PREFACE 



The writer on Insects in this series of volumes, setting 

 forth various groups of creatures from the biological point 

 of view, has the advantage of his subject in a class of 

 animals comprising the largest number of diverse forms 

 whence he may choose examples of life relations. He has 

 also the disadvantage which follows inevitably from this 

 richness of the available material ; many highly interesting 

 features of insect life must be neglected or treated in- 

 adequately if the book is to be kept within reasonable 

 compass. He must therefore acknowledge himself charge- 

 able with the offence of omitting many subjects which 

 might be expected to appear in a survey of the Biology of 

 Insects. 



In this volume structural features are described only 

 so far as seems necessary for the understanding of function 

 and behaviour, while questions of systematic entomology 

 are discussed only as they bear on problems of ecology 

 and evolution. The author's indebtedness to those who 

 have studied and written upon the various aspects of 

 Insect Biology is apparent, and, he trusts, duly acknow- 

 ledged, both in the text and in the descriptions of those 

 photographs and figures which have been borrowed or 

 copied for illustration. He desires to express gratefully 

 his appreciation of the help and encouragement accorded by 

 his friend, Professor J. Arthur Thomson, the editor of this 

 series, whose suggestions and criticisms have contributed 



