THE ALPS OF CENTRAL EUROPE, WITH CHARACTERISTIC ANIMALS.
THE ALPS OF CENTRAL EUROPE, WITH CHARACTERISTIC ANIMALS.
Plate I.—Illustrating the Zoology of Central Europe.—Before considering the distribution of the other classes of vertebrata, it will be convenient to introduce our first illustration, which represents a scene in the Alps of Central Europe, with figures of some of the most characteristic Mammalia and Birds of this sub-region. On the left is the badger (Meles Taxus) one of the weasel family, and belonging to a genus which is strictly Palæarctic. It abounds in Central and Northern Europe and also extends into North Asia, but is represented by another species in Thibet and by a third in Japan. 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). It is found in the high mountains from the Alps to the Himalayas, and is allied to the Cornish chough, which is still found on our south-western coasts, and which ranges to Abyssinia and North China. The Alpine chough differs in having a shorter bill of an orange colour, and vermilion red feet as in the other species. In the foreground are a pair of ruffs (Machetes pugnax) belonging to the Scolopacidæ or snipe family, and most nearly allied to the genusTringaor sandpiper. This bird is remarkable for the fine collar of plumes which adorns the males in the breeding season, when they are excessively pugnacious. It is the only species of its genus, and ranges over all Europe and much of Northern Asia, migrating in the winter to the plains of India, and even down the east coast of Africa as far as the Cape of Good Hope; but it only breeds in the Palæarctic region, over the greater part of which it ranges.
Reptiles and Amphibia.—There are no genera of reptiles peculiar to this sub-region. Both snakes and lizards are comparatively scarce, there being about fourteen species of the former and twelve of the latter. Our common snake (Tropidonotus natrix) extends into Sweden and North Russia, but the viper (Viperus berus) goes further north, as far as Archangel (64° N.), and in Scandinavia (67° N.), and is the most Arctic of all knownsnakes. Of the lizards,Lacerta stirpium(the sand lizard) has the most northerly range, extending into Poland and Northern Russia; andAnguis fragilis(the blind or slow-worm) has almost an equal range.
Amphibia, being more adapted to a northern climate, have acquired a more special development, and thus several forms are peculiar to the North European sub-region. Most remarkable isProteus, a singular eel-like aquatic creature with small legs, found only in the subterranean lakes in Carniola and Carinthia;Alytes, a curious toad, the male of which carries about the eggs till they are hatched, found only in Central Europe from France to the east of Hungary; andPelodytes, a frog found only in France. Frogs and toads are very abundant all over Europe, the common frog (Rana temporaria) extending to the extreme north. The newts (Triton) are also very abundant and widely spread, though not ranging so far north as the frogs. The generaBombinator(a toad-like frog), andHyla(the tree frog) are also common in Central Europe.
Freshwater Fish.—Two genera of the perch family (Percidæ) are peculiar to this sub-region,—Percarina, a fish found only in the river Dniester, andAspro, confined to the rivers of Central Europe. Of the very characteristic forms are,Gasterosteus(stickle-back), which alone forms a peculiar family—Gasterosteidæ;Perca,AcerinaandLucioperca, genera of the perch family;Silurus, a large fish found in the rivers of Cenrtal Europe, of the family Siluridæ;Esox(the pike), of the family Esocidæ;Cyprinus(carp),Gobio(gudgeon),Leuciscus(roach, chub, dace, &c.),Tinca(tench),Abramus(bream),Alburnus(bleak),Cobitis(loach), all genera of the family Cyprinidæ.
Insects—Lepidoptera.—No genera of butterflies are actually confined to this sub-region, but many are characteristic of it.Parnassius,Aporia,Leucophasia,Colias,Melitæa,Argynnis,Vanessa,Limenitis, andChionobas, are all very abundant and widespread, and give a feature to the entomology of most of the countries included in it.
