The Geographical Distribution of Animals/Chapter 14
PART III. (continued.)
A REVIEW OF THE CHIEF FORMS OF ANIMAL LIFE IN THE SEVERAL REGIONS AND SUB-REGIONS, WITH THE INDICATIONS THEY AFFORD OF GEOGRAPHICAL MUTATIONS.
THE NEOTROPICAL REGION.
This region, comprehending not only South America but Tropical North America and the Antilles, may be compared as to extent with the Ethiopian region; but it is distinguished from all the other great zoological divisions of the globe, by the small proportion of its surface occupied by deserts, by the large proportion of its lowlands, and by the altogether unequalled extent and luxuriance of its tropical forests. It further possesses a grand mountain range, rivalling the Himalayas in altitude and far surpassing them in extent, and which, being wholly situated within the region and running through eighty degrees of latitude, offers a variety of conditions and an extent of mountain slopes, of lofty plateaus and of deep valleys, which no other tropical region can approach. It has a further advantage in a southward prolongation far into the temperate zone, equivalent to a still greater extension of its lofty plateaus; and this has, no doubt, aided the development of the peculiar alpine forms of life which abound in the southern Andes. The climate of this region is exceptionally favourable. Owing to the lofty mountain range situated along its western margin, the moisture-laden trade winds from the Atlantic have free access to the interior. A sufficient proportion of this moisture reaches the higher slopes of the Andes, where its condensation gives rise to innumerable streams, which cut deep ravines and carry down such an amount of sediment, that they have formed the vast plains of the Amazon, of Paraguay, and of the Orinooko out of what were once, no doubt, arms of the sea, separating the large islands of Guiana, Brazil, and the Andes. From these concurrent favourable conditions, there has resulted that inexhaustible variety of generic and specific forms with a somewhat limited range of family and ordinal types, which characterise neotropical zoology to a degree nowhere else to be met with.
Together with this variety and richness, there is a remarkable uniformity of animal life over all the tropical continental portions of the region, so that its division into sub-regions is a matter of some difficulty. There is, however, no doubt about separating the West Indian islands as forming a well-marked subdivision; characterised, not only by that poverty of forms which is a general feature of ancient insular groups, but also by a number of peculiar generic types, some of which are quite foreign to the remainder of the region. We must exclude, however, the islands of Trinidad, Tobago, and a few other small islands near the coast, which zoologically form a part of the main land. Again, the South Temperate portion of the continent, together with the high plateaus of the Andes to near the equator, form a well-marked subdivision, characterised by a peculiar fauna, very distinct both positively and negatively from that of the tropical lowland districts. The rest of Tropical South America is so homogeneous in its forms of life that it cannot be conveniently subdivided for the purposes of a work like the present. There are, no doubt, considerable differences in various parts of its vast area, due partly to its having been once separated into three or more islands, in part to existing diversities of physical conditions; and more exact knowledge may enable us to form several provinces or perhaps additional sub-regions. A large proportion of the genera, however, when sufficiently numerous in species, range over almost the whole extent of this sub-region wherever the conditions are favourable. Even the Andes do not seem to form such a barrier as has been supposed. North of the equator, where its western slopes are moist and forest-clad, most of the genera are found on both sides. To the south of this line its western valleys are arid and its lower plains almost deserts; and thus the absence of a number of groups to which verdant forests are essential, can be traced to the unsuitable conditions rather than to the existence of the mountain barrier. All Tropical South America, therefore, is here considered to form but one sub-region.
The portion of North America that lies within the tropics, closely resembles the last sub-region in general zoological features. It possesses hardly any positive distinctions; but there are several of a negative character, many important groups being wholly confined to South America. On the other hand many genera range into Mexico and Guatemala from the north, which never reach South America; so that it is convenient to separate this district as a sub-region, which forms, to some extent, a transition to the Nearctic region.
General Zoological Features of the Neotropical Region.—Richness combined with isolation is the predominant feature of Neotropical zoology, and no other region can approach it in the number of its peculiar family and generic types. It has eight families of Mammalia absolutely confined to it, besides several others which are rare elsewhere. These consist of two families of monkeys, Cebidæ and Hapalidæ, both abounding in genera and species; the Phyllostomidæ, or blood-sucking bats; Chinchillidæ and Caviidæ among rodents; besides the greater part of the Octodontidæ, Echimyidæ and Cercolabidæ. Among edentata, it has Bradypodidæ, or sloths, Dasypodidæ, or armadillos, and Myrmecophagidæ, or anteaters, constituting nearly the entire order; while Procyonidæ, belonging to the carnivora, and Didelphyidæ, a family of marsupials, only extend into the Nearctic region. It has also many peculiar groups of carnivora and of Muridæ, making a total of full a hundred genera confined to the region. Hardly less remarkable is the absence of many wide-spread groups. With the exception of one genus in the West Indian islands and a Sorex which reaches Guatemala and Costa Rica, the Insectivora are wholly wanting; as is also the extensive and wide-spread family of the Viverridæ. It has no oxen or sheep, and indeed no form of ruminant except deer and llamas; neither do its vast forests and grassy plains support a single form of non-ruminant ungulate, except the tapir and the peccary.
Birds.—In birds, the Neotropical region is even richer and more isolated. It possesses no less than 23 families wholly confined within its limits, with 7 others which only extend into the Nearctic region. The names of the peculiar families are: Cœrebidæ, or sugar-birds; Phytotomidæ, or plant-cutters; Pipridæ, or manakins; Cotingidæ, or chatterers; Formicariidæ, or ant-thrushes; Dendrocolaptidæ, or tree-creepers; Pteroptochidæ; Rhamphastidæ, or toucans; Bucconidæ, or puff-birds; Galbulidæ, or jacamas; Todidæ, or todies; Momotidæ, or motmots; Steatornithidæ, the guacharo, or oil-bird; Cracidæ, or curassows; Tinamidæ, or tinamous; Opisthocomidæ, the hoazin; Thinocoridæ; Cariamidæ; Aramidæ; Psophiidæ, or trumpeters; Eurypygidæ, or sun-bitterns; and Palamedeidæ, or horned-screamers. The seven which it possesses in common with North America are: Vireonidæ, or greenlets; Mniotiltidæ, or wood-warblers; Tanagridæ, or tanagers; Icteridæ, or hang-nests; Tyrannidæ, or tyrant-shrikes; Trochilidæ, or humming-birds; and Conuridæ, or macaws. Most of these families abound in genera and species, and many are of immense extent; such as Trochilidæ, with 115 genera, and nearly 400 species; Tyrannidæ, with more than 60 genera and nearly 300 species; Tanagridæ, with 43 genera and 300 species; Dendrocolaptidæ with 43 genera and more than 200 species; and many other very large groups. There are nearly 600 genera peculiar to the Neotropical region; but in using this number as a basis of comparison with other regions we must remember, that owing to several ornithologists having made the birds of South America a special study, they have perhaps been more minutely subdivided than in the case of other entire tropical regions.
Distinctive Characters of Neotropical Mammalia.—It is important also to consider the kind and amount of difference between the various animal forms of this region and of the Old World. To begin with the Quadrumana, all the larger American monkeys (Cebidæ) differ from every Old World group in the possession of an additional molar tooth in each jaw; and it is in this group alone that the tail is developed into a prehensile organ of wonderful power, adapting the animals to a purely arboreal life. Four of the genera, comprising more than half the species, have the prehensile tail, the remainder having this organ either short, or lax as in the Old World monkeys. Other differences from Old World apes, are the possession of a broad nasal septum, and a less opposable thumb; and the absence of cheek-pouches, ischial callosities, and a bony ear-tube. The Hapalidæ, or marmozets, agree with the Cebidæ in all these characters, but have others in addition which still more widely separate them from the Simiidæ; such as an additional premolar tooth, acute claws, and thumb not at all opposable; so that the whole group of American monkeys are radically different from the remainder of the order.
The Procyonidæ are a distinct family of Carnivora, which make up for the scarcity of Mustelidæ in South America. The Suidæ are represented by the very distinct genus Dicotyles (Peccary) forming a separate sub-family, and differing from all other genera in their dentition, the absence of tail and of one of the toes of the hind feet, the possession of a dorsal gland, and only two mammæ. The rodents are represented by the Chinchillidæ and Caviidæ, the latter comprising the largest animals in the order. The Edentata are almost wholly confined to this region; and the three families of the sloths (Bradypodidæ), armadillos (Dasypodidæ), and ant-eaters (Myrmecophagidæ), are widely separated in structure from any Old World animals. Lastly, we have the opossums (Didelphyidæ), a family of marsupials, but having no close affinity to any of the numerous Australian forms of that order. We have already arrived at the conclusion that the presence of marsupials in South America is not due to any direct transference from Australia, but that their introduction is comparatively recent, and that they came from the Old World by way of North America (vol. i., p. 155). But the numerous and deep-seated peculiarities of many other of its mammalia, would indicate a very remote origin; and a long-continued isolation of South America from the rest of the world is required, in order to account for the preservation and development of so many distinct groups of comparatively low-type quadrupeds.
Distinctive Characters of Neotropical Birds.—The birds which are especially characteristic of this region, present similar distinctive features. In the enormous group of Passerine birds which, though comprising nearly three-fourths of the entire class, yet presents hardly any well-marked differences of structure by which it can be subdivided—the families confined to America are, for the most part, more closely related to each other than to the Old World groups. The ten families forming the group of "Formicaroid Passeres," in our arrangement (vol. i., p. 94), are characterised by the absence of singing muscles in the larynx, and also by an unusual development of the first primary quill; and seven of this series of families (which are considered to be less perfectly developed than the great mass of Old World passeres) are exclusively American, the three belonging to the Eastern hemisphere being of small extent. Another group of ten families—our "Tanagroid Passeres," are characterised by the abortion or very rudimentary condition of the first quill; and of these, five are exclusively American, and have numerous genera and species, while only two are non-American, and these are of small extent. On the other hand the "Turdoid Passeres," consisting of 23 families and comprising all the true "singing-birds," is poorly represented in America; no family being exclusively Neotropical, and only three being at all fully represented in South America, though they comprise the great mass of the Old World passeres. These peculiarities, which group together whole series of families of American birds, point to early separation and long isolation, no less surely than the more remarkable structural divergences presented by the Neotropical mammalia.
In the Picariæ, we have first, the toucans (Rhamphastidæ); an extraordinary and beautiful family, whose enormous gaily-coloured bills and long feathered tongues, separate them widely from all other birds. The Galbulidæ or jacamars, the motmots (Momotidæ), and the curious little todies (Todidæ) of the Antilles, are also isolated groups. But most remarkable of all is the wonderful family of the humming-birds, which ranges over all America from Tierra del Fuego to Sitka, and from the level plains of the Amazon to above the snow-line on the Andes; which abounds both in genera, species, and individuals, and is yet strictly confined to this continent alone! How vast must have been the time required to develop those beautiful and highly specialized forms out of some ancestral swift-like type; how complete and long continued the isolation of their birthplace to have allowed of their modification and adaptation to such divergent climates and conditions, yet never to have permitted them to establish themselves in the other continents. No naturalist can study in detail this single family of birds, without being profoundly impressed with the vast antiquity of the South American continent, its long isolation from the rest of the land surface of the globe, and the persistence through countless ages of all the conditions requisite for the development and increase of varied forms of animal life.
Passing on to the parrot tribe, we find the peculiar family of the Conuridæ, of which the macaws are the highest development, very largely represented. It is in the gallinaceous birds however that we again meet with wholly isolated groups. The Cracidæ, including the curassows and guans, have no immediate relations with any of the Old World families. Professor Huxley considers them to approach nearest to (though still very remote from) the Australian megapodes; and here, as in the case of the marsupials, we probably have divergent modifications of an ancient type once widely distributed, not a direct communication between the southern continents. The Tinamidæ or tinamous, point to a still more remote antiquity, since their nearest allies are believed to be the Struthiones or ostrich tribe, of which a few representatives are scattered widely over the globe. The hoazin of Guiana (Opisthocomus) is another isolated form, not only the type of a family, but perhaps of an extinct order of birds. Passing on to the waders, we have a number of peculiar family types, all indicative of antiquity and isolation. The Cariama of the plains of Brazil, a bird somewhat intermediate between a bustard and a hawk, is one of these; the elegant Psophia or trumpeter of the Amazonian forests; the beautiful little sun-bittern of the river banks (Eurypyga); and the horned screamers (Palamedea), all form distinct and isolated families of birds, to which the Old World offers nothing directly comparable.
Reptiles.—The Neotropical region is very rich in varied forms of reptile life, and the species are very abundant. It has six altogether peculiar families, and several others which only range into the Nearctic region, as well as a very large number of peculiar or characteristic genera. As the orders of reptiles differ considerably in their distributional features, they must be considered separately.
The snakes (Ophidia) differ from all other reptiles, and from most other orders of vertebrates, in the wide average distribution of the families; so that such an isolated region as the Neotropical possesses no peculiar family, nor even one confined to the American continent. The families of most restricted range are—the Scytalidæ, only found elsewhere in the Philippine islands; the Amblycephalidæ, common to the Oriental and Neotropical regions; and the Tortricidæ, most abundant in the Oriental region, but found also in the Austro-Malay islands and Tropical South America. Sixteen of the families of snakes occur in the region, the Colubridæ, Amblycephalidæ, and Pythonidæ, being those which are best represented by peculiar forms. There are 25 peculiar or characteristic genera, the most important being Dromicus (Colubridæ); Boa, Epicrates, and Ungalia (Pythonidæ); Elaps (Elapidæ); and Craspedocephalus (Crotalidæ).
The lizards (Lacertilia) are generally more restricted in their range; hence we find that out of 15 families which inhabit the region, 5 are altogether peculiar, and 4 more extend only to N. America. The peculiar families are Helodermidæ, Anadiadæ, Chirocolidæ, Iphisiadæ, and Cercosauridæ; but it must be noted that these all possess but a single genus each, and only two of them (Chirocolidæ and Cercosauridæ) have more than a single species. The families which range over both South and North America are Chirotidæ, Chalcidæ, Teidæ, and Iguanidæ; the first and second are of small extent, but the other two are very large groups, the Teidæ possessing 12 genera and near 80 species; the Iguanidæ 40 genera and near 150 species; the greater part of which are Neotropical. There are more than 50 peculiar or highly characteristic genera of lizards, about 40 of which belong to the Teidæ and Iguanidæ, which thus especially characterize the region. The most important and characteristic genera are the following; Ameiva (Teidæ); Gymnophthalmus (Gymnophthalmidæ); Celestus and Diploglossus (Scincidæ); Sphærodactylus (Geckotidæ); Liocephalus, Liolæmus, Proctotretus, and many smaller genera (Iguanidæ). The three extensive Old World families Varanidæ, Lacertidæ, and Agamidæ, are absent from the entire American continent.
In the order Crocodilia, America has the peculiar family of the alligators (Alligatoridæ), as well as several species of true crocodiles (Crocodilidæ). The Chelonia (tortoises) are represented by the families Testudinidæ and Chelydidæ, both of wide range; but there are six peculiar genera,—Dermatemys and Staurotypus belonging to the former family,—Peltocephalus, Podocnemis, Hydromedusa, and Chelys, to the latter. Some of the Amazon river-turtles of the genus Podocnemis rival in size the largest species of true marine turtles (Cheloniidæ), and are equally good for food.
