Part 3

A second fancy which I wish to combat is, that of analogy and affinity; and as Mr. MacLeay is by far the most learned and competent advocate of these distinct descriptions of resemblance, and as I cannot pretend to refer to or cope with the voluminous writings extant on this subject, I am necessitated to allude to his work alone. It will be seen by the _Horæ Entomologicæ_, (a work which I have already spoken of with unfeigned admiration,) that Mr. MacLeay considers that relation observable in the general appearance, habit, food, metamorphosis, &c. of insects, a relation of analogy, while that dependent solely on a fancied resemblance in the mouth he considers a relation of affinity: thus classes V. and VI., which, in five characters out of six, agree as closely as such comprehensive classes can do, he considers related by analogy, and classes I. and VI., which, in five characters out of six, are as unlike as insects can be, he considers related by affinity;[25] so Dr. Johnson, when he calls affinity "resemblance," must have made a capital blunder, for Mr. MacLeay proves clearly that it means dissimilarity. Classes I. and VI. however, I find will meet as the line becomes bent into a circle, and therefore we must conclude it to be a hidden affinity, for it certainly is not apparent; and moreover it must be remarked, that the relation between classes is but little apparent generally, except they are taken in pairs: thus, between I. and II., between III. and IV., and between V. and VI., the relation is real and readily ascertained, although distant; while between II. and III., between IV. and V., and between VI. and I., it becomes scarcely traceable. It is also worthy of notice, that the contents of either pair of classes, with the addition of class VII., may be formed into a tolerably perfect chain of genera, indeed with much less appearance of disconnexion than is observable on passing from either pair into the next pair,--a fact which attaches a degree of importance to the number three, on which, perhaps, at a future time, more may be said,--and thus a chain of relation would be established in each instance, leaving four whole classes entirely out of the question;--a chain which would steadily pursue its way, regardless and in open violation of all established laws of analogy, affinity and dichotomy; laws which I hope ere long to see pining away like Echo, until they also are really what I now fully believe them to be, _vox et præterea nihil_.

[25] Horæ Entomologicæ, p. 367.

Mr. MacLeay found that in his quinary groups one of each five contained genera or species related to other genera or species in each of the other four groups. That I may be thoroughly understood, I will quote the author's own words:--"In almost every group which has been set before the reader, he must have perceived that one of the five minor groups into which it is resolvable, bears a resemblance to all the rest; or, more strictly speaking, contains types which represent each of the four other groups, together with a type peculiar to itself."[26] As far as my observation has extended, this is universally the case; and whether the total number of groups be five or seven, I think I am safe in asserting that the only possible way of making these types, thus representing groups, approach such groups, is to place the heterogeneous group in the centre, and the homogeneous groups around it; taking care that the type peculiar to itself be its very centre, its "heart's core." Such a heterogeneous group, then, is Neuroptera: its characters as given,[27] I believe, perfectly correct; and can any one say they are sufficient? Certainly not; but had I described it thus--Class VII. Neuroptera, central, partaking of the characters of all the others, I think a better character could not have been given. This class contains a type peculiar to itself--the genus Libellula of Linnæus: a genus so distinct, that several authors have supposed it to constitute one of the primary divisions of Insecta. It is, however, merely the Neuropterous type, the very essence of the class; and many of its species, Anax Imperator for instance, proclaim themselves by their imperial flight, their enormous size, their richly variegated colours, their despotic and cruel habits, emperors of the insect world. In this group we find the organs of sight, manducation, and locomotion, carried to a greater degree of perfection than we ever meet with, except in similar centres: like the king of birds, the dragonfly is unrivalled among his kind. From Libellula, the centre, we descend at once to Tinodes, or Psyche, on the circumference of the circle. Supposing Psyche to be the approaching genus to Lepidoptera, I think I need not enter very diffusely on the similarities. Passing to the right, we find that Diptera will next touch the central class; in which, after leaving the Phryganeæ, we have now arrived among the next group, or sub-class, Ephemeræ: and here, as we might expect, the inferior wings become much diminished--at the point of contact obsolete.[28] The flight, instead of being solitary, is in company, gracefully and gently rising and falling. The parts of manducation are become obsolete; while, in habit and appearance, the insect imitates the Tipulæ and Chironomi, so exactly that the naturalist is foiled in his endeavours to distinguish between them, as they joyously dance together by myriads in the rays of the setting sun.

[26] Horæ Entomologicæ, p. 518.

[27] See the Table.

