Pale Tussock-moth at rest.
In describing a moth various markings, etc., have to be referred to, and as it may assist the reader more easily to locate the usual position of such characters the accompanying diagram has been prepared. The lines crossing the fore wings from the front edge, or margin (costa), to the inner edge, or margin (dorsum), are generally styled transverse lines; the short one is the basal; the first long one is the inner, or antemedial; the second is the outer, or postmedial; and the third is the submarginal, or subterminal. The whole wing, less the margins, is sometimes called the disc; but it is more convenient to divide the fore wing into three parts, naming that between the base of the wing and the first line the basal area; the space between the first and second lines the central or median area, and the part beyond the second line the outer area. The more or less round or oval rings or dashes on
the central area are the stigmata, and these characters occur more especially in the Noctuidæ. The hind wings usually have a fine short line, crescent, or spot, at the end of the cell, as in the butterflies, and there is generally a line or band beyond.
Immediately behind the head and covering the front part of the thorax is a tippet-like arrangement of scales; this is the collar. On each side of the thorax there is a shoulder lappet (patagium) which has its base on the front part of the thorax also. Both tippet and lappet are often peculiarly ornamented, and the former is sometimes strikingly coloured. The thorax is sometimes crested, and more frequently the body is furnished with tufts of erect hair scales.
The number of moths occurring in the British Islands is well over two thousand. The majority of these hardly ever find favour with the collector. This is probably owing in a large measure to the fact that they belong to a division of the moth tribe which has been dubbed Micro-lepidoptera. It happens, however, that quite a number of the species included in that division are actually larger than many kinds that were placed in the other contingent styled Macro-lepidoptera. According to the most recent authorities the division of moths into two such main groups as those adverted to is entirely fictitious and misleading. Possibly, when this new order of things is more generally understood the so-called "Micros" will receive their proper share of attention.
In the older systems of classification the Clear wings (Sesiidæ) were associated with the Hawk-moths (Sphingidæ), but the former family is now considered to be more closely connected with the Tineidæ. The Goat-moth (Cossus ligniperda) has been removed from among the Bombyces, its name changed to Trypanus cossus, and placed in the family Trypanidæ, which is relegated to the neighbourhood of the Tortricidæ. The Burnets (Zygænidæ), together with Heterogenea limacodes and H. asella (Cochliopodidæ), also Macrogaster castaneæ and Zeuzera pyrina (Cossidæ
part) are removed by Meyrick to the Psychina, a group placed between that author's Pyralidina and Tortricina. The Swifts (Hepialidæ) are grouped with Micropterygidæ, which are considered to be primitive forms of Lepidoptera originating in the Caddis-flies or Trichoptera—a division of the Order Neuroptera.
Except that the Cymbidæ and Arctiidæ are placed just before the Noctuidæ instead of after the Geometridæ, the arrangement of families, genera, and species adopted in the present work is very much the same as that in the 1901 edition of Staudinger's Catalogue. Many British entomologists are now interested in the lepidopterous insects of the Palæarctic, or at least the European, fauna, of which our islands furnish but a relatively small number of species. Others, who at the present time are perhaps but beginners, may very possibly desire, later on, to extend their collections and their knowledge by making entomological expeditions to various parts of the continent. It seemed therefore desirable that in an introductory book on British moths its method of arrangement should at least be founded on some generally accepted system.