Coleoptera.—This sub-region is very rich in Carabidæ; the generaElaphrus,Nebria,Carabus,Cychrus,Pterostichus,Amara,TrechusandPeryphusbeing especially characteristic. Staphylinidæ abound. Among Lamellicorns the genusAphodiusis most characteristic. Buprestidæ are scarce; Elateridæ more abundant. Among MalacodermsTelephorusandMalachiusare characteristic. Curculionidæ abound:Otiorhyuchus,Omias,Erirhinus,Bagous,RhynchitesandCeutorhynchusbeing very characteristic genera. Of LongicornsCallidium,Dorcadion,Pogonochærus,PachytaandLepturaare perhaps the best representatives.Donacia,Crioceris,Chrysomela, andAltica, are typical Phytophaga; whileCoccinellais the best representative of the Securipalpes.
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. This may be accounted for by the smaller area and less varied surface of the latter island; and it may also be partly due to the great extent of low land, so that a very small depression would reduce it to the condition of a cluster of small islands capable of supporting a very limited amount of animal life. Yet further, if after such a submergence had destroyed much of the higher forms of life in Great Britain and Ireland, both were elevated so as to again form part of the Continent, a migration would commence by which they would be stocked afresh; but this migration would be a work of time, and it is to be expected that many species would never reach Ireland or would find its excessively moist climate unsuited to them.
Some few British species differ slightly from their continental allies, and are considered by many naturalists to be distinct. This is the case with the red grouse (Lagopus scoticus) among birds; and a few of the smaller Passeres have also been found to vary somewhat from the allied forms on the Continent, showing that the comparatively short interval since the glacial period, and the slightly different physical conditions dependent oninsularity, have sufficed to commence the work of specific modification. There are also a few small land-shells and several insects not yet found elsewhere than in Britain; and even one of the smaller Mammalia—a shrew (Sorex rusticus). These facts are all readily explained by the former union of these islands with the Continent, and the alternate depressions and elevations which are proved by geological evidence to have occurred, by which they have been more than once separated and united again in recent times. For the evidence of this elevation and depression, the reader may consult Sir Charles Lyell'sAntiquity of Man.
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. According to Professor Newton, ninety-five species have been observed; but many of these are mere stragglers. 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.
1. Peculiar species.—Troglodytes borealis(closely allied to the common wren, found also in the Faroe Islands);Falco islandicus(closely allied toF. gyrfalco);Lagopus islandorum(closely allied toL. rupestrisof Greenland).
2. European species resident in Iceland.—Emberiza nivalis,Corvus corax,Haliæetus albicilla,Rallus aquaticus,Hæmatopus ostralegus,Cygnus ferus,Mergus(two species),Phalacocorax(twospecies),Sula bassana,Larus(two species),Stercorarius catarractes,Puffinus anglorum,Mergulus alle,Uria(three species),Alca torda.
3. American species resident in Iceland.—Clangula islandica,Histrionicus torquatus.
4. Annual visitants from Europe.—Turdus iliacus,Ruticilla tithys,Saxicola ænanthe,Motacilla alba,Anthus pratensis,Linota linaria,Chelidon urbica,Hirundo rustica,Falco æsalon,Surnia nyctea,Otus brachyotus,Charadrius pluvialis,Ægialites hiaticula,Strepsilas interpres,Phalaropus fulicarius,Totanus calidris,Limosa(species),Tringa(three species),Calidris arenaria,Gallinago media,Numenius phæopus,Ardea cinerea,Anser(two species),Bernicla(two species),Anas(four species),Fuligula marila,Harelda glacialis,Somateria mollissima,Œdemia nigra,Sterna macrura,Rissa tridactyla,Larus luecopterus,Stercorarius(two species),Fratercula artica,Colymbus(two species),Podiceps cornutus.
5. Annual visitant from Greenland.—Falco candicans.
6.—Former resident, now extinct.—Alca impennis(the great auk).
II.—Mediterranean Sub-region.
