«T. 17. FLIES OF THE GENUS TACHYTEECHUS GREENE. 17 



Length 5 mm. 



Type locality. — Webber Lake, Sierra County, Sierra Nevada, 

 July 22, two males. Osten Sacken. 



Type.—li\ Museum of Comparative Zoology, Cambridge, Massa- 

 chusetts. Sixteen specimens deposited in United States National 

 Museum Collection by J. M. Aldrich. 



DistHhution. — Craig's Mountain, Idaho, Longmire's Springs, 

 Mount Rainier, Washington, August 2, 1905 ; Fallen Leaf, California, 

 6500 feet, July 16, 1917; Emigrants Canj^on, Wasatch Mountains, 

 Utah, July 8, 1911, 7000 feet, July 21, 1917 ; Mono Lake, California, 

 July 22, 1911, Tennessee Pass, Colorado, 10240 feet, July 11, 1919. 



Feviale. — Very much like the male except the arista are short and 

 normal; legs mostly black. 



14. TACHYTRECHUS GRANDITARSUS, new species. 



Fig. 16. 



Male. — Face nearly twice as wide on lower part as immediately 

 below antennae ; face stops far short of lower edge of eyes ; face and 

 entire front green coated with a dull, yellowish dust. Ocelli yellow- 

 ish. Orbital cilia black on upper third, lower two thirds white. 

 Antennae short, black, joints of nearly equal length; first joint with 

 % few black hairs at the apex on the upper side: arista black and 

 long. Thorax and scutellum bright green well covered with a white 

 dust. Abdomen bright green, in certain lights well covered with a 

 white dust. Hypopygium large and coated with a white dust, it is 

 quite changeable according to the light, varying from white to pur- 

 ple and dark blue ; lamellae very long, brown black, tapering gradu- 

 ally from the base to the apex, much narrower at the apex, width of 

 base about one-sixth of the total length, inner edge of lamella nearly 

 straight; all the hair of the lamella black except that on the outer 

 edge which is white and quite long. Legs lightly dusted with white. 

 Basal two thirds of front femora green, that of middle and hind 

 pairs more bluish, tips of all femora, all tibiae and bases of fore 

 and middle tarsi yellow, hind tarsi all brownish black. Middle tarsi 

 are greatly modified, all the joints are very broad and flattened, 

 second joint about four times as long as broad and appearing slightly 

 twisted, the short bristly hairs are arranged in rows. Wings broad 

 and hyaline. Tegulae pale 3'^ellow with a small tuft of short black 

 bristles on upper side, near the middle, stems brownish yellow. 



Female. — Very similar except the face and front are slightly wider 

 and the middle tarsi are normal. 



Length 5-6 mm. 