Amphibia.—The Neotropical region possesses representatives of sixteen families of Amphibia of which four are peculiar; all belonging to Anoura or tail-less Batrachians. The Cæciliadæ or snake-like amphibia, are represented by two peculiar genera, Siphonopsis and Rhinatrema. Tailed Batrachians are almost unknown, only a few species of Spelerpes (Salamandridæ) entering Central America, and one extending as far south as the Andes of Bogota in South America. Tail-less Batrachians on the other hand, are abundant; there being 14 families represented, of which 4,—Rhinophrynidæ, Hylaplesidæ, Plectromantidæ, and Pipidæ are peculiar. None of these families contain more than a single genus, and only the second more than a single species; so that it is not these which give a character to the South American Amphibia-fauna. The most important and best represented families are, Ranidæ (true frogs), with eleven genera and more than 50 species; Polypedatidæ (tree-frogs) with seven genera and about 40 species; Hylidæ (tree-frogs) with eight genera and nearly 30 species; Engystomidæ (toads) (5 genera), Bombinatoridæ (frogs), (4 genera), Phryniscidæ and Bufonidæ (toads), (each with 2 genera), are also fairly represented. All these families are widely distributed, but the Neotropical genera are, in almost every case, peculiar.
Fresh-water fishes.—The great rivers of Tropical America abound in fish of many strange forms and peculiar types. Three families, and three sub-family groups are peculiar, while the number of peculiar genera is about 120. The peculiar families are Polycentridæ, with two genera; Gymnotidæ, a family which includes the electric eels, (5 genera); and Trygonidæ, the rays, which are everywhere marine except in the great rivers of South America, where many species are found, belonging to two genera. Of the extensive family Siluridæ, three sub-families Siluridæ anomalopteræ, S. olisthopteræ, and S. branchiolæ, are confined to this region. The larger and more important of the peculiar genera are the following: Percilia, inhabiting Chilian and Percichthys South Temperate rivers, belong to the Perch family (Percidæ); Acharnes, found only in Guiana, belongs to the Nandidæ, a family of wide range in the tropics; the Chromidæ, a family of exclusively fresh-water fishes found in the tropics of the Ethiopian, Oriental and Neotropical regions, are here represented by 15 genera, the more important being Acara (17 sp.), Heros (26 sp.), Crenicichla (9 sp.), Satanoperca (7 sp.). Many of these fishes are beautifully marked and coloured. The Siluridæ proteropteræ are represented by 14 genera, of which Pimelodus (42 sp.), and Platystoma (11 sp.), are the most important; the Siluridæ stenobranchiæ by 11 genera, the chief being Doras (13 sp.), Auchenipterus (9 sp.), and Oxydoras (7 sp.). The Siluridæ proteropodes are represented by 16 genera, many of them being among the most singular of fresh-water fishes, clothed in coats of mail, and armed with hooks and serrated spines. The following are the most important,—Chætostomus (25 sp.), Loricaria (17 sp.), Plecostomus (15 sp.) and Callichthys (11 sp.). The Characinidæ are divided between Tropical America and Tropical Africa, the former possessing about 40 genera and 200 species. The Haplochitonidæ are confined to South America and Australia; the American genus being Haplochiton. The Cyprinodontidæ are represented by 18 genera, the most important being, Pœcilia (16 sp.), Girardinus (10 sp.), and Gambusia (8 sp.) The Osteoglossidæ, found in Australian and African rivers, are represented in South America by the peculiar Arapaima, the "pirarucu" of the Amazon. The ancient Sirenoidei, also found in Australia and Africa, have the Lepidosiren as their American representative. Lastly, Ellipesurus is a genus of rays peculiar to the fresh waters of South America. We may expect these numbers to be largely increased and many new genera to be added, when the extensive collections made by Agassiz in Brazil are described.
Summary of Neotropical Vertebrates.—Summarizing the preceding facts, we find that the Neotropical region possesses no less than 45 families and more than 900 genera of Vertebrata which are altogether peculiar to it; while it has representatives of 168 families out of a total of 330, showing that 162 families are altogether absent. It has also representatives of 131 genera of Mammalia of which 103 are peculiar to it, a proportion of 4⁄5; while of 683 genera of land-birds no less than 576 are peculiar, being almost exactly 5⁄6 of the whole. These numbers and proportions are far higher than in the case of any other region.
The Neotropical region is so excessively rich in insect life, it so abounds in peculiar groups, in forms of exquisite beauty, and in an endless profusion of species, that no adequate idea of this branch of its fauna can be conveyed by the mere enumeration of peculiar and characteristic groups, to which we are here compelled to limit ourselves. Our facts and figures will, however, furnish data for comparison; and will thus enable those who have some knowledge of the entomology of any other country, to form a better notion of the vast wealth of insect life in this region, than a more general and picturesque description could afford them.
Lepidoptera.—The Butterflies of South America surpass those of all other regions in numbers, variety and beauty; and we find here, not only more peculiar genera and families than elsewhere, but, what is very remarkable, a fuller representation of the whole series of families. Out of the 16 families of butterflies in all parts of the world, 13 are found here, and 3 of these are wholly peculiar—Brassolidæ, Heliconidæ, and Eurygonidæ, with a fourth, Erycinidæ, which only extends into the Nearctic region; so that there are 4 families peculiar to America. These four families comprise 68 genera and more than 800 species; alone constituting a very important feature in the entomology of the region. But in almost all the other families there are numbers of peculiar genera, amounting in all to about 200, or not far short of half the total number of genera in the world—(431). We must briefly notice some of the peculiarities of the several families, as represented in this region. The Danaidæ consist of 15 genera, all peculiar, and differing widely from the generally sombre-tinted forms of the rest of the world. The delicate transparent-winged Ithomias of which 160 species are described, are the most remarkable. Melinæa, Napeogenes, Ceratina and Dircenna are more gaily coloured, and are among the chief ornaments of the forests. The Satyridæ are represented by 25 peculiar genera, many of great beauty; the most remarkable and elegant being the genus Hætera and its allies, whose transparent wings are delicately marked with patches of orange, pink, or violet. The genus Morpho is perhaps the grandest development of the butterfly type, being of immense size and adorned with the most brilliant azure tints, which in some species attain a splendour of metallic lustre unsurpassed in nature. The Brassolidæ are even larger, but are crepuscular insects, with rich though sober colouring. The true Heliconii are magnificent insects, most elegantly marked with brilliant and strongly contrasted tints. The Nymphalidæ are represented by such a variety of gorgeous insects that it is difficult to select examples. Prominent are the genera Catagramma and Callithea, whose exquisite colours and symmetrical markings are unique and indescribable; and these are in some cases rivalled by Agrias and Prepona, which reproduce their style of coloration although not closely allied to them. The Erycinidæ, consisting of 59 genera and 560 species, comprise the most varied and beautiful of small butterflies; and it would be useless to attempt to indicate the unimaginable combinations of form and colour they present. It must be sufficient to say that nothing elsewhere on the globe at all resembles them. In Lycænidæ the world-wide genus Thecla is wonderfully developed, and the South American species not only surpass all others in size and beauty, but some of them are so gorgeous on the under surface of their wings, as to exceed almost all the combinations of metallic tints we meet with in nature. The last family, Hesperidæ, is also wonderfully developed here, the species being excessively numerous, while some of them redeem the character of this generally sober family, by their rich and elegant coloration.
In the only other group of Lepidoptera we can here notice, the Sphingina, the Neotropical region possesses some peculiar forms. The magnificent diurnal butterfly-like moths, Urania, are the most remarkable; and they are rendered more interesting by the occurrence of a species closely resembling them in Madagascar. Another family of day-flying moths, the Castniidæ, is almost equally divided between the Neotropical and Australian regions, although the genera are more numerous in the latter. The American Castnias are large, thick-bodied insects, with a coarse scaly surface and rich dull colours; differing widely from the glossy and gaily coloured Agaristas, which are typical of the family in the East.
Coleoptera.—This is so vast a subject that, as in the case of the regions already treated, we must confine our attention to a few of the more important and best known families as representatives of the entire order.
Cicindelidæ.—We find here examples of 15 out of the 35 genera of these insects; and 10 of these genera are peculiar. The most important are Oxychila (11 sp.), Hiresia (14 sp.), and Ctenostoma (26 sp.). Odontochila (57 sp.) is the most abundant and characteristic of all, but is not wholly peculiar, there being a species in the Malay archipelago. Tetracha, another large genus, has species in Australia and a few in North America and Europe. The small genus Peridexia is divided between Brazil and Madagascar,—a somewhat similar distribution to that of Urania noticed above. One genus, Agrius, is confined to the southern extremity of the continent.
Carabidæ.—Besides a considerable number of cosmopolitan or wide-spread genera, this family is represented by more than 100 genera which are peculiar to the Neotropical region. The most important of these are Agra (150 sp.), Ardistomus (44 sp.), Schizogenius (25 sp.), Pelecium (24 sp.), Calophena (22 sp.), Aspidoglossa (21 sp.), and Lia, Camptodonotus, Stenocrepis, and Lachnophorus, with each more than 12 species. These are all tropical; but there are also a number of genera (26) peculiar to Chili and South Temperate America. The most important of these are Antarctia (29 sp,), all except two or three confined to South Temperate America; Scelodontis (10 sp.), mostly Chilian; Feronomorpha (6 sp.) all Chilian; and Tropidopterus (4 sp.), all Chilian. Helluomorpha (18 sp.), is confined to North and South America; Galerita, Callida, and Tetragonoderus, are large genera which are chiefly South American but with a few species scattered over the other tropical regions, Casnonia and Lebia are cosmopolite, but most abundant in South America. Pachyteles is mostly South American but with a few species in West Africa; while Lobodonotus has one species in South America and two in Africa.
Lucanidæ.—The Neotropical species of this family almost all belong to peculiar genera. Those common to other regions are Syndesus, confined to Tropical South America and Australia, and Platycerus which is Palæarctic and Nearctic, with one species in Brazil. The most remarkable genus is undoubtedly Chiasognathus, confined to Chili. These are large insects of metallic green colours, and armed with enormous serrated mandibles. The allied genera, Pholidotus and Sphenognathus, inhabit Tropical South America. Streptocerus confined to Chili, is interesting, as being allied to the Australian Lamprima. The other genera present no remarkable features; but Sclerognathus and Leptinoptera are the most extensive.
Cetoniidæ.—These magnificent insects are but poorly represented in America; the species being mostly of sombre colours. There are 14 genera, 12 of which are peculiar. The most extensive genus is Gymnetis, which, with its allies Cotinis and Allorhina, form a group which comprehends two-thirds of the Neotropical species of the family. The only other genera of importance are, Inca (7 sp.), remarkable for their large size, and being the only American group in which horns are developed on the head; and Trigonopeltastes (6 sp.), allied to the European Trichius. The non-peculiar genera are, Stethodesma, of which half the species are African and half tropical American; and Euphoria, confined to America both North and South.
Buprestidæ.—In this fine group the Neotropical region is tolerably rich, having examples of 39 genera, 18 of which are peculiar to it. Of these, the most extensive are Conognatha and Halecia, which have a wide range over most parts of the region; and Dactylozodes, confined to the south temperate zone. Of important genera which range beyond the region, Dicerca is mainly Nearctic and Palæarctic; Cinyra has a species in North America and one in Australia; Curis is divided between Chili and Australia; the Australian genus Stigmodera has a species in Chili; Polycesta has a species in Madagascar, two in the Mediterranean region, and a few in North America; Acherusia is divided between Australia and Brazil; Ptosima has one species in south temperate America, the rest widely scattered from North America to the Philippines; Actenodes has a single species in North America and another in West Africa; Colobogaster has two in West Africa, one in Java and one in the Moluccas. The relations of South America and Australia as indicated by these insects has already been sufficiently noticed under the latter region.
Longicornia.—The Neotropical Longicorn Coleoptera are overwhelming in their numbers and variety, their singularity and their beauty. In the recent Catalogue of Gemminger and Harold, it is credited with 516 genera, 489 of which are peculiar to it; while it has only 5 genera in common (exclusively) with the Nearctic, and 4 (in the same way) with the Australian region. Only the more important genera can be here referred to, under the three great families into which these insects are divided.
The Prionidæ are excessively numerous, being grouped in 64 genera, more than double the number possessed by any other region; and 61 of these are peculiar. The three, common to other regions, are, Parandra and Mallodon, which are widely distributed; and Ergates, found also in California and Europe. The most remarkable genera are, the magnificently-coloured Psalidognathus and Pyrodes; the large and strangely marked Macrodontia; and Titanus, the largest insect of the entire family.
Of the Cerambycidæ there are 233 genera, exceeding by one-half, the number in any other region; and 225 of these are peculiar. Only 2 are common to the Neotropical and Nearctic regions exclusively, and 3 to the Neotropical and Australian. The most extensive genera are the elegant Ibidion (80 sp.); the richly-coloured Chrysoprasis (47 sp.); the prettily-marked Trachyderes (53 sp.); with Odontocera (25 sp.); Criodon (22 sp.); and a host of others of less extent, but often of surpassing interest and beauty. The noteworthy genera of wide range are, Oeme and Cyrtomerus, which have each a species in West Africa, and Hammatocerus, which has one in Australia.
The Lamiidæ have 219 genera, and this is the only tropical region in which they do not exceed the Cerambycidæ. This number is almost exactly the same as that of the Oriental genera, but here there are more peculiar groups, 203 against 160 in the other region. The most extensive genera are Hemilophus (80 sp.), Colobothea (70 sp.), Acanthoderes (56 sp.), Oncoderes (48 sp.), Lepturgus (40 sp.), Hypsioma (32 sp.), and Tæniotes (20 sp.). Macropus longimanus, commonly called the harlequin beetle, is one of the largest and most singularly-marked insects in the whole family. Leptostylus has a single species in New Zealand; Acanthoderes has one species in Europe, W. Africa, and Australia, respectively; Spalacopsis has a species in W. Africa; Pachypeza is common to S. America and the Philippines; Mesosa is Oriental and Palæarctic, but has one species on the Amazon; Apomecyna ranges through the tropics of the Eastern Hemisphere, but has two species in S. America; Acanthocinus has one species in Tasmania, and the rest in South America, North America, and Europe; Phæa is wholly Neotropical, except two species in the Philippine Islands.
General Conclusions as to the Neotropical Insect-fauna.—Looking at the insects of the Neotropical region as a whole, we are struck with the vast amount of specialty they present; and, considering how many causes there are which must lead to the dispersal of insects, the number of its groups which are scattered over the globe is not nearly so great as we might expect. This points to a long period of isolation, during which the various forms of life have acted and reacted on each other, leading to such a complex yet harmoniously-balanced result as to defy the competition of the chance immigrants that from time to time must have arrived. This is quite in accordance with the very high antiquity we have shown most insect-forms to possess; and it is no doubt owing to this antiquity, that such a complete diversity of generic forms has been here brought about, without any important deviation from the great family types which prevail over the rest of the globe.
Land Shells.—The Neotropical region is probably the richest on the globe in Terrestrial Mollusca, but this is owing, not to any extreme productiveness of the equatorial parts of the continent, where almost all other forms of life are so largely developed, but to the altogether exceptional riches of the West India Islands. The most recent estimates show that the Antilles contain more species of land shells than all the rest of the region, and almost exactly as many as all continental America, north and south.
Mr. Thomas Bland, who has long studied American land shells, points out a remarkable difference in the distribution of the Operculated and Inoperculated groups, the former being predominant on the islands, the latter on the continent. The Antilles possess over 600 species of Operculata, to about 150 on the whole American continent, the genera being as 22 to 14. Of Inoperculata the Antilles have 740, the Continent 1,250, the genera being 18 and 22. The proportions of the two groups in each country are, therefore:
|West India Islands.||American Continent.|
The extensive family of the Helicidæ is represented by 22 genera, of which 6 are peculiar. Spiraxis is confined to Central America and the Antilles; Stenopus and Sagda are Antillean only; Orthalicus, Macroceramus, and Bulimulus have a wider range, the last two extending into the southern United States. Important and characteristic genera are, Glandina, in all the tropical parts of the region; Cylindrella, in Central America and the Antilles; Bulimus, containing many large and handsome species in South America; Stenogyra, widely spread in the tropics; and Streptaxis, in Tropical South America.
