124 Bulletin of the Brooklyn Entomological Society Vol. XVI 



constricted basally, or the third antennal joint greatly en- 

 larged; males dichoptic. (Sphegini and Pelecocerini) 14. 

 Alula broader than second basal cell; anal furrow distinct 

 and of normal length; males holoptic except in Chal- 

 comyia 2. 



2. Face entirely black {Chilosini, in general) 3. 



Face more or less yellow (gray in Brachyopa vacua). 



(Brachyopini, in general) 9- 



3. Oral opening broadly oval and without indentations ; face 



very gently and evenly con vexed, completely clothed with 



rather long, loose pile Pipisa. 



Oral opening irregular in outline, having a dorsally directed 

 indentation at the front margin 4. 



4. Antennae very elongate, with a terminal style .... Callicera. 

 Antennae of normal length and with dorsal arista 5. 



5. Face flat^ with the epistoma protruding anteriorly 6. 



Face either tuberculate (Chilosia type) or concave {Xylota 



type) 7- 



6. Abdomen inflated, the disc shining; face and frons without 



transverse wrinkles ; rather pilose species Psilota. 



Abdomen depressed, the disc flat and dull; face and frons 

 usually with transverse wrinkles ; pile very short and 

 scant Chrysogaster. 



7. Fourth vein joining the third much before the wing margin ; 



a chitinous projection extending from the face upwards 

 between the antennas to join a similar downward projec- 

 tion of the frons ; face tuberculate in both sexes ; arista 

 frequently more or less plumose. Many species bearing 

 bristles on thorax Chilosia, 



Fourth vein joining third at a very acute angle close to wing 

 margin ; space between antennae pale and membranous ; 

 arista bare ; no bristles on thorax 8. 



^ Certain mahis of Chrysogaster have a very small central 

 ^nob but these can easily be placed generically by the fiat, dull 

 -disc of the abdomen. 



