X PREFACE 



Journal of Economic Biology for permission to 

 reprint the twelfth chapter, of this book, and 

 I offer them my thanks. I also thank Mr. 

 Hugh Scott (the University Curator in Ento- 

 mology), and Professor G. H. Carpenter of the 

 Royal College of Science, Dublin, for much 

 kindly help. 



A E. SHIPLEY. 



Chbist's Colleqe Lodge, Cambeidqe, 

 April 1916. 



