PREFACE. 



Twenty-four years ago the writer began the publica- 

 tion, in the Bulletin of the Brooklyn Entomological 

 Society, of a series of synoptic papers on the families and 

 genera of North American Diptera. Previous to that 

 time but seven of the sixty odd families had thus been 

 rendered accessible to the American student in the works 

 of Loew and Osten Sacken. In 1888 these synopses 

 w^ere revised and published, with others, in a pamphlet 

 of 88 pages entitled ' Synopsis of the Families and 

 Genera of North American Diptera, exclusive of the 

 Nematocera and Muscidae.' It contained tabular defini- 

 tions of about three hundred and fifty genera, all at that 

 time known from the United States in the families treated. 

 In the succeeding eight years the writer's acquaintance, 

 especially with the southern forms, had been so widened 

 that he attempted a similar review of all the North and 

 Middle American genera, aided by Professor Aldrich in 

 the Dolichopodidae and Mr. Snow in the Ortalidse. Re- 

 gretfully the very large and almost chaotic families 

 Dexiidse and Tachinidae were not included. Eight hun- 

 dred and twenty-six genera were defined in this 'second 

 edition' more or less accurately, very nearly all of which, 

 save those of the Dolichopodidse, had been studied by 

 the writer in its preparation. The continued use of this 

 work, both in America and abroad, has been very grati- 

 fying to the author, a use that has made him the more 

 desirous that a better and more complete edition should 

 be prepared, one that would be of greater service to the 

 amateur, whose interests have been paramount. For such 

 an edition the present time seemed opportune, since the 

 recently published catalogue of the Diptera of North 



