100 DIPTERA OF NORTH AMERICA. 



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

 nonia, 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. 



0. 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 terebrJl obscurius flavis. 



Whitish, wings whitish, without spots, front, pleurae, scntellum and the 

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

 antennae, legs and borer of the 9 darker yellow. Long. corp. 0.13 

 0.17. Long. al. 0.150.16. 



Antennae of moderate length ; tip of the third joint round, 

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

 cheeks 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. 



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

 boracensis, iron weed, together with the two following species, 

 and with T. obliqua Say; in August.) 



19. T. alMdipennis LOEW. $ and 9 (Loew, Berl. Entom. Zeit- 

 Bchr. 1861, p. 345.) Nigro-cinerea, thoracis dorso albicante, capite, tho- 

 racis vitta lateral! scutelloque sulphureis, alarum albidarum stigmate 

 fusco, terebra fceminse atra. 



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. 



Antennas moderate, ferruginous-yellow, tip of the third joint- 

 rounded, bristle almost bare. Eyes large, almost round ; cheeks 

 moderate; proboscis not geniculated, palpi short. Thorax dusted 



