Part 7

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The systematic arrangement of this tribe of insects has always been considered a task of great difficulty. So convinced of this was Latreille, who had himself studied the subject profoundly, that he says a classification of lepidoptera may be considered the touchstone of entomologists. This difficulty arises chiefly from the uniformity of organization which prevails throughout the order--a uniformity occasioned by all of them being designed to subsist on liquid food, and to imbibe it in the same manner. The oral organs, therefore, which are of the first importance in classifying other tribes--the coleoptera, for example, in which they undergo almost endless variations of form and consistency to fit them for consuming every kind of organic substance, from semi-fluid animal or vegetable matter to the hardest ligneous tissue--are, in this instance, of comparatively little avail. Recourse must be had to secondary and subordinate characters; and even when we are convinced that, owing to a peculiar facies, and the concurrence of many minute resemblances, certain groups should be regarded as distinct, it is found difficult to define them in a satisfactory manner. Neither has the difficulty been much lessened by the manner in which the subject has been handled by many modern naturalists. The numerous illustrations of lepidoptera published of late years, have been partial, being either selections from the whole class, or forming part of a local fauna. In either case, the subject is regarded in too insulated a light. The illustrator of foreign butterflies selects a species, and by giving prominence to all its minute characters, proposes it with considerable plausibility as a distinct genus. The local faunist divides his groups in reference to his own limited sphere of observation. Neither contemplates the possibility of being ever called upon to elaborate a general system, and he leaves it to those who are to reconcile all existing inconsistences. Hence it follows, that so many of the genera proposed in local and partial works can find no place in a general one; for however specious they may appear when standing alone, it is often found that they will not unite into a consistent whole, and they may therefore be said still further to embroil the very subject they were designed to elucidate.

The Linnean distribution was vague and unsatisfactory, even at the time when it was first produced, and soon became utterly inapplicable when the amount of known species was increased. But it did not fail to exercise, like every other system emanating from that gifted mind, a powerful influence on the progress of the science, and is interesting on account of its ingenuity and poetical elegance. “It is an attempt,” says Dr. Shaw, “to combine, in some degree, natural and civil history, by attaching the memory of some illustrious ancient name to an insect of a particular cast.” The first Linnæan division consists of Equites, which are distinguished by the shape of the upper wings; these are longer, measured from their posterior angle to their anterior extremity, than from the same point to the base; the antennæ sometimes filiform. The equites are denominated Troes or Trojans, distinguished by having blood-coloured spots on each side of the breast: or Achivi, Greeks, which are without red marks on the breast, of gayer colours, and having an eye-shaped spot on the anal angle of the inferior wings. The second division consists of Heliconii, which are distinguished by having the wings narrow and entire, often naked or without scales; the superior oblong, the inferior very short. The third division consists of the Danai, so called from the sons and daughters of Danaus. They are divided into Danai candidi, or such as have whitish wings, and Danai festivi, in which the ground colour is never white, and the surface variegated. The fourth division consists of the Nymphales, distinguished by the edges of the wings being scolloped or indented; it is subdivided into N. gemmati, in which the wings are marked with ocellated spots, and N. Phalerati, without these spots. The fifth division contains the Plebeii. These are commonly smaller than the preceding butterflies, and are subdivided into rurales and urbicolæ; the former having the wings marked with obscure spots, the latter for the most part with transparent spots.

