PART I.
INTRODUCTORY.
As mentioned in "Butterflies of the British Isles," there is, speaking generally, no clear line of division between moths and butterflies, and, as Dr. Sharp, in "Insects," puts the case, "the only definition that can be given of Heterocera [moths] is the practical one that all Lepidoptera that are not butterflies are Heterocera." Now, it happens that all the butterflies occurring in these islands have the tips of the horns (antennæ) clubbed; and, although there is much variety in the structure of the horns of our moths, none of them have the tips knobbed.
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Like the butterflies, moths pass through the stages of egg, caterpillar, and chrysalis before they attain the perfect state (imago), and the duration of the several stages is just as variable. The majority assume the moth condition but once in the year, but some species have two, or even three, generations in the twelve months, whilst others occupy twenty-four months in completing the life cycle. In one or two species the chrysalis stage may last four, five, or even six years.
Diversity of form and structure is considerable in the early stages as well as in the perfect insects, and this is shown in the selection of life-history details figured on the black and white plates in this volume.
Fig. 1. Convolvulus Hawk-moth and flower of Nicotiana. (Photos by W. J. Lucas.)
Except that it is generally less prominent, the head, with the various parts thereof, is pretty much the same as in the butterflies. In a few families, however, the "tongue" (proboscis) is only rudimentary or even entirely absent; while in others it is very long. The Convolvulus Hawk-moth has the proboscis of such length that it is able to reach the deep-seated nectary of such tubular flowers as those of Nicotiana affinis. In the illustration the "tongue" of the moth and the sweet-scented tobacco blossom are shown on exactly the same scale.
Fig. 2 represents some forms of antennæ found in moths. A, thickened and spreading out towards the tip (dilate); B, simple, thread-like (filiform) structure, without teeth, hairs, or bristles; C, fringed with fine hairs (ciliate); D, fringed with fine hairs, and with longer bristles at the joints (setose ciliate); E, the fringe in tufts (fasciculate); F, toothed, with fine hairs on the teeth (dentate ciliate); G, toothed with hairs in tufts from the teeth (dentate fasciculate); H, I, with double rows of hair scales (bipectinate); in I the projections are continued to the tip, and are themselves fringed with fine hairs, giving the antennæ a very feather-like appearance—the term "plumose" is sometimes used to describe this form of antennæ; in H the pectinations do not reach the apical fourth, which is simple. J, the lamellate, that is, the undersides of the rings or joints are made up of minute plates.
Fig. 2. Antennæ of Moths.
Fig 3. Connecting Bristle and Catch.
The wings of a moth are practically identical with those of a butterfly (see diagram "Butterflies of the British Isles," p. 12). Normally the fore wings have twelve ribs or veins, and the hind wings eight, but in some genera a rib, or perhaps two, may be absent from the fore or the hind wings; or an extra rib, sometimes two, may be found on the hind wings. These modifications, and others, of the general plan of neuration have been employed as a basis upon which to found genera, or to group them together in classification.
Fig. 4. The Jugum, or Yoke.
Fig. 3 shows the arrangement by which the upper and lower wings of a moth are united in flight. The bristle (frenulum) arising from the base of the hind wing is held in place by the catch (retinaculum) on the costal nervure of the fore wing. It will be noticed that the bristle of the male is longer and firmer than that of the female. The latter, moreover, is usually made up of two or more strands; the catch, too, in the female is on the median instead of the costal nervure. These structures are found on the under side of the wings of most moths, but they are absent in all butterflies. The Emperor, Kentish Glory, and Eggars may be mentioned as examples of moths lacking the connecting bristle, but all these have feather-like antennæ, which terminate in a point. The Burnets have the antennæ gradually thickened towards the tip (A. Fig. 2), and in this respect are somewhat butterfly-like, but these moths have a frenulum.
The hind wings of the Swifts, and a few others grouped with them, have twelve veins, and these moths have a jugum, or yoke (see Fig. 4). This is a flap-like projection from the inner margin, near the base, of the fore wing; it may serve to connect the wings when the insect flies, but it does not seem to be capable of giving much help in that way.