This is by far the richest portion of the Palæarctic region, for although of moderate extent much of it enjoys a climate in which the rigours of winter are almost unknown. It includes all the countries south of the Pyrenees, Alps, Balkans, and Caucasus mountains; all the southern shores of the Mediterranean to the Atlas range, and even beyond it to include the extra-tropical portion of the Sahara; and in the Nile valley as far as the second cataract. Further east it includes the northern half of Arabia and the whole of Persia, as well as Beluchistan, and perhaps Affghanistan up to the banks of the Indus. This extensive district is almost wholly a region of mountains and elevated plateaus. On the west, Spain is mainly a table-land of more than 2000 feet elevation, deeply penetrated by extensive valleys and rising into lofty mountain chains. Italy, Corsica, Sardinia, and Sicily, are all verymountainous, and much of their surface considerably elevated. Further east we have all European Turkey and Greece, a mountain region with a comparatively small extent of level plain. In Asia the whole country, from Smyrna through Armenia and Persia to the further borders of Affghanistan, is a vast mountainous plateau, almost all above 2000, and extensive districts above 5000 feet in elevation. The only large tract of low-land is the valley of the Euphrates. There is also some low-land south of the Caucasus, and in Syria the valley of the Jordan. In North Africa the valley of the Nile and the coast plains of Tripoli and Algiers are almost the only exceptions to the more or less mountainous and plateau-like character of the country. Much of this extensive area is now bare and arid, and often even of a desert character; a fact no doubt due, in great part, to the destruction of aboriginal forests. This loss is rendered permanent by the absence of irrigation, and, it is also thought, by the abundance of camels and goats, animals which are exceedingly injurious to woody vegetation, and are able to keep down the natural growth of forests. Mr. Marsh (whose valuable workMan and Naturegives much information on this subject) believes that even large portions of the African and Asiatic deserts would become covered with woods, and the climate thereby greatly improved, were they protected from these destructive domestic animals, which are probably not indigenous to the country. Spain, in proportion to its extent, is very barren; Italy and European Turkey are more woody and luxuriant; but it is perhaps in Asia Minor, on the range of the Taurus, along the shores of the Black Sea, and to the south of the Caucasus range, that this sub-region attains its maximum of luxuriance in vegetation and in animal life. From the Caspian eastward extends a region of arid plains and barren deserts, diversified by a few more fertile valleys, in which the characteristic flora and fauna of this portion of the Palæarctic region abounds. Further east we come to the forests of the Hindoo Koosh, which probably form the limit of the sub-region. Beyond these we enter on the Siberian sub-region to the north, and on the outlying portion of the Oriental region on the south.
In addition to the territories now indicated as forming part of the Mediterranean sub-region, we must add the group of Canary Islands off the west coast of Africa which seem to be an extension of the Atlas mountains, and the oceanic groups of Madeira and the Azores; the latter about 1,000 miles from the continent of Europe, yet still unmistakably allied to it both in their vegetable and animal productions. The peculiarities of the faunas of these islands will be subsequently referred to.
It seems at first sight very extraordinary, that so large and wide a sea as the Mediterranean should not separate distinct faunas, and this is the more remarkable when we find how very deep the Mediterranean is, and therefore how ancient we may well suppose it to be. Its eastern portion reaches a depth of 2,100 fathoms or 12,600 feet, while its western basin is about 1,600 fathoms or 9,600 feet in greatest depth, and a considerable area of both basins is more than 1,000 fathoms deep. But a further examination shows, that a comparatively shallow sea or submerged bank incloses Malta and Sicily, and that on the opposite coast a similar bank stretches out from the coast of Tripoli leaving a narrow channel the greatest depth of which is 240 fathoms. Here therefore is a broad plateau, which an elevation of about 1,500 feet would convert into a wide extent of land connecting Italy with Africa; while the same elevation would also connect Morocco with Spain, leaving two extensive lakes to represent what is now the Mediterranean Sea, and affording free communication for land animals between Europe and North Africa. That such a state of things existed at a comparatively recent period, is almost certain; not only because a considerable number of identicalspeciesof mammalia inhabit the opposite shores of the Mediterranean, but also because numerous remains of three species of elephants have been found in caves in Malta,—now a small rocky island in which it would be impossible for such animals to live even if they could reach it. Remains of hippopotami are also found at Gibraltar, and many other animals of African types in Greece; all indicating means of communication between South Europe and North Africa which no longer exist. (See Chapter VI. pp. 113-115.)