In his earlier works, Mantissa and Species, Fabricius made no important change on the Linnæan method; but the many additional species which had come to his knowledge when he drew up his Systema glossatarum, led him to establish many new genera, and remodel the arrangement of the old ones. This method consists of forty-one genera, most of which have been adopted by subsequent authors; but it is less complete than it might otherwise have been rendered, owing to the death of the author before it was finished. Latreille did not deviate materially from the Fabrician method, adopting nearly all the genera; but he did not derive the distinctive characters exclusively from the antennæ and palpi, as the Danish entomologist had done, but had recourse to other parts of structure, and likewise judiciously took into account the peculiarities of the caterpillar and chrysalis. Several arrangements were proposed subsequent to or contemporaneous with that of Latreille, such as those of Lamarck, Dumeril, Dalman, &c. but most of them are of little importance. The last mentioned individual, however, appears to have been the first to apply to actual practice, in his description of the lepidoptera of Sweden, characters derived from the neuration of the wings, the value of which were first pointed out by Mr. Jones, in a paper in the Linnæan Transactions, published in 1794. Godart, without appearing to have been acquainted with what had been done by Dalman, likewise had recourse to the structure of the wings in his arrangement, as published in the Encyclopédie Methodique, and Lepidoptera of France. In the latter work, the diurnal series is classified with reference to the appearance of the discoidal cell in the inferior wings; and by adopting this excellent character, he has, in most instances, greatly improved on Latreille’s method.

In 1776, an arrangement was proposed which attracted little attention at the time, but which has since risen to considerable distinction. It is that exhibited in the Systematic Catalogue of the Lepidoptera found in the neighbourhood of Vienna, by MM. Denis and Schiffermüller. This original and highly valuable system is entirely founded on the appearance of the caterpillars. It is singular that characters almost exclusively drawn from that state, should confirm the classifications founded on characters afforded by the imago or complete insect. But to such a degree does this coincidence obtain, that almost all the families proposed by the Austrian naturalists have been adopted as genera by those who were guided by other principles. This method remained for a long time almost unknown to the naturalists of this country, and even on the continent its excellence seems to have been but inadequately appreciated, except among the Germans. The only authors that have acted upon it are Ochsenheimer, and his continuator Treitschke, in their valuable and extensive work on the Lepidoptera of Europe.

But there can be little doubt that those arrangements are the most accurate and philosophical which are founded on characters derived from all the different states in which these insects exist. This conviction seems now to be generally entertained, and most writers of very recent date have seen the propriety of acting upon it. In the works of Curtis, Stephens, Horsfield, &c. it has been adhered to to a greater or less extent, and in a general work on Lepidoptera lately published by Dr. Boisduval of Paris, nearly equal importance is assigned to the peculiarities of the caterpillar, chrysalis, and butterfly. As this method presents some new features, and is the last that has been laid before the public, we shall give an account of it along with the accompanying remarks in the authors own words:--“It is not till after a most attentive study of the butterflies of Europe in their different states, and after having collected a certain number of materials on the metamorphoses of exotic species, that we have attempted to group the lepidoptera in a manner different from that hitherto followed, not neglecting, at the same time, the study of those authors who have occupied themselves with this order, that we might be enabled to combine the results of their labours with our own. We do not flatter ourselves, however, that the combinations which we have made are altogether free from blame, any more than those of our predecessors. When occupied with the productions of a single country, the classification is much more easy; the greater number of species associate pretty well with each other, and, if we except a few of the most anomalous, a series is obtained free from much irregularity. In this way, the European species form a pretty homogeneous assemblage, and the same thing holds with regard to those of South America, New Holland, or any other country taken by itself; but when we attempt to classify those of the whole globe, we frequently meet with intermediate genera which interrupt this harmony. If we even take a somewhat numerous genus belonging at the same time to several different countries, we find species which form a passage to other races proper to each of these countries. For example, the genus Pieris of Latreille offers species in America (genus Leptalis) which bear a perfect resemblance to the Heliconii in their colour, the length of their bodies, and narrowness of the wings. Others of the same country (genus Euterpe) insensibly unite with that division of American Papiliones which is of a black colour with red spots; those of Europe, on the contrary, present certain relations to Parnassius, Pieris Cratægi appearing to form the passage to P. Mnemosyne, while those of India gradually approach Colias through P. Judith and P. Panda, and to Danais with green spots through P. Valeria. All other genera of some extent, and distributed over several countries, are in the same condition.

