Part 28
With regard to their _characters_, we are not to place our groups upon Procrustes' bed, and lop or torture them to accommodate them to every standard we may have fixed for them: assuming one set of characters for suborders, another for tribes, and so for every other group; for the value of characters varies,--those that in some cases are common to an _Order_, in others indicate only _sections_, or _tribes_, or _genera_ and _species_, or sometimes even _sexes_. What is constant in one group is not so in another, and _vice versâ_; so that it is a vain labour to search for a _universal_ character. If it is our wish really to trace the labyrinth of nature, we can only accomplish it by a careful perusal and examination of her various groups. It is singular how much and how far various Entomologists, and those of the very highest class, have been misled by a kind of _favouritism_ to give too universal a currency to certain characters for which they have conceived a predilection. Some have been the champions of the _antennæ_; others of the _trophi_; others again of the _wings_; and others of the _metamorphosis_. These are all characters which within certain limits lead us right, and are an index to a natural group; but if we follow them further, we leave the system of nature, and are perplexed in the mazes of a _method_[1264].
Let us now see whether we can pitch upon any suborder which will afford an example of every group that we have lately named. Mr. MacLeay, from a consideration of the larvæ of that Order, has divided the _Coleoptera_ into five primary groups that may be denominated _Suborders_. Whether these are all natural groups has not yet been made sufficiently evident. It answers my present purpose, however, to assume it as proved. I select therefore his _Chilopodimorpha_ for my suborder, altering the name as above proposed to _Chilopodimorph_it_a_: for my _Section_ I take the Predaceous beetles, or _Adephaga_ of M. Clairville, distinguished by having the upper lobe of their maxillæ biarticulate and palpiform;--these I would denominate _Adephag_an_a_, or devourers. They consist of two groups forming two subsections, the one _terrestrial_ and the other _aquatic_; which I would name, following Mr. MacLeay, _Geodephag_en_a_ and _Hydrodephag_en_a_. These two subsections are each resolvable into two _Tribes_ constituted by Linné's four genera _Cicindela_ and _Carabus_; _Dytiscus_ and _Gyrinus_. The first tribe, remarkable for the swiftness of their _flight_, I would name _Eupter_in_a_, or fliers; the second, equally noted for _running_, _Eutrech_in_a_, or runners; the third _Eunech_in_a_, or swimmers; and the fourth _Gyronech_in_a_, or swimmers in a circle. The second of these groups, the _Eutrech_in_a_, are resolvable into two other groups or _Subtribes_; one distinguished by having the cubit or anterior tibia _notched_, (which, from their being in general not very brilliant in colour, I would call _Amaur_on_a_, or obscure); the other having the cubit without a notch, (which, from the brilliancy of many of them, I would name _Lampr_on_a_, or splendid). These subtribes are both further resolvable into two or more _races_ (_Stirpes_). I select that to which the _crepitant_ _Eutrech_in_a_ belong, containing those which from their usually truncated elytra MM. Latreille and Dejean have named _Truncatipennes_[1265]: these, to shorten the name, I call _Truncipenn_un_a_. This brings us down to the lowest group formed out of genera and subgenera: or the _family_, which from its principal genus is named _Brachinidæ_, and which leads us to the _genus Brachinus_, and the _subgenus Aptini_. Thus we get the following scale, expressing every division of an Order, till we arrive at its lowest term, or the _species_ that compose it.
SUBORDER
_Chilopodimorph_it_a_ M^cL.
SECTION
_Adephag_an_a_ Clairv.
SUBSECTION
_Geodephag_en_a_ M^cL.
TRIBE
_Eutrech_in_a_
SUBTRIBE
_Amaur_on_a_
STIRPS
_Truncipenn_un_a_ Latr.
FAMILY
_Brachinidæ_
GENUS
_Brachinus_
SUBGENUS
_Aptini_.
