100 DIPTERA OF NORTH AMERICA. 



Hab. Indiana. (Say.) Pennsylvania. (Osten-Sacken, on Ver- 

 no?iia, in August.) 



Note. — The above description, which is Say's, will be sufficient for the 

 recognition of the species. I have modified the terminology to make it 

 agree with that used in this publication, and will only add that the third 

 longitudinal vein bears some black bristles, that both cross-veins are 

 oblique, that the posterior portion of the fourth vein is distinctly arcuated 

 at its base, and that the tip of the wing has a peculiar whitish reflection. 



O. S. 



18. T. alba Loew. % and 9. (Loew, Berl. Entom. Zeitschr. 1861, 

 p. 345.) — Albida, alis concoloribus immaculatis, fronte, pleuris, scutello, 

 segmentorumque abdominalium singulorum margine postico pallide sul- 

 phureis, facie cum antennis, pedibus et terebra obscurius flavis. 



Whitish, wings whitish, without spots, front, pleurse, scutellum and the 

 posterior border of the abdominal segments pale sulphur-yellow ; face, 

 antenna?, legs and borer of the 9 darker yellow. Long. corp. 0.13 — 

 0.17. Long. al. 0.15—0.10. 



Antennre of moderate length ; tip of tbe third joint round, 

 bristles with a very short pubescence. Eyes large, almost round; 

 checks moderate. Oral opening moderate, rounded, proboscis not 

 geniculated, palpi short. Scutellum flat, with four bristles. Borer 

 of the 9 flattened, ferruginous-yellow, longer than the three last 

 segments of the abdomen taken together. Wings whitish, all the 

 veins very pale, and, except the first longitudinal one, bare ; pos- 

 terior angle of the anal cell acute. 



Hab. Pennsylvania. (Osten-Sacken; taken on Vernonia novce- 

 borace?isis, iron weed, together with the two following species, 

 and with T. obliqua Say; in August.) 



19. T. ;i lMdipenn is Loew. % and 9 . (Loew, Berl. Entom. Zeit- 

 schr. 1861, p. 345.) — Nigro-cinerea, thoracis dorso albicante, oapite, tho- 

 racis vitta laterali scutelloque sulphureis, alarum albidarum stigmate 

 fusco, terebra fcemime atrft. 



Blackish cinereous, thorax more whitish above, head, a lateral stripe on 

 the thorax, and the scutellum sulphur-yellow, wings whitish, stigma 

 fuscous, borer of 9 black. Long. corp. 0.17 — 0.20. Long. al. 0.18 — 

 0.19. 



Antenna? moderate, ferruginous-yellow, tip of the third joint 

 rounded, bristle almost bare. Eyes largo, almost round ; checks 

 moderate; proboscis not geniculated, palpi short. Thorax dusted 



