I have previously given, in a note, a list of the genera which are usually considered as Bombyces, and ought, therefore, if properly placed, to be included in the sub-class Phalæna; five of those genera yet remain, and at present must be excluded from the sub-class: Penthophera, Heterogena, and Limacodes, because I know nothing of their history; Nudaria and Psyche, because, in the larva, pupa, and imago states, they have the habit and appearance of another class (Neuroptera). The time of their dwelling with Lepidoptera is over and gone; they have already occupied too long a position to which they were not entitled. The difficulty of assigning a situation to Limacodes I hope to see removed, as the larva is occasionally to be met with. I must also remark, that although I have proposed a situation for Endromis, I feel very doubtful as to its being the correct one. These doubts and difficulties will probably gain me much censure; but I must endeavour to shelter myself in some degree, by observing, that I am the first who has ever deviated from the original Linnæan arrangement of Lepidoptera, the first who has ever thought of appealing to nature in support of theory, or rather has waited for nature to supply him with theory; and surely some allowance is to be made for a first attempt of any kind. I would also plead the poverty of our British Fauna in the sub-class, and my almost entire ignorance of exotic Phalænæ. Even supposing myself acquainted with all our indigenous species, they will barely furnish a systematist with a clew to the truth: you may pick up a single link of a chain, yet fail to discover the length of that chain, or the situation in that chain which the link originally possessed.
Having, then, pointed out, as clearly as my limited knowledge of the subject will permit, not only the principal contents of the class Lepidoptera, but endeavoured to establish them in appointed and fixed stations, and to show their mutual approaches, at least those of the most striking kind and essential to my purpose, I must now proceed to make a few remarks on the nature of these approaches. It will be observed, that they are, almost without an exception, what Mr. MacLeay considers relations of affinity, that is, the relation is between species which, in their imago state, have a real and positive similarity to each other; so much so, that entomologists, unacquainted with the prior states, and frequently even in direct defiance of their own knowledge of those states, place them in orders, and even sub-classes to which they do not belong; to which fact all our systems and catalogues bear most ample testimony. This similarity is by no means confined to a cursory glance at the insects, but bears the test of a minute anatomical investigation, the antlia, palpi and antennæ demonstrating the approach quite as forcibly as the form and appearance of the whole insect. Where a tribe has short biarticulate palpi, a genus departing from the type will assume elongated and triarticulate palpi, should another tribe with those characters approach it: again, should a tribe with long antlia approach a tribe whose character it is to have none, we shall be sure to find a genus without antlia at the point of approach. On the other hand, the very egg, the larva, the pupa, the mode of feeding and description of food, the mode of metamorphosis, and, in fact, every prior quality, or state, from which distinctions could be obtained, differ so decidedly, that the characters of these often bear as near an approach to those of Hymenoptera, Neuroptera, and even Coleoptera, as to those of their own kindred, into immediate contact with which these approaches will be found inevitably to bring them. What term can then be applied to designate the real value of this species of approach? Supposing the terms analogy and affinity to have had good, sound, and distinct meanings, as originally employed and explained by great naturalists, they have now been so confused, confounded, and utterly misunderstood by ignorant persons, that either of these terms is entirely out of the question:[54] in fact, a suitable term by which to designate this peculiar species of relation or approach, I neither know where to find, or how to invent; and, therefore, I shall purpose simply to call it relation of larva, relation of pupa, or relation of imago, as the case may be.
In one instance, the relation of imago is, from several combining causes, which it will be unavailing to recapitulate, uncertain enough—that of Barbicornis and Lasiocampa; but I would ask the impartial reader, is it half so far-fetched and untenable as those in common use? Can human sagacity, in sheer wantonness, invent combinations more unnatural than ——, twenty or thirty of which we could all point to in our own cabinets? For the value of the other relations (eleven others) I appeal to the judgment of the assiduous collector, the experienced observer, the real nature-loving naturalist,—to him who has spent days in the woods, and not only captured but observed these delightful beings,—to him who never invented or supported a theory,—to him who is pledged to no system, to no party,—I ask him, nothing doubting of his concurrence, whether these relations do not too plainly bear the impression of nature's seal, to allow him to doubt one instant of their reality.
