224 



NORTH AMERICAN DIPTERA 



Dolichopidaj IV. — 40. Hypochaiassus; 41. Dolichopus ; 42. Sympjcnus; 43, Hydrophorus; 

 44, Tachytrechus sanus ; 45, Paraphrosylus; 46, Petastoneurus ; 47, Rhaphium ; 48, Mesorhaga, 

 head from in front; 49, Rhaphium abdomen from side; 50, Neosyntormon ; 51, Mesorhaga; 52, 

 Neurigona; 53, Sympycnus; 54, Parasyntormon; 55, Gymnopternus; 56, Hydrophorus; 57, 

 Dolichopus, 1st segment of posterior tarsus; 58, Asyndetus syntormoidcs ; 59, Thrypticus; 60, 

 Xanthochlorus; 61, Hcrcostomus ; 62, Achalcus; 63, Medeterus. 



