VI PREFACE 



Laboratory exercises have been omitted, as the intelligent teacher 

 is in a better position than the author to prepare practicums adapted to 

 local conditions. 



It was thought advisable to limit the species discussed mainly to 

 those belonging to the Northern United States and Canada, i.e., to 

 the Canadian, Transition, and Upper Austral Zones. It was also 

 deemed advisable to make but brief mention of the insects affecting 

 forest trees. Students interested in such studies are referred to the 

 recent bulletins of A. D. Hopkins of Washington and J. M. Swaine of 

 Ottawa for the results of the latest investigations. 



The author is indebted to many fellow-teachers and workers for valu- 

 able aid and suggestions in the preparation of this book. In most 

 respects it is a compilation from recent text-books, bulletins, and arti- 

 cles. In a work of this kind errors are likely to appear in spite of 

 every precaution, but considerable care has been taken to reduce them 

 to a minimum. 



Special mention must be made of the kindness of many authors 

 and publishers in furnishing illustrations, and the writer here thanks 

 his friend and teacher. Professor J. H. Comstock of Cornell University, 

 for permission to use illustrations of wing- venation from his recent 

 work, "The Wings of Insects;" Dr. C. G. Hewitt, Dominion Entomolo- 

 gist, for free use of cuts from the publications of the Canadian Ento- 

 mological Branch; Dr. L. O. Howard, Chief of the U. S. Bureau of 

 Entomology, for many electrotypes of the Bureau illustrations; Pro- 

 fessor J. H. Sanders of the Pennsylvania Agricultural Experiment 

 Station, for permission to use his admirable figures of pygidia of scale 

 insects; Mr. J. J. Davis, Federal Agent of the U. S. Bureau of Entomol- 

 ogy, Lafayette, Indiana, for several photographs of breeding cages, 

 etc.; Professor L. Caesar of the Ontario Agricultural College, and Dr. S. 

 Hadwen, Dominion Pathologist, Health of Animals Branch, Ottawa, 

 for furnishing several cuts; Mr. Arthur Gibson, Entomological Branch, 

 Ottawa; Professor W. H. Brittain of the Truro Agricultural College; 

 Professor P. J. Parrott of the New York Agricultural Experiment 

 Station; Professors Herrick, Crosby and Johannsen of Cornell Univer- 

 sity; Professor W. A. Riley of the Minnesota Agricultural College; Dr. 

 Edith Patch of the Maine Agricultural Experiment Station; Professor 

 W. E. Britton of the Connecticut Agricultural Experiment Station; 

 Professor V. L. Kellogg of the Leland Stanford Jr. University, Professor 



