278 DIPTERA FROM SOUTHWESTERN UNITED STATES 



4. Hind tibia with a series of short bristles of almost equal length upon an- 



tero-dorsal surface, none of which are distinctly longer than diameter 

 of tibia; abdomen almost cylindrical, with a slender dorso-central 

 black line; wings yellowish, the veins scarcely darker than the mem- 

 brane nitens Stein 



Hind tibia with a series of bristles of irregular lengths, the longest very 

 much longer than the diameter of the tibia; wings subhyaline or sub- 

 fuscous, the veins black or dark brown 5 



5. Mid femur with a few bristly hairs on apical third of antero-ventral and 



postero-ventral surfaces, none of which exceed in length the diameter 

 of the femur; hind tibia transverse at apex, not with a short blunt protu- 

 berance on ventral surface similis sp. n. 



Mid femur with a number of bristles on apical third of antero-ventral 

 and postero-ventral surfaces, several of which greatly exceed in length 

 the diameter of the femur; hind tibia with a short blunt protuberance 

 at apex on ventral surface 6 



6. Postero-ventral surface of mid femur with five to seven long slender 



bristles on apical half, the longest of which is at least twice as long 

 as diameter of the femur, Imsal half of same surface with minute hairs; 

 antero-ventral surface with long bristles on apical three-fourths of its 

 length; dorsum of abdomen pruinescent and with poorly defined black 



central stripe; wings hyaline except at base minor sp. n. 



Mid femur with long bristly hairs in a rather closely placed series from 

 base to near apex on postero-dorsal surface, those on basal half much 

 longer than those on. apical half; antero-ventral surface with four to 

 five long, strong bristles on apical two-fifths; dorsum of abdomen not 

 distincth- pruinescent; wings infuscated, very noticeably so at base. 



aldrichi sp. n. 



Females 



1. Mid tibia wuth one or more antero-ventral bristles 2 



Mid tibia without antero-ventral bristles 6 



2. Thorax with four pairs of postsutural dorso-central bristles 3 



Thorax with three pairs of postsutural dorso-central bristles 4 



3. Wings yellowish at base, the veins conspicuously so except at extreme 



base; pteropleura with one to two long erect hairs. 



A relic species not included 



Wings fuscous at base, the veins entirely black or fuscous; pteropleura 



bare alpicola Rondani 



4. Mid femur without a continuous series of bristles on antero- and postero- 



ventral surfaces; arista with short hairs, the longest of which is equal 

 in length to the basal diameter of the arista; frons over one-third as 



wide as head latifrons sp. n. 



Mid femur with a continuous series of bristles on antero-ventral surface 

 and another, weaker, on the postero-ventral; arista with very short 

 pubescence 5 



