British Insects: the Pug-moths (Lepidoptera-Geometridae)


L. Watson and M. J. Dallwitz


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 aim to offer at least partial identification and information retrieval facilities via the interactive program Intkey. However, the Lepidoptera component goes further than the rest. The present subset is an extension to species level from our Genera of Geometridae package, itself developed from the Families of Lepidoptera subset (q.v., with which a more detailed Introduction is provided). The classification, formal nomenclature and English common names used here follow Bradley’s (2000) Check List. Common names, the usefulness of which is alluded to in the introduction to the accompanying Lepidoptera Families subset, may be accessed via the ‘Refer common names to genera and species’ (target) button in the Intkey main toolbar.

The data currently represent initial encoding and automation of Meyrick’s (1927) descriptions and key, augmented by information from other works listed in the References (notably South 1909 and 1961), and subsequently edited and extended with reference to the indispensable 2003 monograph by Riley and Prior. The latter contains a wealth of valuable information on the taxonomy, morphology and general biology of British and Irish Pugs, with details of the early stages and distributional data, and is copiously illustrated with good photographs and line drawings of imagines (including genitalia) and larvae, but it offers neither comparative descriptions nor a key. Having been assured that “the most accurate, efficient and indeed easiest means of identifying Pugs is by comparison with good quality illustrations of both fresh and also old and worn specimens, supported by a succinct diagnostic text”, would-be identifiers are required first to select likely possibilities from life-size photographs, then pursue these via comments appearing under “Characteristic features” of the species, which are accompanied by brief comments on “similar species” and sometimes by line drawings; with additional resort to distribution maps and proximity of foodplants (etc.). The “succinct diagnostic texts” are not genuine diagnostic descriptions, and are sometimes ambiguous; and in any case, identifications cannot be reliably confirmed without access to adequate comparative descriptions. Failure to offer a key even as an alternative procedure is defended solely on the grounds that dichotomous keys published by earlier authors “ ... are not wholly satisfactory for the identification of ... Pugs ... due to their overdependence on colour or shades of colour.” In fact, Meyrick’s efforts at comparative morphological descriptions and keys for this and other groups were very commendable. They should have been improved upon and extended by his successors, and competent taxonomic practice automatically links improved comparative data with better keys. Furthermore, interactive identification associated with automation of taxonomic procedures, as exemplified by the present suite of packages and the DELTA system, has many indisputable advantages over printed keys and has been a practicable option for nearly thirty years.

The present offering incorporates scans with updated legends from Barrett’s plates (1904, including larvae), South’s plates (1909), adaptations of Swain’s coloured figures (1961), Newman’s excellent woodcuts (1869; see Notes on Edward Newman’s British Moths and British Butterflies), and scans from volume 5 of Hübner’s Sammlung europäischer Schmetterlinge which incorporate the original illustrations of numerous pug species described by him. The descriptive data are at a very early stage of development, and there is abundant scope for additional characters, refinement of the character state definitions, and for checking of descriptions against specimens. The impossibility of reliably identifying many Pugs from photos taken ‘in the field’, or from worn and faded specimens, will be apparent from photographic illustrations (e.g., south095.jpg, south099.jpg) in which similar species are displayed side by side; nevertheless, this package if used properly and cross referenced with the Riley and Prior monograph should at least offer a reasonable prospect of identifying fresh specimens of most Check-listed British species without resort to the genitalia.

The data from which the present descriptions and key derive are readily accessible for editing, correcting and extending. 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 entomologist or organization interested in developing it further.