Alfred Russel Wallace

“ Now this explanation of the facts is not only simple and probable in itself, but it also serves to explain in a remarkable manner some of the peculiarities and deficiencies of the Madeiran insect fauna, in harmony with the view (supported by the distribution of the birds and land shells, and in particular by the immigrant birds and insects of the Azores) that all the insects have been derived from the continent or from other islands, by immigration across the ocean, in various ways and during a long period. ”

“ On a map of sufficiently large scale, therefore, it would be necessary to extend our present sub-region westward along the Himalayas, in a narrow strip just below the upper limits of forests. It is evident that the large number of Fringillidæ, Corvidæ, Troglodytidæ, and Paridæ, often of south Palæarctic forms, that abound in the higher Himalayas, are somewhat out of place as members of the Oriental fauna, and are equally so in that of Thibet and Siberia; but they form a natural portion of that of North China on the one side, or of South Europe on the other. ”

“ Another most remarkable feature of the Madeiran Coleoptera is the unusual prevalence of apterous or wingless insects. This is especially the case with groups which are confined to the Atlantic islands, many of which consist wholly of wingless species; but it also affects the others, no less than twenty-two genera which are usually or sometimes winged in Europe, having only wingless species in Madeira; and even the same species which is winged in Europe becomes, in at least three cases, wingless in Madeira, without any other perceptible change having taken place. ”

“ On the other hand, a genus consisting of numerous species ranging over an entire region or the greater part of one, is a dominant group, which has most likely been for some time extending its range, and whose origin dates back to a remote period. ”

“ A considerable number of genera which are well developed in the high Himalayas, and some which are peculiar to that district, have hitherto always been classed as Indian, and therefore Oriental groups; but they more properly belong to this sub-region. Many of them frequent the highest forests, or descend into the Himalayan temperate zone only in winter; and others are so intimately connected with Palæarctic species, that they can only be considered as stragglers into the border land of the Oriental region. ”

“ Even now, that portion of the Palæarctic region between Western Asia and Japan is, for the most part, a bleak and inhospitable region, abounding in desert plateaus, and with a rigorous climate even in its most favoured districts, and can, therefore, support but a scanty population of snakes, and of such groups of insects as require flowers, forests, or a considerable period of warm summer weather; and it is precisely these which are represented in Japan and North China by tropical forms. ”

“ It is also evident that Japan has a more equable and probably moister climate than the opposite shores of China, and has also a very different geological character, being rocky and broken, often volcanic, and supporting a rich, varied, and peculiar vegetation. It would thus be well adapted to support all the more hardy denizens of the tropics which might at various times reach it, while it might not be so well adapted for the more boreal forms from Mongolia or Siberia. ”

“ There are, however, one or two curious exceptions to the absence of these wholly apterous European genera in Madeira, and as in each case the reason of their being exceptions can be pointed out, they are eminently exceptions that prove the rule. Two of the apterous species common to Europe and Madeira are found always in ants' nests; and as ants, when winged, fly in great swarms and are carried by the wind to great distances, they may have conveyed the minute eggs of these very small beetles. ”

“ Although the sub-region we are considering is, for its extent and latitude, richly peopled with animal life, the number of genera altogether peculiar to it is not great. There are, however, several which are very characteristic, and many species, both of the smaller mammalia and of birds, are wholly restricted to it. ”

“ Far more of the birds and insects are identical with those of Europe than in the other islands, and this difference is clearly traced to the more tempestuous atmosphere, which is shown to be even now annually bringing fresh immigrants (both birds and insects) to its shores. We here see nature actually at work; and if the case of Madeira rendered her mode of action probable, that of the Azores may be said to demonstrate it. ”

“ The whole of this sub-region is well watered, being penetrated by rivers in every direction; and it consists mainly of plains and undulating country of moderate elevation, the chief mountain ranges being those of Scandinavia in the north-west, and the extensive alpine system of Central Europe. But these are both of moderate height, and a very small portion of their surface is occupied either by permanent snow-fields, or by barren uplands inimical to vegetable and animal life. ”

“ Japan is volcanic and mountainous, with a fine climate and a most luxuriant and varied vegetation. Manchuria is hilly, with a high range of mountains on the coast, and some desert tracts in the interior, but fairly wooded in many parts. Much of northern China is a vast alluvial plain, backed by hills and mountains with belts of forest, above which are the dry and barren uplands of Mongolia. We have a tolerable knowledge of China, of Japan, and of the Amoor valley, but very little of Corea and Manchuria. ”

“ Iceland is the only other island of importance belonging to this sub-region, and it contrasts strongly with Great Britain, both in its Arctic climate and oceanic position. It is situated just south of the Arctic circle and considerably nearer Greenland than Europe, yet its productions are almost wholly European. The only indigenous land mammalia are the Arctic fox (Canis lagopus) , and the polar bear as an occasional visitant, with a mouse (Mus islandicus) , said to be of a peculiar species. Four species of seals visit its shores. The birds are more interesting. ”

“ The Canaries are inhabited by a little over 1,000 species, Madeira by about 700, while 240 are common to both; but it is believed that many of these have been introduced by man. In the Azores, 212 species have been obtained, of which 175 are European; showing, as in the birds, as closer resemblance to the European fauna than in the other islands which, although nearer to the continent, offer more shelter and are situated in a less tempestuous zone. Of the non-European species in the Azores, 19 are found also in the other groups of islands, 14 are peculiar, while 3 are American. ”

“ Add to this the fact, that the number of species diminishes in the group as we go from east to west, and that the islands are subject to fierce and frequent storms blowing from every point of the compass,—and we have all the facts requisite to enable us to understand how this remote archipelago has become stocked with animal life without ever probably being much nearer to Europe than it is now. ”

