British Insects: the Families of Diptera

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L. Watson and M. J. Dallwitz

Introduction

This data set is generated from a DELTA database (Dallwitz 1980; Dallwitz, Paine, and Zurcher 1993). The original intention of the ‘British Insects’ suite of packages, of which it forms part, was primarily to present scans of the fine hand-coloured engravings of insects in John Curtis’s British Entomology: illustrations and descriptions of the genera of insects found in Great Britain and Ireland (1824–1840). The first 12 volumes of the first edition (up to 1835) were directly available to us, and pages issued from 1836-1840 have been accessed from other sources (see Notes on John Curtis’s British Entomology).

In addition to presenting Curtis’s and other early illustrations, all the ‘British Entomology’ subsets incorporate descriptive data organized under the DELTA system, and purport to offer facilities for attempting at least partial identification and for information retrieval, via the interactive program Intkey. The present subset encompasses all the families of British Diptera, described via standard morphological and ecological characters. It is unlikely to achieve its objectives satisfactorily at this early stage of development, but in any case the DELTA data (from which updates of the interactive package are easily generated) are readily accessible for improving, correcting and extending.

Family descriptions were initially compiled for this purpose using Unwin’s (1981) key to the British families and the detailed family descriptions provided by Colless and McAlpine (1970), supplemented from Imms (1950). They were then checked, and greatly improved and extended, with reference to the copious descriptive information and keys provided by Colyer and Hammond (1968); and the set of family illustrations obtained from Curtis has been extended via comprehensive scans of the engravings in Walker’s early, classic work on the British Diptera (1851–1856), as well as those from J.F. Stephens’s Illustrations of British Entomology (Supplement, 1846). Of the present 102 families, 29 have fewer than five species, and 15 are additional to Unwin’s (1981) list; and of the 20 or so families not yet exemplified here by at least one illustration, most comprise taxa relatively recently promoted to family level, many of which are small in terms of numbers of British species and genera.

Assignments to Orders, Families, and sub-familial groupings have been aligned with Chandler (1998), and the nomenclature employed by early authors has been laboriously updated with reference to the same work in conjunction with Kloet and Hincks (1945), and subsequently via recent, invaluable Internet postings (well exemplified by the Fauna Europaea Web Service, see References). While pursuit of outstanding queries over the identifications and nomenclature of early entomologists continues, it is obviously impracticable in the present context to keep abreast of nomenclatural recombinations, generation of which continues apace. We hope, however, that names given with the illustrations in these ‘British Insects’ packages should at least permit them to be used in connection with modern texts. The few Curtis names not yet located are indicated by quotation marks in the Intkey displays of descriptions and images, and the plates involved are presented under the pseudo-taxon ‘Unidentified Images’ Images’ (see also Updated insect names for John Curtis’s British Entomology). Some of them may denote adventives or taxa erroneously admitted to the British list, but others may represent names that have never been formally linked with taxa recognised in modern times.

Curtis’s and Walker’s plates are cited in the Intkey displays of taxon images, and for all the genera and species originally described and illustrated ‘British Entomology’, these are accompanied by scans of the text. As well as legends for the illustrations and formal taxonomic descriptions, the latter offer numerous examples of his entertaining, informative and elegantly expressed notes on sources of specimens, morphological interpretations, classificatory methodology, general biology, etc.

Family assignments of the insects illustrated have been checked at family level to some extent, in effect with reference to the family descriptions in the cited works, by ‘identifying’ the illustrations using the Intkey package. While it has thus been ascertained that the they conform reasonably well with the family assignments, checking on the generic and specific identities of the flies depicted has so far been very limited indeed. Biologists wishing to use the pictures for their own purposes should therefore take the necessary precautions for themselves.

All the compilations in our ‘British Insects’ series, including this one, are organized under the Delta system and are readily accessible for extending, improving and making corrections. Informed criticism and constructive input are of course welcome, and will be appropriately acknowledged. Alternatively, complete Delta data sets can be donated if required for teaching purposes, or to any professional or amateur entomologist or organization interested in developing them further.


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