viii PREFATORY NOTE 



pertaining to the groups treated, but introduce and give special 

 attention to the economic relations of various particular mem- 

 bers of the groups. Finally in still later chapters, segregated 

 in a separate section of the book, there is presented a sort of 

 encyclopedic treatment of a considerable body of facts wholly 

 economic in aspect. These chapters are to be used as reference 

 matter, collateral reading, and matter to suggest practical 

 work, rather than as material for recitation. Of the numerous 

 insect kinds treated in the chapters on injurious insects, only a 

 certain few will be found in any single region. Those few are 

 the ones intended for study by pupils in that region. The 

 study should be mostly field work. 



We wish to thank Professor Harold Heath for his kindly 

 critical reading of much of the manuscript of the book. The 

 sources of such illustrations as are not original with us are 

 pointed out in the subscriptions to the figures. We owe thanks 

 to many friends in this connection. 



V. L. K. 

 R. W. D. 



STANFORD UNIVERSITY, CALIFORNIA, 



December, 1914. 



