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. 



IS. T. alba LOEW. and 9. (Loew, Berl. Entom. Zeitschr. 1861, 

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

 segmentorumque abdonainalium singulorum margine postico pallide sul- 

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



Whitish, wings whitish, without spots, front, pleurae, 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 0.1G. 



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. 



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

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

 and with T. oUiqua Say; in August.) 



19. T. alTjidipeniiis LOEW. % and J . (Loew, Berl. Entorn. Zeit- 

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

 racis vitta lateral! scutelloque sulphureis, alarum albidarum stigmate 

 fusco, terebra foeminse 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. 



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

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

 moderate; proboscis not genicnlated, palpi short. Thorax dusted 



