224 DIPTERA 
the second basal cell therefore small, no fold in the wing membrane beneath the humeral crossvein, anal i 
crossvein abruptly reflexed, the outer border of the second basal and anal cells nearly continuous, . d 
oblique, anal vein thin and short, anal angle very poorly developed, blunt. 5 
But a single species is known, occurring Sin streams in wooded regions of the Nortb-western pes 
United States. ; 
Geographical distribution. 
1. O. felobs, Melander, Trans. Amer. Ent. Soc. Vol. 28, p. 233 (1902). — nr Washington. 
PI. 2, T 17. 
IO. GENUS HELEODROMI|A, HALIDAY 
Heleodromia, Haliday, Ent. Mag. London, Vol. 1, p. 159 (1833); Curtis, Brit. Ent. Vol. 8, p. 513 
(1834); Coquillett, Proc. Ent. Soc. Wash. Vol. 5, p. 250, 260 (1903); Melander, Williston's Man. 
N. Amer. Dipt. p. 224 (1998); Coquillett, Proc. U. S. Nat. Mus. Vol. 37, p. 550 (1910); Pe 
Deutsche Ent. Zeitschrift, 1918, p. 3 (1918). 3 
Macroura, Zetterstedt, MS. (not Loew, 1845 [amber Tifulidz]; not Reittor, 1873 [Coleoptera Nüitidu- 
lide] Fauna Ins. Lappon. p. 572 (1838); Scudder, Nomencl. p. 199, Index, p. 185 (1882). 
Microcera, Zetterstedt (not Meigen, 1803 [— Pifunculus Latreille]; not Mannerheim, 1830 [Coleoptera]; 
not Lioy, 1864 [— Hydrotza Desvoidy]); Zetterstedt, Fauna Ins. Lappon. p. 572 (1838); Dipt. —— : 
Scand. Vol. 1, p. 440 (1842); Coquillett, Proc. Ent. Soc. Wash. Vol. 5, p. 233 (1993); Proe. V. Per 
S. Nat. Mus. Vol. 37, p. 569 (1910). je 
Sciodromia, Haliday, Westwood : Gen. Syn. p. 132 (1840); Walker, Ins. Brit. Dipt. Vol. zr, p. 107 | k 
(1851); Bigot, Ann. Soc. Ent. France (3), Vol. 5, p. 563 (1857); Schiner, Fauna Dipt. Austr. 
Vol. 1, p. 85 (1862); Róder, Wien. Ent. Zeit. Vol. 6, p. 169 (1887); Bigot, Ann. Soc. Ent. - : 
France (6), Vol. 9, p. 122 [1889] (Seiodromyia); Coquillett, Proc. U. S. Nat, Mus. Vol. 17, p. 390 
(1895); Melander, Trans. Amer. Ent. Soc. Vol. 28, p. 345 (1902); Coquillett, Proc. Ent. 
Soc. Wash. Vol. 5, p 257(1903); Kertész, Cat. Dipt. Vol. 6, p. 129 (1909); Coquillett, Proc. — 
U. S. Nat. Mus. Vol. 37. p. 604 (1910); Wahlgren, Ent. Tidskr. Vol. 31, p. 45, 86 (1910). 
Characters. — Slender, black dusted species with narrow face, lengthened proboscis, globose 
Pygidium, simple third vein and truncate anal cell. Head rotund, eyes bare, narrowly separated on the 
face, the vertex broad, lower anterior facets much enlarged in both sexes; basal joint of the antennz 
minute, middle joint spherical, third joint oval or ovate, with a slender, terminal, apparently two-jointed 
arista, in reality the first joint of the arista is a terminal process of the third joint; proboscis cylindrical, 
obliquely projecting, shorter than the head, somewhat fleshy, palpi small, oval, hairy; cheeks obliterated; 
ocellar and vertical bristles present, lower occiput nearly bare. Thorax short, completely coated with 
fine dust, bristles small to moderate, one humeral, four dorsocentral, one supraalar, one postalar two 
scutellar, no acrostichals; metathorax not declivous, prosternum shorter than the mesosternum, 
metapleurze bare, at most with one or two minute hairs. Abdomen long, segments marked with pits, 
the terminal segments of the male not reduced, pygidium large, globose, terminal, the valves small, 
.uncinate, horny, penis hidden; last (seventh) tergite of the female densely pectinate apically with long 
seti, Legslong, slender and blackish, no bristles or spurs, the claws, pulvilli and empodium minute. 
Wings narrow, cuneate, the anal angle scarcely developed and broadly rounded, costa encompassing 
the entire wing, no basal bristle or costal setulzs, auxiliary vein attaining the costa, first vein ending 
beyond the middle of the wing, third vein simple, discal cell complete and long, posterior cells sessile, 
