4 NORTH AMERICAN DIPTERA. 



10. Empodia developed imlvilliforni, tliat is three nearh' equal iiieniliranoiis 



apjiendages on the under side of the claws. .... 20 



ICnipodia wanting, rudimentary or linear, never developed like the 



pulvilli 22 



20. Tegulaj very large; thorax and abdomen inflated; head small, eyes 



large; neuration varied Acroceuid.e.7^ 



TegulcB of moderate size or rudimentary. ..... 21 



21. Middle tibi;i3 at least with spurs; no bristles on femora or tibiae; third 



longitudinal vein furcate; five posterior cells present (four in 

 Dialijsis); anterior cross-vein always distinct; third joint of the an- 

 tennas with a bristle or slender style, usually terminal. Leptid.k. 

 Not such flies 22 



22. Third longitudinal vein of the wings not furcate. ... SI 

 Third longitudinal vein furcate, two or more submarginal cells 



present 2o 



23. Arista or style of antenna; when present always terminal. . . 24 

 Arista dorsal, always present .'](:> 



24. Vertex and front distinctly hollowed out between the eyes; eyes of 



male never contiguous; basal cells large; mostly large flies. . 25 

 Front and vertex plane or convex. ...... 2(5 



25. Proboscis with fleshy labella at the tip ; neuration complicated, the 



fourth vein at least curves forward to terminate before the tip of the 

 wing; palpi rudimentary or wanting. .... Mydaid.ic. ^% 

 Proboscis without fleshy labella at tip, the imder part forming a liorny 

 sheath ; five posterior cells always jiresent ; palpi usually j>rominent. 



AsiLiDyi:. -J^ 



26. Five posterior cells in the wing; basal cells large. ... 29 

 Never more than four posterior cells in the wing. ... 27 



27. Third antennal joint without bristle or style ; three posterior cells; first 



posterior cell narrowed or closed, the fourth longitudinal vein termi- 

 nating at or before the tip of the wing. . . Scenopinid.k. ^^ 

 Third antennal joint usually with terminal style; four or three poste- 

 rior cells; the fourth vein terminates bej'ond the tip of the wing. 28 



28. Anal cell narrowly open, or closed near the margin; discal cell j)res- 



ent. ......... BoMBVLiiD.i:. 6^ 



Anal cell closed remote from the border, sometimes wanting; if closed 

 near tl-.e border (/Jilorimorj/ha), the discal cell wanting. E.mimd.k. 



29. Neuration intricate, the anterior cross-vein wanting or rudimentary, 



owing to the coalescence of the third and fourth veins for a longer 

 or shorter distance ; tibia; without terminal spurs; empodia and pul- 

 villi iHem))i-nnous, l)ut freciueiilly minute. . . Nemisthinidi.. ^f^* 



