CHAPTER VII.

CONCLUSION

Depositâ sarcinâ, levior volabo ad coe lum.--_S. Jerome._

Having now completed the short task which I had undertaken to perform, I will, in conclusion, offer a few brief comments on the results at which we have arrived, and endeavour to realize to what extent the consideration of them is likely to be found useful, during our inquiries into the general subject of entomological geography.

Commencing with the thesis, that specific variation, whether as a matter of experience or as probable from analogy, does _ipso facto_ exist; I have endeavoured to maintain that position, by evidence of divers kinds; and I have sought to strengthen the inferences deduced, by an appeal to some of those external agents and circumstances which may be reasonably presumed (if not indeed actually demonstrated) to have had a considerable share in bringing it about. I have also suggested what the principal organs and characters are, in the Insecta, which would appear to be more peculiarly sensitive to the action of local influences; and I have then diverged to the question of topographical distribution, in connection with the geological changes on the earth's surface; and, lastly, to some practical hints arising out of a proper interpretation of the generic theory. How far I have succeeded in elucidating the several points which I proposed to examine, is a problem which must be solved by others; meanwhile, if I have failed at times to interpret what seems scarcely to admit of positive proof, I shall at least have had the advantage of propounding the enigmas for discussion, and of so paving the way for future research. We must remember, however, that, where certainty is not to be had, probability must be accepted in its stead; or, as an old writer has well expressed it: "That we ought to follow probability when certainty leaves us, is plain,--because it then becomes the only light and guide that we have. For, unless it is better to wander and fluctuate in _absolute_ uncertainty than to follow such a guide; unless it be reasonable to put out our candle because we have not the light of the sun, it _must_ be reasonable to direct our steps by probability, when we have nothing clearer to walk by".[84]

What my chief aim in the present treatise has been, will be easily perceived,--namely, to substantiate, as such, those _elements of disturbance_ (on the outward contour of the Annulose tribes) with which the physical world does everywhere abound: and, thereupon, to provoke the inquiry, whether entomologists, as a mass, have usually taken them into sufficient account, when describing as "species," from distant quarters of the globe, insects which recede in only minute particulars from their ordinary states. My own impression is, that they have not done so; and, moreover, that, if they had, our catalogues would have worn a very different appearance to what they now do: for, when once the subject is fairly looked into and analysed, it is impossible not to be convinced, that the _primâ-facie_ aspect of these creatures is eminently beneath the control of the several conditions to which they have been long exposed. But let me not be misunderstood in the conclusion which I have been thus compelled to endorse, or be supposed to ignore the fact that truly _representative species_ may frequently occur in countries far removed from each other; which cannot therefore be regarded as modifications of a common type. I believe, however, that this doctrine of _representation_, whatever truth it may contain, has been too much relied upon; and that we have been over-ready to take advantage of it (unproved as it is) for the multiplication of our, so called, "specific novelties." I suspect, indeed, that _actual_ representative species (if they may be thus expressed) are more often to be recognized on the isolated portions of a formerly continuous tract, than in regions which have been widely separated since the last creative epoch; and that, in the instances where beings of a _nearly_ identical aspect are detected in opposite divisions of the earth, it is more often the case that members of them have been transported at a remote period (either by natural or artificial means) from their primæval haunts, and have become gradually altered by the circumstances amongst which they have been placed, than that the respective phases were produced _in situ_ on patterns almost coincident.

I have before announced my conviction, that _generic areas_ have a real existence in Nature's scheme; and that, consequently, where species which are so intimately allied that they can with difficulty be distinguished, prevail, there is presumptive reason to suspect (until at least the contrary is rendered probable) that the areas which they now colonize were once connected by an intervening land,--or, in other words, that the migrations of the latter were brought about, through ordinary diffusive powers, from specific centres within a moderate distance of each other. I say "_presumptive_ reason," because there are undoubted exceptions to this law (as to every other), and it can therefore be only judged of on a broad scale. Still, I contend that in a wide sense it holds good; and that, consequently, if closely related "species" are traceable in countries which geology demonstrates to have been far asunder during the _entire_ interval since the first appearance of the present animals and plants upon our earth, there is at any rate an _à priori_ probability that they are no _species_ at all,--but permanent geographical states, which have been slowly matured since their casual introduction beyond their legitimate bounds.

If we except those forms which are in reality but modifications, from climatal and other causes (and which have, therefore, been wrongly quoted as distinct); I believe that a vast proportion of the species which have been usually considered to be "representative" ones, were members, in the first instance, of the self-same assemblages,--which had wandered to a distance from their primæval haunts, and were afterwards, through the submergence of the intervening land, cut off from their allies. I have adduced, in a preceding chapter, some remarkable examples in illustration of this hypothesis,--an hypothesis which I believe to be the true clue to a very large item of the "specific representation" theory. A considerable number of the Madeiran _Helices_ may be cited (which I have already done[85]) as, in the strictest sense, representative of each other,--and as therefore specifically distinct: and I may add, that it is to island groups that we must mainly look for this system in its full development.

But, apart from the fact that I would not wish to resign _in toto_ the doctrine of "specific representation," even as frequently understood (that is to say, as recognizable in countries which have been altogether disconnected since the last creative epoch), and therefore, _à fortiori_, in what I conceive to be its truer meaning; there is yet another point on which I would desire to be interpreted aright, whilst endeavouring to substantiate the action of local influences on the members of the insect world. It has been my aim, in the preceding pages, to call attention to the importance of external circumstances and conditions in regulating, within definite limits, the outward aspect of the Articulate tribes.

