AUTHORS' PREFACE 



Throughout this volume an attempt has been made to keep the 

 parasitic relationship in the foreground. In Part I we have dealt with 

 the more general aspect of the subject, and in Part III a brief survey is 

 given of the various groups of parasites which attack birds in Great 

 Britain. In Part II we have tried to present a close-up of two contrast- 

 ing types of parasitic insects, the feather lice and fleas, in order to 

 illustrate in greater detail the intimate relationship which exists between 

 host and parasite. 



The ground we have had to cover is extensive. Some of the groups 

 of bird parasites contain hundreds of species of which many are well 

 known to specialists but are not yet described or named. In the fleas, 

 louse-flies, ticks and tongue-worms only, four exceptionally small 

 groups, we have been able to give a complete list of the species recorded 

 from British birds. In other sections, notably the worms, mites and the 

 fauna of nests, we have merely skimmed the surface of the subject. In 

 those classes in which the existing classification is considered un- 

 satisfactory and probably of a temporary nature only, references to 

 sub classes and orders have been avoided as far as possible. In this 

 edition (third edition, fourth impression) space has not permitted 

 alterations in the text, but merely the correction of errors and mis- 

 prints, and we have included some new and very important references 

 in the bibUographical appendix. We have also tried to keep the four 

 small groups mentioned above up to date by noting the recent addi- 

 tions on pages xiii to xiv. We have attempted to define "parasitism," 

 "commensalism" and "symbiosis" in the text. The American Society 

 of Parasitology's Committee of Terminology decided that "the present 

 confusion necessitates the definition of the term [symbiosis] whenever 

 it is used" and we think this is true of all three terms. We should, 

 however, like to draw the reader's attention to the rather different 

 definition of these terms by authors such as Davenport (1955) and 

 Allee et al. (1949). In order not to overburden the text with "Latin" 



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