PREFACE TO THE FIRST EDITION. 



The subject treated in the following chapters, Agricultural 

 Zoology, has perhaps been more neglected in England than 

 any other branch of science applied to agriculture : even the 

 name itself is hardly at present understood. It is true, indeed, 

 that the labours of Curtis, and in later years of Miss Ormerod, 

 have developed one branch of economic zoology — namely, the 

 part played by insects in causing disease amongst animals and 

 plants ; it is true also that some of our veterinary surgeons 

 have done excellent work on the other parasitic diseases of 

 animals ; but there remains a vast portion of the subject that 

 has neither gained the attention of English scientific men 

 nor been summarised in an English text-book. Agricultural 

 Zoology treats of the life-histories, the habits, the peculiarities 

 of all the animals which afTect for good or for evil our stock 

 and crops, whether on the farm or in the garden, and the 

 structure and development of domestic animals. Parasitism 

 plays an important part in this subject, especially in the 

 protozoa and worms ; but the economic effects of parasites are 

 not confined to protozoa and worms — the parasitic insects and 

 mites equally take their annual and preventable toll of our 

 flocks and herds. Nor, again, is parasitism always an injuri- 

 ous phenomenon : its beneficial effects are equally marked and 

 equally under control, given only the requisite knowledge. In 



