VIII INTRODUCTION 



acters by which each species has been identified. The locality and 

 (late records are arranged under each species alphabetically by States 

 and should prove useful to those compiling State lists and State rec- 

 ords of insects as well as to students of geographic distribution. Each 

 specimen involved in the study has been examined individually under 

 a binocular microscope, and each bears an identification label. In 

 almost all cases the genitalia of the male have been removed and 

 mounted on a paper point just beneath the specimen itself. Part 4 

 is the bibliography which has been prepared during the course of 

 the work and which it is believed is practically complete. 



It is too much to expect that the work is entirely free from errors, 

 but I have spared no pains to reduce their number to a minimum. 



The work could not have been completed, in fact it could not have 

 been undertaken at all, were it not for the cooperation and assistance 

 which I have received from many individuals and institutions during 

 the course of the study. While at the University of Nebraska I was 

 privileged to receive the suggestions, encouragement, and advice of 

 Profs. Lawrence Bruner, Myron H. Swenk, and R. W. Dawson. I am 

 most indebted to Dr. R. N. Chapman, Dr. William A. Riley, Dr. 

 H. H. Knight, Prof. A. G. Ruggles, and Dr. O. W. Oestlund for the 

 opportunities, encouragements, helpful criticisms, and inspiration 

 which I have received at the University of Minnesota. Without 

 their cooperation nothing could have been accomplished. The 

 Elizabeth Thompson Science Fund, Dr. E. B. Wilson, chairman, 

 made it possible for me to examine the type specimens of nearly all 

 the species of DasymutiUa by granting $275 for travel expenses for 

 that puipose. With the aid of this fund I was able to study the type 

 specimens deposited in the collections of the United States National 

 Museum, Washington, D. C. ; the American Entomological Society, 

 Philadelphia ; the American Museum of Natural Historj^, New York 

 City; the Museum of Comparative Zoology, Cambridge, Mass.; and 

 of Abbe Provancher, Quebec, Canada. This study enabled me to 

 clear up many problems that could not otherwise have been solved. 

 I have received encouragement and suggestions from Mr. S. A. 

 Rohwer, chief of the division of taxonomic investigations, United 

 States Bureau of Entomology, throughout the course of the work; 

 his cooperation has been invaluable. 



I am indebted to Miss Harriet Sewall, librarian of the University 

 of Minnesota department of agriculture, and Miss L. Mae Centerwall, 

 her assistant, for the opportunity of seeing many of the papers listed 

 in the bibliography. I am especially indebted to Dr. Walther Horn, 

 Berlin, Germany, for his active interest in obtaining a loan of 

 Fabricius's specimens of MutiUa fen^igata for me from the authori- 

 ' ties of the Kiel Museum. He was also kind enough to secure and 