I do not, however, assert that _every_ species is liable to be interfered with _ab extra_; that is a question which the greater or less susceptibility of the several races, as originally constituted, can alone decide; still less would I willingly lend a helping hand to that most mischievous of dogmas, that they are _all_-important in their operation,--or, in other words, that they possess within themselves the inherent power (though it may not invariably be exercised) of shaping out (provided a sufficient time be granted them, and in conjunction with the advancing requirements of the creatures themselves) those permanent organic states to which the name of species (in a true sense) is now applied. Such a doctrine is in reality nothing more than the transmutation theory, in all its unvarnished fulness; and I do not see how it can be for a moment maintained, so long as facts (and not reasoning only) are to be the basis of our speculations. I repeat, that it is merely _within fixed specific bounds_ that I would advocate a freedom of development, in obedience to influences from without: only I would widen those limits to a much greater extent than has been ordinarily done,--so as to let in the controlling principle of physical agents, as a significant adjunct for our contemplation.

It does indeed appear strange that naturalists, who have combined great synthetic qualities with a profound knowledge of minutiæ and detail, should ever have upheld so monstrous a doctrine as that of the transmission of one species into another,--a doctrine, however, which arises almost spontaneously,--if we are to assume that there exists in every race the tendency to _an unlimited progressive improvement_. There are certainly no observations on record which would, in the smallest degree, countenance such an hypothesis. Many animals and plants, it is true, are capable of considerable modifications and changes, for the better,--very much more than is the case with others. But what does this prove, except that their capacity for advancement has a slightly wider compass than that of their allies? It touches not the fact, that the boundaries of their respective ranges are absolutely and critically defined. It is moreover a singular phænomenon, and one in which the strongest proofs of design (or a primary adjustment of limits with a view to the future) may be discerned, that the members of the organic creation which display the greatest adaptive powers, are those which were apparently destined to become peculiarly attendant upon man. "The best-authenticated examples," says Sir Charles Lyell, "of the extent to which species can be made to vary may be looked for in the history of domesticated animals and cultivated plants. It usually happens that those species which have the greatest pliability of organization, those which are most capable of accommodating themselves to a great variety of new circumstances, are most serviceable to man. These only can be carried by him into different climates, and can have their properties or instincts variously diversified by differences of nourishment and habits. If the resources of a species be so limited, and its habits and faculties be of such a confined and local character, that it can only flourish in a few particular spots, it can rarely be of great utility. We may consider, therefore, that in the domestication of animals and the cultivation of plants, mankind have first selected those species which have the most flexible frames and constitutions, and have then been engaged for ages in conducting a series of experiments, with much patience and at great cost, to ascertain what may be the greatest possible deviation from a common type which can be elicited in these extreme cases[86]."

The fact, however, that all areas of aberration (however large they may be) are positively circumscribed, need scarcely be appealed to, in exposing the absurdity of the transmutation hypothesis. The whole theory is full of inconsistencies from beginning to end; and from whatever point we view it, it is equally unsound. How, for instance, can any amount of local influences, or the progressive requirements of the creatures themselves, give rise to the appearance of several well-marked representatives of a genus on the self-same spot,--where the physical conditions for each of them are absolutely the same? Look, for example, at the _Tarphii_ (to which I have already alluded[87]) of Madeira: I have detected about eighteen abundantly defined species; and, as stated in a previous chapter, I have but little doubt, from their sedentary habits, and the evident manner in which they are adjusted to the peculiarities of the region in which they obtain, that they are strictly an esoteric assemblage, inhabiting the actual sites (or nearly so) of their original _début_ upon this earth. Here, then, we have a sufficient length of time for developments to have taken place; they are all exposed to the self-same agencies from without (for they live principally in communion); yet, though I have examined carefully more than a thousand specimens (a large proportion of them beneath the microscope), I have never discovered a single intermediate link which could be regarded as in a transition state between any of the remainder. But how is this?--Is it possible to account for differences so decided, yet each of such amazing constancy, amongst the several creatures of a central type which have been exposed to identical conditions through, at any rate, generations innumerable? They clearly cannot be explained on the doctrine of transmutation: yet they are no exceptions to the ordinary rule,--occupying an analogous position to the members of every other endemic group.

But I will not occupy more space on the transmutation theory: suffice it to have shown that, in thus conceding a legitimate power of self-adaptation, in accordance with external circumstances, to the members of the insect world; and in suggesting the inquiry, whether the action of physical influences has been adequately allowed for by entomologists generally (or, in other words, whether the small shades of difference which have often, because permanent, been at once regarded as specific, may not be _sometimes_ rendered intelligible by a knowledge of the localities in which the creatures have been matured), I do not necessarily open the door to the disciples of Lamarck, or infringe upon the strict orthodoxy of our zoological creed. On the contrary, indeed, I believe that the actual reverse is nearer the truth; and, moreover, that those very hyper-accurate definers who recognize a "species" wheresoever the minutest decrepancy is shadowed forth, will be found eventually (however unaware of it themselves) to have been the most determined abettors of that dogma,--seeing that their species, if such they be, do most assuredly pass into each other.

We must not, however, omit to notice, briefly, how this perversion of Nature's economy took its rise. It was from the desire, which is almost inherent within us, to account for everything by physical laws; and to dispense with that constant intervention of the direct creative act which the successive races of animals and plants, such as are proved by geology to have made their appearance at distinct epochs upon this earth, would seem to require. Or, which amounts to the same thing, it resulted through an endeavour to explain by material processes what is placed beyond their reach. But, if this be the case, it may be reasonably asked,--Are material laws then not to be inquired into, and should the various influences which operate in the organic world around us be debarred from analysis? Unquestionably not. Truth is truth, under whatever aspect it may come; and cannot possibly contradict another truth. To exercise our intellectual faculties, by tracing out, through slow, inductive methods, the _modus operandi_ of even a single natural law, is an honourable task; nor should the apparent smallness of the media which we are at times compelled to employ, render it less so (else would this present treatise, like many others of a kindred stamp, have been best unwritten): but it is from the conceit that our own imperfect interpretations have left nothing more to be found out, that the great danger is to be anticipated. An effect may be literally dependent upon a certain proximate cause; and if we be so fortunate as to ascertain that cause, we have done something; but it does not necessarily follow that we have done _much_. On the contrary, it often happens that, in so doing, we have achieved wonderfully little,--seeing that the problem may be self-evident. Behind that "cause," we should recollect, others lie concealed, of a far deeper nature, each depending upon the next in succession to it; until, in the order of causation, we are at length led back, step by step, to the Final One,--with which alone the mind can be thoroughly content. "We make discovery after discovery," says Dr. Whewell, "in the various regions of science; each, it may be, satisfactory, and in itself complete, but none final. Something always remains undone. The last question answered, the answer suggests still another question. The strain of music from the lyre of Science flows on, rich and sweet, full and harmonious; but never reaches a close: no cadence is heard with which the intellectual ear can feel satisfied[88]."