[28] In Cloëon.

We now approach mandibulated orders, and we shall see the loss of mandibles in Phryganea and Ephemera, although apparently resulting naturally enough from their distance from the type Libellula, has yet another cause--the proximity of classes that have no mandibles: in the city-building Ants, the mandibles are very perfect, and, therefore, we may expect them, and we find them in the city-building Termites. The opinion of philosophers, such as the authors of the _Introduction to Entomology_, is always worth having, although I am doubtful of assertions about insects, when unconfirmed by thorough entomologists; and I believe as yet no entomologist is sufficiently acquainted with the real history of white ants, to decide positively as to their different stages of existence. The following quotation contains also a corroboration of the propriety of this approach:--"The white ants, though they belong to the Neuroptera order, borrow their instinct from the hymenopterous social tribes, and, in conjunction with the ants, (Formica,) connect the two orders. Their societies consist of five descriptions of individuals:--workers, or larvæ; nymphs, or pupæ; neuters, or soldiers; males and females."[29] The class Coleoptera now approaches the Neuroptera, and on each side the boundary we find larvæ digging pitfalls in the sand to catch their prey, and having tubular mandibles to extract its juices when caught. We find them spinning silken cocoons, in which they change into quiescent pupæ, incapable of taking nutriment; which may fairly be supposed a symptom of approach; but there is no insect whose imago I would venture to place on the circumference of the neuropterous circle at the point.

[29] Introduction to Entomology, Vol. II. p. 32.

When we find an insect so doubtfully situated between two classes, that Linnæus placed it in Neuroptera, Fabricius in Orthoptera, Latreille, in two of his works, in Orthoptera, and in two others in Neuroptera, MacLeay in Neuroptera, and Kirby and Spence in Orthoptera, I think it but fair to conclude, that the orders must approach very nearly to admit of this difference of opinion: such is Mantispa; and Mantis-like as it really is, it only borrows that appearance from being on the extreme circumference of the Neuropterous circle, and touching the Orthopterous one where Mantis must evidently be situated. Lastly, we see in Psocus the form, wings, and whole appearance of Aphis, so exquisitely imitated, that practised entomologists often, nay mostly, fail in separating them correctly: thus we find that class VII. contains five natural orders, the contents of which have been--and may be again, should the linear and dichotomous system continue in vogue--placed either in the class to which they truly belong, or respectively in classes I. II. III. V. and VI. at the mere option and caprice of the systematist. I have already admitted that I find no neuropterous insect sufficiently related, in its final state to class IV. to warrant my placing it in contact with that class; and that I may not be accused of assuming facts which exist only in my imagination, I am perfectly willing to conclude that no such insect is to be found; a conclusion that time and discovery, by falsifying, can only add yet one more buttress to a tower, which nature seems to point out as built by herself.

There are a few little insects which, like the spiders which crept across Richard's brain, are somewhat perplexing to the naturalist, yet he cannot dispose of them as the monarch did of his spiders; I mean Pulex, Stylops, Thrips, Forficula. But, in truth, the first attempt of the systematist should be to place classes properly, and these disconnected species will, after a time, find appropriate places: they were no more created without a design than man; and their Creator, doubtless, has appointed them a station, although man, whose wisdom is utter ignorance, has not yet been able to discover it. It is impossible for the entomologist not to observe the general similarity, the family likeness if I may so express it, which exists between these genera; they appear a little way removed from Coleoptera, yet will not harmoniously join that class. Thrips is evidently mandibulated, although the dichotomists call it haustellated, and comes nearer to Stylops[30] than any other known genus: its larva is, I believe, unknown; but in March you may observe an active hexapod, lizard-like animal, running about the flowers of Ranunculus ficaria on sunny banks, and two or three months later you will find Thrips abundant on the same flowers in the same spots: this is no proof of their identity; but as the larva of Thrips and the imago of the said hexapod are equally unknown, there may be a surmise expressed on the subject. Mr. Kirby calls this hexapod Pediculus Melittæ, and has given a description and plate of it in his _Monographia Apum_.[31] He there asserts that De Geer considered it the larva of the Melöe proscarabæus, and some observations of my esteemed friend, Mr. Doubleday, who succeeded in obtaining the larva of Melöe from the egg, certainly tended to corroborate De Geer. But I am rather wandering from my subject, and, therefore, will consider these little creatures also, wandering like comets in eccentric courses over the whole system, now approaching Staphylinus, and anon Ichncumon, and, as they draw near, borrowing a character from each: they may, on the other hand, constitute disconnected links of some other mighty chain, the intervening parts of which are for a time hidden from the sight of man, and perhaps hereafter may be revealed; perhaps, again, they may occupy some of the chasms I have been compelled to leave vacant: but I deprecate, I detest the idea, of forcing any creature into a situation which nature has not evidently pointed out as its appropriate one, for the ignoble purpose of giving plausibility and imperfect perfection to a scheme.

