496 PROCEEDINGS OF THE XATIOyAL MUSEUM. vol.43. 



abdomen black (brownish in female), tapering in male, and %vith 

 the second segment elongated and broadest posteriorly, sixth seg- 

 ment elongate and with a few hair-like preapical bristles, hypopygium 

 with ventral processes distinct, anal protuberance small, yellow, with 

 the terminal hairs weak, female abdomen with segments siibequal, 

 hind femora strong, darkened, no distinct setulas except some of 

 those on the middle of the hind tibiae in male which are rather stronger 

 than elsewhere on tibiee, wings yellowish, costa distinctly short of 

 middle, first division distinctly longer than other two together, 

 fringe short, not much longer at its longest part than twice the diam- 

 eter of costa, fourth vein nearly straight at base and running sHghtly 

 upward on apical half, ending distinctly in front of wing tip, fifth 

 vein regularly divergent from fourth; halteres yellowish white. 



Length, 1-1 1 mm. 



There has been considerable confusion regarding this species. 

 Aldrich described setacea from one male and four females, taken at 

 Brookings, South Dakota.^ Afterwards Brues writes ^ that Aldrich 

 had females of A. agarid, Lintner, and not of setacea which was a 

 distinct species represented by the male (type). This type-specimen 

 is now before me. Brues states that several of his specimens are 

 considerably larger than the type (2-2|^ mm.), which leads me to sup- 

 pose that he had also two species before him. This supposition is 

 strengthened by reference to his description of the species which can- 

 not have been drawn from the type, as will be seen if his description 

 is compared with the foregoing and his drawing of the wing with that 

 given herewith. I am confident that the larger specimens he mentions 

 belong to some other species, because they evidently had a much 

 broader frons, a longer fringed costa, and were twice as large as the 

 type which being a female, and not as he supposed a male, would 

 represent the largest sex as is always the case in this group. There 

 is in most species a very small amount of variation in the size except 

 as between the sexes, and though it would be bad policy to describe a 

 species as new because it only dififered from a known species in the 

 matter of size, when there are, as in this case, so pronounced differ- 

 ences it is quite conceivable that there has been a mistake made. 

 There is besides the female already mentioned one male from Wash- 

 ington, District of Columbia (collection Coquillett); no other data. 



APmOCafiTA ALBmOHALTERIS Felt. 



Male and feTTiale. — Black subshining; frons distinctly broader than 

 long, lower pair of post-antennal bristles very minute, the upper pair 

 of moderate size, bristles of first row forming an almost straight 

 transverse line with the post-antennal pair, antennae in male rather 

 larger than normal, in female normal, palpi yellow. , normal; thorax 



• Can. Ent., vol. 24, p. 144. » Trans. Amer. Ent. Soc., vol. 29, p. 370. 



