138 DIPTERA OF NORTH AMERICA. [PART IV. 



Nephrotoma. t The first joint is very short, the second almost 

 rudimental ; the third joint (first joint of the flagelluni) is more 

 than four times the length of the first and second taken together ; 

 it is subcylindrical, with a rounded projection on the under side 

 near the tip ; the fourth joint has about four-fifths of the length 

 of the third; it has almost the shape of a recumbent #; it is 

 attenuated at the basis and in the middle, whereas the inter- 

 mediate parts are incrassated, as also the tip of the joint which 

 projects distinctly on the under side; the following joints (from 

 the fifth to the fifteenth) have exactly the same shape as the 

 fourth, only they very gradually decrease in length and this 

 peculiar shape becomes less and less distinct ; the sixteenth and 

 last joint is subcylindrical and almost rudimental. The joints of 

 the flagellum are densely clothed with a delicate down ; each of 

 them bears two longer hairs on the upper side near the basis, and 

 two similar, only shorter hairs, on the projecting sinuosities of the 

 under side. 



The collare is narrow and but little developed. The thorax 

 has on the upper side, between the transverse suture and the 

 scutellum, a pair of peculiar pits or impressions, originating on 

 each side near the root of the wing and running towards the 

 middle (I do not know whether they were not accidental in the 

 described specimen). I cannot say anything positive about the 

 male genitals, except that they do not give to the tip of the abdo- 

 men a club-shaped appearance. The feet (the specimen had only 

 a single anterior foot left) are. very long ; their pubescence is short 

 and not at all striking. Ko spurs are perceptible at the tip of the 

 tibiee. The last joint of the tarsi of the male has no excision on 

 the under side. 



The wings are rather long and moderately broad. The marginal 

 cross-vein is very little before the tip of the first longitudinal vein. 

 The stigma is inclosed between the subcostal and marginal cross- 

 veins. The origin of the second longitudinal vein is rather before 

 the middle of the anterior margin ; the prasfurca forms a straight 

 line with the third longitudinal vein ; first submarginal cell shorter 

 than the second ; the latter very square at its basis, nearly of the 

 same length with the first posterior; the cliscal cell somewhat 

 elongated. 



The coloring of the only species I have seen is yellow (it will 

 be published shortly in Mr. Bellardi's work on Mexican Diptcra). 