[30] For a beautiful and accurate figure and dissections of this rare insect, see Curtis's Entomology, pl. 226: for a _popular_ figure, _Professor-edly_ of the same insect, see Insect Transformations, p. 67.

A little knowledge is a dangerous thing. Drink deep, or taste not the Pierian spring.

[31] Monographia Apum, Vol. II. p. 168.

ON THE SUB-CLASSES, &c. OF LEPIDOPTERA.

It may be thought a strange propensity to grapple with difficulties, that leads me to select Lepidoptera as a class, by which to exemplify, in detail, the septenary and circular arrangement. There is no class so puzzling to systematists, or for which science has done so little--no class is at present so badly arranged, and in none are barbarous combinations so much in vogue. Linnæus founded divisions at the outset, on characters, "loose, vague, and insufficient:"[32] modern genera have a little improved minor details, and but little, for their places appear to have been assigned them by lot, and without the slightest regard to similarity or approach: in a word, the arrangement of Lepidoptera appears to have been conducted by collectors, who aimed rather at a pretty picture than a related series; and all our writers have rushed headlong by the same path, without staying an instant to consider whether they were right or wrong, like boys playing at follow-the-leader,[33] each occasionally leaping some wider gap, or descending some more dangerous precipice than his predecessor, as though for the very love of frolic and bravado. _One_, a talented writer, an assiduous collector, a most accurate observer, hesitated awhile, it is true, and it was thought he would have broken the line, but no,--he kept precisely to the track of Linnæus and the rest of them, through Papilio, Sphinx, Bombyx, Noctua, Geometra, Pyralis, Tortrix, and Tinea; but, as he stood pledged to traverse no more than five fields, he hit on the ingenious expedient of asserting roundly, that the four last named were but one. In fact, the whole of this immense class presents, at this hour, nothing but a vast chaos, which seems to await the operation of some predicted spell to call it into order.

[32] Particularly in the sections of Papilio.

[33] Linnæus.

These were apparent difficulties only; for, as no system existed to direct, so none existed to encumber or perplex. Too much is known now of Linnæan combinations, to assert, that he always thought correctly; and since his day no one has thought at all. Now, if you cannot obtain a nicely drawn plan, you prefer having a blank sheet of paper to one covered all over with scorings and markings, and then you may set to work and make your plan yourself. So, in natural history, contrariety of opinion perplexes, while the absence of opinion leaves the systematist perfectly unbiassed in the formation of his own. Again, copious and well-named[34] collections of this favourite class are by no means uncommon;[35] and through, the liberality of my friends, I had often been permitted to inspect them, and had gained a sufficient superficial knowledge of their contents, to be enabled, with the assistance of my own specimens, to cluster them pretty well into seven great families or sub-classes; and although, as I have noticed, nothing available existed on the subject of arrangement of Lepidoptera, either in essay, or treatise, or catalogue, or cabinet, yet there was to be found, up and down, much valuable matter, in the shape of what might be termed natural history of Lepidoptera. Finally, I knew, that could I master this class, I could stand my ground, because I had previously tried the experiment on the classes Hymenoptera and Coleoptera, and had found that, at the word seven, they fell into instant order, as at the touch of a magician's wand; and, as for the other classes, we are in such innocent and blissful ignorance of their contents, that were a scheme ever so futile, a century at least must elapse before its futility could be proved by Orthoptera, Hemiptera, or Diptera.

[34] I mean each species labelled with _a_ name.

[35] _British_ collections.

