PREFACE TO THE FIRST EDITION 



During the past fifteen years entomology has accumulated a 

 multitude of facts and has advanced along many paths of inquiry. 

 It attracts to-day a larger band of investigators and devotees than 

 any other province of zoology. The day of the general entomo- 

 logist is passing by, and it is becoming increasingly difficult for any 

 one individual to view the subject in full perspective. The tracing 

 of its many-sided recent developments, not only in the field of 

 purely scientific research but also in more direct relation to human 

 activities, has become a task of considerable magnitude. This 

 book makes no claim to fulfil so ambitious a scheme. It attempts 

 to review and discuss certain aspects of the subject along which 

 recent advances have been fertile in new facts and ideas. Short- 

 comings will inevitably assert themselves in this connection, and 

 specialists will perhaps maintain that the treatment meted out to 

 their particular spheres is lacking in detail, or that other aspects 

 of entomology have been omitted altogether. In answer to just 

 criticism of this kind it can only be urged that the dimensions of 

 the book necessarily limit its scope. Also, it does not presume to 

 instruct the specialist in his own field. Further, the theory and 

 practice of insecticides, along with certain other aspects of applied 

 entomology, have been omitted for the reason that they have 

 already been adequately treated in more than one very recent 

 text-book. 



It is hoped that this book will enable the student to become 

 better acquainted with some of the more recent developments in 

 entomology. Particular stress has been laid upon aspects of the 

 subject that are but little discussed in modern text-books. A 

 general elementary knowledge of the subject on the part of the 

 reader is assumed, and the bibliographies provided at the ends of 

 the chapters will serve as a guide to the sources of further informa- 

 tion, In addition to students of entomology, there is a growing 