Among the Operculata, the Aciculidæ are mostly Antillean, two genera being peculiar there, and one, Truncatella, of wide distribution, but most abundant in the West Indian Islands. The Cyclostomidæ are represented by 15 genera, 9 being peculiar to the region, and 5 of these (belonging to the sub-family Licinidæ) to the Antilles only. Of these peculiar genera Cistula and Chondropoma are the most important, ranging over all the tropical parts of the region. Other important genera are Cyclotus and Megalomastoma; while Cyclophorus also occurs all over the region. The Helicinidæ are mostly Neotropical, six out of the seven genera being found here, and four are peculiar. Stoastoma, is one of the largest genera; and, with Trochatella and Alcadia, is confined to the Antilles, while the wide-spread Helicina is most abundant there.
The Limacidæ, or Old World slugs, are absent from the region, their place being taken by the allied family, Oncidiadæ.
Marine Shells.—We go out of our usual course to say a few words about the marine shells of this region, because their distribution on the two sides of the continent is important, as an indication of the former separation of North and South America, and the connection of the Atlantic and Pacific Oceans. It was once thought that no species of shells were common to the two sides of the Central American Isthmus, and Dr. Mörch still holds that opinion; but Dr. Philip Carpenter, who has paid special attention to the subject, considers that there are at least 35 species absolutely identical, while as many others are so close that they may be only varieties. Nearly 70 others are distinct but representative species. The genera of marine mollusca are very largely common to the east and west coasts, more than 40 being so named in the lists published by Mr. Woodward. The West Indian Islands being a rich shell district, produce a number of peculiar forms, and the west coast of South America is, to some extent, peopled by Oriental and Pacific genera of shells. On the west coast there is hardly any coral, while on the east it is abundant, showing a difference of physical conditions that must have greatly influenced the development of mollusca. When these various counteracting influences are taken into consideration, the identity or close affinity of about 140 species and 40 genera on the two sides of the Isthmus of Panama becomes very important; and, combined with the fact of 48 species of fish (or 30 per cent. of those known) being identical on the adjacent coasts of the two oceans (as determined by Dr. Günther), render it probable that Central America has been partially submerged up to comparatively recent geological times. Yet another proof of this former union of two oceans is to be found in the fossil corals of the Antilles of the Miocene age, which Dr. Duncan finds to be more allied to existing Pacific forms, than to those of the Atlantic or even of the Caribbean Sea.
In the concluding part of this work devoted to geographical zoology, the sub-regions are arranged in the order best adapted to exhibit them in a tabular form, and to show the affinities of the several regions; but for our present purpose it will be best to take first in order that which is the most important and most extensive, and which exhibits all the peculiar characteristics of the region in their fullest development. We begin therefore with our second division.
II. Tropical South-America, or the Brazilian Sub-region.
This extensive district may be defined as consisting of all the tropical forest-region of South America, including all the open plains and pasture lands, surrounded by, or intimately associated with, the forests. Its central mass consists of the great forest-plain of the Amazons, extending from Paranaiba on the north coast of Brazil (long. 42° W.) to Zamora, in the province of Loja (lat. 4° S., long. 79° W.), high up in the Andes, on the west;—a distance in a straight line of more than 2,500 English miles, along the whole of which there is (almost certainly) one continuous virgin forest. Its greatest extent from north to south, is from the mouths of the Orinooko to the eastern slopes of the Andes near La Paz in Bolivia and a little north of Sta. Cruz de la Sierra (lat. 18° S.), a distance of about 1,900 miles. Within this area of continuous forests, are included some open "campos," or patches of pasture lands, the most important being,—the Campos of the Upper Rio Branco on the northern boundary of Brazil; a tract in the interior of British Guiana; and another on the northern bank of the Amazon near its mouth, and extending some little distance on its south bank at Santarem. On the northern bank of the Orinooko are the Llanos, or flat open plains, partly flooded in the rainy season; but much of the interior of Venezuela appears to be forest country. The forest again prevails from Panama to Maracaybo, and southwards in the Magdalena valley; and on all the western side of the Andes to about 100 miles south of Guayaquil. On the N.E. coast of Brazil is a tract of open country, in some parts of which (as near Ceara) rain does not fall for years together; but south of Cape St. Roque the coast-forests of Brazil commence, extending to lat. 30° S., clothing all the valleys and hill sides as far inland as the higher mountain ranges, and even penetrating up the great valleys far into the interior. To the south-west the forest country reappears in Paraguay, and extends in patches and partially wooded country, till it almost reaches the southern extension of the Amazonian forests. The interior of Brazil is thus in the position of a great island-plateau, rising out of, and surrounded by, a lowland region of ever-verdant forest. The Brazilian sub-region comprises all this forest-country and its included open tracts, and so far beyond it as there exists sufficient woody vegetation to support its peculiar forms of life. It thus extends considerably beyond the tropic in Paraguay and south Brazil; while the great desert of Chaco, extending from 25° to 30° S., lat. between the Parana and the Andes, as well as the high plateaus of the Andean range, with the strip of sandy desert on the Pacific coast as far as to about 5° of south latitude, belong to south temperate America, or the sub-region of the Andes.
Having already given a sketch, of the zoological features of the Neotropical region as a whole, the greater part of which will apply to this sub-region, we must here confine ourselves to an indication of the more important groups which, on the one hand, are confined to it, and on the other are absent; together with a notice of its special relations to other regions.
Mammalia.—Many of the most remarkable of the American monkeys are limited to this sub-region; as Lagothrix, Pithecia, and Brachyurus, limited to the great Amazonian forests; Eriodes to south-east Brazil; and Callithrix to tropical South America. All the marmosets (Hapalidæ) are also confined to this sub-region, one only being found at Panama, and perhaps extending a little beyond it. Among other peculiar forms, are 8 genera of bats; 3 peculiar forms of wild dog; Pteronura, a genus of otters; Inia, a peculiar form of dolphin inhabiting the upper waters of the Amazon; tapirs of the genus Tapirus (a distinct genus being found north of Panama); 4 genera of Muridæ; Ctenomys, a genus of Octodontidæ; the whole family of Echimyidæ, or spiny rats, (as far as the American continent is concerned) consisting of 8 genera and 28 species; Chætomys, a genus of Cercolabidæ; the capybara (Hydrochœrus) the largest known rodent, belonging to the Caviidæ; the larger ant-eaters (Myrmecophaga); sloths of the genus Bradypus; 2 genera of armadillos (Dasypodidæ); and two peculiar forms of the opossum family (Didelphyidæ). No group that is typically Neotropical is absent from this sub-region, except such as are peculiar to other single sub-regions and which will be noticed accordingly. The occurrence of a solitary species of hare (Lepus braziliensis) in central Brazil and the Andes, is remarkable, as it is cut off from all its allies, the genus not being known to occur elsewhere on the continent further south than Costa Rica. The only important external relation indicated by the Mammalia of this sub-region is towards the Ethiopian region, 2 genera of Echimyidæ, Aulacodes and Petromys, occurring in South and South-east Africa.
Plate IV. Characteristic Neotropical Mammalia.—Our illustration represents a mountainous forest in Brazil, the part of South America where the Neotropical Mammalia are perhaps best developed. The central and most conspicuous figure is the collared ant-eater, (Tamandua tetradactyla), one of the handsomest of the family, in its conspicuous livery of black and white. To the left are a pair of sloths (Arctopithecus flaccidus) showing the curious black spot on the back with which many of the species are marked, and which looks like a hole in the trunk of a tree; but this mark seems to be only found on the male animal. The fur of many of the sloths has a greenish tinge, and Dr. Seemann remarked its resemblance to the Tillandsia usneoides, or "vegetable horsehair," which clothes many of the trees in Central America; and this probably conceals them from their enemies, the harpy-eagles. On the right are a pair of opossums (Didelphys azaræ), one of them swinging by its prehensile tail. Overhead in the foreground are a group of howling monkeys (Mycetes ursinus) the largest of the American Quadrumana, and the noisiest of monkeys. The large hollow vessel into which the hyoid bone is transformed, and which assists in producing their tremendous howling, is altogether unique in the animal kingdom. Below them, in the distance, are a group of Sapajou monkeys (Cebus sp.); while gaudy screaming macaws complete the picture of Brazilian forest life.
Birds.—A very large number of genera of birds, and some entire families, are confined to this sub-region, as will be seen by looking over the list of genera at the end of this chapter. We can here only notice the more important, and summarize the results. More than 120 genera of Passeres are thus limited, belonging to the following 12 families: Sylviidæ (1), Troglodytidæ (2), Cœrebidæ (4), Tanagridæ (26), Fringillidæ (8), Icteridæ (5), Pteroptochidæ (3), Dendrocolaptidæ (12), Formicariidæ (16), Tyrannidæ (22), Cotingidæ (16), Pipridæ (10). Of the Picariæ there are 76 peculiar genera belonging to 9 families, viz., Picidæ (2), Rhamphastidæ (1), Cuculidæ (1), Bucconidæ (2), Galbulidæ (5), Momotidæ (2), Podargidæ (1), Caprimulgidæ (4), Trochilidæ (58). There are 3 peculiar genera of Psittaci, 8 of Gallinæ, the only genus of Opisthocomidæ, 3 of Accipitres, 1 of Rallidæ, Psophia and Eurypyga types of distinct families, and 1 genus of Ardeidæ, Palamedeidæ, and Anatidæ respectively. The preceding enumeration shows how very rich this sub-region is in peculiar types of all the most characteristic American families, such as the Tanagridæ, Tyrannidæ, Cotingidæ, Formicariidæ, Trochilidæ, and Galbulidæ. A considerable proportion of the genera of the Chilian and Mexican sub-regions also occur here, so that out of about 680 genera of Neotropical land-birds more than 500 are represented in this sub-region.
A BRAZILIAN FOREST, WITH CHARACTERISTIC MAMMALIA.
Without entering minutely into the distribution of species it is difficult to sub-divide this extensive territory with any satisfactory result. The upland tract between the Amazon and Orinooko, which may be termed Guiana, was evidently once an island, yet it possesses few marked distinctive features. Brazil, which must have formed another great island, has more speciality, but the intermediate Amazonian forests form a perfect transition between them. The northern portion of the continent west of the Orinooko has more character; and there are indications that this has received many forms from Central and North America, and thus blended two faunas once more distinct than they are now. The family of wood-warblers (Mniotiltidæ) seems to have belonged to this more northern fauna; for out of 18 genera only 5 extend south of the equator, while 6 range from Mexico or the Antilles into Columbia, some of these being only winter immigrants and no genus being exclusively South American. The eastern slopes of the Andes constitute, however, the richest and best marked province of this sub-region. At least 12 genera of tanagers (Tanagridæ) are found here only, with an immense number of Fringillidæ,—the former confined to the forests; the latter ranging to the upland plains. The ant-thrushes (Formicariidæ) on the other hand seem more abundant in the lowlands, many genera being peculiar to the Amazonian forests. The superb chatterers (Cotingidæ) also seem to have their head-quarters in the forests of Brazil and Guiana, and to have thence spread into the Amazonian valley. Guiana still boasts such remarkable forms as the cardinal chatterer (Phœnicocercus), the military chatterer (Hæmatoderus), as well as Querula, Gymnoderus, and Gymnocephalus; but the first three pass to the south side of the Lower Amazon. Here also belong the cock of the rock (Rupicola), which ranges from Guiana to the Andes, and the marvellous umbrella-birds of the Rio Nigro and Upper Amazon (Cephalopterus), which extends across the Ecuadorean Andes and into Costa Rica. Brazil has Ptilochloris, Casiornis, Tijuca, Phibalura, and Calyptura; while not a single genus of this family, except perhaps Heliochæra, is confined to the extensive range of the Andes. Almost the same phenomena are presented by the allied Pipridæ or manakins, the greater part of the genera and species occurring in Eastern South America, that is in Brazil, Guiana, and the surrounding lowlands rather than in the Andean valleys. The same may be said of the jacamars (Galbulidæ) and puff-birds (Bucconidæ); but the humming-birds (Trochilidæ) have their greatest development in the Andean district. Brazil and Guiana have each a peculiar genus of parrots; Guiana has three peculiar genera of Cracidæ, while the Andes north of the equator have two. The Tinamidæ on the other hand have their metropolis in Brazil, which has two or three peculiar genera, while two others seem confined to the Andes south of the equator. The elegant trumpeters (Psophiidæ) are almost restricted to the Amazonian valley.
Somewhat similar facts occur among the Mammalia. At least 3 genera of monkeys are confined to the great lowland equatorial forests and 1 to Brazil; Icticyon (Canidæ) and Pteronura (Mustelidæ) belong to Guiana and Brazil; and most of the Echimyidæ are found in the same districts. The sloths, ant-eaters, and armadillos all seem more characteristic of the eastern districts than of the Andean; while the opossums are perhaps equally plentiful in the Andes.
The preceding facts of distribution lead us to conclude that the highlands of Brazil and of Guiana represent very ancient lands, dating back to a period long anterior to the elevation of the Andean range (which is by no means of great geological antiquity) and perhaps even to the elevation of the continuous land which forms the base of the mountains. It was, no doubt, during their slow elevation and the consequent loosening of the surface, that the vast masses of debris were carried down which filled up the sea separating the Andean chain from the great islands of Brazil and Guiana, and formed that enormous extent of fertile lowland forest, which has created a great continent; given space for the free interaction of the distinct faunas which here met together, and thus greatly assisted in the marvellous development of animal and vegetable life, which no other continent can match. But this development, and the fusion of the various faunas into one homogeneous assemblage must have been a work of time; and it is probable that most of the existing continent was dry land before the Andes had acquired their present altitude. The blending of the originally distinct sub-faunas has been no doubt assisted by elevations and depressions of the land or of the ocean, which have alternately diminished and increased the land-area. This would lead to a crowding together at one time, and a dispersion at others, which would evidently afford opportunity for many previously restricted forms to enter fresh areas and become adapted to new modes of life.
From the preceding sketch it will appear, that the great sub-region of Tropical South America as here defined, is really formed of three originally distinct lands, fused together by the vast lowland Amazonian forests. In the class of birds sufficient materials exist for separating these districts; and that of the Andes contains a larger series of peculiar genera than either of the other sub-regions here adopted. But there are many objections to making such a sub-division here. It is absolutely impossible to define even approximate limits to these divisions—to say for example where the "Andes" ends and where "Brazil" or "Amazonia" or "Guiana" begins; and the unknown border lands separating these are so vast, that many groups, now apparently limited in their distribution, may prove to have a very much wider range. In mammalia, reptiles, and insects, it is even more difficult to maintain such divisions, so that on the whole it seems better to treat the entire area as one sub-region, although recognizing the fact of its zoological and geographical diversity, as well as its vast superiority over every other sub-region in the number and variety of its animal forms.
The reptiles, fishes, mollusca, and insects of this sub-region have been sufficiently discussed in treating of the entire region, as by far the larger proportion of them, except in the case of land-shells, are found here.
