SOUTH AMERICAN DIPTERA. 259 



that the tibij?e and tarsi are yellow. The description, with that ex- 

 ception, applies (I do not possess the described specimen). 



The genus Microdon I have found the most difficult one in the 

 family, so far as identifications go. There seems to be considerable 

 variation in not a few species, and, in the descriptions hitherto, almost 

 none of the numerous structural characters have been made use of. 



7. Nausigaster piinctiilata Williston, Synopsis N. A. Syrphidfe, p. 21. — 

 United States, Mexico. 

 Three specimens from Chapada agree with the one mentioned by 

 me from Tehuantepec. Whether they belong to a distinct species or 

 not I cannot say. 



TUICHOPSOMYIA geu. iiov. 



Small, wdiolly black, shining or opaque, moderately pilose species. 

 Antenme elongate, slender ; first two joints of nearly equal length, 

 third longer than the first two together ; arista Ijasal, small, bare. 

 Face broad, pilose, with an obtuse tubercle, the epistoma receding. 

 Frontal triangle of male large, broad, flattened, swollen on upper 

 part ; eyes in male narrowly, but closely contiguous, the ocellar tu- 

 bercle prominent. Front in female broad, modei-ately narrowed 

 above; the upper margin of head tumid and projecting. Scutellum 

 triangidar. Abdomen elongate oval. Legs of moderate strength ; 

 tarsi short, especially the front pair; metatarsi of front and hind 

 pairs thickened, the remaining joints flattened ; hind femora elon- 

 gate and more or less thickened, the hind tibios arcuate and dilated : 

 all the femora and tibiae ciliate, of the hind legs conspicuously so. 

 Wings as in Plplza (Fipizella) : posterior cross-vein rectangular, 

 straight, last section of fourth vein bent or angulated. Eyes irregu- 

 larly pilose. 



This genus is allied to Pipizella, but will be at once distinguished 

 by the vertex in the female and the frontal triangle in the male. 

 The irregularly pilose eyes, with bare patches, will also serve to dis- 

 tino-uish them. The neuration in all the species described l)elow 

 agrees closely, and is very like that of P. pulche/la Will. — Synopsi.-^ 

 N. A. Syrphidfe, pi. ii, fig. 1. The species resemble each other nuich 

 in color markings ; the following description will apply to the known 

 species ; 



Face and front shining black, clothed with sparse long white pubescence or 

 pile, which has a flattened or curled appearance ; on the uppermost swollen pait 



