The Fauna of British India, including Ceylon and Burma/Butterflies/Volume 1/Introduction

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The Lepidoptera or scaled-wing insects comprise the Butterflies and Moths of popular Entomology. These, under the respective names of Rhopalocera and Heterocera, in allusion to the difference in the form of the antennæ, were regarded as suborders. Of late years, however, it has been recognized that not only are the distinctions between the divisions, as above indicated, not sharply defined, but that differences exist among the groups of the Heterocera quite as, if not more, important than between the two Suborders. In consequence, various revisions of the Order have been proposed.

Comstock (‘Manual for the Study of Insects’) divides the Lepidoptera into two Suborders:—

A. The Jugate Lepidoptera.—“Moths in which the two wings of each side are united by a jugum”^[1].

B. The Frenate Lepidoptera.—“Moths, Skippers, Butterflies, in which the two wings on each side are united by a frenulum^[2], or by its substitute a large humeral angle to the hind wing.”

In the lesser divisions of the Frenates, the Skippers and the Butterflies form two groups, Hesperiina and Papilionina.

Much can be said for the separation of the Skippers from the rest of the Butterflies, and there is no doubt that in the existing fauna the former stand as an isolated group, in some respects very different from the true Butterflies.

Meyrick (‘Handbook of British Lepidoptera’) divides the Order into nine main groups, of which the Papilionina (= Papilionina + Hesperiina of Comstock) forms one. Accepting this arrangement, the forms in the group of the Papilionina can be distinguished from the rest of the Lepidoptera, (1) by the ​entire absence of jugum or frenulum^[3], though their substitute, the enlarged humeral angle to the hind wing, is always present; (2) by the knobbed, or dilated, or hooked antennæ. In certain families of the other main groups of the Lepidoptera, the jugum and frenulum are also absent; but then the antennæ are not knobbed, while in the families in which the antennæ are gradually thickened into a club, or are hooked like the antennæ of the Skippers, a frenulum is always present.

This work is primarily intended for collectors, and as an aid to the identification of Indian butterflies; no account, therefore, of the internal anatomy of the insects, in any stage, seems necessary, for little or no use has been made of internal differences for purposes of classification.

All Lepidopterous insects undergo a great and, to all appearance, an abrupt metamorphosis. In their life-cycle there are four stages:—

(1) The egg, which is round or oval, sometimes elongate, often flattened, and very frequently beautifully sculptured on the outside.

(2) The larva or caterpillar (fig. 1, I.), generally cylindrical, with or without a clothing of hair, often provided with protective tubercles, spines, or special fleshy filamentous processes. It is composed of a head and thirteen segments. Of the latter the first three are thoracic and bear pairs of jointed legs, the succeeding one or two simple without appendages, and one or more of the rest have fleshy feet or “prolegs” in pairs; the posterior pair, slightly different from the rest, are called claspers.

(3) The pupa or chrysalis (fig. 1, II.), more or less fusiform in shape, appendages cemented to the body by a corneous outer covering, often studded with tubercles or spines, or with strangely-formed, sometimes wing-like projections.

(4) The imago or perfect insect. Among the Papilionina, four ​wings and six legs attached to the thorax are always present. Figs. 2-11 represent the chief external parts of the imago. These are shown more or less in outline, and full details with explanation are given under the figures.

Fig. 2.—I. Head (Argynnis). a, proboscis; b, b, labial palpi; c, clypeus; d, d, compound eyes; e, e, antennæ.—II. Single antenna, a, shaft; b, club.—III. Side view of head, thorax, and abdomen, without the wings (Charaxes). a, proboscis; b, labial palpi (the maxillary palpi, much aborted and rudimentary, are not shown); c, compound eye; d, antenna; e, pronotum; f, patella; g, mesonotum; h, episternum; i, i, i, coxæ; k, k, k, femora; l, l, l, tibiæ; m, m, m, tarsi; n, scutellum of mesothorax; o, post-scutellum; p, metathorax; 1-9, segments of the abdomen.