Plate XV. Characteristic Neotropical Birds.—To illustrate the ornithology of South America we place our scene on one of the tributaries of the Upper Amazon, a district where this class of animals is the most prominent zoological feature, and where a number of the most remarkable and interesting birds are to be found. On the left we have the umbrella-bird (Cephalopterus ornatus), so called from its wonderful crest, which, when expanded, completely overshadows its head like an umbrella. It is also adorned with a long tassel of plumes hanging from its breast, which is formed by a slender fleshy tube clothed with broad feathers. The bird is as large as a crow, of a glossy blue-black colour, and belongs to the same family as the exquisitely tinted blue-and-purple chatterers. Flying towards us are a pair of curl-crested toucans (Pteroglossus beauharnaisii), distinguished among all other toucans by a crest composed of small black and shining barbless plumes, resembling curled whalebone. The general plumage is green above, yellow and red beneath, like many of its allies. To the right are two of the exquisite little whiskered hummers, or "frill-necked coquettes," as they are called by Mr. Gould, (Lophornis gouldi). These diminutive birds are adorned with green-tipped plumes springing from each side of the throat, as well as with beautiful crests, and are among the most elegant of the great American family of humming-birds, now numbering about 400 known species. Overhead are perched a pair of curassows (Crax globulosa), which represent in America the pheasants of the Old World. There are about a dozen species of these fine birds, most of which are adorned with handsome curled crests. That figured, is distinguished by the yellow caruncular swellings at the base of the bill. The tall crane-like bird near the water is one of the trumpeters, (Psophia leucoptera), elegant birds with silky plumage peculiar to the Amazon valley. They are often kept in houses, where they get very tame and affectionate; and they are useful in catching flies and other house insects, which they do with great perseverance and dexterity.
A FOREST SCENE ON THE UPPER AMAZON, WITH SOME CHARACTERISTIC BIRDS.
Islands of Tropical South America.
These are few in number, and, with one exception, not of much interest. Such islands as Trinidad and Sta. Catherina form parts of South America, and have no peculiar groups of animals. The small islands of Fernando Noronha, Trinidad, and Martin Vaz, off the coast of Brazil, are the only Atlantic islands somewhat remote from land; while the Galapagos Archipelago in the Pacific is the only group whose productions have been carefully examined, or which present features of special interest.
Galapagos Islands.—These are situated on the equator, about 500 miles from the coast of Ecuador. They consist of the large Albemarle island, 70 miles long; four much smaller (18 to 25 miles long), named Narborough, James, Indefatigable, and Chatham Islands; four smaller still (9 to 12 miles long), named Abingdon, Bindloes, Hood's, and Charles Islands. All are volcanic, and consist of fields of black basaltic lava, with great numbers of extinct craters, a few which are still active. The islands vary in height from 1,700 to 5,000 feet, and they all rise sufficiently high to enter the region of moist currents of air, so that while the lower parts are parched and excessively sterile, above 800 or 1,000 feet there is a belt of comparatively green and fertile country.
These islands are known to support 58 species of Vertebrates,—1 quadruped, 52 birds and 5 reptiles, the greater part of which are found nowhere else, while a considerable number belong to peculiar and very remarkable genera. We must therefore notice them in some detail.
Mammalia.—This class is represented by a mouse belonging to the American genus Hesperomys, but slightly different from any found on the continent. A true rat (Mus), slightly differing from any European species, also occurs; and as there can be little doubt that this is an escape from a ship, somewhat changed under its new conditions of life (the genus Mus not being indigenous to the American continent), it is not improbable, as Mr. Darwin remarks, that the American mouse may also have been imported by man, and have become similarly changed.
Birds.—Recent researches in the islands have increased the number of land-birds to thirty-two, and of wading and aquatic birds to twenty-three. All the land birds but two or three are peculiar to the islands, and eighteen, or considerably more than half, belong to peculiar genera. Of the waders 4 are peculiar, and of the swimmers 2. These are a rail (Porzana spilonota); two herons (Butorides plumbea and Nycticorax pauper); a flamingo (Phœnicopterus glyphorhynchus); while the new aquatics are a gull (Larus fuliginosus), and a penguin (Spheniscus mendiculus).
The land-birds are much more interesting. All except the birds of prey belong to American genera which abound on the opposite coast or on that of Chili a little further south, or to peculiar genera allied to South American forms. The only species not peculiar are, Dolichonyx oryzivorus, a bird of very wide range in America and of migratory habits, which often visits the Bermudas 600 miles from North America,—and Asio accipitrinus, an owl which is found almost all over the world. The only genera not exclusively American are Buteo and Strix, of each of which a peculiar species occurs in the Galapagos, although very closely allied to South American species. There remain 10 genera, all either American or peculiar to the Galapagos; and on these we will remark in systematic order.
1. Mimus, the group of American mocking-thrushes, is represented by three distinct and well-marked species. 2. Dendrœca, an extensive and wide-spread genus of the wood-warblers (Mniotiltidæ), is represented by one species, which ranges over the greater part of the archipelago. The genus is especially abundant in Mexico, the Antilles, and the northern parts of tropical America, only one species extending south as far as Chili. 3. Certhidea, a peculiar genus originally classed among the finches, but which Mr. Sclater, who has made South American birds his special study, considers to belong to the Cœrebidæ, or sugar-birds, a family which is wholly tropical. Two species of this genus inhabit separate islands. 4. Progne, the American martins (Hirundinidæ), is represented by a peculiar species. 5. Geospiza, a peculiar genus of finches, of which no less than eight species occur in the archipelago, but not more than four in any one island. 6. Camarhynchus (6 sp.) and 7. Cactornis (4 sp.) are two other peculiar genera of finches; some of the species of which are confined to single islands, while others inhabit several. 8. Pyrocephalus, a genus of the American family of tyrant-flycatchers (Tyrannidæ), has one peculiar species closely allied to T. rubineus, which has a wide range in South America. 9. Myiarchus, another genus of the same family which does not range further south than western Ecuador, has also a representative species found in several of the islands. 10. Zenaida, an American genus of pigeons, has a species in James Island and probably in some of the others, closely allied to a species from the west coast of America.
It has been already stated that some of the islands possess peculiar species of birds distinct from the allied forms in other islands, but unfortunately our knowledge of the different islands is so unequal and of some so imperfect, that we can form no useful generalizations as to the distribution of birds among the islands themselves. The largest island is the least known; only one bird being recorded from it, one of the mocking-thrushes found nowhere else. Combining the observations of Mr. Darwin with those of Dr. Habel and Prof. Sundevall, we have species recorded as occurring in seven of the islands. Albemarle island has but one definitely known species; Chatham and Bindloe islands have 11 each; Abingdon and Charles islands 12 each; Indefatigable island and James island have each 18 species. This shows that birds are very fairly distributed over all the islands, one of the smallest and most remote (Abingdon) furnishing as many as the much larger Chatham Island, which is also the nearest to the mainland. Taking the six islands which seem tolerably explored, we find that two of the species (Dendrœca aureola and Geospiza fortis) occur in all of them; two others (Geospiza strenua and Myiarchus magnirostris) in five; four (Mimus melanotis, Geospiza fuliginosa, G. parvula, and Camarhynchus prosthemelas) in four islands; five (Certhidea olivacea, Cactornis scandens, Pyrocephalus nanus), and two of the birds of prey, in three islands; nine (Certhidea fusca, Progne concolor, Geospiza nebulosa, G. magnirostris, Camarhynchus psittaculus, C. variegatus, C. habeli and Asio accipitrinus) in two islands; while the remaining ten species are confined to one island each. These peculiar species are distributed among the islands as follows. James, Charles and Abingdon islands, have 2 each; Bindloes, Chatham, and Indefatigable, 1 each. The amount of speciality of James Island is perhaps only apparent, owing to our ignorance of the fauna of the adjacent large Albemarle island; the most remote islands north and south, Abingdon and Charles, have no doubt in reality most peculiar species, as they appear to have. The scarcity of peculiar species in Chatham Island is remarkable, it being large, very isolated, and the nearest to the mainland. There is still room for exploration in these islands, especially in Albemarle, Narborough, and Hood's islands of which we know nothing.
Reptiles.—The few reptiles found in these islands are very interesting. There are two snakes, a species of the American genus Herpetodryas, and another which was at first thought to be a Chilian species (Psammophis Temminckii), but which is now considered to be distinct. Of lizards there are four at least, belonging to as many genera. One is a species of Phyllodactylus, a wide-spread genus of Geckotidæ; the rest belong to the American family of the Iguanas, one being a species of the Neotropical genus Leiocephalus, the other two very remarkable forms, Trachycephalus and Oreocephalus (formerly united in the genus Amblyrhynchus). The first is a land, the second a marine, lizard; both are of large size and very abundant on all the islands; and they are quite distinct from any of the very numerous genera of Iguanidæ, spread all over the American continent. The last reptile is a land tortoise (Testudo nigra) of immense size, and also abundant in all the islands. Its nearest ally is the equally large species of the Mascarene Islands; an unusual development due, in both cases, to the absence of enemies permitting these slow but continually growing animals to attain an immense age. It is believed that each island has a distinct variety or species of tortoise.
Insects.—Almost the only insects known from these islands are some Coleoptera, chiefly collected by Mr. Darwin. They consist of a few peculiar species of American or wide-ranging genera, the most important being, a Calosoma, Pœcilus, Solenophorus, and Notaphus, among the Carabidæ; an Oryctes among the Lamellicornes; two new genera of obscure Heteromera; two Curculionidæ of wide-spread genera; a Longicorn of the South American genus Eburia; and two small Phytophaga,—a set of species highly suggestive of accidental immigrations at rare and distant intervals.
Land-Shells.—These consist of small and obscure species, forming two peculiar sub-genera of Bulimulus, a genus greatly developed on the whole West coast of America; and a single species of Buliminus, a genus which ranges over all the world except America. As in the case of the birds, most of the islands have two or three peculiar species.
General Conclusions.—These islands are wholly volcanic and surrounded by very deep sea; and Mr. Darwin is of opinion, not only that the islands have never been more nearly connected with the mainland than at present, but that they have never been connected among themselves. They are situated on the Equator, in a sea where gales and storms are almost unknown. The main currents are from the south-west, an extension of the Peruvian drift along the west coast of South America. From their great extent, and their volcanoes being now almost extinct, we may assume that they are of considerable antiquity. These facts exactly harmonize with the theory, that they have been peopled by rare accidental immigrations at very remote intervals. The only peculiar genera consist of birds and lizards, which must therefore have been the earliest immigrants. We know that small Passerine birds annually reach the Bermudas from America, and the Azores from Europe, the former travelling over 600, the latter over 1000 miles of ocean. These groups of islands are both situated in stormy seas, and the immigrants are so numerous that hardly any specific change in the resident birds has taken place. The Galapagos receive no such annual visitants; hence, when by some rare accident a few individuals of a species did arrive, they remained isolated, probably for thousands of generations, and became gradually modified through natural selection under completely new conditions of existence. Less rare and violent storms would suffice to carry some of these to other islands, and thus the archipelago would in time become stocked. It would appear probable, that those which have undergone most change were the earliest to arrive; so that we might look upon the three peculiar genera of finches, and Certhidea, the peculiar form of Cœrebidæ, as among the most ancient inhabitants of the islands, since they have become so modified as to have apparently no near allies on the mainland. But other birds may have arrived nearly at the same time, and yet not have been much changed. A species of very wide range, already adapted to live under very varied conditions and to compete with varied forms of life, might not need to become modified so much as a bird of more restricted range, and more specialized constitution. And if, before any considerable change had been effected, a second immigration of the same species occurred, crossing the breed would tend to bring back the original type of form. While, therefore, we may be sure that birds like the finches, which are profoundly modified and adapted to the special conditions of the climate and vegetation, are among the most ancient of the colonists; we cannot be sure that the less modified form of tyrant-flycatcher or mocking-thrush, or even the unchanged but cosmopolitan owl, were not of coeval date; since even if the parent form on the continent has been changed, successive immigrations may have communicated the same change to the colonists.
The reptiles are somewhat more difficult to account for. We know, however, that lizards have some means of dispersal over the sea, because we find existing species with an enormous range. The ancestors of the Amblyrhynchi must have come as early, probably, as the earliest birds; and the same powers of dispersal have spread them over every island. The two American genera of lizards, and the tortoises, are perhaps later immigrants. Latest of all were the snakes, which hardly differ from continental forms; but it is not at all improbable that these latter, as well as the peculiar American mouse, have been early human importations. Snakes are continually found on board native canoes whose cabins are thatched with palm leaves; and a few centuries would probably suffice to produce some modification of a species completely isolated, under conditions widely different from those of its native country. Land-shells, being so few and small, and almost all modifications of one type, are a clear indication of how rare are the conditions which lead to their dispersal over a wide extent of ocean; since two or three individuals, arriving on two or three occasions only during the whole period of the existence of the islands, would suffice to account for the present fauna. Insects have arrived much more frequently; and this is in accordance with their habits, their lower specific gravity, their power of flight, and their capacity for resisting for some time the effects of salt water.
We learn, then, from the fauna of these islands, some very important facts. We are taught that tropical land-birds, unless blown out of their usual course by storms, rarely or never venture out to sea, or if they do so, can seldom pass safely over a distance of 500 miles. The immigrants to the Galapagos can hardly have averaged a bird in a thousand years. We learn, that of all reptiles lizards alone have some tolerably effective mode of transmission across the sea; and this is probably by means of currents, and in connection with floating vegetation. Yet their transmission is a far rarer event than that of land-birds; for, whereas three female immigrants will account for the lizard population, at least eight or ten ancestors are required for the birds. Land serpents can pass over still more rarely, as two such transmissions would have sufficed to stock the islands with their snakes; and it is not certain that either of these occurred without the aid of man. It is doubtful whether mammals or batrachians have any means of passing, independently of man's assistance; the former having but one doubtfully indigenous representative, the latter none at all. The remarkable absence of all gay or conspicuous flowers in these tropical islands, though possessing a zone of fairly luxuriant shrubby vegetation, and the dependence of this phenomenon on the extreme scarcity of insects, has been already noticed at Vol. I. p. 461, when treating of a somewhat similar peculiarity of the New Zealand fauna and flora.
I. South Temperate America, or the Chilian Sub-region.
This sub-region may be generally defined as the temperate portion of South America. On the south, it commences with the cold damp forests of Tierra del Fuego, and their continuation up the west coast to Chiloe and northward to near Santiago. To the east we have the barren plains of Patagonia, gradually changing towards the north into the more fertile, but still treeless, pampas of La Plata. Whether this sub-region should be continued across the Rio de la Plata into Uruguay and Entre-rios, is somewhat doubtful. To the west of the Parana it extends northward over the Chaco desert, till we approach the border of the great forests near St. Cruz de la Sierra. On the plateau of the Andes, however, it must be continued still further north, along the "paramos" or alpine pastures, till we reach 5° of South latitude. Beyond this the Andes are very narrow, having no double range with an intervening plateau; and although some of the peculiar forms of the temperate zone pass on to the equator or even beyond it, these are not sufficiently numerous to warrant our extending the sub-region to include them. Along with the high Andes it seems necessary to include the western strip of arid country, which is mostly peopled by forms derived from Chili and the south temperate regions.