In the next place a question occurs, how is the relative position of the sub-classes proved to be correct, seeing it is so totally at variance with what we have from our childhood been perfectly satisfied with?[55] It is proved correct, simply and solely by the harmony with which each flows into each,—with which neighbour meets neighbour,—comparable somewhat to that exquisite feeling which induces a man to bend to the peculiarities, and perhaps even little failings of a friend, until he makes them almost his own. It can hardly be supposed that the sub-classes naturally fell into the positions which I have assigned to them, without some little endeavour, on my part, to produce this harmony. This was far from the case. The discovery, if it be one, was the result of serious and deliberate study. Even after arriving at their present state, I have twice endeavoured to alter these positions, once in hopes of making some of the Tortrices meet the Papilionidæ, as I had an idea that that very assiduous and ingenious naturalist, Dr. Horsfield, had mentioned the discovery of such an approach.[56] In vain, however, did I strive to discover such an approach, in either larva, pupa, or imago, while these points of resemblance were most abundant between the Geometræ and Papiliones; the pupa, as though in sport, being now suspended by the tail, now girted round the waist, now enveloped in a silken web; sometimes round-headed, sometimes pointed, sometimes eared; now smooth, anon angulated, black, brown, yellow, pure green, clouded, or spotted: of these, and a thousand other peculiarities, which tended to corroborate my ideas of arrangement, I refused invariably to avail myself, trusting to one guide only, which seems as steadfast as a rock: that relation of imago constitutes approach of divisions; relation of larva is the tie which holds divisions together. The second alteration I endeavoured to make, was to place the Papiliones in the centre, a situation to which their splendour and magnitude would really appear to give them a title. This idea seems every way so plausible, and so likely to be proposed by entomologists, should any such see merit enough in this system to give their attention to its minutiæ, that I am compelled to consider it more at large.
To a sub-class selected for a centre, two qualities are indispensably requisite. They have been previously given from Mr. MacLeay, who, it will be remembered, discovered that one of each of his five groups contained types of the other four, besides a type peculiar to itself. This quality must hold good in any group thus selected for a centre; it must contain types of the six surrounding groups in the first place. Now, is this applicable to Papilio? Have we not already experienced the greatest difficulty in finding three good approaches, the smallest number which a sub-class can possess? How then can we hope, by any good fortune in discovery, to make ourselves masters of three other entirely new ones, and these to sub-classes to which it is confessedly the most unlike? Phalæna, on the contrary, presents us with Lasiocampa, Ægeria, Cilix, Lithosia, Apatela and Orgyia, five of which genera beautifully typify the approximating sub-classes. The preference on this score then is decidedly with Phalæna.
The second position, that it should contain a type peculiar to itself, is almost a matter of course; but my own idea is, that the very centre should not only be a type of the genus, or order, or sub-class, but of the class itself of which it is the centre. From this position, then, a further and still more important question arises,—What is the type of Lepidoptera? The parts which afford the generic characters of Lepidoptera, and, I believe, generic characters in the perfect state are the only ones of any value, are these—the mouth, palpi, antennæ and wings; and, as no medium can constitute a type, the excess of these characters, whether superlatively or diminutively considered, must be resorted to as the most probable means we possess of discovering what this type may really be. First, then, the mouth. In Lepidoptera, we find two distinct characters in this;—first, its entire absence; secondly, its being furnished with prodigiously long antlia. The first character is that of Phalæna, the second that of Sphinx. Next, the palpi are either entirely obsolete or exceedingly prominent, the first in Phalæna, the second in Pyralis. Thirdly, the antennæ are remarkably pectinated, or clavated, or setaceous: the first character is that of Phalæna, the second that of Papilio, the third that of Noctua. Fourthly, the wings are enormously expansive in proportion to the body, or remarkably small,—the first is the character of Phalæna, the second that of Sphinx. It need scarcely be added, that all these characters are to be met with in every intermediate degree of intensity. Now, it appears, that Phalæna possesses an extreme of each of the four principal characters, Sphinx of two, Noctua of one, and Papilio of one; therefore Phalæna is the typical genus, Phalænæ the typical order, and Phalæna the typical sub-class of Lepidoptera: and a necessary conclusion from this fact is, the type of Lepidoptera is an insect without antlia or palpi, with very pectinated antennæ and enormously expansive wings, and we may add nocturnal flight: so that such peculiar characters as the thick full body and prodigiously long antlia of Sphinx, the clavate antennæ, erect wings, and diurnal flight of Papilio, argue a departure from, and not an approach to, the type.
