224 U.S. NATIONAL MUSEUM BULLETIN 2 77 



Abdomen with 8th segment only slight longer than wide, marked with black 

 areas dorsally and ventrally (Mexico) P. longurio Loew 



6. Halter knob white 7 



Halter knob with at least the base marked with brown 11 



7. Antenna brown P. albocincta Van Duzee 



Antenna red-brown, black-brown, or orange 8 



8. Antenna red-brown or black-brown 9 



Antenna orange P. melanderi, new species 



9. Antenna black-brown 10 



Antenna red-brown P. morlani, new species 



10. Head longer than high P. parva D. E. Hardy 



Head higher than long P. bryanti, new species 



11. Halter knob with base brown, remainder white 12 



Halter knob with more than just the base brown 17 



12. Antenna red-brown or black-brown 13 



Antenna black P. garretti, new species 



13. Antenna red-brown 14 



Antenna black-brown 16 



14. Vein R4 ending even with the end of cell R5 15 



Vein R4 ending well beyond the end of cell R5 . P. biacristerna, new species 



15. Vein R4 branching from just beyond the middle of cell R5 



P. atombomba, new species 

 Vein R4 branching from near the distal fourth of cell R5 



P. cajoni, new species 



16. Eighth sternum notched on the posterior midline . P. evergreeni, new species 

 Eighth sternum gently rounded on posterior margin 



P. unicolor, Coquillett 



17. Halter knob with base and dorsal rib red-brown, remainder white ... 18 

 Halter knob with dorsal surface cream, brown or black-brown .... 21 



18. Red-brown not bleeding into the white 19 



Red-brown bleeding into the white 24 



19. Antenna black-brown 20 



Antenna black P. leechi, new species 



20. Vein R4 ending opposite the end of cell R5 . . . . P. bakeri, new species 

 Vein R4 ending well beyond the end of cell R5 . . P. barnesi, new species 



21. Antenna brown, black-brown or black 22 



Antenna orange, vein R4 ending before the end of cell R5 



P. saccharcupa, new species 



22. Antenna brown or black-brown 23 



Antenna black, R4 ending before the end of cell R5 . P. convexa, new species 



23. Antenna brown, R4 ending beyond the end of cell R5, small, under 5 mm. 



P. concava, new species 

 Antenna black-brown, R4 ending beyond the end of cell R5, large, over 7 mm. 



P. cockerelli, new species 



24. Halter knob with dorsal rib red-brown, remainder cream 25 



Halter knob with dorsal surface brown or black-brown 26 



25. Antenna black-brown P. eaithales, new species 



Antenna orange P, howdeni, new species 



26. Halter knob with dorsal surface brown, ventral surface white 27 



Halter knob all brown except for a small white ventral spot, antenna black 



P. peromysci, new species 



27. Antenna orange-brown, frons narrow only as wide as the ocellar tubercle 



P. sabroskyi, new species 