Mammalia.—This sub-region is well characterised by the possession of an entire family of mammalia having Neotropical affinities—the Chinchillidæ. It consists of 3 genera—Chinchilla (2 sp.), inhabiting the Andes of Chili and Peru as far as 9° south latitude, and at from 8,000 to 12,000 feet altitude; Lagidium (3 sp.), ranging over the Andes of Chili, Peru, and South Ecuador, from 11,000 to 16,000 feet altitude; and Lagostomus (1 sp.), the "viscacha," confined to the pampas between the Uruguay and Rio Negro. Many important genera are also confined to this sub-region. Auchenia (4 sp.), including the domesticated llamas and alpacas, the vicugna which inhabits the Andes of Peru and Chili, and the guanaco which ranges over the plains of Patagonia and Tierra del Fuego. Although this genus is allied to the Old World camels, it is a very distinct form, and its introduction from North America, where the family appear to have originated, may date back to a remote epoch. Ursus ornatus, the "spectacled bear" of the Chilian Andes, is a remarkable form, supposed to be most allied to the Malay bear, and probably forming a distinct genus, which has been named Tremarctos. Four genera of Octodontidæ are also peculiar to this sub-region, or almost so; Habrocomus (1 sp.) is Chilian; Spalacopus (2 sp.) is found in Chili and on the east side of the southern Andes; Octodon (3 sp.) ranges from Chili into Peru and Bolivia; Ctenomys (6 sp.) from the Straits of Magellan to Bolivia, with one species in South Brazil. Dolichotis, one of the Cavies, ranges from Patagonia to Mendoza, and on the east coast to 37½° S. latitude. Myopotamus (1 sp.), the coypu (Echimyidæ), ranges from 33° to 48° S. latitude on the west side of the Andes, and from the frontiers of Peru to 42° S. on the east side. Reithrodon and Acodon, genera of Muridæ, are also confined to Temperate South America; Tolypeutes and Chlamydophorus, two genera of armadillos, the latter very peculiar in its organization and sometimes placed in a distinct family, are found only in La Plata and the highlands of Bolivia, and so belong to this sub-region. Otaria, one of the "eared seals" (Otariidæ), is confined to the coasts of this sub-region and the antarctic islands. Deer of American groups extend as far as Chiloe on the west, and the Straits of Magellan on the east coast. Mice of the South American genera Hesperomys and Reithrodon, are abundant down to the Straits of Magellan and into Tierra del Fuego, Mr. Darwin having collected more than 20 distinct species. The following are the genera of Mammalia which have been observed on the shores of the Straits of Magellan, those marked * extending into Tierra del Fuego: *Pseudalopex (two wolf-like foxes), Felis (the puma), Mephitis (skunks), Cervus (deer), *Auchenia (guanaco), *Ctenomys (tucu-tucu), *Reithrodon and *Hesperomys (American mice).
Birds.—Three families of Birds are confined to this sub-region,—Phytotomidæ (1 genus, 3 sp.), inhabiting Chili, La Plata, and Bolivia; Chionididæ (1 genus, 2 sp.) the "sheath-bills," found only at the southern extremity of the continent and in Kerguelen's Island, which with the other antarctic lands perhaps comes best here; Thinocoridæ (2 genera, 6 species) an isolated family of waders, ranging over the whole sub-region and extending northward to the equatorial Andes. Many genera are also peculiar: 3 of Fringillidæ, and 1 of Icteridæ; 9 of Dendrocolaptidæ, 6 of Tyrannidæ, 3 of Trochilidæ, and 4 of Pteroptochidæ,—the last four South American families. There is also a peculiar genus of parrots (Henicognathus) in Chili; two of pigeons (Metriopelia and Gymnopelia) confined to the Andes and west coast from Peru to Chili; two of Tinamous, Tinamotis in the Andes, and Calodromas in La Plata; three of Charadriidæ, Phegornis, Pluvianellus, and Oreophilus; and Rhea, the American ostriches, inhabiting all Patagonia and the pampas. Perhaps the Cariamidæ have almost as much right here as in the last sub-region, inhabiting as they do, the "pampas" of La Plata and the upland "campos" of Brazil; and even among the wide-ranging aquatic birds, we have a peculiar genus, Merganetta, one of the duck family, which is confined to the temperate plateau of the Andes.
Against this extensive series of characteristic groups, all either of American type or very distinct forms of Old World families, and therefore implying great antiquity, we find, in mammalia and birds, very scanty evidence of that direct affinity with the north temperate zone, on which some naturalists lay so much stress. We cannot point to a single terrestrial genus, which is characteristic of the north and reappears in this south temperate region without also occurring over much of the intervening land. Mustela seems only to have reached Peru; Lepus is isolated in Brazil; true Ursus does not pass south of Mexico. In birds, the northern groups rarely go further south than Mexico or the Columbian Andes; and the only case of discontinuous distribution we can find recorded is that of the genus of ducks, Camptolæmus, which has a species on the east side of North America and another in Chili and the Falkland Islands, but these, Professor Newton assures me, do not properly belong to the same genus. Out of 30 genera of land-birds collected on the Rio Negro in Patagonia, by Mr. Hudson, only four extend beyond the American continent, and the same exclusively American character applies equally to its southern extremity. No list appears to have been yet published of the land-birds of the Straits of Magellan and Tierra del Fuego. The following is compiled from the observations of Mr. Darwin, the recent voyage of Professor Cunningham, and other sources; and will be useful for comparison.
|1.||Turdus falklandicus.||*23.||Campephilus magellanicus.|
|*4.||Phrygilus gayi.||26.||Eustephanus galeritus.|
|*7.||" xanthogrammus||27.||Conurus patagonus.|
|9.||Sturnella militaris.||29.||Sarcorhamphus gryphus.|
|11.||Hirundo meyeni.||31.||Buteo erythronotus.|
|12.||Tænioptera pyrope.||34.||Cerchneis sparverius.|
|13.||Myiotheretes rufiventris.||35.||Milvago albogularis.|
|14.||Muscisaxicola mentalis.||36.||Polyborus tharus.|
|17.||Elainea griseogularis.||37.||Asio accipitrinus.|
|18.||Upucerthia dumetoria.||40.||Glaucidium nana.|
|*19.||Cinclodes patagonicus.||41.||Syrnium rufipes.|
In the above list the species marked * extend to Tierra del Fuego. It is a remarkable fact that so many of the species belong to genera which are wholly Neotropical, and that the specially South American families of Icteridæ, Tyrannidæ, Dendrocolaptidæ, Pteroptochidæ, Trochilidæ, and Conuridæ, should supply more than one-third of the species; while the purely South American genus Phrygilus, should be represented by four species, three of which abound in Tierra del Fuego.
Plate XVI. A Scene in the Andes of Chili, with characteristic Animals.—The fauna of South Temperate America being most fully developed in Chili, we place the scene of our illustration in that country. In the foreground we have a pair of the beautiful little chinchillas (Chinchilla lanigera), belonging to a family of animals peculiar to the sub-region. There are only two species of this group, both confined to the higher Andes, at about 8000 feet elevation. Coming round a projecting ridge of the mountain, are a herd of vicunas (Auchenia vicugna), one of that peculiar form of the camel tribe found in South America and confined to its temperate and alpine regions. The upper bird is a plant-cutter (Phytotoma rara), of sober plumage but allied to the beautiful chatterers, though forming a separate family. Below, standing on a rock, is a plover-like bird, the Thinocorus orbignianus, which is considered to belong to a separate family, though allied to the plovers and sheath-bills. Its habits are, however, more those of the quails or partridges, living inland in dry and desert places, and feeding on plants, roots, and insects. Above is a condor, the most characteristic bird of the high Andes.
Reptiles and Amphibia.—These groups show, for the most part, similar modifications of American and Neotropical forms, as those we have seen to prevail among the birds. Snakes do not seem to go very far south, but several South American genera of Colubridæ and Dendrophidæ occur in Chili; while Enophrys is peculiar to La Plata, and Callorhinus to Patagonia, both belonging to the Colubridæ. The Elapidæ do not extend into the temperate zone; but Craspedocephalus, one of the Crotalidæ, occurs at Bahia Blanca in Patagonia (Lat. 40° S.)
THE CHILIAN ANDES, WITH CHARACTERISTIC ANIMALS.
Lizards are much more numerous, and there are several peculiar and interesting forms. Three families are represented; Teidæ by two genera—Callopistes peculiar to Chili, and Ameiva which ranges over almost the whole American continent and is found in Patagonia; Geckotidæ by four genera, two of which,—Caudiverbera and Homonota—are peculiar to Chili, while Sphærodactylus and Cubina are Neotropical, the former ranging to Patagonia, the latter to Chili; and lastly the American family Iguanidæ represented by eight genera, no less than six being peculiar, (or almost so,) to the South temperate region. These are Leiodera, Diplolæmus and Proctrotretus, ranging from Chili to Patagonia; Leiolæmus, from Peru to Patagonia; Phymaturus, confined to Chili, and Ptygoderus peculiar to Patagonia and Tierra del Fuego. The other two genera, Oplurus and Leiosaurus, are common to Chili and tropical South America.
Tortoises appear to be scarce, a species of Hydromedusa only being recorded. Of the Amphibia, batrachia (frogs and toads) alone are represented, and appear to be tolerably abundant, seventeen species having been collected by Mr. Darwin in this sub-region. Species of the South American genera Phryniscus, Hylaplesia, Telmatobius, Cacotus, Hylodes, Cyclorhamphus, Pleurodema, Cystignathus, and Leiuperus, are found in various localities, some extending even to the Straits of Magellan,—-the extreme southern limit of both Reptilia and Amphibia, except one lizard (Ptygoderus) found by Professor Cunningham in Tierra del Fuego. There are also four peculiar genera, Rhinoderma belonging to the Engystomidæ; Alsodes and Nannophryne to the Bombinatoridæ; Opisthodelphys to the Hylidæ; and Calyptocephalus to the Discoglossidæ.
It thus appears, that in the Reptiles all the groups are typically American, and that most of the peculiar genera belong to families which are exclusively American. The Amphibia, on the other hand, present some interesting external relations, but these are as much with Australia as with the North temperate regions. The Bombinatoridæ are indeed Palæarctic, but a larger proportion are Neotropical, and one genus inhabits New Zealand. The Chilian genus Calyptocephalus is allied to Australian tropical genera. The Neotropical genera of Ranidæ, five of which extend to Chili and Patagonia, belong to a division which is Australian and Neotropical, and which has species in the Oriental and Ethiopian regions.
Fresh-water Fishes.—These present some peculiar forms, and some very interesting phenomena of distribution. The genus Percilia has been found only in the Rio de Maypu in Chili; and Percichthys, also belonging to the perch family, has five species confined to the fresh waters of South Temperate America, and one far away in Java. Nematogenys (1 sp.) is peculiar to Chili; Trichomycterus reaches 15,000 feet elevation in the Andes,—both belonging to the Siluridæ; Chirodon (2 sp.), belonging to the Characinidæ, is peculiar to Chili; and several other genera of the same family extend into this sub-region from Brazil. The family Haplochitonidæ has a remarkable distribution; one of its genera, Haplochiton (2 sp.), inhabiting Tierra del Fuego and the Falkland Islands, while the other, Prototroctes, is found only in South Australia and New Zealand. Still more remarkable is Galaxias (forming the family Galaxidæ), the species of which are divided between Temperate South America, and Australia, Tasmania, and New Zealand; and there is even one species (Galaxias attenuatus) which is found in the Chatham Islands, New Zealand, and Tasmania, as well as in the Falkland Islands and Patagonia. Fitzroya (1 sp.) is found only at Montevideo; Orestias (6 sp.) is peculiar to Lake Titicaca in the high Andes of Bolivia; Jenynsia (1 sp.) in the Rio de la Plata—all belonging to the characteristic South American family of the Cyprinodontidæ.
Insects.—It is in insects more than in any other class of animals, that we find clear indications of a not very remote migration of northern forms, along the great mountain range to South Temperate America, where they have established themselves as a prominent feature in the entomology of the country. The several orders and families, however, differ greatly in this respect; and there are some groups which are only represented by modifications of tropical forms, as we have seen to be almost entirely the case in birds and reptiles.
Lepidoptera.—The butterflies of the South Temperate Sub-region are not numerous, only about 29 genera and 80 species being recorded. Most of these are from Chili, which is sufficiently accounted for by the general absence of wood on the east side of the Andes from Buenos Ayres to South Patagonia. The families represented are as follows: Satyridæ, with 11 genera and 27 species, are the most abundant; Nymphalidæ, 2 genera and 8 species; Lemoniidæ, 1 genus, 1 species; Lycænidæ, 3 genera, 8 species; Pieridæ, 6 genera, 14 species; Papilionidæ, 2 genera, 8 species; Hesperidæ, 4 genera, 13 species. One genus of Satyridæ (Elina) and 2 of Pieridæ (Eroessa and Phulia) are peculiar to Chili. The following are the genera whose derivation must be traced to the north temperate zone:—Tetraphlebia, Neosatyrus, and 3 allied genera of 1 species each, were formerly included under Erebia, a northern and arctic form, yet having a few species in South Africa; Argyrophorus, allied to Æneis, a northern genus; Hipparchia, a northern genus yet having a species in Brazil;—all Satyridæ. The Nymphalidæ are represented by the typical north temperate genus Argynnis, with 7 species in Chili; Colias, among the Pieridæ, is usually considered to be a northern genus, but it possesses representatives in South Africa, the Sandwich Islands, Malabar, New Grenada, and Peru, as well as Chili, and must rather be classed as cosmopolitan. These form a sufficiently remarkable group of northern forms, but they are accompanied by others of a wholly Neotropical origin. Such are Stibomorpha with 6 species, ranging through South America to Guatemala, and Eteona, common to Chili and Brazil (Satyridæ); Apodemia (Lemoniidæ) confined to Tropical America and Chili. Hesperocharis and Callidryas (Pieridæ), both tropical; and Thracides (Hesperidæ) confined to Tropical America and Chili. Other genera are widely scattered; as, Epinephile found also in Mexico and Australia; Cupido, widely spread in the tropics; Euryades, found only in La Plata and Paraguay, allied to South American forms of Papilio, to the Australian Eurycus, and the northern Parnassius; and Heteropterus, scattered in Chili, North America, and Tropical Africa. We find then, among butterflies, a large north-temperate element, intermingled in nearly equal proportions with forms derived from Tropical America; and the varying degrees of resemblances of the Chilian to the northern species, seems to indicate successive immigrations at remote intervals.
Coleoptera.—It is among the beetles of South Temperate America that we find some of the most curious examples of remote affinities, and traces of ancient migrations. The Carabidæ are very well represented, and having been more extensively collected than most other families, offer us perhaps the most complete materials. Including the Cicindelidæ, about 50 genera are known from the South Temperate Sub-region, the greater part from Chili, but a good number also from Patagonia and the Straits of Magellan. Of these more than 30 are peculiar, and most of them are so isolated that it is impossible to determine with precision their nearest allies.
The only remarkable form of Cicindelidæ is Agrius, a genus allied to the Amblycheila and Omus of N.W. America. Two genera of Carabidæ, Cascellius and Baripus, are closely allied to Promecoderus, an Australian genus; and another, Lecanomerus, has one species in Chili and the other in Australia. Five or six of the peculiar genera are undoubtedly allied to characteristic Palæarctic forms; and such northern genera as Carabus, Pristonychus, Anchomenus, Pterostichus, Percus, Bradycellus, Trechus, and Bembidium, all absent from Tropical America, give great support to the view that there is a close relation between the insects of the northern regions and South Temperate America. A decided tropical element is, however, present. Tropopterus is near Colpodes, a Tropical and South American genus; Mimodromius and Plagiotelium are near Calleida, a South American genus; while Pachyteles, Pericompsus, Variopalpus, and Calleida are widely spread American groups. The preponderance of northern forms seems, however, to be undoubted.
Six Carabidæ are known from Juan Fernandez, 3 being identical with Chilian species and 3 peculiar. As the island is 350 miles from the mainland, we have here a proof of how readily insects may be transported great distances.