In the construction of this scale I have endeavoured to steer clear of being led by any system, but, with the exception of the _Suborder_, which I assume, to resolve it into natural groups gradually decreasing in value, or tending to the lowest term, which appear all of them to have been considered as such by preceding Entomologists. The four _Tribes_ into which the two subsections _Geodephag_en_a_ and _Hydradephag_en_a_ appear resolvable, are not only distinguished by the characters of the perfect insect, but likewise by those of their larvæ, which are constructed on four distinct types; those of the _Gyronech_in_a_ being the most perfectly Chilopodimorphous of the whole, and those of the _Eunech_in_a_ the least so[1266]. The former appear rather to form an osculant tribe, or one without the circle, than one within it; and to be going off towards another section, including _Hydrophilus_, _Sphæridium_, &c. I must observe, that between _Dytiscus_ and _Hydrophilus_ there is a striking agreement both in their form and habits in the larvæ[1266], and even in several characters in the perfect insect; so as in many respects to generate a doubt whether they ought not to enter the same circle and to follow each other. Yet the change of habits in the latter, which from a carnivorous larva becomes a herbivorous beetle; the consequent change of structure in their oral organs, their antennæ, and other striking differences; and the evident intervention of the _Gyronech_in_a_ and some other osculant tribes between the two, forbid their union in one and the same circle.
vi. I need not say more on those larger groups of an Order which conduct us to what are denominated its _genera_; but upon these last it will not be a waste of your time to enlarge a little. In the last edition of the _Systema Naturæ_, and in its appendixes, Linné has described 2840 species of _Insecta_ and _Arachnida_, which he divided into 83 genera, allowing upon an average nearly 35 species to each genus. From the paucity of the materials, therefore, of which his system was constructed, there was no loud call upon him for numerous genera. But now more than thirty times that number are said to have found a place in the cabinets of collectors[1267], and there is good reason for thinking that perhaps half that are in existence are as yet undiscovered;--this makes it a matter of absolute necessity to subdivide the Linnean genera, which in fact, with regard to the majority of them, were the _primary_ groups of his Orders, rather than an approximation to the _ultimate_. But this principle may be carried too far: for it is the nature of man to pass from one extreme to the other: and this seems to me to be the case when it is proposed to make genera the _extreme_ term of subdivision before you arrive at species. But it is argued by a very acute Zoologist, that simplicity, perspicuity, and room for necessary variations are best preserved by distinguishing these subdivisions each by an appropriate name[1268]:--Granted. But still it is only a choice of evils. It would require probably more than 10,000 names to designate them, were every extreme group distinguished by a name: but if Mr. MacLeay's admirable pattern exhibited in his genus _Phanæus_[1269] were followed, it would not call for more than 2000--could the trifling difficulty occasioned sometimes by the discovery of a new group, be set against the advantage of having only 2000 names to commit to memory instead of 10,000[1270]? But if, after all, it is judged best to name subgenera, M. Savigny's excellent plan of distinguishing them by a plural termination would diminish the weight of the above objection, and might be used with advantage.
When the component parts of any minor group differ from another,--for the most part in important characters, indicating some tangible difference in their habits and economy, and confirmed by peculiarities in their larvæ; and these differences run through the whole, except that as usual they grow weaker as it is passing off to another; especially where they are striking in the centre or type of the group,--this is always a legitimate genus: but where the characters assumed are very slight, and nothing peculiar in its habits, economy or larva, warrant such distinction, it ought not to be conferred.