Mammalia.—There are a few groups of Palæarctic Mammalia that are peculiar to this sub-region. Such are,Dama, the fallow deer, which is now found only in South Europe and North Africa;Psammomys, a peculiar genus of Muridæ, found only in Egypt and Palestine; whileCtenodactylus, a rat-like animal classed in the South American family Octodontidæ, inhabits Tripoli. Among characteristic genera not found in other sub-regions, are,Dysopes, a bat of the family Noctilionidæ;Macroscelides, the elephant shrew, in North Africa;Genetta, the civet, in South Europe;Herpestes, the ichneumon, in North Africa and (?) Spain;Hyæna, in South Europe;Gazella,Oryx,Alcephalus, andAddax, genera of antelopes in North Africa and Palestine;Hyrax, in Syria; andHystrix, the porcupine, in South Europe. Besides these, the camel and the horse were perhaps once indigenous in the eastern parts of the sub-region; and a wild sheep (Ovis musmon) still inhabits Sardinia, Corsica, and the mountains of the south-east of Spain. The presence of the large feline animals—such as the lion, the leopard, the serval, and the hunting leopard—in North Africa, together with several other quadrupeds not found in Europe, have been thought by some naturalists to prove, that this district should not form part of the Palæarctic region. No doubt several Ethiopian groups and species have entered it from the south; but the bulk of its Mammalia still remains Palæarctic, although several of the species have Asiatic rather than European affinities. TheMacacus innuusis allied to an Asiatic rather than an African group of monkeys, and thus denotes an Oriental affinity. Ethiopian affinity is apparently shown by the three genera of antelopes, byHerpestes, and byMacroscelides; but our examination of the Miocene fauna has shown that these were probably derived from Europe originally, and do not form any part of the truly indigenous or ancient Ethiopian fauna. Against these, however, we have the occurrence in North Africa of such purely Palæarctic and non-Ethiopian genera asUrsus,Meles,Putorius,Sus,Cervus,Dama,Capra,Alactaga; together with actual European or West Asiatic species ofCanis,Genetta,Felis,Putorius,Lutra, many bats,Sorex,Crocidura,Crossopus,Hystrix,Dipus,Lepus, andMus. 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. It must be remembered, also, that the lion inhabited Greece even in historic times, while large carnivora were contemporary with man all over Central Europe.
Birds.—So many of the European birds migrate over large portions of the region, and so many others have a wide permanent range, that we cannot expect to find more than a few genera, consisting of one or two species, each, confined to a sub-region; and such appear to be,LusciniolaandPyrophthalma, genera of Sylviidæ. But many are characteristic of this, as compared with other Palæarctic sub-regions; such as,Bradyptetus,Aedon,Dromolœa, andCercomela, among Sylviidæ;CrateropusandMalacocercus, among Timaliidæ;Telophonusamong Laniidæ;CerthilaudaandMirafraamong larks;Pastoramong starlings;Upupa, the hoopoe;HalyconandCeryleamong kingfishers;TurnixandCaccabisamong Gallinæ, and the pheasant as an indigenous bird; together withGyps,VulturandNeophron, genera of vultures. 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. We must bear in mind that the great depression of the Dead Sea has a tropical climate, which accounts for the presence here only, of such a tropical form as the sun-bird (Nectarinea osea).
The total number of the birds of Palestine is 322, and of these no less than 260 are European, at once settling the question of the general affinities of the fauna. Of the remainder eleven belong to North and East Asia, four to the Red Sea, andthirty-one to East Africa, while twenty-seven are peculiar to Palestine. It is evident therefore that an unusual number of East African birds have extended their range to this congenial district, but most of these are desert species and hardly true Ethiopians, and do not much interfere with the general Palæarctic character of the whole assemblage. As an illustration of how wide-spread are many of the Palæarctic forms, we may add, that seventy-nine species of land birds and fifty-five of water birds, are common to Palestine and Britain. The Oriental and Ethiopian generaPycnonotusandNectarineaare found here, whileBessornisandDromolæaare characteristically Ethiopian. Almost all the other genera are Palæarctic.
