Syrphidae of Nebraska 33 



the antennae 4 



4. Arista microscopically bare; eyes often with a horizontal bare 

 stripe Pipizella 



Arista microscopically pilose to the end; eyes always evenly 

 pilose 5 



5. Venter of fourth segment in the male only half as long as its 

 dorsum; middle tibiae in female slender; third antennal joint 



in female elongate Heringia 



Venter of fourth segment three-fourths as long as its dorsum; 

 middle tibiae in female rounded in front, in male produced 

 anteriorly; trochanters in male usually with long process Cnemodon 



6. Face and front usually with transverse wrinkles; smaller 

 species Chrysogaster 



Face and front not with transverse wrinkles; larger species 7 



7. Petiole beyond union of third and fourth longitudinal veins 

 much longer than anterior cross-vein 8 



Petiole shorter 9 



8. Eyes hairy; antennal pits separated Chilosia 



Eyes bare; antennal pits confluent Cartosyrphus 



9. Scutellum unusually large, nearly quadrate; males dichoptic; 

 face concave Chalcomyia 



Scutellum normal; males holoptic; face concave in the females, 

 tuberculate in males Myiolepta 



10. Epistoma produced into a long porrect snout; costal vein con- 

 tinued well beyond apex of wing; the usual hairs on the base of 

 the costa reduced to minute spines Rhingia 



Epistoma not produced snout-like 11 



11. Arista shorter than antennae; epistoma produced downwards; 

 face in profile gently concave Neoascia 



Arista longer than antennae; epistoma produced anteriorly; 

 face in profile deeplj' concave Sphegina 



139 



