SMITHSONIAN MISCELLANEOUS COLLECTIONS. 

 MONOGRAPHS 



D I P T E R A 



NORTH AMERICA. 



PREPARED FOR THE SMITHSONIAN INSTITUTION 



BY 

 II . L E W. 



PART I. 



EDITED, WITH ADDITIONS, 



R. OSTEN SAC KEN 



WASHINGTON: 



SMITHSONIAN INSTITUTION 



AI'KIL, 1SG2. 



