1SS2.] '^'-"^ [Williston. 



XII. 



J J. — Small cross-vein at or beyond the middle of discal cell. 

 a. — Arista dorsal. 

 ;?;?. — Third longitudinal vein gently curved. 

 8. — Arista feathery plumose. 

 £. — Marginal cell open. 



b. — Thickly pilose ; abdomen without bands, short, thick, arched ; hind 

 femora strongly thickened, tibi* much bent ; face straight, extend- 

 ing back under the eyes, conical, pointed ; wings with a brown 

 spot *Arctophila. 



*Akctophila flagkans O. S., West. Dipt., 335. Colorado Mountains. 



bb.— Less pilose ; abdomen with bands ; hind femora slender ; face trun- 

 cate Sericomyia. 



Sericomyia chalcopyga Lw., Cent, iii, 20. Washington Territory, 

 Mt. Hood, Oregon ! Sitka. A dozen specimen from the two former lo- 

 calities, I have no doubt belong here ; the male not described by Loew, 

 diflers in having the third segment wholly opaque. 



XIII. 



J J. — Small cross-vein at or beyond the middle of discal cell. 

 a. — Arista dorsal. ' 

 /9/3. — Third longitudinal vein gently curved. 

 ££. — Arista bare or pubescent. 



c. — Marginal cell closed ; thorax with yellow markings ; abdomen fasci- 



ate ; antenna short Milesia. 



cc. — Marginal cell open. 



d. — Long, slender, abdomen narrower toward the base (wings more 



or less bi'ownish) Ocyptamus (JBacha). 



dd. — Abdomen never linear or club-shaped. 



e. — Face distinctly carinate, convex or nearly perpendicular in 

 profile, hyperstoma not produced, ej^es bare, hind femora 

 incrassate, with a triangular protuberance Tropidia. 



Tropidia quadrata (Say). Compl. Wr. 1, 14 {Xylota). Washington 

 Terr., California, New England ! * 



ee. — Face without a distinct median ridge or carina, or if somewhat 

 carinated, the hyperstoma produced. 

 f. — "All the femora strongly thickened and spinose below ; tarsi 

 crassate. Face tuberculate ; antenna; short, third joint as long 

 as two preceding. Small cross-vein subnormal ; first posterior 

 cell acute at outer anterior angle, rounded on outer posterior 

 part, the section of vein at distal end of cell, sinuate. Body 

 proportionately short and broad, bare, with minute sqnam*." 



Loew, Century v, 38. Small species *Lepidomyia. 



ff. — All the femora not strongly thickened and spinose below. Mostly 

 large species. 



g. — Nearly bare species, especially on the abdomen, the pile 

 never long nor dense ; eyes bare. 