vii. I must next say a word concerning species and varieties. A _species_ is a natural object whose differences from those most nearly related to it had their origin when it came from the hands of its CREATOR; while those that characterize a _variety_, have been produced since that event. As we do not know the value and weight of the momenta by which climate, food, and other supposed fortuitous circumstances operate upon animal forms, we cannot point out any certain diagnostic by which in all cases a species may be distinguished from a variety;--for those characters that in some are constant, in others vary. In general, where there is no difference in _form_, _appendages_ and _organs_, _sculpture_, _proportions_ and _larvæ_,--_colour_ alone, especially in insects inhabiting the same district, only indicates a casual variety. Thus _Aphodius luridus_ has sometimes pale elytra with the striæ black (_Scarabæus nigro-sulcatus_ Marsh.): at others it has black spots between the striæ, as in the type: in a third variety the elytra are black at the base and pale at the apex (_Sc. varius_ Marsh.); and lastly, in a fourth they are intirely black (_Sc. gagates_ Marsh.);--yet all these in every other respect precisely correspond. But the converse of this will scarcely hold good; for doubtless minor differences of structure are sometimes produced by a different food and climate: which may probably account for some variations observable in the individuals apparently of the same species obtained from different countries.
* * * * *
Having considered the kind and value of the groups into which _Annulose_ animals, and more especially insects, may be divided, I shall next call your attention to their _composition_. There are _five_ numbers and their multiples which seem more particularly to prevail in nature: namely, _Two_--_Three_--_Four_--_Five_ and _Seven_. But though these numbers are _prevalent_, no one of them can be deemed _universal_. The _binary_ number, which affords the most simple, and for that reason perhaps not the least valuable, mode of arrangement, we see exemplified when two branches, so to speak, diverge from a common stem,--as in the _Vegetable_ and _Animal_ kingdoms; the _terrestrial_ and _aquatic_ Predaceous beetles; in the _thalerophagous_ and _saprophagous Lamellicorn_ ones; in the _Anoplura_ and _Thysanura_; the _Chilopoda_ and _Chilognatha_ amongst _Apterous_ insects; in the _Scorpionidea_ and _Aranidea_ amongst the _Arachnida_; and in the _Macrura_ and _Brachyura_ amongst the Decapod _Crustacea_. Again, in other cases _three_ seems to be the most prominent number: this takes place sometimes with regard to the _primary_ groups of an Order, or what I denominate the _Suborders_. Thus we have the _Diurnal_, _Crepuscular_, and _Nocturnal Lepidoptera_[1271]; the Linnean genera _Blatta_, _Mantis_, and _Gryllus_ constitute the _Orthoptera_; and other instances of this number might be produced in some minor groups. But that which appears to prevail most widely in nature is what may be called the _quaterno-quinary_; according to which, groups consist of four minor ones; one of which is excessively capacious in comparison of the other three, and is always divisible into two; which gives _five_ of the same degree, but of which, two have a greater affinity to each other than they have to the other three[1272]. Mr. W. S. MacLeay, in the progress of his inquiries to ascertain the station of _Scarabæus sacer_, discovered that the thalerophagous and saprophagous Petalocerous beetles resolved themselves each into a circle containing _five_ such groups. And having got this principle, and finding that this number and its multiples prevailed much in nature, he next applied it to the Animal Kingdom in general: and from the result of this investigation, it appeared to him that it was nearly, if not altogether, universal[1273]. Nearly at the same time a discovery almost parallel was made and recorded by three eminent Botanists, MM. Decandolle, Agardh, and Fries, with regard to some groups of the Vegetable Kingdom[1274]; and more recently Mr. Vigors thinks he has discovered the same quinary arrangement in various groups of birds[1275]. This is a most remarkable coincidence, and seems a strong argument in favour of Mr. MacLeay's system. I should observe, however, that according to that system, as stated in his _Horæ Entomologicæ_, if the osculant or transition groups are included, the total number is _seven_[1276]:--these are groups small in number both of genera and species, that intervene between and connect the larger ones. Each of these osculant groups may be regarded as divided into _two_ parts, the one belonging to the _upper_ circle and the other to the _lower_; so that each circle or larger group is resolvable into five _interior_ and two _exterior_ ones, thus making up the number _seven_. Though Mr. MacLeay regards this quinary arrangement of natural objects as very general, it does not appear that he looks upon it as absolutely universal,--since he states organized matter to begin in a dichotomy[1277]: and he does not resolve its ultimate groups into five species; nor am I certain that he regards the penultimate groups as invariably consisting of five ultimate ones. In _Copris_ I seem in my own cabinet to possess ten or twelve distinct types[1278]; and in _Phanæus_, the fifth type, which Mr. MacLeay regards as containing insects resembling all the other types[1279], appears to me rather divided into _two_; one formed by _P. carnifex_, _Vindex_, _igneus_, &c., and the other by _P. splendidulus_, _floriger_, _Kirbii_, &c.