Persia is another remote region generally associated with the idea of Oriental and almost tropical forms, but which yet undoubtedly belongs to the Palæarctic region. Mr. Blanford's recent collections in this country, with other interesting information, is summarised in Mr. Elwes's paper on the "Geographical Distribution of Asiatic Birds" (Proc. Zool. Soc.1873, p. 647). No less than 127 species are found also in Europe, and thirty-seven others belong to European genera; seven are allied to birds of Central Asia or Siberia, and fifteen to those of North-East Africa, while only three are purely of Indian affinities. This shows a preponderance of nearly nine-tenths of Palæarctic forms, which is fully as much as can be expected in any country near the limits of a great region.
Reptiles and Amphibia.—The climatal conditions being here more favourable to these groups, and the genera being often of limited range, we find some peculiar, and several very interesting forms.Rhinechis, a genus of Colubrine snakes, is found only in South Europe;Trogonophis, one of the Amphisbænians—curious snake-like lizards—is known only from North Africa;Psammosaurus, belonging to the water lizards (Varanidæ) is found in North Africa and North-West India;Psammodromus, a genus of Lacertidæ, is peculiar to South Europe;Hyalosaurus, belonging to the family Zonuridæ, is a lizard of especial interest, as it inhabits North Africa while its nearest ally is theOphisaurusor "glass snake" of North America; the family ofthe scinks is represented byScincusfound in North Africa and Arabia. Besides theseSeps, a genus of sand lizards (Sepidæ) andAgama, a genus of Agamidæ, are abundant and characteristic.
Of Amphibia we haveSeiranota, a genus of salamanders found only in Italy and Dalmatia;Chioglossa, in Portugal, andGeotriton, in Italy, belonging to the same family, are equally peculiar to the sub-region.
Freshwater Fish.—One of the most interesting isTellia, a genus of Cyprinodontidæ found only in alpine pools in the Atlas mountains.Paraphoxinius, found in South-East Europe, andChondrostoma, in Europe and Western Asia, genera of Cyprimidæ, seem almost peculiar to this sub-region.
Insects—Lepidoptera.—Two genera of butterflies,ThaisandDoritis, are wholly confined to this sub-region, the former ranging over all Southern Europe, the latter confined to Eastern Europe and Asia Minor.AnthocharisandZegrisare very characteristic of it, the latter only extending into South Russia, whileDanais,Charaxes, andLibytheaare tropical genera unknown in other parts of Europe.
Coleoptera.—This sub-region is very rich in many groups of Coleoptera, of which a few only can be noticed here. Among Carabidæ it possessesProcerusandProcrustes, almost exclusively, whileBrachinus,Cymindis,Lebia,Graphipterus,Scarites,Chlænius,Calathus, and many others, are abundant and characteristic. Among Lamellicorns—Copridæ, Glaphyridæ, Melolonthidæ, and Cetoniidæ abound. Buprestidæ are plentiful, the generaJulodis,Acmæodera,Buprestis, andSphenopterabeing characteristic. Among Malacoderms—Cebrionidæ, Lampyridæ, and Malachiidæ abound. The Tenebrioid Heteromera are very varied and abundant, and give a character to the sub-region. The Mylabridæ, Cantharidæ, and Œdemeridæ are also characteristic. Of the immense number of Curculionidæ—Thylacites,Brachycerus,Lixus, andAcallesmay be mentioned as among the most prominent. Of Longicorns there are few genera especially characteristic, but perhapsPrinobius,Purpuricenus,Hesperophanes, andParmenaare most so. Of the remaining families, we may mention Clythridæ, Hispidæ, and Cassididæ as being abundant.
The Mediterranean and Atlantic Islands.—The various islands of the Mediterranean are interesting to the student of geographical distribution as affording a few examples of local species of very restricted range, but as a rule they present us with exactly the same forms as those of the adjacent mainland.[6]Their peculiarities do not, therefore, properly come within the scope of this work. The islands of the Atlantic Ocean belonging to this sub-region are, from their isolated position and the various problems they suggest, of much more interest, and their natural history has been carefully studied. We shall therefore give a short account of their peculiar features.
