128 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 115 



In addition to the specimens listed above, I have studied an addi- 

 tional female that differs in some particulars and possibly represents 

 a distinct species. In USNM: 1 female, Topaz Lake, Mono Co., 

 July 25, 1948, light trap, R. Coleman. 



Subfamily Diamesinae 



Pseudodiatnesa {Pseudodianiesa) branicki (Nowicki) 



Although this species was not represented by males in the collection 

 at hand, the characteristics given by Oliver (1959) for the female are 

 considered diagnostic. In the two specimens that I have seen, the 

 thorax is blackish-brown with only the pronotum and scutellum a 

 lighter brown. The halteres are yellowish-white with the stalk 

 infuscate. Wing length 5.73, 5.92 (2); fore tarsi missing; venarum 

 ratio 0.72, 0.76 (2). 



Material examined: 2 females, Blanco's Corral, White Mt., Mono 

 Co., July 7, 1953, elevation 10,000 feet, W. D. McLellan. 



Pseudodiamesa {Pseudodiamesa) diastena, new species 



Figures 7b,c 



Holotype male: USNM 65522, Mill Valley, Marin Co., Apr. 12, 

 1953, H. L. Mathis. 



Antenna! flagellum heavily haired. Postocular bristles in single 

 row below eyes, expanding to form staggered double row behind eyes, 

 then becoming staggered single row toward dorsal part of head; each 

 row terminates even with narrow dorsal eye extension. Eyes bare. 

 About 10 clypeal bristles. Palpi with first and second segments fused, 

 indicated by constriction, ratio 41(13 + 28) :30:35. Antenna! ratio 

 2.75. 



Head, thorax, and abdomen black. Prothorax with only 14 lateral 

 bristles; no dorsal bristles; somewhat narrowed dorsally; two halves 

 contiguous. Halteres dark. Prealar bristles 15; dorsolateral bristles 

 partially in double row, forming cluster of 7 bristles just anterior to 

 scutellum; scutellum with about 48 strewn bristles; anterolateral 

 bristles absent. 



Fourth tarsal segment on hind leg cylindrical. Fore leg with single 

 long straight tibial spur, ratio of spur length: diameter of tibial apex 

 70:50. Tibial spurs of middle leg with many encircling fine hairlike 

 denticles, ratio of length of spurs 50:60. Hind tibial spurs as middle 

 leg, ratio 55:75. Comb of 10 bristles at apex with 3 rows of equal- 

 sized bristles just basally, each row decreasing in number. 



Leg proportions: 



Leg 

 Tai Taz Ta* Ta-, Ratio 



27 19 8 0.57 



