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Britain's Hoverflies: An Introduction to the Hoverflies of Britain by Stuart Ball and Roger Morris. 2013. Princeton University Press, New Jersey/Oxfordshire (http://press.princeton.edu/titles/9849.html). Softback. 296 pp. 569 colour photos. 161 colour distribution maps. ISBN 9780691156590, $35.00/ £24.95.

There is a long tradition of amateur entomology in Great Britain, arguably the most flourishing of all countries. Within this tradition, hoverflies are one of the most popular subjects of study. Ever since Verrall's British Flies (1901), British dipterologists have tried to unveil the world of Syrphidae for an audience outside the realm of professionals. As taxonomy progressed, new books aimed at hoverfly identification appeared, probably the most influential of these being British Hoverflies by Alan Stubbs and Steven Falk (1983, revised edition 2002).

Until now, hoverfly identification guides relied heavily on dichotomous keys. Stuart Ball and Roger Morris have now published an identification guide for hoverflies in a new fashion. Its format will be familiar to those naturalists focusing on other disciplines, like bird- or butterfly-watchers. For hoverfly-watchers, however, the format is quite novel: photographs of living hoverflies on the right-hand pages, with coloured lines drawing attention to important characters, and accompanying species accounts on the left. A total number of 165 British species is covered.

The illustrations are of excellent quality. Habitus photographs show living specimens in the field, ‘acting naturally’, as one is likely to encounter them in the field. Close-up images of body parts explain which details are important for distinguishing closely similar species, such as front legs of Platycheirus species, and hind femora of Xylota species. These images were chosen carefully, are of good quality and show what needs to be shown. The species accounts provide additional characters for identification, along with observation tips, indicating the habitat and habits of the species. A distribution map and flight diagram are given, based on the large dataset that resulted from the extensive British hoverfly recording scheme, which has been led by the authors for many years.

In an identification guide based on photographs, beginners may find themselves lost in a myriad images of superficially similar species. This risk is especially high in a speciose group of insects like the hoverflies, with 281 species presently recorded from Britain. The authors recognized this problem, and solved it by including keys to tribes, genera and other larger groups of species, such as honeybee mimics and wasp mimics. These keys are welcome signposts for beginners, who don't yet know their way among (for instance) the many small, slender species with pale spots on the abdomen.

Ball and Morris have certainly taken hoverfly-watching in Britain one step further. For hoverfly-watchers in other north-west European countries, this guide will also prove useful, but they have to bear in mind that several species are lacking in Great Britain and are therefore not covered. Among them are some relatively widespread and conspicuous species, such as Temnostoma species and Criorhina pachymera. Certain other widespread north-west European species, such as Chrysotoxum vernale, are rare in Britain and mentioned only in the text. On the other hand, a few species unknown from other parts of north-west Europe, such as Callicera spinolae and Hammerschmidtia ferruginea, have their own account in the book.

The wisdom of the authors' decision not to include all 281 British species, but only 165 of them, is debatable. The introduction states that the book concentrates ‘on the ones you are most likely to find’. Of course, novices would probably not be too concerned that they had found the very common Neoascia podagrica rather than the uncommon Neoascia obliqua. But those who become infected with hoverfly fever are likely to be. They will find that the characters mentioned to distinguish Chrysotoxum vernale from the similar Chrysotoxum festivum are quite unsatisfactory: ‘The differences are subtle and involve the shape of the abdomen markings and the extent of dark markings on the legs.’ Such enthusiasts can buy British Hoverflies by Stubbs and Falk, which considers all species, but wouldn't it be nice to have a book like Britain's Hoverflies that covers all the species living in your own country? Will it discourage beginners to see that there actually are 10 highly similar species of Sphaerophoria instead of only one? Not necessarily. It may be just as discouraging to know that there are more species than the one depicted, while not having enough information to delve any further. By including all species, each user can decide where to stop identifying; for some, knowing the genus will be enough, for others not. This works in bird guides, which contain hundreds of species, some of which are very similar, so why wouldn't it work for hoverflies?

This consideration aside, Ball and Morris have produced a splendid book. The layout is attractive, and the information is accurate and up-to-date. The book starts with some clear and concise chapters on hoverfly biology, discovering and identifying hoverflies. This, together with the species information, provides beginners with all the elementary information needed to get started. It's an example to follow for other European countries. This book may well propel hoverfly-watching into serious competition with butterfly- and dragonfly-watching!