By a reference to the Diagrams exhibiting the classes of Insecta, and the sub-classes of Lepidoptera, it will at once be observed, that the central group in each case contains types of the surrounding groups. Now after a central group has thrown off a set of six forms, each representing, in general appearance, some group equally extensive with such central group, the faculty or power of throwing off such forms becomes, in a good degree, extinct, or, at any rate, very much debilitated. This can be no unforeseen, but a perfectly natural, and absolutely necessary consequence; for taking either of the two classes which are at present sought after, Lepidoptera and Coleoptera, we must observe, that did either of them possess as varied forms and characters as are to be found in Neuroptera, the essential and distinguishing character of that class, viz. variety, and the harmonious arrangement of the whole sub-kingdom, would both be entirely lost; and it would remain for human ingenuity to locate either of the classes centrally or externally, as caprice, or the love of differing from others, might dictate. I wish it to be observed, that Neuroptera, in the genera Psyche, Cloëon, Termes, Psocus and Mantispa, does not merely assume the form of the genera, Tinea, Chironomus, Formica, Aphis and Mantis, but actually possesses the characters and appearance of the classes Lepidoptera, Diptera, Hymenoptera, Hemiptera and Orthoptera. The obviously homogeneous character of Lepidoptera and Coleoptera, although, probably, containing in every sub-class more species than the whole of Neuroptera, clearly disproves the existence of variety amongst their contents, equal to that amongst the contents of Neuroptera. Yet the power, although weakened, is by no means extinct; for, amongst the central group, Phalæna, we find the sub-classes, Papilio, Sphinx, Pyralis, Tinea, Noctua and Geometra, most faithfully pourtrayed in Lasiocampa, Ægeria, Cilix, Lithosia, Apatela and Orgyia, and not merely the individual genera which may happen to approach. As far as I can discover, after this second series of types the faculty becomes much weaker, and, after a third, ceases entirely. A decided difference existing between the first and second series of types, must on no account be lost sight of, because it so decidedly proclaims the superiority of the first: in the first instance, the whole character of the central type, Libellula, is completely lost in each of the varying types; whereas, in the second instance, the characters of Phalæna are preserved most decidedly to the remotest ramifications of the class, subject, however, to the variations already pointed out.
The natural order, Cossi, of which the larva and pupa have been already described, contains but ten genera, even including those whose claim to a place in the order is somewhat doubtful; and these ten are readily referable to six families. The genus, Stygia, of New Holland, seems from Latreille's description, decidedly to belong to this order. Speaking of Stygia Australis, he says, "M. Villiers la considère comme intermediare entre les Sesies et les Zygènes; mais elle n'a point de trompe; ses palpes sont ceux de Cossus; ses antennes sont courtes, et nullement en fuse, et plus analogues a celles de certains Bombyx qu'a celles des Sesies et des Zygènes."[57] Now the fact, as M. Latreille supposes, of having no antlia, argues most forcibly the impossibility of uniting this genus either with Sphinx or Zygæna; for the sub-class Sphinx not only possesses the most elongate and conspicuous antlia of any sub-class, but retains this character to its very circumference, and imparts it to approaching groups, whose types will be found entirely aglossate: its similarity therefore in shape to the Sesiæ, which tribe is generally understood to include the Ægeriæ, is merely that relation of imago which I have before so repeatedly pointed out. The situation, which without this genus must have been vacant, thus filled, gives us a most perfect chain of families throughout the order, except at the point of connexion with Phalæna, a point of no consequence, because it too much favours old theories to be contested.
It is rather remarkable, that in this order no instance should occur of more than three genera belonging to any one family, a number which I should hardly suppose complete, because a difficulty must always occur in placing, as in discovering the typical genus or species, where the number is confined to three.
The introduction of a new generic name, after what has been said on that subject, may appear rather an inconsistency, but I found it indispensable, as the species in question would not bend to either of the established genera, Trochilium or Ægeria; it will, moreover, afford those whose labours in this way I have somewhat deprecated, a fair opportunity for retaliation. The families and their relative situations, as far as my immature and hastily-formed judgment will allow me to decide, I have shown in the annexed diagram: but it is now time for me to describe the species whose situation I am endeavouring to point out.