XX BULLETIN 31, UNITED STATES NATIONAL MUSEUM. 



female there is scarcely any appreciable difference, at least in the former 

 genus. Fyrophccna is au excellent example of a faulty taxonomic clas 

 sitication ; while the flattening of the forelegs is made a generic char- 

 acter in Flatychincs, much greater structural differences in the legs of 

 Pijrophoemc only receive a specific valuation. Undoubtedly, should the 

 number of species warrant it, a generic line will be drawn between P. 

 ocymi and P. rosarum, but on the basis of natural classification it should 

 not matter whether a genus contained one or one thousand species. 



It may be objected that this group is not entitled to the rank I give 

 it; but if it be united with the Si/rphini, the CMlosini must be also. 

 Shall we place CItrysogaster and Syrphus in one group? As well place 

 the whole family in one group. 



SYRPHINI. 



BlacTc or greenish-black species, usually tcith yellow abdominal bands, 

 the face tcholiy or in part yellow. Marginal cell of the wings icide open, 

 third vein ra/ely (Didea) curved into the first posterior cell, anterior cross- 

 vein near the base of the discal cell. Antetinw short, face tuberciilate, 

 abdomen usually oval, legs slender, hind femora rarely thiclened (Meso- 

 grapta sp.). 



a. Thickl^ pilose species ; abdomen quite oval, broader beyond the middle. Basal por- 



tion of abdomen yellow, terminal portion black 



Leucozona Scbiner. 

 aa. Eatber bare species ; abdomen not so marked. 



b. Thorax never with yellow lateral markings. 



0. Sixth abdominal segment of the male as long as the two preceding together, but 

 narrower, somewhat tubular, unsymmetrical ; on underside of the 

 seventh segment with two long linear subparallel appendages, 

 arcuate, bidenticulate at the end, embedded in grooves when at 

 rest. In the female the fifth segment half as long as the preceding. 



Scutellum much raised, exposing metanotum Eupeodes O. S. 



CO. Hypopygium without slender appendages, sixth segment of male not peculiar; 

 fifth segment of female one-third or one-fourth as long as preceding 

 segment. 



d. Third longitudinal vein with a distinct curvature into the first posteror cell ; 



third joint of the antennaB elongate-oval Didea Macq. 



dd. Third longitudinal vein straight or gently curved; third joint of antennte short 

 oval. 



e. Eyes of male with an area of enlarged facets above; front very convex; hypopy- 



gium very small Catabomba O. S. 



ee. Eyes of male without an area of enlarged facets above; front moderately convex; 



hypopygium not very small Syrphus Fabr. 



bb. Thorax with yellow lateral stripes. 

 /. Eyes of male with an area of enlarged facets above; fourth segment of abdomen 



in both sexes with two median yellow stripes and an oblique spot 



on each side Allograpta O. S. 



ff. Eyos of male wholly without an area of enlarged facets above; fourth segment of 



abdomen not so marked. 



