AMERICAN DIPTERA. 3 



First joint about tliree times as long as the second, third elongate, fourth and 

 fifth of nearly equal length, third and fourth at the tip with two lobes, or 

 processes, reaching to about tlie middle of the following joint. 



Myelaphns. 

 14.— Style of antennae short, thick, obtuse, not easily distinguished from the third 

 joint, or if so, forming an apparent joint. Small or rather small species, 

 nearly bare, shining or metallic black, with narrow or cylindrical abdo- 

 men and large wings: face flattened, bare except below, hind tibiae pilose 



ou the inner side 15. 



Terminal style small, more slender than the joint, apparent, antenna; shorter 

 if elongate and style indistinguishable; the species not bare but thickly 



pilose U;. 



15. — All the tibiae and the hind femora with short strong setae Kcfliodopa. 



Hind femora without such selpe Dioclria. 



16. — Face distinctly convex in profile, swollen or gibbose* 1 7. 



Face flattened or gently convex. 19. 



17. — Head as broad or broader than the thorax, front at base of antennae flattened, 

 not projecting in profile; terminal style of antennae slender or differ- 

 entiated from the joint 18. 



Head narrow. Antennae situated upon a convexity, thence receding to the 

 facial tubercle which is at the lower part of the face; antennae elongate, 

 style short, obtuse; abdomen short: thickly pilose species, the bristles few 



and hair-like Dicolonus. 



18. — Thickly pilose species: the gibbosity of tiie face reaithes to the base of the 



antennae; anal cell usually open* Cyrtopogon. 



Thinly pilose, more pollinose species, the convexity of the face on tlic lower 



part, anal cell usually closed Daiilopogoii. 



19. — Abdomen elongate; front broad anterioi-ly, narrow behind. ..Plesiomiiia. 



Front not narrowed behind 20. 



20. — Hind tibiae toward the tip, and their metatarsi, much thickened 21. 



Hind tibiae not, or but sliglitly, thickened toward the tip; metatarsi not 



thickened 22. 



21. — Head much broader than high, transverse, "'goggle" like: abdomen short, 



wings large Holcocephala. 



Head only moderately broader than high, not at all spectacle-like in appear- 

 ance Ilolopogon. 



22. — Abdomen witii thick recumbent pile above; thickly pilose s])ecies: antennae 



slender Pycnopogoii. 



Abdomen without such pile above 23. 



2.3. — Slender, nearly bare species; face perpendi<Milar. straight or gently concave, 



narrowed above, bare, except on oral margin 24. 



Face gently rounded, not prominent below, in large part hairy, not or but 



slightly narrowed above ; 25. 



24. — Thickly whitish pollinose; abdomen flattened, usually reflected upward, 

 third joint of antennae and style both slender Stlchopogon. 



* Several species are placed provisionally under Cyrtopogon in which the facial 

 gibbosity is small, and the bodv thinly pilose. They may be distinguished by the 

 abdomen not being broad, and having white pollinose cross-bands: in some the 

 wings have small but distinct clouds on the cross-veins. 



