Book reviews Butterflies of Britain and Ireland mapped

J Asher, M Warren, R Fox, P Harding
2001 unpublished
Millennium project organized by Butterfly Conservation , Biological Records Centre and the Dublin Naturalists' Field Club in Britain and Ire-land have produced a unique set of results that have now been published in the form of a book. The data on the distribution of butterflies that is summarized in the book has been collected by an incredible 10 000 people over a relatively short period of five years (1995-1999) and covers almost all of the land surface of Britain and Ireland. The results are
more » ... nd. The results are presented in a remarkably clear fashion, inviting the reader to explore the book in more detail. There is no doubt in my mind that this book will become a standard work of reference for many years to come. So what does the book offer? It is organized in 7 chapters, starting with a general chapter on the background of the project and a brief overview of the history of butterfly recording in Brit-ain and Ireland. The second chapter gives information on the major habitats of butterflies with photographs of 22 representative habitats. The second chapter also has several very useful geographical maps of Britain and Ireland, showing the topography, distributions of different soils and bedrock, annual precipitation and temperatures of the islands. It was very instructive to compare these maps against some of the species distributions. The third and fourth chapters give specific information about how the data were collected and interpreted, respectively. Here we learn that all records of butterflies starting from 1800 (!) have been included in the maps. The results of the project have been interpreted with due caution, as recording effort is variable across the islands. Indeed towards the end of the survey, areas that had not been covered were identified and targeted to fill in the gaps. The result is that 98.7 % of all 10 ¥ 10-km squares in Britain and Ireland have been surveyed for their butterfly fauna-a remarkable achievement! However there is a distinct cline in the recording effort going from south to north, with thousands of records in the southern 10 ¥ 10-km squares to only a few records in the most northern 10 ¥ 10-km squares. These problems and other biases are duly noted and taken into account when interpreting the results. The bulk of the book is in the fifth chapter, where each resident and common migrant species is given four pages and the rarer migrants two pages. This chapter is a gold mine of information. In addition to the distribution map of each species based on the Millennium survey, we find information about the general biology of each species (life cycle, host plants, habitat, population structure), the changes in distribution over 200 years, a comparison with what is known about the species on continental Europe and a look forward into the future of each species in Britain and Ireland. Exceedingly useful is also a list of key references for each species where one can find more information about an interesting species (something not possible in most European countries !). Each species account usually has two photographs , one of the adult butterfly and one of the egg or larva. The distribution map shows all records of the Millennium survey at the 10 ¥ 10-km scale in three classes: 1 record, 2-9 individuals seen and 10+ individuals seen. The maps also show all records prior to 1970 and all records from the previous survey done during 1970-1982 (see Heath et al. 1984). This allows one to easily see whether there have been any drastic reductions in distribution over the 200-year period. In cases of range increase, there usually is a smaller map or two showing the distribution of the species prior to the Millennium survey.