The Palæarctic affinity of the South Temperate Carabidæ may be readily understood, if we bear in mind the great antiquity of the group, and the known long persistence of generic and specific forms of Coleoptera; the facility with which they may be transported to great distances by gales and hurricanes, either on land or over the sea; and, therefore, the probability that suitable stations would be rapidly occupied by species already adapted to them, to the exclusion of those of the adjacent tracts which had been specialised under different conditions. If, for example, we carry ourselves back to the time when the Andes had only risen to half their present altitude, and Patagonia had not emerged from the ocean (an epoch not very remote geologically), we should find nearly all the Carabidæ of South America, adapted to a warm, and probably forest-covered country. If, then, a further considerable elevation of the land took place, a large temperate and cold area would be formed, without any suitable insect inhabitants. During the necessarily slow process of elevation, many of the tropical Carabidæ would spread upwards, and some would become adapted to the new conditions; while the majority would probably only maintain themselves by continued fresh immigrations. But, as the mountains rose, another set of organisms would make their way along the highest ridges. The abundance and variety of the North Temperate Carabidæ, and their complete adaptation to a life on barren plains and rock-strewn mountains, would enable them rapidly to extend into any newly-raised land suitable to them; and thus the whole range of the Rocky Mountains and Andes would obtain a population of northern forms, which would overflow into Patagonia, and there, finding no competitors, would develope into a variety of modified groups. This migration was no doubt effected mainly, during successive glacial epochs, when the mountain-range of the Isthmus of Panama, if moderately increased in height, might become adapted for the passage of northern forms, while storms would often carry insects from peak to peak over intervening forest lowlands or narrow straits of sea. If this is the true explanation, we ought to find no such preponderant northern element in groups which are proportionally less developed in cold and temperate climates. Our further examination will show how far this is the case.
Lucanidæ.—Only four genera are known in the sub-region. Two are peculiar, Chiasognathus and Streptocerus, the former allied to Tropical American, the latter to Australian genera; the other two genera are exclusively South American.
Cetoniidæ.—These seem very scarce, only a few species of the Neotropical genus Gymnetis reaching Patagonia.
Buprestidæ.—These are rather numerous, many very beautiful species being found in Chili. Nineteen genera are represented in South Temperate America, and 5 of these are peculiar to it; 3 others are South American genera; 2 are Australian, and the remainder are wide-spread, but all are found also in Tropical America. The only north-temperate genus is Dicerca, and even this occurs also in the Antilles, Brazil, and Peru. Of the peculiar genera, the largest, Dactylozodes (26 sp.), has one species in South Brazil, and is closely allied to Hyperantha, a genus of Tropical America; Epistomentis is allied to Nascis, an Australian genus; Tyndaris is close to Acmæodera, a genus of wide range and preferring desert or dry countries. The other two are single species of cosmopolitan affinities. On the whole, therefore, the Buprestidæ are unmistakeably Neotropical in character.
Longicorns.—Almost the whole of the South Temperate Longicorns inhabit Chili, which is very rich in this beautiful tribe. About 75 genera and 160 species are known, and nearly half of the genera are peculiar. Many of the species are large and handsome, rivalling in beauty those of the most favoured tropical lands. Of the 8 genera of Prionidæ 6 are peculiar, but all are allied to Tropical American forms except Microplophorus, which belongs to a group of genera spread over Australia, Europe, and Mexico. The Cerambycidæ are much more abundant, and their affinities more interesting. Two (Syllitus and Pseudocephalus) are common to Australia and Chili. Twenty-three are Neotropical; and among these Ibidion, Compsocerus, Callideriphus, Trachyderes, and Xylocharis, are best represented. Twenty are altogether peculiar, but most of them are more or less closely allied to genera inhabiting Tropical America. Some, as the handsome Cheloderus and Oxypeltus, have no close allies in any part of the world. Holopterus, though very peculiar, shows most resemblance to a New Zealand insect. Sibylla, Adalbus, and Phantagoderus, have Australian affinities; while Calydon alone shows an affinity for north-temperate forms. One species of the northern genus, Leptura, is said to have been found at Buenos Ayres.
The Lamiidæ are less abundant. Nine of the genera are Neotropical. Two (Apomecyna and Exocentrus) are spread over all tropical regions. Ten genera are peculiar; and most of these are related to Neotropical groups or are of doubtful affinities. Only one, Aconopterus, is decidedly allied to a northern genus, Pogonochærus. It thus appears, that none of the Lamiidæ exhibit Australian affinities, although these are a prominent feature in the relations of the Cerambycidæ.
It is evident, from the foregoing outline, that the insects of South Temperate America, more than any other class of animals, exhibit a connection with the north temperate regions, yet this connection is only seen in certain groups. In Diurnal Lepidoptera and in Carabidæ, the northern element is fully equal to the tropical, or even preponderates over it. We have already suggested an explanation of this fact in the case of the Carabidæ, and with the butterflies it is not more difficult. The great mass of Neotropical butterflies are forest species, and have been developed for countless ages in a forest-clad tropical country. The north temperate butterflies, on the other hand, are very largely open-country species, frequenting pastures, mountains, and open plains, and often wandering over an extensive area. These would find, on the higher slopes of mountains, a vegetation and conditions suited to them, and would occupy such stations in less time than would be required to adapt and modify the forest-haunting groups of the American lowlands. In those groups of insects, however, in which the conditions of life are nearly the same as regards both temperate and tropical species, the superior number and variety of the tropical forms has given them the advantage. Thus we find that among the Lucanidæ, Buprestidæ, and Longicorns, the northern element is hardly perceptible. Most of these are either purely Neotropical, or allied to Neotropical genera, with the admixture, however, of a decided Australian element. As in the case of the Amphibia and fresh-water fishes, the Australian affinity, as shown by insects, is of two kinds, near and remote. We have a few genera common to the two countries; but more commonly the genera are very distinct, and the affinity is shown by the genera of both countries belonging to a group peculiar to them, but which may be of very great age. In the former case, we must impute some of the resemblance of the two faunas to an actual interchange of forms within the epoch of existing genera—a period of vast and unknown duration in the class of insects; while in the latter case, and perhaps also in many of the former, it seems more in accordance with the whole of the phenomena, to look upon most of the instances as survivals, in the two southern temperate areas, of the relics of groups which had once a much wider distribution. That this is the true explanation, is suggested by the numerous cases of discontinuous and scattered distribution we have had to notice, in which every part of the globe, without exception, is implicated; and there is a reason why these survivals should be rather more frequent in Australia and temperate South America, inasmuch as these two areas agree in the absence of a considerable number of otherwise cosmopolitan vertebrate types, and are also in many respects very similar in climatic and other physical conditions. The preponderating influence of the organic over the physical environment, as taught by Mr. Darwin, leads us to give most weight to the first of the above-mentioned causes; to which we may also impute such undoubted cases of survival of ancient types as the Centetidæ of the Antilles and Madagascar—both areas strikingly deficient in the higher vertebrate forms. The probable mode and time of the cross migration between Australia and South America, has been sufficiently discussed in our chapter on the Australian region, when treating of the origin and affinities of the New Zealand fauna.
Islands of the South Temperate Sub-region.
These are few, and of not much zoological interest. Tierra del Fuego, although really an island, is divided from the mainland by so narrow a channel that it may be considered as forming part of the continent. The guanaco (Auchenia huanaco) ranges over it, and even to small islands further south.
The Falkland Islands.—These are more important, being situated about 350 miles to the east of Southern Patagonia; but the intervening sea is shallow, the 100 fathom line of soundings passing outside the islands. We have therefore reason to believe that they have been connected with South America at a not distant epoch; and in agreement with this view we find most of their productions identical, while the few that are peculiar are closely allied to the forms of the mainland.
The only indigenous Mammals are a wolf-like fox (Pseudalopex antarcticus) said to be found nowhere else, but allied to two other species inhabiting Southern Patagonia; and a species of mouse, probably one of the American genera Hesperomys or Reithrodon.
Sixty-seven species of Birds have been obtained in these islands, but only 18 are land-birds; and even of these 7 are birds of prey, leaving only 11 Passeres. The former are all common South American forms, but one species, Milvago australis, seems peculiar. The 11 Passeres belong to 9 genera, all found on the adjacent mainland. Three, or perhaps four, of the species are however peculiar. These are Phrygilus melanoderus, P. xanthogrammus, Cinclodes antarcticus, and Muscisaxicola macloviana. The wading and swimming birds are of little interest, except the penguins, which are greatly developed; no less than eight species being found, five as residents and three as accidental visitors.
No reptiles are known to inhabit these islands.
Juan Fernandez.—This island is situated in the Pacific Ocean, about 400 miles west of Valparaiso in Chili. It is only a few miles in extent, yet it possesses four land-birds, excluding the powerful Accipitres. These are Turdus falklandicus; Anæretes fernandensis, one of the Tyrannidæ; and two humming-birds, Eustephanus fernandensis and E. galeritus. The first is a widespread South Temperate species, the two next are peculiar to the island, while the last is a Chilian species which ranges south to Tierra del Fuego. But ninety miles beyond this island lies another, called "Mas-a-fuero," very much smaller; yet this, too, contains four species of similar birds; one, Oxyurus mas-a-fueræ, allied to the wide-spread South Temperate O. spinicauda, and Cinclodes fusus, a South Temperate species—both Dendrocolaptidæ; with a humming-bird, Eustephanus leyboldi, allied to the species in the larger island. The preceding facts are taken from papers by Mr. Sclater in the Ibis for 1871, and a later one in the same journal by Mr. Salvin (1875). The former author has some interesting remarks on the three species of humming-birds of the genus Eustephanus, above referred to. The Chilian species, E. galeritus, is green in both sexes. E. fernandensis has the male of a fine red colour and the female green, though differently marked from the female of E. galeritus. E. leyboldi (of Mas-a-fuera) has the male also red and the female green, but the female is more like that of E. galeritus, than it is like the female of its nearer ally in Juan Fernandez. Mr. Sclater supposes, that the ancient parent form of these three birds had the sexes alike, as in the present Chilian bird; that a pair (or a female having fertilised ova) reached Juan Fernandez and colonised it. Under the action of sexual selection (unchecked by some conditions which had impaired its efficacy on the continent) the male gradually assumed a brilliant plumage, and the female also slightly changed its markings. Before this change was completed the bird had established an isolated colony on Mas-a-fuera; and here the process of change was continued in the male, but from some unknown cause checked in the female, which thus remains nearer the parent form. Lastly the slightly modified Chilian bird again reached Juan Fernandez and exists there side by side with its strangely altered cousin.
All the phenomena can thus be accounted for by known laws, on the theory of very rare accidental immigrations from the mainland. The species are here so very few, that the greatest advocate for continental extensions would hardly call such vast causes into action, to account for the presence of these three birds on so small and so remote an island, especially as the union must have continued down to the time of existing species. But if accidental immigration has sufficed here, it will also assuredly have sufficed where the islands are larger, and the chances of reaching them proportionately greater; and it is because an important principle is here illustrated on so small a scale, and in so simple a manner as to be almost undeniable, that we have devoted a paragraph to its elucidation.
A few Coleoptera from Juan Fernandez present analogous phenomena. All belong to Chilian genera, while a portion of them constitute peculiar species.
Land-shells are rather plentiful, there being about twenty species belonging to seven genera, all found in the adjacent parts of South America; but all the species are peculiar, as well as four others found on the island of Mas-a-fuera.
III. Tropical North America, or the Mexican Sub-region.
This sub-region is of comparatively small extent, consisting of the irregular neck of land, about 1,800 miles long, which connects the North and South American continents. Almost the whole of its area is mountainous, being in fact a continuation of the great range of the Rocky Mountains. In Mexico it forms an extensive table-land, from 6,000 to 9,000 feet above the sea, with numerous volcanic peaks from 12,000 to 18,000 feet high; but in Yucatan and Honduras, the country is less elevated, though still mountainous. On the shores of the Caribbean Sea and Gulf of Mexico, there is a margin of low land from 50 to 100 miles wide, beyond which the mountains rise abruptly; but on the Pacific side this is almost entirely wanting, the mountains rising almost immediately from the sea shore. With the exception of the elevated plateaus of Mexico and Guatemala, and the extremity of the peninsula of Yucatan, the whole of Central America is clothed with forests; and as its surface is much broken up into hill and valley, and the volcanic soil of a large portion of it is very fertile, it is altogether well adapted to support a varied fauna, as it does a most luxuriant vegetation. Although many peculiar Neotropical types are absent, it yet possesses an ample supply of generic and specific forms; and, as far as concerns birds and insects, is not perhaps inferior to the richest portions of South America in the number of species to be found in equal areas.
Owing to the fact that the former Republic of Mexico comprised much territory that belongs to the Nearctic region, and that many Nearctic groups extend along the high-lands to the capital city of Mexico itself, and even considerably further south, there is much difficulty in determining what animals really belong to this sub-region. On the low-lands, tropical forms predominate as far as 28° N. latitude; while on the cordilleras, temperate forms prevail down to 20°, and are found even much farther within the tropics.
Mammalia.—Very few peculiar forms of Mammalia are restricted to tropical North America; which is not to be wondered at when we consider the small extent of the country, and the facility of communication with adjacent sub-regions. A peculiar form of tapir (Elasmognathus bairdi) inhabits Central America, from Panama to Guatemala, and, with Myxomys, a genus of Muridæ, are all at present discovered. Bassaris, a remarkable form of Procyonidæ, has been included in the Nearctic region, but it extends to the high-lands of Guatemala. Heteromys, a peculiar genus of Saccomyidæ or pouched rats, inhabits Mexico, Honduras, Costa Rica, and Trinidad. Five genera of monkeys extend here,—Ateles, Mycetes, Cebus, Nyctipithecus, and Saimiris; the two former alone reaching Mexico, the last only going as far as Costa Rica. Other typical Neotropical forms are Galera, the tayra, belonging to the weasel family; Nasua, the coatimundi; Dicotyles, the peccary; Cercolabes, the tree porcupine; Dasyprocta, the agouti; Cælogenys, the paca; Cholœpus, and Arctopithecus, sloths; Cyclothurus, an ant-eater; Tatusia, an armadillo; and Didelphys, oppossum. Of Northern forms, Sorex, Vulpes, Lepus, and Pteromys reach Guatemala.
Birds.—The productiveness of this district in bird life, may be estimated from the fact, that Messrs. Salvin and Sclater have catalogued more than 600 species from the comparatively small territory of Guatemala, or the portion of Central America between Mexico and Honduras. The great mass of the birds of this sub-region are of Neotropical families and genera, but these are intermingled with a number of migrants from temperate North America, which pass the winter here; with some northern forms on the high-lands; and with a considerable number of peculiar genera, mostly of Neotropical affinities.
The genera of birds peculiar to this sub-region belong to the following families:—Turdidæ (2 genera); Troglodytidæ (1 gen.); Vireonidæ (1 gen.); Corvidæ (2 gen.); Ampelidæ (1 gen.); Tanagridæ (1 gen.); Fringillidæ (2 gen.); Icteridæ (1 gen.); Formicariidæ (2 gen.); Tyrannidæ (2 gen.); Cotingidæ (1 gen.); Momotidæ (1 gen.); Trogonidæ (1 gen.); Trochilidæ (14 gen.); Conuridæ (1 gen.); Cracidæ (2 gen.); Strigidæ (1 gen.); in all 37 genera of land-birds. The Neotropical families that do not extend into this sub-region are, Pteroptochidæ; the sub-family Furnariinæ of the Dendrocolaptidæ; the sub-family Conophaginæ of the Tyrannidæ; the sub-family Rupicolinæ of the Cotingidæ; Phytotomidæ; Todidæ; Opisthocomidæ; Chionididæ; Thinocoridæ; Cariamidæ; Psophiidæ; Eurypygidæ; Palamedeidæ; and Struthionidæ. On the other hand Paridæ, Certhiidæ, Ampelidæ, and Phasianidæ, are northern families represented here, but which do not reach South America; and there are also several northern genera and species, of Turdidæ, Troglodytidæ, Mniotiltidæ, Vireonidæ, Fringillidæ, Corvidæ, Tetraonidæ, and Strigidæ, which are similarly restricted. Some of the most remarkable of the Neotropical genera only extend as far as Costa Rica and Veragua,—countries which possess a rich and remarkable fauna. Here only are found an umbrella bird, (Cephalopterus glabricollis); a bell bird (Chasmorhynchus tricarunculatus); and species of Dacnis (Cœrebidæ), Buthraupis, Eucometis, Tachyphonus (Tanagridæ), Xiphorhynchus (Dendrocolaptidæ); Hypocnemis (Formicariidæ); Euscarthmus (Tyrannidæ); Attila (Cotingidæ); Piprites (Pipridæ); Capito, Tetragonops (Megalæmidæ); Selenidera (Rhamphastidæ); Neomorphus (Cuculidæ); Monasa (Bucconidæ); many genera of Trochilidæ; and Nothocercus (Tinamidæ); none of which extend further north. A considerable number of the peculiar genera noted above, are also found in this restricted area, which is probably one of the richest ornithological districts on the globe.