As regards that most obscure of questions, _what the limits of species really are_, observation alone can decide the point. It frequently happens indeed that even observation itself is insufficient to render the lines of demarcation intelligible,--therefore, how much more mere dialectics! To attempt to argue such a subject on abstract principles, would be simply absurd; for, as Lord Bacon has remarked, "the subtilty of Nature far exceeds the subtilty of reasoning:" but if, by a careful collation of _facts_, and the sifting of minute particulars gathered from without, the problem be fairly and deliberately surveyed, the various disturbing elements which the creatures have been severally exposed to having been duly taken into account, the boundaries will not often be difficult to define. Albeit, we must except those races of animals and plants which, through a long course of centuries, have become modified by man,--the starting-points of which will perhaps continue to the last shrouded in mystery and doubt. It would be scarcely consistent indeed to weigh tribes which have been thus unnaturally tampered with by the same standard of evidence as we require for those which have remained for ever untouched and free,--especially so, since (as we have already observed) it does absolutely appear, that those species, the external aspects of which have been thus artificially controlled, are by constitution more tractile (and possess, therefore, more decided powers for aberration) than the rest. Whether traces of design may be recognized in this circumstance, or whether those forms were originally selected by man _on account_ of their pliability, it is not for me to conjecture; nevertheless, the first of these inferences is the one which I should, myself, be _à priori_ inclined to subscribe to.

In examining, however, this enigma, _of the limits within which variation is_ (as such) _to be recognized_; it should never be forgotten, that it is possible for those boundaries to be absolutely and critically marked out even where we are not able to discern them: so that the difficulty which a few domesticated creatures of a singularly flexible organization present, should not unnecessarily predispose us to dispute the question in its larger and more general bearings. Nor should we be unmindful that (as Sir Charles Lyell has aptly suggested) "some mere varieties present greater differences, _inter se_, than do many individuals of distinct species;" for it is a truth of considerable importance, and one which may help us out of many an apparent dilemma.

But, whatever be the several ranges within which the members of the organic creation are free to vary; we are positively certain that, _unless the definition of a species, as involving relationship, be more than a delusion or romance_, their circumferences are of necessity real, and must be indicated _somewhere_,--as strictly, moreover, and rigidly, as it is possible for anything in Nature to be chalked out. The whole problem, in that case, does in effect resolve itself to this,--Where, and how, are the lines of demarcation to be drawn? No amount of inconstancy, provided its limits be fixed, is irreconcilable with the doctrine of specific similitudes. Like the ever-shifting curves which the white foam of the untiring tide describes upon the shore, races may ebb and flow; but they have their boundaries, in either direction, beyond which they can never pass. And thus in every species we may detect, to a greater or less extent, the emblem of instability and permanence combined: although perceived, when inquired into, to be fickle and fluctuating in their component parts, in their general outline they remain steadfast and unaltered, as of old,--

"Still changing, yet unchanged; still doom'd to feel _Endless mutation, in perpetual rest_."

FOOTNOTES:

[84] Religion of Nature Delineated, p. 103.

[85] Vide _supra_, p. 128.

[86] Principles of Geology, 9th edition, pp. 583, 584.

[87] Vide _supra_, p. 121.

[88] Indications of the Creator (London, 1845), p. 163.

INDEX.

Aberration, perhaps indicated universally, 16, 17, 18.

Aborigines, insect, unimportant for climatal modifications, 25, 26, 27.

_Acalles_, the Canarian type of, apparent on the Salvages and Dezertas, 124.

_---- Neptunus_, Woll., perhaps a state of _A. argillosus_, 124.

_Achatina Eulima_, Lowe, its extinction in Porto Santo, 131.

_Achenium Hartungii_, Heer, a form of _A. depressum_, 65.

_Acherontia Atropos_, Linn., its introduction into Madeira perhaps recent, 74.

_Adimonia_, the capture of, out at sea, 150.

_Aëpus marinus_, Ström., pallid hue of, 64.

_---- Robinii_, Lab., pallid hue of, 64.

_Agabus bipustulatus_, Linn., unaffected by climate, 31.

Alligators, their peculiarity to S. America, 143.

Alpine species, some peculiarly so, 40.

Altitude and latitude, sometimes reciprocal, 35, 114.

_Amyeterus_, its concentration in Australia, 143.

Amyot, M., his 'Méthode Mononomique,' 164.

Analogies, Lord Bacon on the importance of, 13; why necessary to be studied, 14.

Analogy, argument from, 10, 11, 12.

_Anchomenus marginatus_, Linn., slightly modified in Madeira, 38.

Andes, dissimilarity of the fauna on the opposite sides of the, 146.

_Anobium striatum_, Oliv., unaffected by climate, 31.

Antennæ, joints of, said occasionally to vary, 96.

_Anthicus bimaculatus_, Illig., variability of, near the sea, 63.

_---- fenestratus_, Schmidt, slightly modified in Madeira, 38.

_---- humilis_, Germ., variability of in salt places, 63.

_---- instabilis_, Hoffm., pallid hue of, 64.

_Anthonomus ater_, Mshm, very small in Lundy Island, 58, 73.

