PREFACE. 5 



O. A. Johannsen has furnished a new table of the Chiro- 

 nomidae. Professor V. L. Kellogg has done the same for 

 the Blepharoceridae, and has revised the family charac- 

 ters. Professor A. L. Melanderhas treated the Empididae 

 anew; and Professor C. H. T. Townsend has generously 

 criticised the figures of the Dexiidae and Taehinidae, and 

 has furnished important notes on many of the genera. 

 To all these gentlemen the author tenders his sincerest 

 thanks, not only on his own part, but also on the part 

 of those who will have occasion to use the work. 



At the outset it was not contemplated to give many 

 illustrations, chiefly such as would be explanatory of 

 the more important characters. In the end more than 

 six hundred genera have been defined more or less fully 

 and decisively by nearly one thousand figures. Of these 

 figures all these of the Dolichcpodidae and the first plate 

 cf those of the Taehinidae were furnished by Professor 

 Aldrich. Mr. Brues has furnished the figures of the Phori- 

 dae, Professor Hine those of the Tabanidae, and Professor 

 Melauder most of those illustrating the Empididae. Pro- 

 fessor Washburn kindly gave permission to use electro- 

 types of twenty-three figures prepared for his or the late 

 Professor Lugger's reports on Minnesota Diptera. To 

 Professor Kellogg and Henry Holt & Co. the writer is 

 indebted for eight electrotypes of figures in Professor 

 Kellogg's American Insects; and to Professor J. B. Smith 

 his thanks are due for six figures of the Culicidae, orig- 

 inally prepared for his Report on the Mosquitoes of New 

 Jersey. A few other figures have been copied from relia- 

 ble sources, where specimens were not easily accessible, 

 and are likewise credited in each case to its author. All 

 the remainder, whether drawings or photographs, more 

 than eight hundred in number, have been made by the 

 writer from specimens — a task which has involved many 

 months of labor, but which could not, in most cases, have 

 been safely entrusted to a professional draftsman. 