Fig. 5. Wings and Body of a Moth.
h. Head; th. Thorax; col. Collar; lap. Lappet; ab. Abdomen.
b.l. basal line; b.s. basal streak; i.l. inner line; c.s. claviform stigma; o.s. orbicular stigma;
c. central shade; r.s. reniform stigma; o.l. outer line; a.p. apical patch; s.m. submarginal line.
Fig. 6. 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.
Field Work.
Fig. 7. Drinker-moth at rest.
Several methods of moth collecting are in vogue, but space will only permit of a few of those most frequently practised being here referred to, and those suitable for day work will first be considered. Although small woods should not be neglected, large tracts of woodland afford the moth hunter the best chance of success in searching for those species that usually sit during the daytime on the trunks of trees. Many of the moths that rest in this way so admirably blend with their surroundings that they may easily be overlooked; others by their resemblance to feathers, birds' excrement, etc., are also apt to escape detection. Tree trunks, too, abound in moth-like scars, blotches, and knobs, so that the beginner will frequently fail to readily distinguish a moth from such objects, or from the others mentioned. A little practice will soon enable him to tell which is which without having to very closely investigate, or perhaps even touch the suspected object.
Fig. 8. Scarce Merveille du Jour at rest.
As a general rule it is no doubt best to confine ourselves to one thing at a time, if the results are to be satisfactory and the work well done. In the present case, if he feels that way, the collector can relieve the monotony of trunk searching by operating in another direction at the same time. Some moths prefer to repose on the branches, or on the leaves of trees, others among the herbage under trees; these may be disturbed from their lurking places and caused to fall or take wing by jarring the boughs or brushing the undergrowth with a stick.
Fig. 9. Broad-bordered Yellow Underwing at sugar.
Palings, especially old ones and those enclosing wooded parks, etc., are often frequented by numbers of moths. These should be examined as early as possible in the morning, although a later looking over may not be unprofitable. When, however, the wind is dead on them, or where they stand exposed to full sunshine, few insects will be found upon them. Various species are to be obtained from open post and rail fences, and even iron hurdles sometimes yield a good moth or two. Walls are not to be despised, and of course rocks on the moorlands, and the cliffs by the sea afford suitable resting-places for many kinds of moth. As a matter of fact the eyes of the entomologist should always be peering about, as a valuable prize may turn up in the most unexpected places. Hedgerows and bushes in lanes, or bordering fields and woods, afford harbour to many species of moths, and some kinds, not necessarily the commonest, may now and then be beaten from them freely. Herbage on hill or down sides, and on the moor and moorlands is also a favourite hiding-place, as too is the marram grass, etc., on the coast sandhills.
Fig. 10. Purple Clay Moth at rest.
Fig. 11. The Coxcomb at rest.
As the day draws to a close and the night advances, the moths awaken, and first one kind and then another rises on the wing. These, as they fly in the lanes, about the borders or along the rides of woods, and over the vegetation in meadow, fen, or moor, should furnish ample employment and keep the collector actively engaged until the time arrives for a first round of the trees upon which he has spread a dainty repast for the night-flying Noctuidæ, and those members of the Arctiidæ and Geometridæ, etc., that frequently look in where sweets are to be obtained.
Fig. 12. A Ride in the New Forest.
Fig. 13. Moths at a Sugar patch.