_Aphelocheirus æstivalis_, Fabr., the hemelytra of, sometimes fully developed, 100.

_Aphodius nitidulus_, Fabr., paler in Madeira than in Europe generally, 65.

_Aphodius plagiatus_, Linn., usually black in England, 61; two distinct states of, indicated, 105.

_Apocyrtus_, its concentration in the Philippine Islands, 143.

_Apotomus_, common to Madeira and Sicily, 139.

_Argutor_, always apterous in Madeira, 82; trophi of, almost identical with those of _Calathus_, 175.

Armadillos, their peculiarity to S. America, 143.

Armitage, Mr., on _Cicindela fasciatopunctata_ from Mount Olympus, 41.

Arrangement, a lineal one is not indicated in Nature, 163.

Atlantic continent, Prof. E. Forbes on the former existence of, 137.

Atlantis of the ancients, the impossibility of its being identified with a former Atlantic region, 140; perhaps the New World, 141.

_Atlantis_, the genus, a modification of _Laparocerus_, 143.

Azores, the colonization of, by two Madeiran _Helices_, 133.

Bacon, Lord, on the importance of analogies, 13; on the Atlantis of the ancients, 141; on the necessity of observation for forming science, 159.

Banksias, their concentration in Australia, 142.

Barriers, natural, the difference between primary and recent, 145; their hindrance to insect diffusion, 145.

_Bembidium Atlanticum_, Woll., paler in Porto Santo than in Madeira, 66; the variations to which it is subject, 107, 108.

_---- bistriatum_, Dufts., paler in saline districts, 62.

_---- ephippium_, Mshm, pallid hue of, 64.

_---- obtusum_, Sturm, varies in southern latitudes, 33.

_---- pallidipenne_, Illig., pallid hue of, 64.

_---- saxatile_, Gyll., variety of, on the south coast of England, 60.

_---- Schmidtii_, Woll., perhaps a state of _B. callosum_, 66.

_---- scutellare_, Germ., pallid hue of, 64.

_---- tabellatum_, Woll., perhaps a state of _B. tibiale_, 66.

_Berginus_, common to Madeira and Sicily, 139.

Black Rat, nearly exterminated in England, 178.

_Blemus areolatus_, Creutz., paler in brackish places, 62.

_Bolitochara assimilis_, Kby, smallness of, in the Scilly Islands, 73.

_Boromorphus_, common to Madeira and Sicily, 139.

_Brachinus crepitans_, Linn., two distinct sizes of, frequently indicated, 105.

_Bradycellus fulvus_, Mshm, apterous in Madeira, 85.

Bread-fruit Trees, their peculiarity to the South Sea Islands, 142.

_Calathus_, apterous in Madeira, 82; its trophi almost identical with those of _Pristonychus_, 175.

_---- complanatus_, Koll., varies from altitude, 39; variety of, on one of the Madeira Islands, 88.

_---- fuscus_, Fabr., slightly modified in Madeira, 38, 85.

_Calathus melanocephalus_, Linn., smallness of, in the Scilly Islands, 73.

_---- mollis_, Mshm, variable in its wings, 43; lurid colour of, 64.

Calcareous soils, effect of, on the aspect of insects, 66.

Calceolarias, their concentration on the Andes, 142.

_Calosoma_, a species of, ten miles from shore, 147; the genus, mergescgradually into _Carabus_, 175.

_---- Syncophanta_, Linn., its power of crossing the sea, 147.

Canary Islands, migratory direction of their insect population, 119.

_Carabidæ_, inconstant in their organs of flight, 43; family of, nearly similar throughout in its oral organs, 174.

_Carpophilus hemipterus_, Linn., unaffected by climate, 31.

_Caulotrupis conicollis_, Woll., large size of, on one of the Madeira Islands, 88, 109.

_---- lucifugus_, Woll., varies from isolation, 90, 109.

Causes, never final ones which we investigate, 191.

_Centrinus_, its concentration in S. America, 143.

_Ceutorhynchus contractus_, Mshm, smallness of, in Lundy Island, 59, 73.

_Cholovocera_, common to Madeira and Sicily, 139.

_Choreius ineptus_, Westw., on a winged state of, 44.

_Chorosoma miriforme_, the development of the wings of, 100.

_Chrysomela_, apterous in Madeira, 82.

_Chrysomelæ_, vary from altitude, 41.

_Chrysomelidæ_, almost absent in Tierra del Fuego, 47.

_Cicindela fasciatopunctata_, Germ., a state of _C. sylvatica_ 41.

_Cicindelidæ_, often variable, 41.

_Cillenum laterale_, Sam., lurid hue of, 64.

_Cimex apterus_, Linn., the development of the wings of, 100.

_---- lectularius_, Linn., on the development of the wings of, 45.

_Cistela sulphurea_, Linn., its variability near the sea, 60.

_Clausilia deltostoma_, Lowe, a Porto-Santan form of, 134.

Climatal modifications significant, although small, 42.

Climate, not important as a disturbing cause, 23, 24, 31, 32, 42.

Clouded-yellow Butterfly, unaffected by climate, 31.

_Clypeaster pusillus_, Gyll., differs slightly in Madeira, 65.

Coast, inconstancy of insects in the vicinity of the, 57.

_Coccinella 7-punctata_, Linn., unaffected by climate, 31.

_Colias Edusa_, Fabr., unaffected by climate, 31.

Colour, its inconstancy in insects found near the sea, 57, 58.

---- of insects, affected by isolation, 88.

_Colymbetes_, a species of, captured forty-five miles from shore, 149, 150.

Compensation, generally apparent when an insect is deprived of an organ or sense, 81.

_Coranus subapterus_, Curt., the development of the wings of, 101.

Cordillera, Mr. Darwin on the fauna of the, 145.

_Corylophus_, apterous in Madeira, 82.

_Criomorphus_, Curtis, referable to the genus _Delphax_, 45.

