DIPTERA 



i. 



SKETCH OP THE SYSTEMATIC ARRANGEMENT OF DIPTERA: WITH AN 

 ENUMERATION OF THE GENERA HITHERTO RECORDED AS FOUND 

 IN NORTH AMERICA. 



OUR knowledge of the Dipterological Fauna of North America 

 has lately made rapid progress by the great attention paid to it 

 by Baron Osten Sacken daring his residence in Washington. As 

 a preliminary to further investigations, he prepared, in 1858, for 

 publication by the Smithsonian Institution, a Catalogue of the 

 then described North American Diptera, which had the great and 

 essential merit of nearly entire completeness. It pannot but be 

 considered as a wise precaution that he did not enter upon a criti- 

 cal examination of the published species, as he well understood 

 that such an examination could only be the work of the combined 

 efforts of many persons, and the fruit of a long toil of years, and 

 that consequently undertaking it would have indefinitely retarded 

 the publication of such a catalogue, so desirable for the advance- 

 ment of North American Dipterology. The impulse caused by 

 Baron Osten Sacken's Catalogue is already evident, and it has 

 proved a welcome and valuable assistance to every one attempting 

 a more thorough study of North American Diptera, by an intel- 

 ligible arrangement of the already published species, not only 

 sparing him much laborious research, but also giving him the cer- 

 tainty of not overlooking a species already described. But although 

 this Catalogue presents a survey of all papers hitherto published, 

 and of the contributions of each author, it does not, and according 

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