122 Bulletin of the Brooklyn Entomological Society Vol. XVI 



Third longitudinal vein straight or with a gentle downward 

 curve II, 



11. Lateral margins of mesonotum not marked with bright yel- 



low Syrphus.^ 



Lateral margins of mesonotum more or less bright yel- 

 low r 12. 



12. Posterior margin of mouth and the metapleura blackish 



seneous ' 13. 



Region behind mouth bright yellow; metapleura usually 

 bright yellow 14. 



13. Hind femora of male thickened and arcuate, tibiae arcuate 



and dilated at tip ; hind femora of female posteriorly 



with blackened ring . .* Toxomerus. 



Hind femora and tibiae of male normal, hind tibiae of female 

 entirely yellow, rarely (var. hoscii) with blackened ring 

 posteriorly Mesogramma. 



14. Anterior margin of wings brownish ; abdomen, narrow, cylin- 



drical Doros. 



Anterior margin of wings hyaline 15. 



15. Eyes of male above with an area of enlarged facets; fourth 



segment of abdomen, in both sexes, with two median yel- 

 low stripes and oblique side-spots Allograpta. 



Eyes of male normal ; fourth abdominal segment not so 

 marked 16- 



16. Face projecting below ; slender species Sphcerophoria. 



Face receding ; abdomen broadly oval Xanthogramma. 



NAUSIGASTERIN^, new subfamily. 



In many respects this is the most aberrant subfamily (only 

 one genus) of the Syrphidae found in North America. It offers 

 the following unique characters which at the same time show 

 a remarkable instance of parallel development with a group be- 

 longing to the Hymenoptera, the Chrysididae. 



^ Syrphus ribesi is here considered as possessing the "type 

 structure" for Syrphinae. 