The great point which demands our attention in considering a numerical arrangement of the Kingdoms of Nature is the _value_ of the component members of each group. It is by no means difficult to divide a _Kingdom_, a _Class_, or an _Order_ into two, or three, or five, or seven or more groups, according to any system we may be inclined to favour; but it is not so easy to do this so that the groups shall be of equal rank. Yet it seems requisite that in grouping our objects, as we descend towards the lowest term we should resolve each only into its primary elements, and of them form the next group; and so on till we come to species. When I say of _equal rank_, I do not mean an exact parity between the members into which a group is primarily resolvable,--because there will always be a degradation _in descensu_ from the perfection of the type; but merely that parity (to use a metaphor) that there is between children of the same mother, differing in their relative ages and approach to the perfection of their nature. Perhaps it may be observed with respect to the quinary system, that this condition is not complied with, since two of the groups taken _per se_ appear really to form one group; or to be much nearer to each other than to the remaining groups. But when it is taken into consideration that this great group, always resolvable into two, is the typical group, and that the two are really equal, or rather superior in value to the three others, the objection seems to vanish.
With regard to all numerical systems we may observe, that since variation is certainly one of the most universal laws of nature, we may conclude that different numbers prevail in different departments, and that all the numbers above stated as prevalent are often resolvable or reducible into each other. So that where Physiologists appear to differ, or think they differ, they frequently really agree.
II. The ALMIGHTY CREATOR, when he clothed the world that he had made with _plants_, and peopled it with _animals_, besides the manifestation of his own glory, appears to have had _two_ most important purposes in view;--the one to provide a supply for the mutual wants of the various living objects he had created, for the continuance of the species, and for the maintenance of a due proportion, as to numbers, of each kind, so that all might subserve to the good of the whole; and the other, that by them he might _instruct_ his creature man in such civil, physical, moral and spiritual truths, as were calculated to fit him for his station in the visible world, and gradually prepare him to become an inhabitant of that invisible one for which he was destined. The first of these purposes was best promoted by creating things "according to their kind," with sexes monœcious or diœcious; that groups of beings related to each other, and agreeing in their general structure, might discharge a common function. This we see to be the case generally in nature; for where there is an affinity in the _structure_, there is usually an affinity in the _function_. The last,--or the instruction of man in his primeval state of integrity and purity,--was best secured by placing before him for his scrutiny a book of emblems or symbols, in which one thing either by its form or qualities, or both, might represent another. If he was informed by his Creator that the works of creation constituted such a book, by the right interpretation of which he might arrive at spiritual verities as well as natural knowledge, curiosity and the desire of information concerning these high and important subjects would stimulate him to the study of the mystic volume placed before him; in the progress of which he would doubtless be assisted by that DIVINE guidance, which even now is with those who honestly seek the truth. Both divines and philosophers have embraced this opinion, which is built upon the word of GOD itself[1280].
This last purpose of the Creator was the root of the analogies, connecting different objects with each other that have no real affinity, observable in the works of creation: so that from the bottom to the top of the scale of being, there is many a series of analogous forms, as well as of concatenated ones; and the intire system of nature is _representative_, as well as operative: it is a kind of _Janus bifrons_, which requires to be studied in two aspects looking different ways. To what degree of knowledge the primeval races of men attained after the fall, by the contemplation and study of this book of nature, we are no where informed; but we learn from the highest authority that the revelation that GOD thus made of himself was in time corrupted, by those that _professing_ themselves to be _wise_ became _fools_, to the grossest idolatry, which sunk men in the lowest depths of sensuality, vice, and wickedness[1281].