Of the three groups of Atlantic islands belonging to this sub-region, the Canaries are nearest to the Continent, some of the islands being only about fifty miles from the coast of Africa. They are, however, separated from the mainland by a very deep channel (more than 5,000 feet), as shown on our general map. The islands extend over a length of 300 miles; they are very mountainous and wholly volcanic, and the celebrated peak of Teneriffe rises to a height of more than 12,000 feet. The small Madeira group is about 400 miles from the coast of Morocco and 600 from the southern extremity of Portugal; and there is a depth of more than 12,000 feet between it and the continent. The Azores are nearly 1,000 miles west of Lisbon. They are quite alone in mid-Atlantic, the most westerly islands being nearer Newfoundland than Europe, and are surrounded by ocean depths of from 12,000 to 18,000 feet. It will be convenient to take these islands first in order.
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 tofind 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. These genera areCerchneis,Buteo,Asio,Strix,Turdus,Oriolus,Erithacus,Sylvia,Regulus,Saxicola,Motacilla,Plectrophanes,Fringilla,Pyrrhula,Serinus,Sturnus,Picus,Upupa,Columba,Caccabis, andCoturnix. Besides the bullfinch (Pyrrhula) other species show slight differences from their European allies, but not such as to render them more than varieties. The only truly indigenous mammal is a bat of a European species. Nine butterflies inhabit the Azores; eight of them are European species, one North American. Of beetles 212 have been collected, of which no less than 175 are European species; of the remainder, nineteen are found in the Canaries or Madeira, three in South America, while fourteen are peculiar to the islands.
Now these facts (for which we are indebted to Mr. Godman'sNatural History of the Azores) are both unexpected and exceedingly instructive. In most other cases of remote Oceanic islands, a much larger proportion of the fauna is endemic, or consists of peculiar species and often of peculiar genera; as is well shown by the case of the Galapagos and Juan Fernandez, both much nearer to a continent and both containing peculiar genera and species of birds. Now we know that the cause and meaning of this difference is, that in the one case the original immigration is very remote and has never or very rarely been repeated, so that under the unchecked influence of new conditions of life the species have become modified; in the other case, either the original immigration has been recent, or if remote has been so frequently repeated that the new comers have kept up the purity of the stock, and have not allowed time for the new conditions to produce the effect we are sure they would in time produce if not counteracted. For Mr. Godman tells us that many of the birds are modified—instancing the gold-crested wren, blackcap, and rock dove—and he adds, that themodification 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. 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. For the islands are all volcanic, the only stratified rock that occurs being believed to be of Miocene date.
Madeira and the Canaries.—Coming next to Madeira, we find the number of genera of land birds has increased to twenty-eight, of which seventeen are identical with those of the Azores. Some of the commonest European birds—swallows, larks, sparrows, linnets, goldfinches, ravens, and partridges, are among the additions. A gold-crested warbler,Regulus Maderensis, and a pigeon,Columba Trocaz, are peculiar to Madeira.
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.
Land Shells.—The land shells of Madeira offer us an instructive contrast to the birds of the Atlantic Islands. About fifty-six species have been found in Madeira, and forty-two in the small adjacent island of Porto Santo, but only twelve are common to both, and all or almost all are distinct from their nearest allies in Europe and North Africa. Great numbers of fossil shells are also found in deposits of the Newer Pliocene period; andalthough these comprise many fresh species, the two faunas and that of the continent still remain almost as distinct from each other as before. It has been already stated (p.31) that the means by which land mollusca have been carried across arms of the sea are unknown, although several modes may be suggested; but it is evidently a rare event, requiring some concurrence of favourable conditions not always present. 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.
Coleoptera.—The beetles of Madeira and the Canaries have been so carefully collected and examined by Mr. T. V. Wollaston, and those of the Azores described and compared by Mr. Crotch, and they illustrate so many curious points in geographical distribution, that it is necessary to give some account of them. No less than 1,480 species of beetles have been obtained from the Canaries and Madeira, only 360 of which are European, the remainder being peculiar to the islands. 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. 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.
