DRAGONFLIES ARE THE largest, most conspicuous, flying insects one is liable to encounter in Britain in sunny weather. Because during their growth stages dragonflies live in water, the adults are usually encountered near ponds, lakes, streams or rivers, where they can often be seen engaging in elaborate aerobatics. Their vivid colours and aerial agility command, and hold, the attention of any observer. Except in highly specific situations, dragonflies are of no economic importance. Being generalised predators, both as larvae and as adults, they are unlikely ever to suppress the numbers of ‘pest’ organisms down to levels that meet human demands for health, profit or comfort: when one prey organism becomes too scarce to encounter readily, a dragonfly will simply switch its attention to another.
So why are so many people fascinated by dragonflies?
Perhaps the most convincing way to answer this question is to list some of the reasons why we, the authors, have become interested in these insects. An important reason, for any field naturalist, is that dragonflies are sufficiently large and conspicuous that one can often understand what they are doing; and, thanks to the great amount of research conducted by scientists on the behaviour of dragonflies, one can often interpret their actions in terms of their main adaptive needs, such as foraging (i.e. seeking prey) and reproducing. Moreover, for almost all the actions they perform, as larvae as well as adults, one can usually infer the significance of their behaviour in the context of their life history, which is steadily becoming better understood.
In Britain, compared with the continent of Europe, we have a marginal, impoverished fauna and flora. For example, Britain contains (as residents) only about 34 per cent (39/114) of the dragonfly species inhabiting the Continent. Having relatively few species can be an incentive to know them, to record them and to understand what influences their distribution in Britain. And there is the dragonfly life history, in which the larval and adult stages alternate between water and land in an impressive and hazardous transition: at the time of egg laying and then again at emergence (i.e. transformation from larva to adult). These are some of the objective reasons for our interest. Others, equally compelling though thoroughly subjective, lie in the excitement, admiration and awe that we experience whenever we encounter a dragonfly or learn of a newly discovered fact about the life history. We are not alone in our enthusiasm and affection for dragonflies. In addition to the British Dragonfly Society, with its 1,600 or so members, two well-subscribed international societies are devoted to the study of dragonflies, each producing a periodical containing scientific reports about dragonfly biology. Odonatology (the study of dragonflies) receives special mention in Chapter 1, and the history of odonatology in Britain is reviewed in Chapter 10.
This book is not a textbook on dragonflies; nor is it an identification manual. Useful literature of that kind is listed in Chapter 1. This book is about the natural history of dragonflies in Britain. (Our use of the terms ‘Britain’ and ‘British Isles’ is chosen for convenience only, and has no political connotation. We use these designations to denote the archipelago that comprises Britain and Ireland and associated islands.) Because our emphasis is on natural history, we have devoted little attention to the morphology or physiology of dragonflies, sources for which are listed in Chapter 1.
We hope that the information presented in this book will enhance the pleasure and inspiration that people derive from watching and studying dragonflies. We find dragonflies to be limitless sources of wonder and delight, and we regard it as a singular privilege to be able to share these sentiments with others by writing about dragonfly natural history.
This book is intended for the informed enthusiast with a leaning towards natural history. In presenting it, we have four principal aims:
We have adopted certain conventions in the text. Specialised terms are italicised on first mention, thus indicating that they have been defined in the Glossary on pages 373-381. Sources of information are cited in the text by superscript numbers. These correspond to abbreviated references, assembled under chapters in the section Endnotes on pages 382-394, and these in turn correspond to citations given in full in the Bibliography on pages 395-442. There are two indexes at the end of the book: one to authors cited in the text, and one to species, topics and people.
It is a pleasure for us to acknowledge help we have received during preparation of this book.
Our primary debt is to the many odonatologists whose careful (sometimes inspired!) observations, ideas and experiments have yielded the information from which our text is drawn. For the most part they are authors of publications, dating from the eighteenth century to recent times;1 but a few are contemporaries who have devoted their time and expertise to constructive criticism of parts of the text. In this regard we make special mention of our colleagues Mike Parr (Chapters 1 and 7 and Appendix 2), Mike Siva-Jothy (Chapter 9) and Hansruedi Wildermuth (Chapters 3 and 5). We thank the compilers of Odonatological Abstracts (Bastiaan Kiauta) and the Odonatological Abstract Service (Martin Lindeboom and Martin Schorr) for the immensely valuable service they perform in enabling odonatologists to keep track of the many publications that appear annually. We are very grateful to Ann Brooks, Sally Corbet and Sarah Jewell for their valued comments on successive drafts of the text. We thank Robert Thompson for his generosity in allowing us to use a large number of his beautiful colour photographs, the inclusion of which greatly enhances the book’s appearance. We are indebted also to Ann Brooks, Kevin Caley, Steve Cham, Zoë Greenwell, Ruary Mackenzie Dodds, Jürgen Ott and Hansruedi Wildermuth for allowing us to include photographs, the source of which is acknowledged in the captions.
We thank Faber and Faber for permission to reproduce the poem ‘Dragonfly’ by the former Poet Laureate, Ted Hughes.
For permission to reproduce black-and-white illustrations (the figure numbers being recorded in parentheses) we thank the following publishers and copyright holders: American Society of Limnology and Oceanography (55); Blackwell Publishing (44, 69, 73, 85, 86, 88, 89, 120); The British Dragonfly Society (74); K. Caley (128); E.W. Classey (102); S. Eda (for Tombo) (97); Elsevier (45, 117); Finnish Zoological and Botanical Publishing Board (114); Gem Publishing Co. (53, 54); Harley Books (45); HarperCollins (44 by S. Beaufoy); C. Inden-Lohmar (96), B. Kiauta (for Societas Internationalis Odonatologica) (92, 97); The Natural History Museum (57 by A.E. Gardner, 126 (a-d), 127(a-d)); Naturforschenden Gesellschaft in Zürich (101); Royal Entomological Society (59); Springer Verlag (116); F. Weihrauch (for Libellula) (51, 70, 71).
We are indebted to several members of the editorial staff of HarperCollins with whom it has been a pleasure to work. In particular, we thank Helen Brocklehurst, Julia Koppitz and Isobel Smales for their encouragement, forbearance and valued advice.
S.B. is grateful to the Trustees of The Natural History Museum for enabling him to work on this book in official time, and we both thank Professor Quentin Wheeler, former Keeper of Entomology at The Museum, for contributing a Preface.
During our pursuit of odonatology, and during the preparation of this book, we have enjoyed unfailing support from Ann Brooks and Sarah Jewell.
P.S.C.
S.B.
Crean Mill, St Buryan,
Cornwall
and
The Natural History Museum,
Cromwell Road, London.
February 2007