Fig. 3.—Labial palpi (much enlarged), a. Hestia; b. Orsotriæna; c. Hypolimnas; d. Pareba; e. Libythea; f. Abisara; g. Papilio; h. Lampides; j. Colias; k. Tagiades. ​

Fig. 4.—Antennæ (apical portions much enlarged). a. Danais; b. Orsotriaœna; c. Hypolimnas; d. Pareba; e. Libythea; f. Abisara; g. Papilio; h. Pieris, j. Lampides; k. Tagiades.

For classificatory purposes the roost important parts are:—

Head (Fig. 2, I. & II.).—The labial palpi, b, b. These, in all butterflies, are three-jointed and variable in shape and in the clothing of scales or hair, but constant in each genus. They are independently moveable, but their function, if they have any, is unknown. The antennæ (e, e & II., also fig. 4) are evidently organs of perception. They are composed of an indefinite number of joints, and vary greatly in length and thickness, in the shape of the club, in the amount of scaling, and in the arrangement of the sensory hairs and pits. In very many forms they are grooved on the underside^[4].

Thorax.—The appendages, the wings (figs. 5-10) and the legs (fig. 11), are of the utmost importance in classification.

Wings. These are membranous, traversed from the base outwards by nervures (“tubular structures which serve at once as extensions of the tracheal system and to form a stiff framework for the support of the wing”). In the vast majority of the butterflies they are covered on both upper and under sides with flat scales arranged in rows, and often brightly coloured. The usual number of nervures in the wings of butterflies are: fore wing 12; hind wing 9, beside the subcostal, median, and discocellular veins; but one or more of these may be absent, or there may be one or two extra veins or portions of veins developed.

Special note should be taken of fig. 5, as the details given explain the terminology used in the descriptions of the forms throughout this work. This terminology is different from that used in Moore's and de Nicéville's works. The following few additional terms will also be met with:— Anterior or upper and ​

Fig. 5.—Wing of Danais (Nymphalidæ). I. Fore wing: d, discoidal cell; C, costa or costal margin; ap., apex; T, termen or terminal margin; Tor., tornus; D, dorsum or dorsal margin; s.c.v., subcostal vein, extending from base of wing to upper apex of cell; m.v., median vein, extending from base of wing to lower apex of cell; u.d., m.d., l.d., upper, middle, and lower discocellular nervules or discocellulars; v1a-v12, veins; i1a-i12, interspaces. II. Hind wing: d, discoidal cell; C, costa or costal margin; ap., apex; T, termen or terminal margin; Tor., tornus; D, dorsum or dorsal margin; s.c.v., subcostal vein, extending from base of wing to upper apex of cell; m.v., median vein, extending from base of wing to lower apex of cell; u.d., m.d., l.d., upper, middle, and lower discocellular nervules or discocellulars; v1a-v8, veins; pc.c., precostal vein; i1a, i1b-i8, interspaces.

Fig. 6.—Wings of Abisara (Nemeobidæ). Veins numbered similarly.

Fig. 7.—Wings of Papilio (Papilionidæ). Veins numbered similarly. I. Fore wing: Extra veins present: 1 a and a cross vein between median vein and vein 1. II. Hind wing: vein 1 a absent; a cross vein present between vein 8 and precostal vein. ​

Fig. 8.—Wings of Ixias (Pieridæ). Veins numbered similarly. I. Fore wing: vein 9 absent. II. Hind wing: veins 1 a-8 present.

Fig. 9, A & B.—Wings (Lycænidæ). A I. Fore wing: veins 7 and 10 absent. B I. Vein 7 absent. A & B II. Hind wings: precostal veins absent.

Fig. 10.—Wings of Tagiades (Hesperiidæ). I. Fore wing: all veins present and, except 1 and 12, originating from cell. II. Hind wing: vein 5 absent.

posterior or lower, refer to the costal and dorsal portions of the wings respectively. Markings are said to be basal when occurring between base of wing and up to an imaginary line crossing middle of cell; subbasal from that to a similar line crossing just within the apex of cell; discal or medial when they occupy the medial third of the wing; and postdiscal, subterminal, and terminal in succession after that.