The Madeira group has been more thoroughly explored thanany other, and its comparatively remote situation, combined with its luxuriant vegetation, have been favourable to the development and increase of the peculiar forms which characterize all the Atlantic islands in a more or less marked degree. A consideration of some of its peculiarities will, therefore, best serve to show the bearing of the facts presented by the insect fauna of the Atlantic islands, on the general laws of distribution. The 711 species of beetles now known from the Madeira group, belong to 236 genera; and no less than 44 of these genera are not European but are peculiar to the Atlantic islands. Most of them are, however, closely allied to European genera, of which they are evidently modifications. A most curious general feature presented by the Madeiran beetles, is the total absence of many whole families and large genera abundant in South Europe. Such are the Cicindelidæ, or tiger beetles; the Melolonthidæ, or chafers; the Cetoniidæ, or rose-chafers; the Eumolpidæ and Galerucidæ, large families of Phytophagous, or leaf-eating beetles; and also the extensive groups of Elateridæ and Buprestidæ, which are each represented by but one minute species. Of extensive genera abundant in South Europe, but wholly absent in Madeira, areCarabus,Rhizotrogus,Lampyris, and other genera of Malacoderms;Otiorhynchus,Brachycerus, and 20 other genera of Curculionidæ, comprising more than 300 South European and North African species;Pimelia,Tentyra,Blaps, and 18 other genera of Heteromera, comprising about 550 species in South Europe and North Africa; andTimarcha, containing 44 South European and North African species.
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. But there is another most curious fact noticed byMr. Wollaston; that those species which possess wings in Madeira, often have them rather larger than their allies in Europe. These two facts were connected by Mr. Darwin, who suggested that flying insects are much more exposed to be blown out to sea and lost, than those which do not fly (and Mr. Wollaston had himself supposed that the "stormy atmosphere" of Madeira had something to do with the matter); so that the most frequent fliers would be continually weeded out, while the more sluggish individuals, who either could not or would not fly, remained to continue the race; and this process going on from generation to generation, would, on the well-ascertained principles of selection and abortion by disuse, in time lead to the entire loss of wings by those insects to whom wings werenot a necessity. But those whose wings were essential to their existence would be acted upon in another way. All these must fly to obtain their food or provide for their offspring, and those that flew best would be best able to battle with the storms, and keep themselves safe, and thus those with the longest and most powerful wings would be preserved. If however all the individuals of the species were too weak on the wing to resist the storms, they would soon become extinct.[7]
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, byimmigration across the ocean, in various ways and during a long period. These deficiencies are, on the other hand, quite inconsistent with the theory (still held by some entomologists) that a land communication is absolutely necessary to account for the origin of the Madeiran fauna.
First, then, we can understand how the tiger-beetles (Cicindelidæ) are absent; since they are insects which have a short weak flight, but yet to whom flight is necessary. If a few had been blown over to Madeira, they would soon have become exterminated. The same thing applies to the Melolonthidæ, Cetoniidæ, Eumolpidæ, and Galerucidæ,—all flower and foliage-haunting insects, yet bulky and of comparatively feeble powers of flight. Again, all the large genera abundant in South Europe, which have been mentioned above as absent from Madeira, are wholly apterous (or without wings), and thus their absence is a most significant fact; for it proves that in the case of all insects of moderate size, flight was essential to their reaching the island, which could not have been the case had there been a land connection. 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. Two European species ofBlapsoccur in Madeira, but these are house beetles, and are admitted to have been introduced by man. There are also three species ofMeloe, of which two are European and one peculiar. These are large, sluggish, wingless insects, but they have a most extraordinary and exceptional metamorphosis, the larvae in the first state being minute active insects parasitic on bees, and thus easily conveyed across the ocean. This case is most suggestive, as it accounts for what would be otherwise a difficult anomaly. Another case, not quite so easily explained, is that of the genusAcalles, which is very abundant in all the Atlanticislands and also occurs in South Europe, but is always apterous. It is however closely allied to another genus,Cryptorhynchus, which is apterous in some species, winged in others. We may therefore well suppose that the ancestors ofAcalleswere once in the same condition, and that some of the winged forms reached Madeira, the genus having since become wholly apterous.