_Cyclostoma lucidum_, Lowe, its extinction in Porto Santo, 131.

_Cynthia Cardui_, Linn., unaffected by climate, 32.

_Cynucus_, a species of, seventeen miles from shore, 150.

_Cyrtonota_, its concentration in S. America, 143.

Darwin, Mr., on the fauna of the Galapagos, 23; relative proportions of the insect tribes in the tropics, 28, 29; on the insects of Tierra del Fuego, 47; on the natural features of Tierra del Fuego, 50; on the insects of Keeling Island, 55; on the insects of St. Helena, 55; on the insects of Ascension, 55; on the apterous condition of insular species, 86; on the fauna of the Cordillera, 145; on a _Calosoma_ captured at sea, 147; on insects captured in the sea, 149, 150; on the disappearance of animals before more powerful ones than themselves, 178.

Dawson, Rev. J. F., on a variety of _Bembidium saxatile_, 60.

Definition of the term 'species,' 4; of the term 'variety,' 4.

_Delphax_, on the development of the wings of, 45.

_Dermestes vulpinus_, Fabr., unaffected by climate, 31.

_Deucalion_, its occurrence on the Salvages and Dezertas, 125.

_---- Desertarum_, Woll., its sedentary nature, 125, 126, 127.

_Dichelus_, its concentration in S. Africa, 143.

Differences, when to be regarded as specific, 6; too exclusively studied, 12.

Diffusion, various means of, which operate on the insect tribes, 148.

Disturbing agents, Prof. Henfrey on, 8.

_Ditylus_, the same type of, indicated in the Canaries and Salvages, 124.

Domesticated animals, pliable nature of, 187, 192.

_Dromius arenicola_, Woll., representative of _D. obscuroguttatus_, 66.

_---- fasciatus_, Gyll., its paleness near the sea, 63.

_---- negrita_, Woll., perhaps an ultimate state of _D. glabratus_, 85.

_---- obscuroguttatus_, Dufts., its changes in Madeira, 36, 37, 38; apterous in Madeira, 84.

_---- sigma_, Rossi, its colour affected by isolation, 88, 89.

Elevation, sometimes corresponds with latitude, 35, 114.

_Ellipsodes glabratus_, Fabr., singular variety of, on one of the Madeira Islands, 88, 109.

Elytra, connateness of, a variable character, 96.

'Endemic,' to what species the term is applicable, 118.

Entomology, the study of, does not necessarily cramp the mind, 111.

_Ephistemus_, apterous in Madeira, 82.

_Eucalypti_, their concentration in Australia, 142.

_Eunectes sticticus_, Linn., unaffected by climate, 31.

Euphorbias, their concentration in Southern Africa, 142.

_Eurygnathus Latreillei_, Lap., variety of, on one of the Madeira Islands, 88, 109.

Exceptions, not be allowed to negative a law, 72, 73.

Extinction of species, as indicated in the Madeiran _Helices_, 131; the only cause by which genera may be abruptly defined, 176.

Forbes, Prof. E., on the origin of the British animals and plants, 130; his epochs of migration of the British animals and plants, 136; on the existence of a former Atlantic continent, 137.

Forests, the hindrance which they offer to insect-diffusion, 154.

"Fortunate Islands" of the ancients, probably the Canarian group, 141.

Galapagos, fauna of, 23.

Genera, the nature of, often misunderstood, 160; a familiar explanation of, 160, 161, 162; cannot be abrupt except from accident, 169; how to be defined, 169; the types of, usually situated towards the centres of the several groups, 170; the types of, usually evenly balanced in their structural characters, 171, 172; may be abruptly defined from accidental causes, 176, 177.

Generic areas, an important feature throughout Nature, 130, 141, 184.

Geology, a necessary item in the study of insect-diffusion, 113.

Germanic plains, the, probably a primary area of diffusion, 130.

_Gerris_, on the development of the wings of, 100.

Gould, Mr., on the Swallows of Malta, 102.

_Gymnaëtron_, blood-red dashes characteristic of, 62.

_---- Campanulæ_, Linn., its smallness on the Cornish coast, 58.

_---- Veronicæ_, Germ., a variety of _G. niger_, 62.

_Hadrus illotus_, Woll., perhaps a form of _H. cinerascens_, 66.

_Haliplus obliquus_, Gyll., dark state of, in Ireland, 67.

_Haltica exoleta_, Fabr., its variability on the coast, 59.

Harcourt, Mr., on the discovery of Madeira, 49, 50.

_Harpalus vividus_, Dej., changes to which it is subject, 67, 68, 69; variable in the connateness of its elytra, 96, 97.

_Hegeter_, its maximum attained in the Canaries, 120.

_---- elongatus_, Oliv., its migration from the Canaries, 120; of a more adaptive nature than its allies, 121.

_---- latebricola_, Woll., its occurrence in the Salvages, 120.

_Helices_, have often two distinct states, 106; many of them representative in the Madeira Islands, 128, 129; those in the Madeiras chiefly of slow migratory powers, 130, 131.

_Helix attrita_, Lowe, its local character, 132.

_---- Bowdichiana_, Fér., perhaps a gigantic state of _H. punctulata_, 106.

_---- calculus_, Lowe, sedentary nature of, 132.

_Helix commixta_, Lowe, sedentary nature of, 132.

_---- coronata_, Desh., its peculiarity to Porto Santo, 128; its occurrence beneath the surface of the ground, 131.

_---- coronula_, Lowe, its peculiarity to the Southern Dezerta, 128.

_---- Delphinula_, Lowe, the Madeiran representative of _H. tectiformis_ in Porto Santo, 129.

_---- discina_, Lowe, a form of _H. polymorpha_, 133.

_---- erubescens_, Lowe, its powers of diffusion greater than those of its allies, 133; sensitive to external influences, 134.

_---- fluctuosa_, Lowe, its extinction in Porto Santo, 131.

