British Insects: the Genus Phyllonorycter Hübner (Lepidoptera-Gracillariidae)
This data set is generated from a DELTA database (Dallwitz 1980; Dallwitz, Paine, and Zurcher 1993), and is an extension from the ‘British Lepidoptera’ set also included in this package. At its present stage of development, it largely amounts to an automated, interactive version of the treatment of British Lithocolletis (now referred to Phyllonorycter) by Jacobs (1945). His treatment was evidently derived from that of Meyrick (1927), with a modified version of the dichotomous key, extended species descriptions and fine, comprehensive illustrations of wings.
The nomenclature has here been aligned with the Bradley (2000) Check List, cross referenced with the Bradley et al. (1972) version. The present character list and species descriptions have been derived with reference to the Meyrick and Jacobs descriptions and keys, but not all the characters they employed have yet been incorporated. In particular, the spectacular variation in the ground colours of the forewings of these beautiful micros is difficult to describe unambiguously for reliable application to identification, as evidenced by major discrepancies (involving numerous species) in their interpretation by those two authors. The ‘metallic’ wings of most species take on quite different aspects under different lighting conditions, and a character list effective for practical taxonomic purposes would require that the latter be precisely specified. Furthermore, the Jacobs key and descriptions exhibit inconsistencies in this respect, and the key presents contradictions involving the colours of P. sorbi, P. blancardella and P. oxyacanthae. Note that collections of these moths should routinely be accompanied by reliably identified samples of the mined plant material from which they emerged.
Seven species representing additions to the British list subsequent to the Meyrick and Jacobs treatments are included in the current data set, but in the absence of morphological information, the data on them are as yet confined to the larval host plants given by Bradley. Most of them seem to be rare in Britain, and for the time being they are excluded from the list of species accessed automatically via the Intkey ‘Identification’ toolbar button. Attempted identifications using Intkey and the present superficial descriptions will in any case sometimes result in incomplete separations of species, especially in cases where the host plant of a specimen is unknown; but likely determinations should eventuate from comparing the resulting species names or short-lists with the illustrations. The latter are rather laborious derivations from Jacobs’s all-inclusive colour plate, in which his half-moths have been rendered whole, and mounted with representations of larval food-plants; supplemented by retouched scans of the plates from volume 2 (1857) of Stainton’s splendid ‘Natural History of the Tineina’. The botanical images (cf. our Families of Flowering Plants Intkey package) have been adapted mainly from John Curtis’s ‘British Entomology’, with a few from Le Maout and Decaisne (1873), Lindley (1853) and Sowerby and Johnson (1862). For interest, we also include a compilation of the six figures from Vol. VIII of Hübner’s Sammlung europäischer Schmetterlinge (1793-1841), which are generally referred to his genus Phyllonorycter and include four type illustrations. The one of “ulmifoliella” is a good representation of the insect now referred to P. ulmifoliella (Hübner), while those of corylifoliella, cydoniella and mespilella, though absurdly small, are credible depictions of P. corylifoliella (Hübner), P. cydoniella (Denis & Schiffermüller) and P. mespilella (Hübner). The tiny figure labelled “alnifoliella” and ostensibly check listed as P. alnifoliella (Hübner) = P. rajella ( Linn.), however, resembles that species only in size; likewise the one labelled “klemanella” bears little resemblance to P. kleemannella (Fabricius).
The host-plant associations of this genus in Britain are intriguing from the taxonomic standpoint, raising readily investigable questions about the differences in host structure and/or metabolism determining the host plant ranges of the different species. Phyllonorycter corylifoliella, for example, is as notable for the unusually wide range of recorded food-plants, encompassing at least three quite unrelated plant families, as for its apparent taxonomic selectivity within the families it favours. Thus, although ranging widely in the Rosaceae, its hosts therein as recorded by Meyrick, Jacobs and Bradley are confined to the subfamilies Pyroideae and Prunoideae, apparently to the exclusion of not only all the herbaceous forms, but also of such woody members as the ubiquitous Rosa and Rubus. However, proper research (if indeed it has not yet been undertaken) will require that host-plant lists be checked from original sources, with sampling extended beyond the British Isles.
Organization under the Delta system ensures that all these packages are readily accessible for corrections and improvements. Informed criticism and constructive input are of course welcome, and will be appropriately acknowledged. Alternatively, the 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.