The families of British spiders


L. Watson and M. J. Dallwitz


This data set is generated from a DELTA database (Dallwitz 1980; Dallwitz, Paine, and Zurcher 1993), and comprises preliminary family descriptions, comprehensively illustrated from Blackwall’s Spiders of Great Britain and Ireland (1859–1864), with a file of source references and hints on using the program Intkey for interactive identification and information retrieval.

The descriptive content is at present limited to data obtained from the keys and the very brief, non-comparative family descriptions given by Roberts (1985) and Jones-Walters (1994) for British spiders, supplemented from a few other works listed in the References. Our interactive key should permit users to identify any British spider to family level fairly easily, and species will often be recognisable from Blackwall’s illustrations, which represent most of them; but reliable identification will require confirmation at specific level, with reference to detailed descriptions such as those given by Roberts. The excellent Web site of Ed Nieuwenhuys ( provides a wealth of general information on spiders, with special reference to those of North-West Europe and with numerous photographs.

Utilizing Blackwall’s fine illustrations has involved laboriously updating his nomenclature, using Bristowe’s Synonymic Index (1941), cross-referenced with the more recent check lists cited in the accompanying References file; followed by efforts to ensure, first with reference to Roberts, and subsequently via critical input from Mr. Ian Dawson (see Acknowledgements), that the modern names seem reasonably applicable to the individual illustrations. Some nomenclatural information is given in the legends accompanying the taxon images, and illustrations not satisfactorily resolved in this context are presented, with Blackwall’s names, in the pseudo-taxon ‘Unidentified images’. Most of the latter represent names used by Blackwall and listed by Bristowe as unsatisfactorily identifiable. A complete list of Blackwall’s legends, with his names accompanied by their modern equivalents as understood for this package, is available via the ‘Information’ (book) button in the main Intkey toolbar. We emphasize that no original taxonomic research has been brought to bear in preparing this package, nor have any type specimens been examined.

It would have been impossible, with the equipment available, to prepare complete scans of Blackwall’s folio plates: they required two scans each, and had to be scanned sideways before rotating through 90 degrees. It would also have been inappropriate, in view of the extensive cutting and pasting necessary to account for the changes in familial and generic assignments since Blackwall’s time, and in the event, most of the taxon images presented here are restricted each to a few species. Blackwall’s numbering of figures has been retained, to facilitate cross-referencing our images with the original plates. TIF scans at 300 dpi sufficed to capture the details, but rendering even the excerpts into files of sizes practicable for distribution inevitably degrades the quality, and since many of them cannot be reduced to screen size without further, unacceptable loss of resolution, we have been unable to avoid the necessity for scrolling. Blackwall’s indications of actual sizes of the animals, by lines in Vol. I, and by outline representations of spiders in Vol. II, have perforce been replaced by indications of their approximate lengths in millimetres (note that the actual lengths of the ‘length lines’ are not meaningful). The dimensions indicated mostly apply to the females, the few exceptions being indicated either directly on the illustrations or in the legends. Re the illustrations of male palps, to quote from Blackwall, “the palpal organs of the left side are invariably chosen for representation, and, with very few exceptions, as seen directly on the under surface. The palpal organs are nearly all given as magnified fifteen diameters.” Thus, the approximate sizes of palpal organs can be calculated with reference to the depictions of male spiders and to the scales provided.

Informed criticism and constructive input are of course welcome, and will be appropriately acknowledged. Alternatively, the complete Delta data set can be donated to any professional or amateur zoologist or organization interested in developing it further.

The poems were specially written by Giles Watson for this package, and are its only original component.