Legs. These organs, though variable on the whole, are, so far as the perfection or imperfection of the front pair of legs is concerned, constant in the larger divisions of the Papilionina—the families and subfamilies. In the more specialized forms, the fore legs are more or less, sometimes very considerably, reduced in size. In many genera of the Nymphalidæ the fore legs are kept close-pressed to the body, and often appear like mere brushes or tufts of hair; while in nearly all the genera of that family they are useless for walking in both sexes. ​

Fig. 11.—Fore legs, a ♂, b ♀, of I, Hestia (Danainæ); II, Mycalesis (Satyrinæ); III, Cynthia (Nymphalinæ); IV, Pareba (Acræinæ); V, Libythea; VI, Abisara (Nemeobidæ); VII, Papilio (Papilionidæ), claws simple (♂ tibiæ with pad on inner side); VIII, Pieris (Pieridæ), claws bifid; IX, Lampides (Lycanidæ), ♂ tarsus imperfect with only one claw; X, Tagiades (Hesperiidæ), tibiæ with a medial as well as an apical pair of spurs.

The six families under which the Indian butterflies can be arranged may be briefly tabulated as follows:—

A.

Antennæ approximate at base; hind tibiæ with only a terminal pair of spurs; one or more of the veins in the fore wing forked or coincident beyond the cell.

a.

Precostal nervure in hind wing present.

a1.

Front pair of legs imperfect in one or both sexes.

a2.

Front pair of legs imperfect in both sexes[5] .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .

Nymphalidæ.

b2.

Front pair of legs imperfect in ♂, perfect in ♀ .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .

Nemeobidæ.

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b1.

Front pair of legs perfect in both sexes.

a2.

Vein 1 a in hind wing wanting; claws simple .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .

Papilionidæ.

b2.

Vein 1 a in hind wing present; claws bifid .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .

Pieridæ.

b.

Precostal nervure in hind wing absent .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .

Lycænidæ.

B.

Antennæ wide apart at base; hind tibiæ generally with a medial as well as a terminal pair of spurs; all the veins in the fore wing from base or from cell, none forked or coincident beyond .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .     .

Hesperiidæ.

Opinions vary as to the probable line of descent of the butterflies. Packard considers that the moths of the family Castniidæ are their predecessors; Meyrick traces their descent from the Thyrididæ group Pyralidina of the Frenatæ, Hampson from the Zyrgænidæ.

However this may be, a provisional genetic tree for the butterflies can be constructed as below.

The evidence of one family group of the butterflies being derived from another is entirely inconclusive. Specialization of forms has followed often parallel lines in all the families, but similar specialization, when it occurs in different groups, is no proof of genetic descent, but of independent development along similar lines.

The tendency in modern Systematic Natural History is to ​greater subdivision and the multiplication of genera. No criterion exists as to what are generic characters, and as there does not seem to me that any greater convenience is gained by this minute subdivision, I have preferred to arrange the forms under large and comprehensive genera.

With regard to species, it may perhaps be noticed that throughout this work I have avoided using that term. My reason for this is that, although the word “species,” as now generally understood, is not likely to be entirely misinterpreted, the evil connotations of pre-Darwinian times still cling to it, and to many, perhaps unconsciously, convey the idea of fixity. The term “form,” on the other hand, though not entirely satisfactory, at any rate implies the possibility of change. That forms are constantly but slowly changing is a fact that is emphasized by every increase to our knowledge of living things. It is strikingly apparent in the Lepidoptera, of which Dr. D. Sharp says: “A great deal of evidence, both direct and indirect, has accumulated showing that the organization of many Lepidoptera is excessively sensitive, so that slight changes of condition produce remarkable results.” The system of regarding local representatives of typical forms as of equal rank to them seems to me unsatisfactory, as all connection between the two forms is ignored. It is true that in the present state of our knowledge it is often a matter of conjecture as to which is the typical form and which the race, but in my opinion it is of great importance to draw attention to the extremely close relationship existing between many forms, so as to facilitate the tracing-out of the connection between them. In this work, purely as a matter of convenience, the form first described is made the type, its geographically limited representative—differing perhaps very slightly, but constantly—the race; but it must be clearly understood that in many cases the reverse is quite as likely to be the truth.

