FAIMILY BIBIOXID.K THE MARCH FLIES 129 



4. Distance between the fork of the fourth vein and the anterior cross- 



vein more than twice the length of the crossvein (4). 



Hesperinus Walker 



Distance between fork of fourth vein and anterior crossvein much less 

 than twice the length of the crossvein (6) Plecia Wiedemann 



5. Anterior tibi33 produced apically to form two spurs (3) G 



Anterior tibite without such spurs but with two or three series of teeth 



(2) Dilophus Meigen 



6. Third and fourth longitutUnal veins coalescent for a short distance 



( 1 ) Bibiodes Coquillett 



Third and fourth veins not coalescent, joined by the anterior cross- 

 vein (3, 5) Bible Latreille 



Bibionidae. — 1, Bibiodes; 2, Dilophus, front tibia; 3, Bibio, front tibia; 4, Hesperinus; 5, 

 Bibio; 6, Plectia; 7, Cramptonomyia. 



