Introduction 



Many systematic papers have been published by the United 

 States Government through the Smithsonian Institution, the 

 National Museum, the Department of Agriculture, and the 

 Geological and Geographical Surveys. Many of these publica- 

 tions are distributed free of cost to applicants, while others are 

 sold at a moderate price to cover the cost of publication. There 

 is a Government institution known as the Office of the Super- 

 intendent of Documents, Union Building, Washington, which 

 publishes lists of Government publications and sends them free 

 of charge to applicants. From these lists one can see what has 

 been published and what is still on hand for distribution, and 

 what price must be paid for the available ones. Many of them 

 are out of print, but these can be obtained through dealers in 

 second-hand books. There are two large firms of such dealers 

 in Washington, and these make a specialty of Government 

 publications. They are: W. H. Lowdermilk & Company, Cor- 

 coran Building, and Lewis S. Hayden, 1212 F street, N. W. 



The subject of how to collect and preserve the different 

 kinds of insects mentioned in this book is treated in a separate 

 section at the end of the volume. 



The writer owes warm thanks to several of his associates 

 in Washington, all of whom are specialists in certain groups of 

 insects, for advice and suggestions. These are Mr. W. H. Ash- 

 mead, the results of whose labors in the Hymenoptera have been 

 so largely used, and who has read the section relating to this 

 important order; Mr. D. W. Coquillett, a well-known writer on 

 Diptera, who has prepared the table of the higher groups of this 

 order which is given in this volume and who has read the manu- 

 script of the Diptera; Mr. O. Heidemann, to whom the writer is 

 indebted for information concerning the Heteroptera, and who 

 has loaned specimens for illustration from his private collection ; 

 Mr. Nathan Banks and Mr. Rolla P. Currie, who have helped 

 with advice regarding the portions of the book which relate to 

 the insects of the Neuropteroid series; Mr. F. H. Chittenden, who 

 has loaned for illustration insects from his private collection; 

 Mr. F. C. Pratt, whose excellent work in the resetting of the 

 insects illustrated on the plates and in the arrangement and 

 mounting of the plates, a most difficult and laborious task, will, 

 1 trust, be appreciated by the reader. 



I wish especially to thank Dr. E. P. Felt, State Entomologist 