_---- hirsuta_, Say, two distinct states of, 106.

_---- lapicida_, Linn., its extinction in Porto Santo, 131.

_---- latens_, Lowe, the Madeiran representative of _H. obtecta_ in Porto Santo, 129.

_---- lincta_, Lowe, the common Madeiran form of _H. polymorpha_, 134.

_---- Lowei_, Pfr., perhaps a gigantic state of _H. Portosanctana_, 106.

_---- papilio_, Lowe, a form of _H. polymorpha_, 133.

_---- paupercula_, Lowe, its powers of diffusion greater than those of its allies, 133.

_---- polymorpha_, Lowe, sensitive to external influences, and of great diffusive powers, 133.

_---- Portosanctana_, Sow., its peculiarity to Porto Santo, 129.

_---- pulvinata_, Lowe, a form of _H. polymorpha_, 133.

_---- saccharata_, Lowe, a local state of _H. polymorpha_, 134.

_---- senilis_, Lowe, the Dezertan form of _H. polymorpha_, 134.

_---- squalida_, Lowe, the Madeiran representative of _H. depauperata_ in Porto Santo, 129.

_---- tiarella_, Webb, its sedentary nature, 128.

_---- undata_, Lowe, its peculiarity to Madeira proper, 129.

_---- Vulcania_, Lowe, its peculiarity to the Dezertas, 129.

_---- Wollastoni_, Lowe, sedentary nature of, 132.

_Helobia nivalis_, Payk., perhaps a state of _H. brevicollis_, 40.

_Helops_, always apterous in Madeira, 82.

_---- confertus_, Woll., varies from altitude, 39.

_---- futilis_, Woll., varies from isolation, 109.

_---- testaceus_, Küst., pallid hue of, 64.

_---- Vulcanus_, Woll., large size of, on one of the Madeira Islands, 88.

Henfrey, Prof., on disturbing agents, 8.

Herschel, Sir John, on the requisites for an observer, 12.

_Hipparchia Semele_, Linn., has a distinct aspect in Madeira, 34.

_Hipporhinus_, its concentration in S. Africa, 143.

Holme, Mr., on _Olisthopus rotundatus_ in the Scilly Islands, 58, 102; on a winged state of _Phosphuga atrata_, 102.

_Holoparamecus_, common to Madeira and Sicily, 139.

_---- Niger_, Aubé, different in Madeira and Sicily, 33.

Hooker, Dr., on the insects of Kerguelen's Land, 86.

Humboldt, his notice of Sphinxes and flies high up on the Andes, 149.

Humming-Birds, their peculiarity to S. America and the W. Indies, 142.

_Hydrobius_, apterous in Madeira, 82; the capture of, out at sea, 150.

_Hydrometridæ_, on the development of the wings of, 100.

_Hydroporus_, the capture of, out at sea, 150.

_---- confluens_, Fabr., unaffected by climate, 31.

_Hypsonotus_, its concentration in S. America, 143.

Influence of climate not important, 23.

Insect-aberration, perhaps a universal fact, 16, 17, 18.

_Insulæ Fortunatæ_ of Juba, probably the Canarian Group, 141.

Ireland, poverty of the fauna of, 52, 53; the south-west of, has something in common with Madeira, 139.

Islands, faunas of, often too greatly magnified, 70; the species of, generally more isolated in their structure than those of continents, 177.

Isolation, effects of, on insect-stature, 71.

Ixias, their concentration in Southern Africa, 142.

Kangaroos, their concentration in Australia, 142.

Kerguelen's Land, insects of, 86.

Kirby, Rev. W., on insects washed up on the Suffolk coast, 147.

_Læmophloe us pusillus_, Schönh., unaffected by climate, 31.

_Lamprias chlorocephalus_, Ent. H., two distinct sizes of, frequently indicated, 105.

_Laparocerus morio_, Schönh., large size of, on one of the Madeira Islands, 88.

Latitude and altitude, sometimes reciprocal, 35.

_Leistus montanus_, Steph., has been supposed to be equal to _L. fulvibarbis_, 40.

_Lemur_, its peculiarity to Madagascar, 143.

_Litargus_, common to Madeira and Sicily, 139.

_Lixus angustatus_, Fabr., unaffected by climate, 31.

Localities, some naturally more productive than others, 53, 54.

_Longitarsus_, the native species of, apterous in Madeira, 82.

_Loricera_, apterous in Madeira, 82.

Lowe, Rev. R. T., his capture of the _Deucalion Desertarum_, 127.

Lundy Island, smallness of the insects in, 58, 59; occurrence of the Black Rat in, 178.

_Lycæna Phloe as_, Linn., darker in Madeira than in England, 34.

Lyell, Sir Charles, on _Helix hirsuta_, 106; on the fossil period of the Madeiran _Helices_, 129; on insects washed up on the shore, 148; on the effect of gales in the transportation of insects, 148; on the effects of a volcanic eruption in destroying species, 179; on the flexible nature of certain animals and plants, 187; on the greater differences which varieties often present than do species, 193.

_Lygæus brevipennis_, Latr., on the development of the wings of, 101.

_Macronota_, its peculiarity to Java, 143.

Madeira, has some features in common with Tierra del Fuego, 48, 49, 50, 51; former state of, 48, 49; great fire on the southern side of, 49; origin of the name of, 50; the insects of, 55; the tendency of its insects to become apterous, 82; the migratory direction of its insect population, 119; the local nature of its various species, 152, 153.

Magnolias, their concentration in Central America, 142.

Malta, Mr. Gould on the birds of, 102.

_Malthodes Kiesenwetteri_, Woll., perhaps a state of _M. brevicollis_, 66.

Man, agency of, in the destruction of species, 179.

_Mantura Chrysanthemi_, Ent. H., variability of, in Lundy Island, 59.

_Marsupialia_, their concentration in Australia, 142.

Mesembryanthemums, their concentration in Southern Africa, 142.