Reptiles.—These are much less known than the preceding classes, but they afford several peculiar and interesting forms. Snakes are perhaps the least remarkable; yet there are recorded 4 peculiar genera of Calamariidæ, 1 of Colubridæ, 1 of Homalopsidæ, 3 of Dipsadidæ; while Boa and Elaps are in common with South America. Lizards are much more specially developed. Chirotes, one of the Amphisbænians, is confined to Mexico and the southern part of the Nearctic region; Heloderma forming a peculiar family, Helodermidæ, is Mexican only; Abronia and Barissia (Zonuridæ) are also Mexican, as is Siderolamprus belonging to the Scincidæ, while Blepharactitis (same family) inhabits Nicaragua; Brachydactylus, one of the geckoes, is from Costa Rica; while Phymatolepis, Lamanctus, Corytheolus, Cachrix, Corythophanes and Chamæleopsis, all belonging to the Iguanidæ, are confined to various parts of the sub-region. In the same family we have also the Antillean, Cyclura, and the Nearctic Phrynosoma and Tropidolepis, as well as the wide-spread American genus Anolius.
Among the tortoises, Staurotypus, allied to Chelydra, is found in Mexico and Guatemala; and another genus, Claudius, has been lately described from Mexico.
Amphibia.—These are chiefly Batrachians; Rhinophryna (forming a peculiar family) being confined to Mexico; Triprion, a genus of Hylidæ, inhabiting Yucatan, with Leyla and Strabomantis (Polypedatidæ) found only in Costa Rica and Veragua, are peculiar genera. The Salamandridæ, so abundant in the Nearctic region, are represented by a few species of Amblystoma and Spelerpes.
Fresh-water fish.—Since the British Museum catalogue was published, a valuable paper by Dr. Günther, in the Transactions of the Zoological Society for 1868, furnishes much additional information on the fishes of Central America. In that part of the region south of Mexico, 106 species of fresh-water fishes are enumerated; and 17 of these are found in streams flowing into both the Atlantic and Pacific Oceans. On the whole, 11 families are represented among the fresh-water fish, and about 38 genera. Of these, 14 are specially Nearctic,—Amiurus (Siluridæ); Fundulus (Cyprinodontidæ); Sclerognathus (Cyprinidæ); and Lepidosteus (Ganoidei). A much larger number are Neotropical; and several Neotropical genera, as Heros and Pœcilia, are more largely developed here than in any other part of the region. There are also a considerable number of peculiar genera;—Petenia, Theraps, and Neotrophus (Chromides); Ælurichthys (Siluridæ); Chalcinopsis (Characinidæ); Characodon, Belonesox, Pseudoxiphophorus, Platypœcilus, Mollienesia, and Xiphophorus (Cyprinodontidæ). A few peculiar Antillean forms are also present; as Agonostoma (Mugilidæ); Gambusia and Girardinus (Cyprinodontidæ). The other families represented are Percidæ (1 genus); Pristopomatidæ (2 gen.); Gobiidæ (1 gen.); Clupeidæ (2 gen.); and Gymnotidæ (1 genus).
On the whole the fish-fauna is typically Neotropical, but with a small infusion of Nearctic forms. There are a considerable proportion of peculiar genera, and almost all the species are distinct from those of other countries. The predominant family is that of the Cyprinodontidæ, represented by 12 genera; and the genus Heros (Chromidæ) has here its maximum development, containing between thirty and forty species. Dr. Günther considers that a number of sub-faunas can be distinguished, corresponding to some extent, with the islands into which the country would be divided by a subsidence of about 2,000 feet. The most important of these divisions is that separating Honduras from Costa Rica, and as it also divides a very marked ornithological fauna we have every reason to believe that such a division must have existed during the latter portion of the tertiary epoch. We shall find some farther evidence of this division in the next class.
Insects.—The butterflies of various parts of Central America and Mexico, having been largely collected, offer us some valuable evidence as to the relations of this sub-region. Their general character is wholly Neotropical, about one half of the South American genera being found here. There are also a few peculiar genera, as, Drucina (Satyridæ); Microtia (Nymphalidæ); Eumæus (Lycænidæ); and Eucheira (Pieridæ). Clothilda (Nymphalidæ) is confined to this sub-region and the Antilles. The majority of the genera range over the whole sub-region from Panama to Mexico, but there are a considerable number, comprising many of the most characteristic South American forms, which do not pass north of Costa Rica or Nicaragua. Such are Lycorea, Ituna, Thyridia, Callithomia, Oleria and Ceratina,—all characteristic South American groups of Danaidæ; Pronophila and Dynastor (Satyridæ); Protogonius, Pycina, Prepona, Nica, Ectima and Colænis (Nymphalidæ); Eurybia and Methonella (Nemeobiidæ); Hades, and Panthemos (Erycinidæ).
Coleoptera.—These present some interesting features, but owing to their vast number only a few of the more important families can be noticed.
Cicindelidæ.—The only specially Neotropical genera recorded as occurring in this sub-region, are Ctenostoma and Hiresia, both reaching Mexico.
Carabidæ.—Several genera are peculiar. Molobrus is found in all parts of the sub-region, while Onychopterygia, Phymatocephalus, and Anisotarsus are Mexican only. There are about 20 South American genera, most of which extend to Mexico, and include such characteristic Neotropical forms as Agra, Callida, Coptodera, Pachyteles, Ardistomus, Aspidoglossa, Stenocrepis, and Pelecium.
Lucanidæ.—Of this important family there is, strange to say, not a single species recorded in Gemminger and Harold's catalogue up to 1868! It is almost impossible that they can be really absent; yet their place seems to he, to some extent, supplied by an unusual development of the allied Passalidæ, of which there are five South American and six peculiar genera.
Cetoniidæ.—All the larger South American genera extend to Mexico, which country possesses 3 peculiar forms, Ischnoscelis, Psilocnemis, and Dialithus; while Trigonopeltastes is characteristic, having 4 Mexican, 1 Brazilian, and 1 North American species.
Buprestidæ.—In this family there are no peculiar genera. All the large South American groups are absent, the only important and characteristic genus being Stenogaster.
Longicorns.—This important group is largely developed, the country being well adapted to them; and their distribution presents some features of interest.
In the Prionidæ there are 6 peculiar genera, the largest being Holonotus with 3 species; two others, Derotrachus and Mallaspis, are characteristic; 3 more are common to South America, and 1 to Cuba. The Cerambycidæ are much more numerous, and there are 24 peculiar genera, the most important being Sphenothecus, Entomosterna, and Cyphosterna; while Crioprosopus and Metaleptus are characteristic of the sub-region, although extending into South America; about 12 Neotropical genera extend to Mexico or Guatemala, while 12 more stop short, as far as yet known, at Nicaragua. Lamiidæ have a very similar distribution; 13 genera are peculiar, the most important being Monilema, Hammatoderus, and Carneades, while Phæa and Lagochirus are characteristic. About sixteen typical Neotropical genera extend to Mexico, and 15 more only reach Nicaragua, among which are such important genera as Anisopus, Lepturgus, and Callia.
The land-shells are not sufficiently known to furnish any corresponding results. They are however mostly of South American genera, and have comparatively little affinity for those of the Antilles.
Relations of the Mexican sub-region to the North and South American Continents.—The sudden appearance of numerous South American forms of Edentata in temperate North America, in Post-Tertiary times, as narrated in Chapter VII., together with such facts as the occurrence of a considerable number of identical species of sea fish on the two sides of the Central American isthmus, render it almost certain that the union of North and South America is comparatively a recent occurrance, and that during the Miocene and Pliocene periods, they were separated by a wide arm of the sea. The low country of Nicaragua was probably the part submerged, leaving the highlands of Mexico and Guatemala still united with the North American continent, and forming part of the Tertiary "Nearctic region." This is clearly indicated both by the many Nearctic forms which do not pass south of Nicaragua, of which the turkeys (Meleagris) are a striking example, and by the comparative poverty of this area in typical Neotropical groups. During the Miocene period there was not that marked diversity of climate between North and South America that now prevails; for when a luxuriant vegetation covered what are now the shores of the Arctic Ocean, the country south of the great lakes must have been almost or quite tropical. At an early Tertiary period, the zoological differences of the Nearctic and Neotropical regions were probably more radical than they are now, South America being a huge island, or group of islands—a kind of Australia of the New World, chiefly inhabited by the imperfectly organized Edentata; while North America abounded in Ungulata and Carnivora, and perhaps formed a part of the great Old World continent. There were also one or more very ancient unions (in Eocene or Miocene times) of the two continents, admitting of the entrance of the ancestral types of Quadrumana into South America, and, somewhat later, of the Camelidæ; while the isthmus south of Nicaragua was at one time united to the southern continent, at another made insular by subsidence near Panama, and thus obtained that rich variety of Neotropical types that still characterises it. When the final union of the two continents took place, the tropical climate of the lower portions of Guatemala and Mexico would invite rapid immigration from the south; while some northern forms would extend their range into and beyond the newly elevated territory. The Mexican sub-region has therefore a composite character, and we must not endeavour too rigidly to determine its northern limits, nor claim as exclusively Neotropical, forms which are perhaps comparatively recent immigrants; and it would perhaps be a more accurate representation of the facts, if we were to consider all the highlands of Mexico and Guatemala above the limits of the tropical forests, as still belonging to the Nearctic region, of which the whole country so recently formed a part.
The long-continued separation of North and South America by one or more arms of the sea, as above indicated, is further rendered necessary by the character of the molluscan fauna of the Pacific shores of tropical America, which is much more closely allied to that of the Caribbean sea, and even of West Africa, than to that of the Pacific islands. The families and many of the genera are the same, and a certain proportion of very closely allied or identical species, shows that the union of the two oceans continued into late Tertiary times. When the evidence of both land and sea animals support each other as they do here, the conclusions arrived at are almost as certain as if we had (as we no doubt some day shall have) geological proof of these successive subsidences.
Islands of the Mexican Sub-region.—The only islands of interest belonging to this sub-region, are Tres Marias and Socorro, recently investigated by Col. Grayson for some of the American Natural History societies.
Tres Marias consist of four small islands lying off the coast of north-western Mexico, about 70 miles from San Blas. The largest is about 15 miles long by 10 wide. They are of horizontally stratified deposits, of moderate height and flat-topped, and everywhere covered with luxuriant virgin forests. They appear to lie within the 100 fathom line of soundings. Fifty-two species of birds, of which 45 were land-birds, were collected on these islands. They consisted of 19 Passeres; 11 Picariæ (7 being humming-birds); 10 Accipitres; 2 parrots, and 3 pigeons. All were Mexican species except 4, which were new, and presumably peculiar to the islands, and one tolerably marked variety. The new species belong to the following genera;—Parula and Granatellus (Mniotiltidæ); Icterus (Icteridæ); and Amazilia (Trochilidæ). A small Psittacula differs somewhat from the same species on the mainland.
There are a few mammalia on the islands; a rabbit (Lepus) supposed to be new; a very small opossum (Didelphys), and a racoon (Procyon). There are also several tree-snakes, a Boa, and many lizards. The occurrence of so many mammalia and snakes is a proof that these islands have been once joined to the mainland; but the fact that some of the species of both birds and mammals are peculiar, indicates that the separation is not a very recent one. At the same time, as all the species are very closely allied to those of the opposite coasts when not identical, we may be sure that the subsidence which isolated them is not geologically remote.
Socorro, the largest of the Revillagigedo Islands, is altogether different from the Tres Marias. It is situated a little further south (19 S. Latitude), and about 300 miles from the coast, in deep water. It is about 2,000 feet high, very rugged and bare, and wholly volcanic. No mammalia were observed, and no reptiles but a small lizard, a new species of a genus (Uta) characteristic of the deserts of N.-Western Mexico. The only observed land-shell (Orthalicus undatus) also inhabits N.-W. Mexico. Only 14 species of birds were obtained, of which 9 were land-birds; but of these 4 were new species, one a peculiar variety, and another (Parula insularis) a species first found in the Tres Marias. With the exception of this bird and a Buteo, all the land-birds belonged to different genera from any found on the Tres Marias, though all were Mexican forms. The peculiar species belonged to the genera Harporhynchus (Turdidæ); Troglodytes (Troglodytidæ); Pipilo (Fringillidæ); Zenaidura (Columbidæ); and a variety of Conurus holochrous (Psittacidæ).
The absence of mammals and snakes, the large proportion of peculiar species, the wholly volcanic nature of these islands, and their situation in deep water 300 miles from land,—all indicate that they have not formed part of the continent, but have been raised in the ocean; and the close relation of their peculiar species to those living in N.-Western Mexico, renders it probable that their antiquity is not geologically great.
The Cocos Islands, about 300 miles S.-W. of the Isthmus of Panama, are known to possess one peculiar bird, a cuckoo of the Coccyzus type, which is considered by some ornithologists to constitute a peculiar genus, Nesococcyx.
IV. The West Indian Islands, or Antillean Sub-region.
The West Indian islands are, in many respects, one of the most interesting of zoological sub-regions. In position they form an unbroken chain uniting North and South America, in a line parallel to the great Central American isthmus; yet instead of exhibiting an intermixture of the productions of Florida and Venezuela, they differ widely from both these countries, possessing in some groups a degree of speciality only to be found elsewhere in islands far removed from any continent. They consist of two very large islands, Cuba and Hayti; two of moderate size, Jamaica and Portorico; and a chain of much smaller islands, St. Croix, Anguilla, Barbuda, Antigua, Guadeloupe, Dominica, Martinique, St. Lucia, St. Vincent, Barbadoes, and Grenada, with a host of intervening islets. Tobago, Trinidad, Margarita, and Curaçao, are situated in shallow water near the coast of South America, of which they form part zoologically. To the north of Cuba and Hayti are the Bahamas, an extensive group of coral reefs and islands, 700 miles long, and although very poor in animal life, belonging zoologically to the Antilles. All the larger islands, and most of the smaller ones (except those of coral formation) are very mountainous and rocky, the chains rising to about 8,000 feet in Hayti and Jamaica, and to nearly the same height in Cuba. All, except where they have been cleared by man, are covered with a luxuriant forest vegetation; the temperature is high and uniform; the rains ample; the soil, derived from granitic and limestone rocks, exceedingly fertile; and as the four larger islands together are larger than Great Britain, we might expect an ample and luxuriant fauna. The reverse is however the case; and there are probably no land areas on the globe, so highly favoured by nature in all the essentials for supporting animal life, and at the same time so poor in all the more highly organised groups of animals. Before entering upon our sketch of the main features of this peculiar but limited fauna, it will be well to note a few peculiarities in the physical structure of the islands, which have an important bearing on their past history, and will enable us to account for much that is peculiar in the general character of their natural productions.
