60 NORTH AMERICAN DIPTERA. 



On the other hand the structure of the adult insects 

 changes so much somewhere in the vicinity of the Syr- 

 phidse, to say nothing of larval structure and habits, that 

 I believe, if we must have suborders (which to me does 

 not seem imperatively necessary) the place to make 

 the division is somewhere between the Syrphidse and 

 Dolichopodidae. There are groups here which are oscul- 

 ant no doubt a lot of ink has been wasted in their dis- 

 cussion, but so there are in all classifications. The 

 sooner we learn, as learn we must, that dividing lines do 

 not occur in nature except as accidents, that evolution 

 never classified anything and never will, the sooner we 

 shall get over some of the bugbears of taxonomy. The 

 best we can do is to make such groupings as will express 

 most clearly and most conveniently relationships, and 

 especially the phylogeny of organisms. 



As I have already said, a true classification of the dip- 

 tera, as of all other organisms, is desirable, but not pos- 

 sible, for that would mean the absolute perfection of 

 dipterological science. An approximation to that finish- 

 ed perfection is of course attainable, but that approxima- 

 tion must depend upon many factors which have as yet 

 scarcely engaged the attention of students of diptera. 

 Their embryology, geological history, geographic dis- 

 tribution, ethology and comparative anatomy, are among 

 these factors. No dipterologist has ever given serious 

 attention to the study of extinct forms, and no classifica- 

 tion of any group of organisms has ever been satisfactory 

 until such forms have been considered and seriously con- 

 sidered, paleontology and embryology especially, are 

 the sine qua non of any entomological classification, and, 

 considering the relatively slight advances which have 

 been made in the taxonomy of the diptera during the 

 past half century, now seems the opportune time for such 

 studies. What dipterologist will undertake them ? 