_Mesites_, a modification of _Cossonus_, 144.

_---- Maderensis_, Woll., its near relationship to the _M. Tardii_, 141.

_---- Tardii_, Curtis, its variability near the coast, 58.

'Méthode Mononomique,' the unsoundness of, 164-168.

Migratory powers, slowness of, in the Madeiran _Helices_, 130-132.

---- progress, direction of, in the Madeiran animals, 120, 135.

Mimosas, their concentration in Australia, 142.

Mollusca, Terrestrial, often present two distinct states, 106.

_Moluris_, its concentration in S. Africa, 143.

_Monochelus_, its concentration in S. Africa, 143.

Mountain-chains, their hindrance to insect-diffusion, 145.

Mountain-tops, either very prolific in insect life, or else barren, 115.

_Mus Rattus_, almost exterminated in England, 178.

_Mycetoporus pronus_, Erichs., two distinct states of, indicated, 106.

Myrtles, their concentration in Australia, 142.

Naturalist, the, what his province to investigate, 158.

Nature, not irregular because presenting occasional anomalies, 94.

_Naupactus_, its concentration in S. America, 143.

_Nebria complanata_, Linn., unusually pale near Bordeaux, 33; pallid hue of, 64.

New World, some of its insects perhaps but states of those of the Old, 37.

Nomenclature, a binomial system the only true one, 164, 168.

_Notaphus_, the capture of, out at sea, 150.

_Notiophili_, extremely variable, 40.

_Notiophilus geminatus_, Dej., large size of, on one of the Madeira Islands, 88.

Observation, indispensable in natural science, 20, 159, 192.

Ocean, the, its hindrance to insect-diffusion, 145.

_Ochthebius marinus_, Payk., lurid hue of, 64.

_Olisthopus_, apterous in Madeira, 82.

_---- Maderensis_, Woll., large state of, on one of the Madeira Islands, 88, 89.

_---- rotundatus_, Payk., very small in the Scilly Islands, 58, 73; subapterous in the Scilly Islands, 102.

_Omaseus nigerrimus_, Dej., a form of _O. aterrimus_, 33.

_Omias Waterhousei_, Woll., large state of, on one of the Madeira Islands, 88, 109.

_Oncocephalus griseus_, development of the wings of, 101.

_Othius_, apterous in Madeira, 82.

Ourangs, their peculiarity to the Indian Islands, 143.

_Oxyomus_, a modification of _Aphodius_, 144.

_Pachymerus brevipennis_, the development of the wings of, 100.

_Pachyrhynchus_, its concentration in the Philippine islands, 143.

Painted-Lady Butterfly, unaffected by climate, 32.

_Papilio Machaon_, Linn., unaffected by climate, 31.

_Paropsis_, its concentration in Australia, 143.

Patagonia, insects of, distinct from those of Tierra del Fuego, 47, 48.

_Patrobus septentrionis_, Dej., has been supposed to be a state of _P. excavatus_, 40.

_Pecteropus_, its maximum attained in the Canaries, 124.

_---- Maderensis_, Woll., varies from altitude, 39.

_---- rostratus_, Woll., varies from isolation, 90.

Pelargoniums, their concentration in Southern Africa, 142.

_Pelophila borealis_, Payk., larger in Ireland than in the Orkneys, 33.

_Phaleria cadaverina_, Fabr., pallid hue of, 64.

_Philhydrus melanocephalus_, Oliv., two states of, frequently indicated, 105.

_Phlæophagus_, apterous in Madeira, 82.

_Phosphuga atrata_, Linn., taken with the wings developed, 102.

_---- subrotundata_, Leach, the Irish form of the _P. atrata_, 33.

_Phytophaga_, preponderance of, in the tropics, 28, 29.

_Pieris Brassicæ_, Linn., varies in Nepaul and Japan, 34.

_Pissodes notatus_, Fabr., unaffected by climate, 30.

_Platyomus_, its concentration in S. America, 143.

_Platyrrhini_, their peculiarity to S. America, 143.

_Pogonus luridipennis_, Germ., lurid hue of, 64.

_Pontia Brassicæ_, Linn., its introduction into Madeira probably recent, 74.

Porto Santo, origin of the name of, 49; a generic area of radiation for certain _Helices_, 130.

Predacious insects, less numerous in the tropics, 28, 29.

_Prostemma guttula_, Fabr., the development of the wings of, 100, 101.

_Psylliodes_, a variable species of, in Lundy Island, 60.

_---- erythrocephala_, Linn., two distinct states of, frequently indicated, 105.

_---- marcida_, Illig., pallid hue of, 64.

_---- nigricollis_, Mshm, a pale state of the _P. erythrocephala_, 105.

_---- vehemens_, Woll., varies from isolation, 90.

_Pterostichus_, its various divisions are natural ones, 175.

_Ptini_, their stature affected by isolation, 74; which characters of, are the most constant, 104.

_Ptinus albopictus_, Woll., its changes on the islands of the Madeiran Group, 75-77.

_Pupa_, often two distinct states of, 106.

_Purpurariæ_ of the ancients, probably the Madeiran Group, 141.

Pyrenean region, the, perhaps a primary area of diffusion, 130.

Reasoning, not sufficient of itself for the formation of science, 159.

Red-Admiral Butterfly, its introduction into Madeira perhaps recent, 74.

_Reduviadæ_, on the development of the wings of a representative of the, 101.

Representative species, exemplified by the Madeiran _Helices_, 128, 129, 185; where frequently to be recognized, 183.

_Rhyzopertha pusilla_, Fabr., unaffected by climate, 31.

Rivers, their power of transporting insects along their course, 149.

Saline spots, variation of insects in, 57.

Salvages, occurrence of a Canarian form on the, 120, 124.

_Saprinus_, a modification of _Hister_ proper, 143.

_---- nitidulus_, Fabr., two distinct states of, indicated, 106.

