AMERICAN DIPTERA. 251 



with at least some pile; style short, usually thick, obtuse, and 

 not easily distinguishable from the third segment as in vera, 

 or nearly setaceous as in albius, varying in length from one- 

 sixth to one-half the third segment. 



Dorsum of thorax usually with pubescence and weak bris- 

 tles; pleurae polished, with characteristic markings in fine 

 pubescence; scutellum thin, usually projecting and always 

 distinct from the well-rounded metanotum, often with fine 

 short pile on its posterior margin, never or seldom with 

 bristles. Abdomen very narrow and cylindrical, ofter broader 

 beyond the third segment in the female. Legs often slender, 

 hind metatarsi sometimes normal as in albius, or large as in 

 vera. Front tibias without a terminal claw-like spur; hind 

 femora without strong bristles; pulvilli normally developed. 

 Wings rather large; all the posterior and the anal cell wide 

 open. 



Type. — Asilus celandicus. 



SYNOPSIS OF SPECIES. 



1. Wings on the basal half yellow, on the apical half black 2. 



Wings not marked thus, nearly uniformly darkish 3. 



2. Legs wholly black; length 4 mm parvula. 



Legs partly reddish-yellow, length 7 mm sackeni. 



3. Abdomen wholly black 4. 



Abdomen and legs partly reddish 6. 



4. Legs wholly black 5. 



Legs black; tibiae for most part reddish-yellow; mystax black. 



nitida. 

 Femora black above; reddish-yellow below; mystax golden.... vera. 



5. Mystax black albius. 



Mystax fulvous and dense; thorax and abdomen beautifully green- 

 ish-black resplendens. 



6. Antennal style nearly one-half as long as the third segment; coxae 



red pusio. 



Antennal style one-sixth as long as the third segment; coxse black. 



rubida. 

 Dioctria albius (PI. Ill, fig. 8; PI. IX, fig. 8.) 

 Dioctria albius Walker, List, II, 301, 1849. 

 Dioctria albius Osten Sacken, West. Dipt., 287 (notes), 1877. 

 Dioctria albius Williston, Trans. Am. Ent. Soc, XI, 8, 1884. 

 $ 9- — Length 7-9.5 mm. — Wholly polished black, abdomen with cop- 

 pery reflections; face brassy yellow pruinose; thoracic dorsum with 

 golden down; legs wholly black. 



TRANS. AM. ENT. SOC, XXXV. JULY, 1909. 



