118 DIPTERA OF NORTH AMERICA. 



Observation. Tet. sparsa differs too much from Tet. comlinata 

 in the markings of the wings to be considered as identical with it. 

 I have, however, to remind, that they agree much more in their struc- 

 ture than is usual in nearly-related species of this genus, and that 

 my opinion, formed on very scanty materials (1 9 of Tet. combi- 

 nata, 1 and 1 9 of Tet. sparsa), cannot but have a very second- 

 ary weight. Nor will the difference in the markings of the thorax, 

 however striking they may seem, solve the question, since, in some- 

 what immature specimens, they always appear inconstant, and are 

 often variable even in quite mature ones. 



9. T. costalis LOEW. > Seta antennarum albo-plumosa ; thorax 

 vittatus ; alse grosse inaculato-reticulatse, margine antico anguste nigro- 

 limbato, vena transversa posteriore perpendicular!, recta. 



Bristle of the antennae plumose with white, thorax striped, wings reticu- 

 lated with coarse dark spots and the costal border having a narrow black 

 margin, posterior transverse vein perpendicular and straight. Long, 

 corp. 0.17. Long. al. 0.17. 



Yellowish-brown, somewhat tinged with reddish, opaque. Front 

 yellow, with the middle stripe broad, excavated, and polished, not 

 tapering anteriorly ; on each side near the orbit there is a small 

 black dot, and more anteriorly a second larger one between the 

 antenna? and the anterior corner of the eye. Antennas yellow, with 

 the third joint a little longer than the second, but little excised on 

 the upper side, not much pointed. Antennal bristle with the base 

 only yellow and covered with a close white pubescence. Face white, 

 rather considerably receding. Upper side of the thorax dusted 

 with whitish on the lateral borders; in the middle, there are two 

 complete longitudinal stripes, formed of whitish dust and bordered 

 with brownish streaks, which are not quite distinct and interrupted 

 in the middle of the thorax. Superior part of the pleura with a 

 brownish-red longitudinal stripe continued to beneath the poisers. 

 Scutellum yellowish. Abdomen unicolorous, having no trace of 

 darker stripes in the described specimen. Legs whitish-yellow, 

 not distinctly blackened at the end of the tarsi; under side of the 

 posterior femora with small short bristles. Surface of the wings 

 a little yellowish, with the stigma and a margin of the costal border 

 black ; this margin runs from the stigma as far as the fourth longi- 

 tudinal vein, being very narrow as far as the tip of the second 

 longitudinal vein, and then broader; there are about six or seven 