“ As the total number of species at present known to exist in collections is estimated (and perhaps somewhat over-estimated) at 70,000 species, we may be sure that were the whole earth as thoroughly investigated as Europe, the number would be at least doubled, since we cannot suppose that Europe, with the Mediterranean basin, can contain more than one-fifth of the whole of the Coleoptera of the globe. ”

“ So long therefore as a species or genus does not permanently reside considerably beyond the possible limits of this neutral territory, we should not claim it as an inhabitant of the adjacent region. A consideration of perhaps more importance arises, from the varying extent of the range of a genus, over the area occupied by the region. Some genera are represented by single species existing only in a very limited area; others by numerous species which occupy, entirely or very nearly, the whole extent of the region ”

“ If but one very violent storm happened in a century, and ten such storms recurred before a single species of insect was introduced into Madeira, that would be more than sufficient to people it, as we now find it, with a varied fauna. ”

“ The elegantly-formed creatures on the right are chamois (Rupicapra tragus) , almost the only European antelopes, and wholly confined to the higher mountains, from the Pyrenees to the Carpathians and the Caucasus. The chamois is the only species of the genus, and is thus perhaps the most characteristic European mammal. The bird on the left, above the badgers, is the Alpine chough, (Fregilus pyrrhocorax) . ”

“ Against these, however, we have the occurrence in North Africa of such purely Palæarctic and non-Ethiopian genera as Ursus, Meles, Putorius, Sus, Cervus, Dama, Capra, Alactaga; together with actual European or West Asiatic species of Canis, Genetta, Felis, Putorius, Lutra, many bats, Sorex, Crocidura, Crossopus, Hystrix, Dipus, Lepus, and Mus. It is admitted that, as regards every other group of animals, North Africa is Palæarctic, and the above enumeration shows that even in Mammalia, the intermixture of what are now true Ethiopian types is altogether insignificant. ”

“ Azores.—Considering the remoteness of this group from every other land, it is surprising to find as many as fifty-three species of birds inhabiting or visiting the Azores; and still more to find that they are of Palæarctic genera and, with one exception, all of species found either in Europe, North Africa, Madeira, or the Canaries. The exception is a bullfinch peculiar to the islands, but closely allied to a European species. Of land birds there are twenty-two, belonging to twenty-one genera, all European. ”

“ In addition to these, almost all our summer migrants spend their winter in some part of this favoured land, mostly in North Africa, together with many species of Central Europe that rarely or never visit us. It follows, that a large proportion of all the birds of Europe and Western Asia are to be found in this sub-region, as will be seen by referring to the list of the genera of the region. Palestine is one of the remote portions of this region which has been well explored by Canon Tristram, and it may be interesting to give his summary of the range of the birds. ”

“ Most of the northern and much of the central portions of Europe are covered with vast forests of coniferous trees; and these, occupying as they do those tracts where the winter is most severe, supply food and shelter to many animals who could not otherwise maintain their existence. ”

“ North European Islands.—The British Islands are known to have been recently connected with the Continent, and their animal productions are so uniformly identical with continental species as to require no special note. The only general fact of importance is, that the number of species in all groups is much less than in continental districts of equal extent, and that this number is still farther diminished in Ireland. ”

“ The diversity and specialization of the forms of these animals is, therefore, easily explained by the fact, that, once introduced they have been left to multiply under the influence of a variety of local conditions, which inevitably lead, in the course of ages, to the formation of new varieties and new species. ”

“ In the Canaries we find that the birds have again very much increased, there being more than fifty genera of land birds; but the additions are wholly European in character, and almost all common European species. We find a few more peculiar species (five) , while some others, including the wild canary, are common to all the Atlantic Islands or to the Canaries and Madeira. Here, too, the only indigenous mammalia are two European species of bats. ”

“ All the lower parts being situated to the north, have an excessively cold winter, so that the limit of constantly frozen ground descends below the parallel of 60° north latitude. To the south, the land is greatly elevated, and the climate extremely dry. In summer the heat is excessive, while the winter is almost as severe as further north. The whole country, too, is subject to violent storms, both in summer and winter ”

“ There are twenty-three land, and seventy-two aquatic birds and waders. Four or five are peculiar species, though very closely related to others inhabiting Scandinavia or Greenland. Only two or three species are more nearly related to Greenland birds than to those of Northern Europe, so that the Palæarctic character of the fauna is unmistakable. The following lists, compiled from a paper by Professor Newton, may be interesting as showing more exactly the character of Icelandic ornithology. ”

“ Most of the genera, and many even of the species of birds which migrate southwards in winter, have therefore, most likely, always been inhabitants of our present Palæarctic and Nearctic regions; permanent residents during warm epochs, but only able now to maintain their existence by migration in winter. ”

“ The fact that a mixture of such forms occurs there, is then, little to be wondered at, but we may rather marvel that they are not more predominant, and that even in the extreme south, the most abundant forms of mammal, bird, and insect, are modifications of familiar Palæarctic types. ”

“ Godman tells us that many of the birds are modified—instancing the gold-crested wren, blackcap, and rock dove—and he adds, that the modification all tends in one direction—to produce a more sombre plumage, a greater strength of feet and legs, and a more robust bill. We further find, that four of the land-birds, including the oriole, snow-bunting, and hoopoe, are not resident birds, but straggle accidentally to the islands by stress of weather; and we are told that every year some fresh birds are seen after violent storms. ”

“ Of the European species, 132 are found also in the other Atlantic islands, while 43 have reached the Azores only. This is interesting as showing to how great an extent the same insects reach all the islands, notwithstanding the difference of latitude and position; and it becomes of great theoretical importance, when we find how many extensive families and genera are altogether absent. ”