“What we have just stated, applies equally to the correlation of species with each other. If we take, for example, the genus Satyrus of Latreille, we perceive that it is composed of an infinite number of secondary groups, scarcely any of which are proper to one country. Thus, in Europe, we have the division to which Galatea belongs, extending along the basin of the Mediterranean, even into Persia; that of Hermione, which takes the same direction, and continues to Cachmere; that of Norna, proper to the polar regions of the two continents; that of Nigres, which inhabits mountainous countries, and is found only at the Cape and at Chili; finally, that of the Satyres, properly so called, which are connected with the species of New Holland, some of them with those of Chili, of North America, and Siberia. America and the East Indies, likewise, present groups which in general appearance differ widely from our European species; while there are others which resemble several at the same time. A collection of the Satyres of one country would, therefore, form a sufficiently natural series; but it would appear most irregular when the species of several countries were brought together.

“Our method is partly founded on the caterpillar, and partly on the perfect insect. We attach the greatest importance to the caterpillar state, and the characters which it furnishes have often more value in our estimation, than those afforded by the butterfly; but generally these characters confirm each other, in other words, two caterpillars presenting the same characters produce flies which likewise partake of the same generic characters. It will no doubt be objected to us, that it is illogical to deduce characters except from the animals we are attempting to classify. We reply, that by following any other plan we must despair of attaining to a natural method. Besides, it is not necessary to be acquainted with the caterpillars of every species; it is sufficient to study a caterpillar and chrysalis of Vanessa or Pieris to have an exact idea of those of the two genera. Even though it should be very difficult to verify the characters taken from the larva, this is no reason why we should abstain from employing them. It is not merely from the fruit that botanists obtain their characters, but likewise from the flower, and even from the first developement of the vegetable embryo. The flower is to the plant what the caterpillar is to the lepidopteron, and the different modes of metamorphosis have as much value as those of inflorescence.

“It appears to us that Latreille’s three divisions, taken from Linnæus--Diurnal, Crepuscular, and Nocturnal--are too inaccurate to be retained, especially the crepuscular section. The denomination Diurnal not only applies to all the known kinds of day butterflies, but also to an almost infinite number of others forming a part of the two other divisions, such as Macroglossa, Zygenides, Castniariæ, gocerides, &c. That of Crepuscular is adapted more or less to some sphinges, but by no means to the Zygenides, which fly only in the heat of the sun. Finally, the term Nocturnal is not more properly applicable to all the species, since many belonging to this section appear only during the day. In order to avoid these improper denominations, we have substituted for the word Diurnal, that of Rhopaloceres, proposed by M. Dumeril. Being unable to perceive limits between the Crepuscular and Nocturnal divisions of Latreille, we have united those two great sections under the name of Heteroceres. In our method, therefore, the lepidoptera are divided into two grand legions, Rhopaloceres and Heteroceres.”

Dr. Boisduval then proceeds to explain that the first of these divisions is characterised by antennæ thickening to a club at the extremity; and the second, by having these organs variously shaped; this indeed is implied by the words themselves. The first division is subdivided into three sections, according to the manner in which the caterpillars transform themselves into chrysalides. Such as undergo this change by attaching themselves by the tail and a band round the middle, form the first division, named Succincti; such as are suspended by the tail only, the second, Penduli; while those which form a cocoon by rolling leaves together, compose the third division, termed Involuti.

Each of these three sections is then divided into tribes, according to characters derived from the caterpillars and the perfect insect. Among those furnished by the latter, the most important are considered to be the number of ambulatory legs and the form of the palpi. The genera are characterised by the form of the caterpillar and chrysalis, by the dispositions of the nervures of the wings, the form of the antennæ, legs, palpi, thorax, &c. of the perfect insect.

GENUS ORNITHOPTERA.

The present generic group was first separated from Papilio by Dr. Boisduval. None of its characters, taken singly, are very strongly marked, but their aggregate importance is sufficiently considerable to authorise its adoption. As in Papilio the antennæ form an elongate club, having the extremity slightly curved upwards, the palpi are longer than in the genus just named, but they never rise above the forehead. The prothorax is much developed anteriorly, and forms a pretty distinct neck. The abdomen is long and robust, that of the male deeply grooved on the under side, and provided at the anal extremity with two large rounded valves. The wings are large, of a strong texture, and furnished with salient nervures; the anterior pair elongate; the posterior with wide shallow indentations, and never prolonged into a tail.