In no country was this effect more lamentably striking than in Egypt, whose gods were all selected from the animal and vegetable kingdoms.
"Who knows not to what monstrous gods, my friend, The mad inhabitants of Egypt bend? The snake-devouring ibis these inshrine, Those think the crocodile alone divine; Others where Thebes' vast ruins strew the ground, And shatter'd Memnon yields a magic sound, Set up a glittering brute of uncouth shape, And bow before the image of an ape! Thousands regard the hound with holy fear, Not one Diana:--and 'tis dangerous here To violate an onion, or to stain The sanctity of leeks with tooth profane. O holy nations, in whose gardens grow Such deities!" JUV.
This species of idolatry doubtless originally resulted from their having been taught that things _in_ nature were symbols of things _above_ nature, and of the attributes and glory of the Godhead. In process of time, while the corruption _remained_, the knowledge which had been thus abused was _lost_ or dimly seen. The Egyptian priesthood perhaps retained some remains of it; but by them it was made an esoteric doctrine, not to be communicated to the profane vulgar, who were suffered to regard the various objects of their superstitious veneration, not as _symbols_, but as possessed of an _inherent_ divinity: and probably the mysteries of Isis in Egypt, and of Ceres at Eleusis, were instituted, that this esoteric doctrine, which was to be kept secret and sacred from the common people, might not be lost.
But this kind of analogy is of a higher order than that of which I am here principally to speak,--that, namely, which the various objects of nature bear to each other. This, however, though of a lower rank, is essentially connected with the other, and leads to it; for it establishes the principle, that created things are representative or symbolical: and we find, when we view them in this light, that as we ascend from the lowest beings in the scale of creation, we are led from one to another till we reach the summit or centre of the whole, and are thus conducted to the boundaries of this visible and material system; from whence we may conclude that we ought not here to stop, but go on to something invisible and extra-mundane, as the ultimate object intended to be reflected from this great speculum of creation--the CREATOR himself, and all those spirits, virtues, and powers that have emanated from him.
The _analogies_ which the various objects of the animal kingdom mutually exhibit, have for the most part been either overlooked by modern Physiologists, or have been mistaken for characters that indicate _affinity_; a circumstance that has often perplexed or disrupted their systems. Dr. Virey appears to have been one of the first who obtained a general idea of the parallelism of animals in this respect[1282]; and M. Savigny has contrasted the _Mandibulata_ and _Haustellata_ of the insect tribes as presenting analogies to each other[1283]. But a countryman of our own (often mentioned with honour in the course of our correspondence), peculiarly gifted by nature, and qualified by education and his line of study for such speculations, and possessing moreover the invaluable opportunity of consulting at his ease one of the first Entomological cabinets in Europe, in a work that will for ever couple his name with the science that he cultivates[1284],--has first taught the Naturalist the respective value and real distinctions of the two kinds of relationship that I am now discussing. He has opened to the philosopher, the moralist and the divine, that hitherto closed door by which our first parents and their immediate descendants entered the temple of nature, and studied the symbols of knowledge that were there presented to them: and in addition to his labours (in numerous respects successful), in endeavouring to trace out the natural groups of beings connected by _affinity_, has pointed out how they illustrate each other by _analogy_; thus affording, as was before observed[1285], a most triumphant reply to the arguments of those modern sophists, who, from the graduated scale of affinities observable in creation, were endeavouring to prove that animals, in the lapse of ages, were in fact their own creators[1286].
For the more satisfactory elucidation of the subject before us, I shall consider, first, how we are to distinguish affinities from analogies; and then mention some of the various instances of the latter that occur between insects and other animals, and between different tribes of insects themselves.