_Scarabæus_, the capture of, out at sea, 150.

_Scarites abbreviatus_, Koll., large size of, on one of the Madeira Islands, 88; varies both from isolation and altitude, 91.

Sciences, the, should assist rather than oppose each other, 155, 156.

_Scydmænus Helferi_, Schaum, smaller in Madeira than in Sicily, 65.

_Scymnus_, an apterous species of, in Porto Santo, 82.

Sea, inconstancy of insects in the vicinity of the, 57.

Sicily, the fauna of, has much in common with that of Madeira, 139.

_Silpha atrata_, Linn., presents a distinct state in Ireland, 33.

_Silybum Marianum_, Grtn., its stalks the food of a _Ptinus_, 76.

Similitudes, Lord Bacon on the importance of, 13.

_Sitonia gressoria_, Illig., perhaps a form of the _S. grisea_, 33.

_Sitophilus granarius_, Linn., unaffected by climate, 31.

_Sitophilus oryzæ_, Linn., unaffected by climate, 31.

Sloths, their peculiarity to S. America, 143.

Species, definition of the term, 4; familiar explanation concerning the nature of, 161, 162; limitation of, how to be attempted, 192; limits of, real, though often difficult to trace out, 193; in a certain sense both unstable and permanent, 194.

Specific centres of creation, 5.

_Sphinx Convolvuli_, Linn., its introduction into Madeira probably recent, 74.

Spinola, on one of the _Reduviadæ_, 101; on _Oncocephalus griseus_, 101.

Stapelias, their concentration in Southern Africa, 142.

States, large and small ones indicated in some insects, 105.

Stature of insects, smaller in islands than on continents, 70.

_Stenolophus Skrimshiranus_, Steph., perhaps a state of _S. Teutonus_, 63.

_Stenus Heeri_, Woll., two distinct states of, indicated, 106.

Structural characters, seldom variable in the Insecta, 95.

Subsidences, the effect of, on insect life, 114.

Swallow-Tail Butterfly, unaffected by climate, 31.

_Syncalypta_, apterous in Madeira, 82.

_Tachyporus nitidicollis_, Steph., perhaps a state of _T. obtusus_, 33.

_Tarphii_, their economy in the Madeira Group, 121.

_Tarphius_, its maximum attained in Madeira proper, 121; common to Madeira and Sicily, 139.

_---- gibbulus_, Germ., the Sicilian exponent of the genus, 123.

_---- Lowei_, Woll., of a more adaptive nature than its allies, 122.

_Tarus_, always apterous in Madeira, 82.

_---- lineatus_, Schönh., assumes a distinct state in Madeira, 65.

_Telephorus testaceus_, Linn., its variability in Lundy Island, 59.

Thompson, Mr., on the reptiles of Ireland, England, and Belgium, 136.

_Thorictus_, common to Madeira and Sicily, 139.

Tierra del Fuego, insects of, 47; has many characters in common with Madeira, 48-51.

Time, an important item in the question of modifications, 77.

Toucans, their peculiarity to S. America and the W. Indies, 142.

Transmutation-theory, unsoundness of the, 186-189; how it took its rise, 190.

_Trechus_, always apterous in Madeira, 82.

_---- alticola_, Woll., perhaps a state of _T. custos_, 39.

_---- lapidosus_, Daws., pallid hue of, 64.

Tree-Porcupines, their peculiarity to S. America, 143.

_Tribolium ferrugineum_, Fabr., unaffected by climate, 31.

_Trogosita mauritanica_, Linn., unaffected by climate, 31.

Tropics, exuberance of the, 27, 28; relative proportions of the insect tribes within the, 28, 29.

_Tychius_, always apterous in Madeira, 82.

Unity, indicated in the organic creation, 179, 180.

_Vanessa Atalanta_, Linn., has a different aspect in N. America, 34; perhaps a recent introduction into Madeira, 74.

_---- Callirhoë_, Fabr., smaller in Porto Santo than in Madeira, 73.

Variation in the Insecta, a matter of experience, 7, 8, 15; probable from analogy, 15; perhaps indicated in every individual, 16, 17, 18; restricted, 35.

Variety, definition of the term, 4.

_Velia_, on the development of the wings of, 100.

Waterhouse, Mr., his opinion concerning generic types, 172.

Westwood, Mr., on _Papilio Machaon_ from the Himalayas, 32; on American specimens of _Lycæna Phloe as_, 34; on the effect of heat in developing the wings of insects, 44; on a winged state of _Choreius ineptus_, 44; on the development of the wings in _Delphax_, 45; on a winged state of _Cimex lectularius_, 45; on _Aphelocheirus æstivalis_, 100; on the development of the wings of the _Hydrometridæ_, 100; on _Cimex apterus_, 100; on _Prostemma guttala_ and _Coranus subapteras_, 101; on the development of the wings of _Lygæus brevipennis_, 101.

Whewell, Dr., on the natural causes which science has to investigate, 191.

White-Cabbage Butterfly, varies in Nepaul and Japan, 34.

Winds, the effects of, in the diffusion of insects, 148.

Wings of insects, subject to undue development in hot seasons, 43; liable to become gradually obsolete in islands, 81; more variable than other organs, 97.

_Xenostrongylus_, its geographical distribution, 124; common to Madeira and Sicily, 139.

_Zargus pellucidus_, Woll., variety of, on one of the Madeira Islands, 88.

FINIS.

Printed by Taylor and Francis, Red Lion Court, Fleet Street.

Lately published, by the same Author, in large 4to (with Thirteen Coloured Plates), price £2 2_s._,

INSECTA MADERENSIA; BEING AN ACCOUNT OF THE INSECTS OF THE ISLANDS OF THE MADEIRAN GROUP.

London: JOHN VAN VOORST, 1, Paternoster Row.

Transcriber's Notes:

Inconsistent/archaic spelling and punctuation left as in original.