4. Antennae twelve-jointed; anterior cross-vein distinct. 



Hesperinus. 



Antennae sixteen-jointed; anterior cross-vein obsolete, that is the 

 third and fourth veins are coalescent for a short distance. 



Hesperodes. 



5. Front tibiae with a stout spine-like process at tip, ... 6 



Front tibiae with a coronet of spines; antennae ten or eleven-jointed. 



Dilophus. 



6. Anterior cross-vein distinct; antennae ten-jointed (4, 5, 6) . 



Bibio. 

 Anterior cross-vein obsolete; antennae ten-jointed (?) . Bibiodes. 



7. Front tibiae ending in a spine-like process; antennae twelve-jointed. 



(8) Aspistes. 



Front tibiae of the usual structure; antennae nine or ten-jointed (7, 

 7 bis. 7a, 8 bis, 8a) Scatopse) . 



