344 NORTH AMERICAN DIPTERA 



19. Scutellum elongated, the disc flattened (8, 10) . . . .Pseudogaurax Malloch 

 Scutellum normal, the disc gently convex Gaurax Lcew 



20. Only two notopleural bristles on posterior part 22 



At least four notopleural bristles 21 



21. Notopleural bristles four in number; mesonotal setulae in rows. 



Eugaurax Malloch 

 Notopleural bristles very numerous; mesonotum thickly setulose. 



Chaetochlorops Malloch 



22. Distance between the tips of the first and second veins three or four 



times that between the second and third (9) Dicraeus Lcew 



Distance between tips of first and second veins not more than twice 

 that between the second and third 23 



23. Proboscis elongated and geniculate, the terminal section about as long 



as the preceding section (7, 13) Madiza Fallen 



Proboscis shorter, the apical section shorter and more fleshy 24 



24. Mesonotum with three broad longitudinal punctured grooves. Tricimba Lioy 

 Mesonotum with only two narrower grooves or they are weak or absent 



(15, 20, 22) Oscinella Becker 



