THE FLIES OF THE WESTERN MOUNTAINS 



By J. M. ALDRICH, 



Associate Curator, Dix'ision of Insects. U. S. National Miiscinn 



A [any mountainous regions of the western United States have never 

 been visited by an entomologist interested chiefly in flies, and other 

 such regions are poorly represented in the extensive collections of 

 flies in the U. S. National Museum. For these reasons I undertook 

 in the summer of 1927 to visit a numl)cr of localities of special interest 

 in the West. 



The vicinity of Wells, Nevada, was the most important of these. 

 Here there are large mountains, the East Humboldt Range, carrying 

 much snow in early summer and giving rise to several important 

 streams. There is also some seepage from the range which produces 

 marshes a few miles from the base in the high plateau adjacent, which 

 has an altitude of a little more than 5,000 feet. In one of these marshes 

 I had collected for an hour as I stopped between trains in 191 1, with 

 such surprising results (20 or more new species) that I had always 

 intended to visit the place again. This I was enabled to do last summer, 

 spending six days at Wells. 



Next in importance was the Yellowstone National Park, where the 

 forested and well-watered plateau of about 7,500 feet altitude seemed 

 an ideal collecting region, but had been visited hardly at all by col- 

 lectors of flies for the National Museum. My visit in August was a 

 trifle late for the best weather, but the flies were more numerous 

 than in any other place in which I had ever collected. Six days here 

 gave excellent results. 



Lake Tahoe. California, is a large and beautiful lake at 6,200 feet 

 altitude, among the high Sierras. Moist meadows around the south end 

 of the lake provided good collecting, and three days were spent here ; 

 I then moved down the east side of the Sierras past Mono Lake, 

 where the dryness of the season gave no promise of success in col- 

 lecting, and proceeded up Leevining Canyon to a camping place near 

 its head, just above Ellery Lake. The altitude of the camp was about 

 9,500 feet, with large banks of snow only a few yards from the tent. 

 Insects were naturally much less numerous in such a cold place, but 

 those captured were of especial interest because of the great altitude. 



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