952 Charles Paul Alexander 



Antennal flaRellar segments bicolorous, the basal swelling of each segment black, the 

 pedicel vellow. [Proc. Acad. Nat. Sci. Phila., p. 485-487, pi. 16, fig. 10. 1915.] 

 (Plate XLVI, 222, wing; Plate XLIX, 272, ninth tergite; Plate LIII, 325, eighth 

 sternite.) T. cayuga Alex. 



78. Size small, wing 12 mm.; thoracic dorsum dull gray, with four brownish stripes; antennae 



unicolorous, dark brown; pleura clear light gray; sides of postnotum light yellow; 

 ninth tergite (Plate XLIX, 270) with two broad lobes, the notch between deep. 

 [Journ. N. Y. Ent. Soc, vol. 9, fig. 99. 1901.] (Plate XLVI, 225, wing.) 



T. sulphurea Doane 

 Size larger, wing 14 mm. or over; thoracic dorsum not colored as above 79 



79. Antennae bicolorous; thoracic dorsum dull yellow with three brown stripes, the lateral 



pair less distinct than the median one; legs long; male hypopygium with the median 

 lobe of the ninth tergite (Plate XLIX, 268) entire or the bifid nature barely indi- 

 cated. [7'. perlongipes Johns., Proc. Boston Soc. Nat. Hist., vol. 34, p. 131, 1909. 

 T. filipes Walk., preoccupied, List Dipt. Brit. Mus., p. 65, 1848.] (Plate XLVI, 223, 



wing.) T. perlongipes Johns. 



Antennae unicolorous or nearly so; thorax gray, with three broad, more or less distinct, 

 stripes, the median one with a delicate dark brown line; legs short; male hypopygium 

 with the median lobe of the ninth tergite (Plate XLIX, 269) bifid. [Proc. Acad. 

 Nat. Sci. Phila., p. 480-482, pi. 16, fig. 6. 1915.] (Plate XLVI, 224, wing; Plate 

 LIII, 331, lateral aspect of male hypopygium.) T. kennicotti Alex. 



80. Ninth tergite (Plate LII, 309) large, the caudal margin with a small rounded notch on 



either side of a small acute median tooth; eighth sternite with broad, fleshy, lateral 

 lobes directed proximad and with the ventral inner angle produced into a chitinized 

 point and clothed with long yellow hairs; median area of the sternite with a prominent 

 chitinized tooth on either side of the median line, broadly separated by a distance 

 greater than the diameter of one tooth; size large, wing 18-20 mm.; antennae bicolorous. 

 [Berl. Ent. Ztschr., vol. 7, p. 292. 1863.] (Plate XLVII, 236, wing.) 



T. umhrosa Loew 



Ninth tergite not as described; eighth sternite, if with fleshy lateral lobes (7". australis, 



T. valida, and others), without two chitinized teeth on the caudal margin of the 



sternite 81 



81. Size large, wing over 20 mm.; male hypopygium greatly enlarged; eighth sternite with 



elongate lateral lobes and a flattened median lobe (valida group; included also in 

 the section with marked wings, because the tips of the wings are usually of a darker 



gray than the basal part) 82 



Size smaller, wing under 18 mm.; male hj^jopygium not greatly enlarged; eighth sternite 

 not as above 83 



82. Ninth tergite (Plate LI, 303) with the lateral lobes more slender and pronounced; 



eighth sternite without a long brush of hairs. [Berl. Ent. Ztschr., vol. 7, p. 287. 



1863.] (Plate XLVII, 237, wing.) T. valida Loew 



Ninth tergite (Plate LI, 304) with the lateral lobes shorter and blunter; eighth sternite 

 with a brush of long yellow hairs. [Journ. N. Y. Ent. Soc, vol. 9, p. 113. 1901.] 



T. hirsxita Doane 



83. W.ng apex a little grayer than the basal cells of the wings; a brown spot at the origin 



of the sector; male hypopygium with the ninth tergite (Plate LII, 317)_large, deeply 

 split by a broad V-shaped notch, the lateral lobes acutely pointed. (This species is 

 included also in the section with marked wings, because the tips of the wings are 

 usually of a darker gray than the basal part.) [Berl. Ent. Ztschr., vol. 7, p. 288. 



1863.] (Plate XLVII, 239, wing.) T. submaculata Loew 



Wing apex unicolorous or nearly so; ninth tergite not as described 84 



84. Antennae unusually elongated, if bent backward extending to the base of the fifth 



abdominal segment; ninth tergite (Plate LI, 290) with the lateral lobes subacute, 

 the median lobe situated in a deep, shield-shaped depression; eighth sternite unarmed; 

 antemaae unicolorous; abdominal tergites bright yellow, with three distinct brownish 