We may look at this curious subject in another way. The Coleoptera of Madeira may be divided into those which are found also in Europe or the other islands, and those which are peculiar to it. On the theory of introduction by accidental immigration across the sea, the latter must be the more ancient, since they have had time to become modified; while the former are comparatively recent, and their introduction may be supposed to be now going on. The peculiar influence of Madeira in aborting the wings should, therefore, have acted on the ancient and changed forms much more powerfully than on the recent and unchanged forms. On carefully comparing the two sets of insects (omitting those which have almost certainly been introduced by man) we find, that out of 263 species which have a wide range, only 14 are apterous; while the other class, consisting of 393 species, has no less than 178 apterous; or about 5 per cent in the one case, and 45 per cent in the other.[8]On the theory of a land connection as the main agent in introducing the fauna, both groups must have been introduced at or about the same time, and why one set should have lost their wings and the other not, is quite inexplicable.
Taking all these singular facts, in connection with the total absence of all truly indigenous terrestrial mammalia and reptiles from these islands—even from the extensive group of the Canaries so comparatively near to the continent, we are forced to reject the theory of a land connection as quite untenable; and this view becomes almost demonstrated by the case of the Azores, which being so much further off, and surrounded by such a vast expanse of deep ocean, could only have beenconnected with Europe at a far remoter epoch, and ought therefore to exhibit to us a fauna composed almost entirely of peculiar forms both of birds and insects. Yet, so far from this being the case, the facts are exactly the reverse. 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.
Mr. Wollaston has objected to this view that "storms and hurricanes" are somewhat rare in the latitude of Madeira and the Canaries; but this little affects the question, since thetimeallowed for such operations is so ample. 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. But he also adds the important information that the ordinary winds blow almost uninterruptedly from the north-east, so that there would be always a chance of a little stronger wind than usual bringing insect, or larva, or egg, attached to leaves or twigs. Neither Mr. Wollaston, Mr. Crotch, Mr. A. Murray, nor any other naturalist who upholds the land-connection theory, has attempted to account for the fact of the absence of so many extensive groups of insects that ought to be present, as well as of all small mammalia and reptiles.
Cape Verd Islands.—There is yet another group of Atlantic islands which is very little known, and which is usually considered to be altogether African—the Cape Verd Islands, situated between 300 and 400 miles west of Senegal, and a little to the south of the termination of the Sahara. The evidence that we possess as to the productions of these islands, shows that, like the preceding groups, they are truly oceanic, and have probably derived their fauna from the desert and the Canaries to the north-east of them rather than from the fertile and more trulyEthiopian districts of Senegal and Gambia to the east. There is a mingling of the two faunas, but the preponderance seems to be undoubtedly with the Palæarctic rather than with the Ethiopian. I owe to Mr. R. B. Sharpe of the British Museum, a MS. list of the birds of these islands, twenty-three species in all. Of these eight are of wide distribution and may be neglected. Seven are undoubted Palæarctic species, viz.:—Milvus ictinus,Sylvia atricapilla,S. conspicillata,Corvus corone,Passer salicarius,Certhilauda desertorum,Columba livia. Three are peculiar species, but of Palæarctic genera and affinities, viz.:—Calamoherpe brevipennis,Ammomanes cinctura, andPasser jagoensis. Against this we have to set two West African species,Estrilda cinereaandNumida meleagris, both of which were probably introduced by man; and three which are of Ethiopian genera and affinities, viz.:—Halcyon erythrorhyncha, closely allied toH. semicæruleaof Arabia and North-east Africa, and therefore almost Palæarctic;Accipiter melanoleucus; andPyrrhulauda nigriceps, an Ethiopian form; but the same species occurs in the Canaries.
The Coleoptera of these islands have been also collected by Mr. Wollaston, and he finds that they have generally the same European character as those of the Canaries and Madeira, several of the peculiar Atlantic genera, such asAcallesandHegeter, occurring, while others are represented by new but closely allied genera. Out of 275 species 91 were found also in the Canaries and 81 in the Madeiran group; a wonderful amount of similarity when we consider the distance and isolation of these islands and their great diversity of climate and vegetation.
This connection of the four groups of Atlantic islands now referred to, receives further support from the occurrence of land-shells of the subgenusLeptaxisin all the groups, as well as in Majorca; and by another subgenus,Hemicycla, being common to the Canaries and Cape Verd islands. Combining these several classes of facts, we seem justified in extending the Mediterranean sub-region to include the Cape Verd Islands.