20 H. C. HUCKETT 



5. Abdomen j^ellow testacea Stein 



Abdomen graj-ish 6 



6. Thorax with scutellum and humeral callosities testaceous; parafacials and cheeks j^eUow- 



ish; mid tibia vrith one anteioventral bristle depressa Stein 



Thorax uniformly grajish; parafacials and cheeks grayish; mid tibia with two antero- 

 ventral bristles coenosiaeformis Stein 



7. Pra missing 8 



Pra present 9 



8. Gra}"ish species with yellowish poUen; wings and cah^ptrae yellowish. . . .pluvialis Alall. 

 Grajish species with whitish pollen; wings and calj-ptrae whitish albula Fall. 



9. Hind tibia with stout apical bristles on antero- and posteroventral surfaces 10 



Hind tibia with a stout anteioventral apical bristle only; that of posteroventral surface 



wanting; replaced by a fringe of setulae 15 



10. Pra short, less than half length of the following bristle pullula Zett. 



Pra long, exceeding half length of the following bristle 11 



11. Wings grayish; cross-veins clouded; arista bare or minutely pubescent; cruciates weakly 



developed or absent 12 



Wings yellowish; cross-veins clear; arista distinctlj- pubescent; cruciates strongly 

 developed 13 



12. Third antennal segment tapering distad, nearly twice as long as broad; second aristal 



segment twice as long as broad megacephala Mall. 



Third antennal segment nearly as broad as long; second aristal segment nearly as broad 

 as long arnolitra sp. nov. 



13. Blackish species; head, thorax, and abdomen blackish, with whitish poUen; thorax 



with three distinct brownish ^ittae piloseta Mall. 



Grayish or cinereous species; parafacials and cheeks silvery gray pruinose; thorax with 

 slight indefinite traces of %"ittae 14 



14. Abdomen with dense golden poUen inornata Stein 



Abdomen with yellowish graj- pollen seiigera Joh. 



lo. I\Iid tibia with a median anteroventral bristle 16 



!Mid tibia without an anteroventral bristle 19 



16. Tarsal segments 3, 4, and 5 of fore legs noticeablj" broadened latipennis Zett. 



Tarsal segments of fore legs similar in appearance to those of mid and hind legs 17 



17. Arista distinctly pubescent; cruciate bristles weakly developed or absent; parafacials 



reddish : sternopleurals, 1:1 innocua ]MalI. 



Arista bare or minutely pubescent; cruciate bristles strongly developed; parafacials 

 grayish; sternopletirals. 1:2 18 



15. Abdomen fuscous, shining; terminal segments of the ovipositor compressed laterallj-; 



length of pra exceeding half that of the following bristle sepia Meig. 



Abdomen denselj- graj-ish poEinose, with dark dorsocentral %atta; terminal segments of 

 o^-ipositor not noticeabh^ compressed laterally; length of pra less than half that of 

 the following bristle .' setitarsata sp. nov. 



19. Hind tibia yellowish to reddish; fifth abdominal segment elongate, its length nearly equal 



to that of the two preceding segments; tergum 5 sparseh' clothed with setidae; marginal 

 bristles noticeably reduced in numbers with each succeeding segment . . . trivittata Stein 

 Hind tibia blackish; fifth abdominal segment not nearly so long as the two preceding 

 segments; tergum 5 with setulae of the normal number and appearance; marginal 

 bristles normal 20 



20. Fifth abdominal tergimi with semi-erect bristle-like setae on disk amongst the normal 



short appresed setulae 21 



Fifth abdominal tergum clothed on disk with short appressed setulae only 24 



21. Hind femur with one or more median bristles on posteroventral surface and two preapical 



bristles on posterior surface; arista pubescent, the longest hairs exceeding in length 



the diameter at base of arista 22 



Hind femur with posteroventral smface bare except for a few apical and basal bristles; 

 with one preapical bristle on posterior surface; arista minutely pubescent, the longest 

 hairs not so long as the diameter at base of arista 23 



