NORTH AMERICAN DIPTERA 



I N T H ( ) 1) U C T I O N . 



TnK writer has, during the past five years, published in different 

 l)eriodicals various synoptic tables of tiie families and genera of 

 North American Diptera. Tlie intention was, at first, to reprint 

 these with revisions, that tliey might be more accessible to those 

 interested in this order of insects. In order to make, it is trusted, 

 the tables of more service, those of other families have been added, 

 either as compiled or reproduced from standard authorities, or pre- 

 pared from the examination of specimens in the author's collection. 

 It will be understood, however, that, in not a few families, the pres- 

 ent condition of American dipterology does not admit of the prepa- 

 ration of synopses free from error ; the writer's acquaintance, too, 

 with not a few families, has been less complete than with others, 

 and it is very true that only he who has made a critical study of 

 abundant material is competent to compile such tables with mucli 

 success. For this reason, the tables of genera in the Nematocerous 

 and Muscid families have been omitted. It may be mentioned 

 that very nearly all the genera defined in the present work have 

 been examined by the writer, though not all with the same degree 

 of critical study. The faunal limits embraced are those north of 

 Mexico ; and whenever extralimital forms are introduced they will 

 be found preceded by a ^ . 



The student will soon learn that the characters of many flies 

 are not so simple and apparent as a mere synoptic table would 

 indicate them to be. He will often be puzzled at the interpre- 

 tation of characters, even after he has acquired a considerable expe- 

 rience. Furthermore, it is often necessary to study any author a 

 considerable time before he becomes thoroughly familiar with his 

 peculiarities of style and modes of expressi(m ; he must become, one 

 may say, familiar with the personal equation of each writer before 

 he can feel confidence in the results obtained from him. It is pre- 

 cisely those autiiors who reduce that ])ersonal equation to the mini- 

 mum who are most successful as describers. One, for instance, may 

 feel confident of a determination of a species described by Macquart, 