Whoever will give himself the trouble to examine thoroughly a collection of British Lepidoptera, will find a very great majority of them evincing very evident symptoms of relation to one or other of the following species:--Papilio Machaon, Sphinx Ligustri, Pyralis verticalis, Tinea pellionella, Noctua pronuba, and Geometra roboraria; and should any form widely different from either of these occur, it may, if the larva be known, be placed in the centre of a ring formed by the groups, which we will suppose surrounding their six respective types; or, if its larva be unknown, it must await the discovery of that most unerring stage of its existence. I am persuaded, did entomologists know how much depends on the form, habit, food, and clothing of larvæ, they would not be so neglected as they are at present. I have much to regret my own remissness in this respect, for it has seldom happened that I have found the larva of any insect which had not been previously well known, but it has tended to point out some approaches that had never before been thought of,--approaches, even when thus pointed out, totally irreconcilable with existing ideas of arrangement and combination of groups, but which now open to my view the most beautiful chains of affinities; and wonderfully but indubitably prove, that a single individual may be related to three, four, or even more apparently disconnected groups.

Perhaps no better genus was ever formed than Papilio of Linnæus; its diurnal flight, its erect wings, and its clavated antennæ, at first bid defiance to the systematist who attempts to bring any other group into contact with it; indeed, in Britain we have nothing at all that will avail us in this respect, which compels me to have recourse to exotics, an assistance which I shall only avail myself of when I find it quite impracticable to furnish the approaches from indigenous species, the reference to which is attainable by every entomologist. Among foreign Papiliones, especially among those groups which approach our genera, Hesperia, Lycæna, Polyommatus, and Thecla, there appears to be an almost infinite variety of form. Now it is but reasonable to seize on any variations observable in genera or species from the prominent or typical genus or order from which they may be supposed to derive their more conspicuous character, and to employ such variations in arrangement as connecting links between the group to which they more decidedly belong, and the group to which, by such variation, they evince an approach: a precisely intermediate species or genus between two classes or sub-classes, or even orders, I have never met with, notwithstanding the renowned Linnæan maxim, that _Natura saltus non facit_; for did nature make no leaps, surely the question were immediately at rest as to the existence of any other division than species among created beings, a conclusion which even the most strenuous supporters of the Linnæan dogma decidedly resist. Among the Papiliones, this departure from the type may be looked for either in the form of the antennæ, the position of the wings, or the time of flight. The first is obviously the most tangible should it occur, and it does occur. In Urania, the antennæ have become setaceous; the club has entirely disappeared, yet the other peculiarities remain much as in Papilio. This single deviation may be assumed as pointing out a relation to Geometra, which the reader will perceive is supposed to meet the sub-class Papilio at this point. A second peculiarity is to be found in an insect figured by Godart, a Polyommatus in shape, but with pertinated antennæ;[36] the genus he has very suitably named Barbicornis. This deviation, it must be observed, is in favour of the Bombyces, which we therefore suppose touching the sub-class at this point. A third deviation, of a very different kind, is observable in an insect which Latreille has figured in the Règne Animal, and placed among the Sphinges: he calls it Coronis D'Urvillii. The antennæ in this genus, as in Castnia, are gradually incrassated, and they may probably be eventually both considered as Papiliones: of Coronis D'Urvillii, I cannot entertain a doubt, as the wings are too expansive, the antennæ too long, the abdomen too short for it ever to retain its station among the Sphinges; the inferior wings are also very decidedly caudate, a common formation among Papiliones, but unknown among Sphinges; but, let this question be eventually decided _pro_ or _con_, the approach between Hesperiæ and Sphinges is not likely to be disputed, nor the fact that it takes place somewhere in the neighbourhood of the genus Castnia.

[36] Latreille seems to think this to have been a deception, and that the antennæ which Godart found on the insect did not belong to it. I cannot suppose that the latter author could have been so grossly deceived.

The next type is Sphinx Ligustri; and here again our British collections are obliged to plead poverty; few, however, as they are at present, I am compelled, if I purpose consulting nature, to reduce them about half: the Ægeriæ and Zygænæ must be moved elsewhere; they look like Sphinges, but are none. I will begin then with Castnia, of which no more need be said. The next striking departure from the type occurs in having the abdomen furnished with tufts or brushes, which the insect spreads as it hovers over flowers, somewhat in the manner of a bird's tail. The long porrected antlia also has a resemblance, perhaps rather fancied than real, to the slender bill of a humming-bird, whence the tribe has received with us the name of English humming-birds. The genus Sesia I will place on the circumference of the circle, not doubting but nearer approaches to the Cossi may be discovered, or are even now known, but no better exists among our own Sphinges. The next point of contact will be with Pyralis; and here the genus OEgocera, figured in the Règne Animal, seems to claim its station: it is a decided Sphinx, with the palpi of Hypena proboscidalis, and Latreille has placed it between Sesia and Zygæna, from which it will be seen that I differ only in making Zygæna pass over the boundary line and into the next section.