We are very imperfectly acquainted with the natural history of the insects of this group in their early stages. Their remote localities, and the rarity of most of the species, have, for the most part, prevented them from falling under the notice of competent observers. The caterpillar and metamorphoses of one of them (O. Heliacon), however, have been described by Dr. Horsfield. Like the caterpillars of Papilio, it is furnished with two retractile tentacula; the body is large and thick, and bears eight rows of rather long fleshy prominences, of a conical shape. The chrysalis into which it is transformed is somewhat curved, having the head obtuse, and a few projecting points above the middle. It is suspended by the tail, and a transverse band, which, however, does not encompass the body, but is inserted on each side. (See Fig.)

This group is but of limited extent, but it comprehends some of the largest and most beautiful lepidoptera yet known to us. With one exception, which extends over a portion of the Indian continent, they are confined to the Mollucca, Philippine, and others of the numerous and extensive islands of the Indian Archipelago. The species figured, which is the most beautiful of the whole, and to which Linnæus applies the epithet of august, has been long known and highly prized by collectors. It is named

PLATE 1.

1 Ornithoptera Priamus 2 Ornithoptera Remus

Natives of the island of Amboina.]

ORNITHOPTERA PRIAMUS.

PLATE 1. Fig. 1.

Boisd. Species gener. des Lepidop., 173.--Papilio Priamus, Linn. Latr. Godart, Cramer; Papillons exotiques, 23, A, B; Donovan’s Insects of India, Pl. 3.

Female, Pap. Panthous, Linn.; Cramer, 123, A, and 124, A; Don. Ins. of India, Pl. 2.

Such a remarkable discrepancy exists in the appearance of the sexes, that they were always regarded as separate species till lately, when their proper relationship to each other happened to be ascertained. The anterior wings of the male are deep velvety black, with two broad longitudinal stripes of rich silky green, curved, and narrowing at both extremities; between these stripes there is a large brownish spot disposed longitudinally. The hinder wings are silky green, with the posterior margin, and a series of four pretty large circular spots, velvet-black; between the black spots and posterior border are two orange spots, and another of larger size towards the base of the wing. On the under side, the anterior wings have a macular band of gilded green, formed of contiguous wedge-shaped spots, an irregular patch towards the centre, and two streaks near the apex. The under side of the hinder wings corresponds to the surface, but the green is of a more golden hue, and the circular spots larger, and seven in number. The antennæ, head, and thorax, black--the latter with a central line and two posterior spots of golden green; breast spotted with red on the sides; abdomen bright yellow.

The female is considerably larger, frequently measuring nearly eight inches between the tips of the wings. The prevailing colour is dark brown, deepening towards the extremities of the wings; the upper pair traversed by a macular band of impure white, the spots unequal and generally interrupted or notched; the hinder pair having a curved row of six large wedge-shaped spots behind, of a whitish colour powdered with black, the base tinged with yellow, and each with an orbicular black spot in the centre. Head and thorax entirely black, the abdomen whitish yellow above and deep yellow beneath.

Varieties of both sexes have occurred, for there seems little reason to doubt that the insect figured by Guerin (Voyage de la Coquille, Ins., pl. 13, fig. 1 and 2) under the name of P. urvillianus, is a variety of the male, while a female variety is described by Boisduval. In the former, the green of the superior wings is replaced by violet-blue of a very brilliant tint, and in the hinder part that colour runs in a broad stripe along the nervures, dilating considerably towards the posterior margin. This example was found at Offack.

The Priam butterfly is found in the islands of Amboina, Rawack, and Ceram. It has been observed to hover about the Mangifera Indica in preference to other trees, and it has hence been conjectured that it deposits its eggs on the leaves, and that they constitute the food of the caterpillar. It never occurs in large numbers, and is hence somewhat rare in collections. Specimens of both sexes are preserved in the valuable collection of insects belonging to the Edinburgh University Museum.

ORNITHOPTERA REMUS.

PLATE 1. Fig. 2.