C. Martin Drake
RES Insect Identification Handbooks
The Dolichopodidae or long-legged flies are familiar insects to many entomologists and natural historians. They are relatively small flies with a wing length of 1.5-9.5mm, but are easy to find due to their often bottle-green metallic colouration, the elaborate structural ornamentation in males and their complex courtship displays. Perhaps the best known of these, the Semaphore Fly Poecilobothrus nobilitatus, recently appeared in David Attenborough’s television series Secret Garden, and a photograph of the instantly recognisable male adorns the front cover of this handbook.
There are 326 species of dolichopodid fly currently on the British checklist comprising 47 genera placed in twelve subfamilies. The size of this taxon, the amount of information available on the species therein, and the number of historical keys, all present challenges when creating a clear and useable current key placed in its proper biological context. Happily, we are in safe hands and this volume is a tour de force of carefully crafted zoological writing. The author, Martin Drake, is a founder member of the Dipterists’ Forum and has organised the Dolichopodidae recording scheme for many years. The information is therefore accurate, comprehensive, correctly interpreted and contextualised. This handbook has also benefitted from the partnership between the RES and CABI which was formed in 2023 and has brought about improved design and the introduction of fully searchable eBooks.
The colour plates of stacked images are placed at the front of the book, after the Abstract and Acknowledgements and before the Introduction. There is a photo of a representative species from each genus. These are mostly males which are more striking and easier to identify than females. They immediately provide the reader with a sense of the intriguing diversity in this family and offer an enticing invitation to dive into the detail that follows.
The Introduction describes general aspects of the natural history of the family, its importance in nature conservation assessment and the complexity of courtship behaviours which have driven the differences between males and females (sexual dimorphism). The bulk of the book’s content is devoted to keys and species descriptions, but before this there is a logical series of short chapters covering the following areas:
Recognising the Family places the family Dolichopodidae in its taxonomic context within the order Diptera, details its relatively speciose composition worldwide, and comments upon the fossil record in which there are 100 known examples which make up about 5% of all described fossil Diptera. There is a detailed description of the morphological characters used to recognise extant species.
Keys and Species Accounts provides details of how the main section of the handbook is organised, the sources of information used and how they were selected. For example, it describes the extent to which existing keys have been incorporated or modified and gives advice on any potential limitations due to changes in classification. An explanation is given of how the couplet numbering works. The content of the species accounts is outlined which include a summary of specific characters, distributions, habitats and flight times derived from the national recording scheme. A section on measurements includes a useful graphic of the ranges of wing lengths for the species within each genus. The chapter ends with a description of collecting and preserving techniques, including useful tips to avoid damage to specimens.
Morphology of Adults contains high quality diagrams and very clear anatomical descriptions which afford the reader with all the information needed to make best use of the keys. The morphological nomenclature is explained very clearly and is easy to follow. The scope is comprehensive and runs to seven pages.
Phylogeny describes how the understanding of the evolutionary relationships within the taxon has progressed, particularly since the advent of molecular data, and explains where and why there are uncertainties. It therefore sets a framework which can be used to build on existing knowledge and directs the reader to areas where further contributions can be made. There is also a Checklist of species which includes the additions and amendments that have been made since the late Peter Chandler’s Checklist of Insects of the British Isles (Part 1: Diptera) was published in 1998.
The main part of this book is devoted to keys and species descriptions. There are Keys to the Genera (separated into males and females and including some species) after which each genus is dealt with in alphabetical order including keys to species and species descriptions. The line drawings are of superb quality and the layout well spaced and clear. The content is comprehensively referenced and there is a detailed index.
It is easy to run out of superlatives for this book. What may appear to be a highly technical monograph intended for specialists proves to be an exceptionally good read thanks both to its design, and the way it identifies the important biological principles which can be explored by the careful identification of species in this family. Some may prefer stacked photos to diagrams to illustrate morphology, but the quality of the drawings is outstanding and I sometimes find labelled photos harder to interpret. It is a handbook in the broadest sense, a comprehensive manual which equips, enables and encourages anyone interested in natural history to find their inner dipterist and make a contribution to the field. Indeed, there are many aspects of the biology of dolichopodid flies that remain a mystery and are therefore ripe for further studies.
For example, the courtship behaviour of some species has been carefully researched but in many, the role of male ornamentation and the way it correlates to behaviour has not. Comparative studies within the family would contribute much to understanding the origins and advantages of sexual selection along with its role in speciation and phylogenetics. Adults and most larvae are predators, but the life cycles of many species remain undescribed, leaving gaps in our understanding of their ecology. The list goes on and there is much to be done, but this exceptional volume opens the door to anyone with a microscope and an interest in natural history to both enjoy and contribute to the study of these fascinating flies.