This sugaring business is perhaps the most exciting phase of collecting. Having prepared a fine compound of coarse brown or "foots" sugar, treacle, and beer, by boiling down these ingredients to a suitable liquid condition, this is taken to the scene of action in a sugaring tin, a receptacle fitted with a brush which is fixed in the screw-on top; or the attracting medium may be carried in any kind of convenient bottle providing a paintbrush (sash tool) and a jampot or some such article accompany it. Arrived on the ground, preferably a wood, a ride is selected along each side of which are convenient trees. A glade such as that in the New Forest, photographed by Mr. W. J. Lucas, and reproduced in Fig. 12, is an ideal pitch. Just before using, a very small quantity of rum may be added to the mixture, but if "foots" can be obtained the rum is not required. In the autumn I have found a drop or two of the essence of jargonelle pear, or of ribstone pippin, an effective addition. Now comes the initial stage in the night's venture, the "sugar" is put on each tree in a streak extending downwards about a foot from the level of one's chin; if thin enough to spread easily the mixture is almost certain to run further down the trunk. Whilst employed in this somewhat messy preliminary we meditate on the possible result, and hope that if visitors are not numerous they may at least be select. Lighting the lantern, the first round of inspection of the sugar patches is made, but this may not be altogether encouraging; on only one tree are there any moths and these but three in number, and not uncommon kinds (see Fig. 13). The second and even the third rounds do not give the satisfactory results we had anticipated, and we feel inclined to retire discomfited; but as a sort of forlorn hope we try once again, and this time we secure one or two really good things. Another night moths arrive quite early and in large numbers, chiefly commoners, but with a sprinkling of the better sorts among them. Just what meteorological or other conditions are most conducive to a successful sugaring expedition I have never been able to ascertain. Often blanks have been drawn when the weather has seemingly been the most favourable, and quite as frequently good bags have been made when exactly the reverse was thought to be more likely. If the natural attractions in the way of flowers and "honey dew" abound, the insects may possibly ignore the most tempting bait we can contrive for them. There is much uncertainty in this favourite method of collecting, and whether sugar is put on tree trunks, foliage, palings, rocks, or stones, or smeared on rags, and these hung up on barbed wire fences; or daubed on heads of thistles or bunches of grass heads tied together, one must be prepared to accept the disappointments that are inevitable, however careful we may be in the selection of "suitable evenings." It may be added that newly sugared trees are generally less attractive than those that are frequently painted with the mixture.
Fig. 14. Caterpillar of Eyed Hawk-moth.
Caterpillars that feed on the foliage of trees and shrubs may be obtained by beating. The collector with one hand holds an open and inverted umbrella, or a Bignall tray made expressly for the purpose, under a branch, whilst with the other hand, armed with a stick, he strikes the branches from above in the direction of the receiver held below. In conducting such operations some collectors are far too energetic. It should be remembered that it is not hard thrashing, but a sudden jar that dislodges the caterpillars most readily.
Fig. 15. Caterpillar of Privet Hawk-moth.
Although oft-times a somewhat slow process, and to some temperaments, perhaps, rather tedious work, searching for larvæ is not unremunerative when the quality of the material obtained in this way is considered. Some kinds sit in the daytime, or feed, fully exposed, upon the upper sides of the leaves or on the twigs of trees, shrubs, and low herbage; these are not difficult to see. Other kinds conceal themselves under the leaves or on the twigs hidden by the foliage, and these have to be sought for, because many of them cling so tightly to whatever they may be upon that hardly anything short of a fatal blow with the beating-stick will cause them to relax their hold. Others, again, spin two or more leaves together, and in the habitation thus formed they remain throughout the day. The latter are more easy to see than the more readily evicted contingent. All we have to do is to stand under the branches and look upwards and outwards, when the united leaves and the form of the caterpillar between them will be detected. Some, of course, will be high up and out of reach in the ordinary way, but there will be others more accessible. Then, at night, especially in the early spring, we may search, aided by the beam of an acetyline lamp, the plants and undergrowth in wood rides and clearings, borders of woods, and lanes, for caterpillars that are arousing from hibernation. Throughout all searching operations for larvæ the chance finding of eggs under leaves or on twigs or buds is always probable. Cocoons in addition, among the leaves of trees and on stems of low plants and the trunks of trees, may also be revealed.
Fig. 16. Caterpillar of Pale Tussock-moth.
Furnished with a trowel—the ordinary garden kind will do, but the flatter pattern, sold by dealers, is better—the collector may take a turn at digging at the roots of trees for chrysalids. No doubt there are many kinds to be obtained in this way, but I cannot say much for the practice, as my own efforts have not been very highly rewarded. Not a single species was ever obtained by digging that I could not have secured more easily in some other way.
Methods of setting, and after-manipulation have been fully discussed in "Butterflies of the British Isles."