188 Annals Entomological Society of America [Vol. XI, 



6. Hind femora with two strong processes above; fourth vein ending before 



the tip of the wing, first vein ending before the middle of the wing, 

 third section of the costa shorter than either the second or the fourth; 



pygidium large diversa, n. sp. 



Hind femora unarmed; fourth vein ending beyOnd the tip of the wing, first 

 vein ending near the middle of the wing, third section of the costa 

 longer than either the second or the fourth; pygidium minute, tri- 

 angular in outline; front coxae yellowish naica, n. sp. 



7. Pygidium small, not deeply cleft, circular in outline; last abdominal 



segment not fringed 8. 



Pygdium large, deeply cleft, the left valve with bristly fringe; last 

 segment of male abdomen fringed with hairs 9. 



8. Hind metatarsi yellowish; notal hairs obliquely outstanding; hypopygium 



transversely depressed, slightly open on the right side; eastern 



species pilosa, n. sp. 



Tarsi black; notal hairs decumbent; hypopygium globular and closed; 

 western species micropyga, n.sp. 



9. Abdomen and pygidium with fine pale hairs; veins black and thick, the 



third section of the costa much longer than either the second or the 



fourth; tarsi and front tibiae brown aliternigra, n. name 



Pygidium with many coarse black setulae; veins slender, the third section 

 of the costa subequal to the second and the fourth; legs entirely 

 black dividua Melander 



10. Hind tibiae with long, flattened, scale-like hairs along the inner side and 



with only preapical bristles, the apical spur large and lappet-like; 

 third antennal joint short ovate, the arista sulaterminal; third and 



fourth veins converging apically plumipes, n. sp. 



Hind tibiae not plumed with long flexor hairs 11. 



11. Hind tibiae with six short extensor bristles, the terminal spur strong; 



arista subdorsal, third antennal joint short ovate. ..... .dorsiseta, n. sp. 



At most three extensor bristles on the hind tibiae; arista terminal 12. 



12. Hind tibiae prolonged on the inside as a strong lappet projecting beyond 



the insertion of the tarsus, hind metatarsi with strong setulae beneath, 



middle tibiae without extensor bristle; four dorsocentrals 13. 



Hind tibiae not or scarcely prolonged, certainly not lappet-like, metatarsi 

 setulose only in medetera 19. 



13. Front coxae and femora entirely black; anterior cross- vein beyond middle 



of cell; only middle pair of scutellar bristles long 14. 



Front coxae somewhat yellowish; anterior cross- vein at or before middle 

 of cell 16. 



14. Arista 2.5 times as long as the antenna; hind tibiae without extensor 



bristles; upper orbits polished; veins coarse and blackish, the first 



posterior cell narrowed apically nitens, n. sp. 



Arista 1.5 times as long as the antenna; hind tibiae with one or two 

 extensor bristles; occiput poUinose; veins pale, the first posterior 

 cell not markedly narrowed at apex {unipila Loew) 15. 



15. Hind tibiae with one bristle, located at the basal third- • .var. unipila Loew 

 Hind tibiae with two extensor bristles, one before the middle, the other 



at the beginning of the apical third of the tibial length 



var. nitida Melander 



16. Scutellum with four long equal bristles; hind tibiae without extensor 



bristles; hind metatarsi black, darker than the tibia; palpi black. . . . 



quadrisetosa, n. sp. 

 Scutellum with only the middle pair of bristles long; hind metatarsi 

 rarely contrasting 17. 



17. Occipital orbits heavily white pruinose; sides of the middle segments of 



the abdomen white pruinose; posterior cross- vein before the middle 

 of the wing, sections of the fourth vein proportioned 1:1:4, of the 



fifth vein, 1:1 18. 



Orbits not differentiated; sides of the abdomen not pruinose; posterior 

 cross-vein at the middle of the wing, the sections of the fourth vein, 

 1:1.2:2.3, of the fifth vein, 1:0.5, the second, third and fourth sections 

 of the costa, 1.5:2:1 inciilta Coquillett 



