313 



5. Robust species, with spinose sciitellum; niai'i^inal vein encircling 



wing COENOMYIIDAE (p. 351) . 



— Slender species, with nnspined scutellum ; marginal vein ceasing be- 



fore reaching anal angle of wing XvLOPHAcnDAE (p. 346). 



6. Squamae very hxrge, inflated ; robust flies, with very small heads . . . 



Cyrtume (p. 368) . 



— Squamae very small 7 



7. Costa continued round posterior margin of wing 



Leptidae (p. 362). 



— Costa discontinued at apex of wing Nemestrinidae (p. 368). 



8. Anal cell much longer than second basal, closed at or close to wing- 



margin, or open ; third vein usually furcate 9 



— Anal cell absent or, if present, shorter than second basal, or but lit- 



tle longer, and closed some distance from wing-margin; if the 

 apex of this cell is long and pointed the third vein is not forked 

 14 



9. Vertex depressed, seen from in front the upper inner angles of eyes 



are considerablv above the level of the frons ; eyes always separat- 

 ed ". 10 



— Vertex not depressed, at least on a level with upper inner angles 



of eyes ; eyes of male often contiguous 11 



10. Fourth vein curved forward apically, ending at or before tip of 



wing Mydaidae (p. 370) . 



— Fourth vein not curved forward Asilidae (p. 373) . 



11. Posterior cross-vein present, i. e., second basal cell with an obtuse 



apex formed by a cross vein; 5 posterior cells present 12 



— Posterior cross-vein absent, i.e., second basal cell with an acute 



apex; rarely 5 posterior cells present, if present the fifth cell is 

 due to the bisection of the third by a cross vein 13 



12. Fourth vein curved forward and ending before the apex of wing. . . 



Apiocerid.ve (p. 373 ) . 



— Fourth vein not appreciably curved forward, ending behind apex 



of wing Therevidae (p. 396) . 



13. Fourth vein curved forward, ending at or before apex of wing ; pro- 



boscis retracted, fleshy ; antennae without apical style 



SCENOPINIDAE (p. 398) . 



— Fourth vein ending behind apex of wing ; proboscis slender, usually 



much exserted ; antenna usually with a style 



BOMBYLIIDAE (p. 389) . 



14. Discal cell usually separated from the second basal, always at least 



one distinct basal cell ; squamae small ; abdomen of male usually 

 with 7 segments exclusive of the hypopygium; black, brownish, 



or yellowish species, usually with chitinized proboscis 



Empididae (p. 400). 



— Discal cell not separated from second basal, the basal cells small 



and indistinct; squamae moderately large, usually with eon- 