In conclusion, my best thanks are due to the many who have aided me by the gift or loan of specimens. From Sikhim my friend Mr. Fritz Möller has sent me large collections in the most perfect condition. Many of the forms in these were procured at high altitudes, and are most interesting and rare. To Col. E. R. Johnson, late of the Indian Medical Service, I owe the gift of a small but very valuable collection from Simla and from Shillong in Assam. To Col. Swinhoe I am indebted, not only for the gift of many specimens, but for the privilege of examining at leisure the fine series of Indo-Malayan forms contained in his collection. Mr. Gilbert Eogers, of the Imperial Forest Service of India, in the most lavish way, employed native collectors in the Andaman and Nicobar Islands, and has generously placed the material ​collected at my disposal. Messrs. Allan and Craddock, of the Burma Forest Department, have sent me small but very useful collections from Pegu and the Southern Shan States; and to Mr. E. E. Green and to the Hon. F. Mackwood I owe many specimens from Ceylon. Major E. Stokes-Roberts, R.E., sent me several collections made in the Anaimalai and Niligiri Hills in Southern India. These were particularly valuable to me for comparison with the northern Indian forms.

I have to thank the Authorities of the British Museum for the privilege of access to the magnificent series of Indian butterflies contained in the National Collection, and I am specially grateful to Sir G. Hampson and Mr. F. Heron for the facilities afforded me for their examination. Mr. Heron has aided me in every possible way, and his intimate knowledge of many groups of butterflies has been most kindly and unreservedly placed at my service.

The National Collection has of late years been greatly increased and enriched by the donations of the Godinan, Leech, Crowley, and Elwes collections; and it is fortunate that so well-known an authority on Lepidoptera as Mr. Elwes should have undertaken the re-arrangement of the vast material thus brought together. For me it was specially fortunate that previous to commencing the writing of this volume the arrangement of several of the groups of the Nymphalidæ should have been completed. I had thus the advantage of Mr. Elwes’ large experience to guide me.

Turning to books, my obligations to the two previous works on Indian Butterflies have to be acknowledged. I am greatly indebted to the information contained in Mr. Moore’s great work, the ‘Lepidoptera Indica,’ as will be seen from the frequent quotations from and references to the volumes so far completed. Of the three volumes issued of the ‘Butterflies of India,’^[6] the first two are completely out of date and, I believe, out of print. Col. Marshall and Mr. de Nicéville were pioneers in the systematic investigation of the Indian Lepidopterous Fauna; and the impulse given to the study of Indian butterflies by the publication, by the two authors conjointly, of the first volume of the ‘Butterflies of India, Burma and Ceylon,’ and, by the late Mr. de Nicéville alone, of volumes II. and III. cannot be rated too highly. De Nicéville’s enthusiasm communicated itself to others, and his ever ready and generous help encouraged many who, like myself, feel that his early death has been almost an irreparable loss to Indian Entomology. Had my late friend lived, the compilation of the present work would never have been attempted by me; it would have been in his far abler hands. As it is, it will be good news to many that the Trustees of the Indian Museum ​acquired the MSS. of the volumes on the Papilionidæ, Pieridæ and Hesperiidæ left partially incompleted at Mr. de Nicéville’s death. These MSS. have been generously placed at my disposal for use in the compilation of the future volumes of this work.

In connection with this, I ought to add that the unique collection of Indo-Malayan Lepidoptera brought together by the late Mr. de Nicéville was acquired some little time before his death by the Indian Museum, and that through the kindness of Major Alcock, I.M.S., C.I.E., F.R.S., Superintendent Indian Museum, I have had the privilege of examining many of the types.

A few words with regard to the illustrations. This is the first volume of the Fauna series which has had any large number of coloured plates. The ten in this volume have been well executed by Mr. Horace Knight, and reproduced by the modern process of colour-printing which is getting rapidly perfected.