If we draw a line immediately south of St. Croix and St. Bartholomew, we shall divide the Archipelago into two very different groups. The southern range of islands, or the Lesser Antilles, are, almost without exception, volcanic; beginning with the small detached volcanoes of Saba and St. Eustatius, and ending with the old volcano of Grenada. Barbuda and Antigua are low islands of Tertiary or recent formation, connected with the volcanic islands by a submerged bank at no great depth. The islands to the north and west are none of them volcanic; many are very large, and these have all a central nucleus of ancient or granitic rocks. We must also note, that the channels between these islands are not of excessive depth, and that their outlines, as well as the direction of their mountain ranges, point to a former union. Thus, the northern range of Hayti is continued westward in Cuba, and eastward in Portorico; while the south-western peninsula extends in a direct line towards Jamaica, the depth between them being 600 fathoms. Between Portorico and Hayti there is only 250 fathoms; while close to the south of all these islands the sea is enormously deep, from more than 1,000 fathoms south of Cuba and Jamaica, to 2,000 south of Hayti, and 2,600 fathoms near the south-east extremity of Portorico. The importance of the division here pointed out will be seen, when we state, that indigenous mammalia of peculiar genera are found on the western group of islands only; and it is on these that all the chief peculiarities of Antillian zoology are developed.
Mammalia.—The mammals of the West Indian Islands are exceedingly few, but very interesting. Almost all the orders most characteristic of South America are absent. There are no monkeys, no carnivora, no edentata. Besides bats, which are abundant, only two orders are represented; rodents, by peculiar forms of a South American family; and insectivora (an order entirely wanting in South America) by a genus belonging to a family largely developed in Madagascar and found nowhere else. The early voyagers mention "Coatis" and "Agoutis" as being found in Hayti and the other large islands, and it is not improbable that species allied to Nasua and Dasyprocta did exist, and have been destroyed by the dogs of the invaders; though, on the other hand, these names may have been applied to the existing species, which do bear some general resemblance to these two forms.
The Chiroptera, or bats, are represented by a large number of species and by several peculiar genera. The American family of Phyllostomidæ or vampires, has six genera in the Antilles, of which three, Lonchorina, Brachyphylla, and Phyllonycteris, are peculiar, the latter being found only in Cuba. The Vespertilionidæ have four genera, of which one, Nycticellus, is confined to Cuba. There are six genera of Noctilionidæ, of which one, Phyllodia, is confined to Jamaica.
The Insectivora are represented by the genus Solenodon, of which two species are known, one inhabiting Cuba the other Hayti. These are small animals about the size of a cat, with long shrew-like snout, bare rat-like tail, and long claws. Their peculiar dentition and other points of their anatomy shows that they belong to the family Centetidæ, of which five different genera inhabit Madagascar; while there is nothing closely allied to them in any other part of the world but in these two islands.
Seals are said to be found on the shores of some of the islands, but they are very imperfectly known.
The rodents belong to the family Octodontidæ, or, according to some authors, to the Echimyidæ, both characteristic South American groups. They consist of two genera, Capromys, containing three or four species inhabiting Cuba and Jamaica; while Plagiodontia (very closely allied) is confined to Hayti. A peculiar mouse, a species of the American genus Hesperomys, is said to inhabit Hayti and Martinique, and probably other islands. A Dasyprocta or agouti, closely allied to, if not identical with, a South American species, inhabits St. Vincent, St. Lucia, and Grenada, and perhaps St. Thomas, and is the only mammal of any size indigenous to the Lesser Antilles. All the islands in which sugar is cultivated are, however, overrun with European rats and mice, and it is not improbable that these may have starved out and exterminated some of the smaller native rodents.
Birds.—The birds of the Antilles, although very inferior in number and variety to those of the mainland, are yet sufficiently abundant and remarkable, to offer us good materials for elucidating the past history of the country, when aided by such indications as geology and physical geography can afford.
The total number of land-birds which are permanent residents in the West India islands is, as nearly as can be ascertained from existing materials, 203. There are, in addition to this number, according to Prof. Baird, 88 migrants from North America, which either spend the winter in some of the islands or pass on to Central or South America. These migrants belong to 55 genera, and it is an interesting fact that so many as 40 of these genera have no resident representatives in the islands. This is important, as showing that this northern migration is probably a recent and superficial phenomenon, and has not produced any (or a very slight) permanent effect on the fauna. The migratory genera which have permanent residents, and almost always representative species, in the islands, are in most cases characteristic rather of the Neotropical than of the Nearctic fauna, as the following list will show; Turdus, Dendrœca, Vireo, Polioptila, Agelæus, Icterus, Contopus, Myiarchus, Tyrannus, Antrostomus, Chordeiles, Coccyzus, Columba. By far the larger part of these birds visit Cuba only; 81 species being recorded as occurring in that island, while only 31 have been found in Jamaica, 12 in Porto Rico and St. Croix, and 2 in Tobago and Trinidad. Setting aside these migratory birds, as having no bearing on the origin of the true Antillean fauna, we will discuss the residents somewhat in detail.
The resident land-birds (203 in number) belong to 95 genera and 26 families. Of these families 15 are cosmopolitan or nearly so—Turdidæ, Sylviidæ, Corvidæ, Hirundinidæ, Fringillidæ, Picidæ, Cuculidæ, Caprimulgidæ, Cypselidæ, Trogonidæ, Psittacidæ, Columbidæ, Tetraonidæ, Falconidæ, and Strigidæ; 5 are American only—Vireonidæ, Mniotiltidæ, Icteridæ, Tyrannidæ, Trochilidæ; 4 are Neotropical only or almost exclusively—Cœrebidæ, Tanagridæ, Cotingidæ, Conuridæ; 1 is Antillean only—Todidæ; while 1—Ampelidæ—is confined (in the western hemisphere) to North America, and almost to the Nearctic region. Of the 95 genera, no less than 31, or almost exactly one-third, are peculiar; while of the 203 resident species, 177 are peculiar, the other 26 being all inhabitants of South or Central America. Considering how closely the islands approach the continent in several places—Florida, Yucatan, and Venezuela—this amount of speciality in such locomotive creatures as birds, is probably unexampled in any other part of the globe. The most interesting of these peculiar genera are the following: 4 of Turdidæ, or thrushes—1 confined to the large islands, 1 to the whole archipelago, while 2 are limited to the Lesser Antilles; 2 genera of Tanagridæ, confined to the larger islands; 2 of Trogonidæ, also confined to the larger islands; 5 of hummingbirds, 3 confined to the Greater, 1 to the Lesser Antilles; 2 of cuckoos, one represented in all the large islands, the other in Jamaica only; 2 of owls, one peculiar to Jamaica, the other represented in St. Croix, St. Thomas, Portorico, and Cuba; and lastly, Todus, constituting a peculiar family, and having representative species in each of the larger islands, is especially interesting because it belongs to a group of families which are wholly Neotropical—the Momotidæ, Galbulidæ, and Todidæ. The presence of this peculiar form, with 2 trogons; 10 species of parrots, all but one peculiar; 16 peculiar humming-birds belonging to 8 genera; a genus of Cotingidæ; 10 peculiar tanagers belonging to 3 genera; 9 Cœrebidæ of 3 genera; together with species of such exclusively Neotropical genera as Cœreba, Certhiola, Sycalis, Phonipara, Elainea, Pitangus, Campephilus, Chloronerpes, Nyctibius, Stenopsis, Lampornis, Calypte, Ara, Chrysotis, Zenaida, Leptoptila, and Geotrygon, sufficiently demonstrate the predominant affinities of this fauna; although there are many cases in which it is difficult to say, whether the ancestors of the peculiar genera or species may not have been derived from the Nearctic rather than from the Neotropical region.
The several islands differ considerably in their apparent productiveness, but this is, no doubt, partly due to our knowledge of Cuba and Jamaica being much more complete than of Hayti. The species of resident land-birds at present known are as follows:—
If we count the peculiar genera of each island, and reckon as (½) when a genus is common to two islands only, the numbers are as follows:—Cuba 7½, Hayti 3½, Jamaica 8½, Portorico 1, Lesser Antilles 3½. These figures show us, that although Jamaica is one of the smaller and the most isolated of the four chief islands, it yet stands in the first rank, both for the number of its species and of its peculiar forms of birds,—and although this superiority may be in part due to its having been more investigated, it is probably not wholly so, since Cuba has also been well explored. This fact indicates, that the West Indian islands have undergone great changes, and that they were not peopled by immigration from surrounding countries while in the condition we now see them; for in that case the smaller and more remote islands would be very much poorer, while Cuba, which is not only the largest, but nearest to the mainland in two directions, would be immensely richer, just as it really is in migratory birds.
The number of birds common to the four larger islands is very small—probably not more than half a dozen; between 20 and 30 are common to some two of the islands (counting the Lesser Antilles as one island) and a few to three; but the great mass of the species (at least 140) are confined each to some one of the five islands or groups we have indicated. This is an amount of isolation and speciality, probably not to be equalled elsewhere, and which must have required a remarkable series of physical changes to bring about. What those changes probably were, we shall be in a better position to consider when we have completed our survey of the various classes of land animals.
A SCENE IN CUBA, WITH CHARACTERISTIC ANIMALS.
In the preceding enumeration the Bahamas have been included with Cuba, as regards the birds they have in common; but they possess some half dozen species not found elsewhere, and even one central American genus of humming-birds (Doricha) not found in any other part of the Antilles. We have thus given Cuba rather more peculiar species than it really possesses, so that the proportionate richness of Jamaica is rather greater than shown by our figures.
The destruction of the forests and the increase of population, with, perhaps, the use of firearms, seem to have led to the extermination of some species of birds in the smaller islands. Professor Newton has called attention to the work of M. Ledru, who, in 1796, described the birds of St. Thomas. He mentions a parrot and a parroquet in the island, the latter only being now known, and very scarce; also a green pigeon and a tody, both now unknown. No less than six species of parrots are said to have been formerly found in Guadeloupe and Martinique, which are now extinct.
Plate XVII. Illustrating the peculiar Mammalia and Birds of the Antilles.—The scene of this illustration is Cuba, the largest of the West Indian islands, and one in which all its peculiar zoological features are well developed. In the foreground is the agouta (Solenodon cubanus), a remarkable insectivorous animal which, with another species inhabiting Hayti, has no allies on the American continent; nor anywhere in the world but in Madagascar, where a group of animals are found constituting the family Centetidæ, to which Solenodon is said undoubtedly to belong. Above it are a pair of hutias (Capromys fournieri), rat-like animals belonging to the South American family Octodontidæ. They live in the forests, and climb trees readily, eating all kinds of vegetable food. Three species of the genus are known, which are found only in Cuba and Jamaica. Just above these animals is a white-breasted trogon (Prionoteles temnurus), confined to Cuba, and the only species of the genus. Near the top of the picture are a pair of todies (Todus multicolor), singular little insectivorous birds allied to the motmots, but forming a very distinct family which is confined to the islands of the Greater Antilles. They are beautifully-coloured birds,—green above, red and white beneath, and are exceedingly active in their movements. To the right are a pair of small humming-birds (Sporadinus ricordi), not very remarkable in this beautiful family, but introduced here because they belong to a genus which is confined to the Greater Antilles.
Table of distribution of West-Indian Birds.—As the birds of the West Indian islands are particularly interesting and their peculiarities comparatively little known, we give here a table of the genera of land-birds, compiled from all available sources of information. Owing to the numerous independent observations on which it is founded, the discrepancies of nomenclature, and uncertainty in some cases as to the locality of species, it can only be looked upon as an approximative summary of the existing materials on Antillean ornithology.
TABLE OF THE RESIDENT LAND-BIRDS OF THE ANTILLES.
Note.—Genera confined to the West Indies are in Italics. An (a) after (1) indicates a species common to two islands: but where there are two or more species in an island, or the localities are doubtful, this indication cannot be given. All species not otherwise noted are peculiar to the Antilles.
Key to columns:
Column 1 Cuba.
" 2 Bahamas.
" 3 Hayti.
" 4 Jamaica.
" 5 Portorico & St. Croix.
" 6 Lesser Antilles.
" 7 Total resident species.
|Family and Genus.||Number of Species in each Island.||7||Remarks.|
|Turdus||—||—||—||1||—||—||1||Five species migrate to Cuba|
|Margarops||—||—||1a||—||1a||3||4||Martinique, St. Lucia, Guada.|
|Rhamphocinclus||—||—||—||—||—||1||1||Martinique and St. Lucia|
|Cinclocerthia||—||—||—||—||—||3||3||Nevis to St. Lucia|
|Mimus||1||1||—||1||(?)||—||3||Another species migrates to the Antilles|
|Vireosylvia||1||—||1||1||1||1||2||One S. American species|
|Vireo||1||1||—||1||1||—||4||Five species migrate to Cuba|
|Cyanocorax||—||—||—||1||—||—||1||S. American species|
|Perissoglossa||1||—||1||—||1||—||1||N. American species|
|Dendrœca||2||2||1||3||1||1||7||Twelve sp. migrate to W. I.|
|Certhiola||—||1||1||1||2||2||7||Dominica and Martinique|
|Cœreba||1||—||—||—||—||—||1||S. American species|
|Dulus||(?)||—||1||(?)||(?)||(?)||2||One species locality unknown|
|Hirundo||1||—||1a||1a||—||—||2||One S. American species|
|Euphonia||1a||—||1a||1||1||1||4||St. Bartholom. & Martinique|
|Saltator||—||—||—||—||—||1||1||Guadeloupe and St. Lucia|
|Loxigilla||—||—||1||1||—||1||3||Martinique and Dominica|
|Sycalis||—||—||—||1||—||—||1||S. American species|
|Phonipara||3||—||3||3||2||—||4||One S. American species|
|Quiscalus||—||—||1||1||2||2||4||St. Lucia, Martinique and Barbadoes|
|Myiarchus||2||—||1||3||1||1b||7||One S. American species (b)|
|Tyrannus||2||—||—||1b||1b||2b||3||One sp. in Cen. America (b)|
|Coccygus||1||—||2||1||1||1||3||Dominica, St. Lucia, all Neotropical species|
|Crotophaga||1||—||—||1||1||1||2||N. & Cen. American species|
|Antrostomus||2||—||—||1||—||1||2||One Neotropical species|
|Stenopsis||—||—||—||—||—||1||1||Martinique (S. America sp.)|
|Panyptila||—||—||1||—||—||—||1||S. American species|
|Eulampis||—||—||—||—||1||2||2||St. Croix, Dominica, St. Lucia, Martinique|
|Orthorhynchus||—||—||—||—||1||2||3||Domin., Martini., St. Lucia|
|Ara||1||—||—||—||—||—||1||S. American species|
|Columba||1||—||1||2||2||1||3||One in Honduras|
|Geotrygon||2||—||1||2||1||2||5||St. Lucia, Martinique, one species Mexican|
|Nyctalops||1||—||—||—||—||—||1||S. American species|
|Gymnoglaux||1||—||—||—||1||—||2||St. Croix and St. Thomas|
|Totals||Number||of||families of||resident||land-birds||in the||Antilles||26|
Reptiles and Amphibia.—These classes not having been systematically collected, and the numerous described genera not having undergone careful revision, little trustworthy information can be derived from them. The following enumeration of the chief groups hitherto noticed or described, will, however, show very similar features to those presented by the birds—a general relation to Neotropical forms, a more special relation to those of Central America and Mexico, and a considerable number of peculiar types.
Snakes.—Arrhyton (Calamariidæ) from Cuba, Hypsirhynchus from Barbadoes, Cryptodacus from Cuba, Ialtris from Hayti, and Coloragia from Cuba (all Colubridæ), have been described as genera peculiar to the Antilles. Phylodryas and Dromicus (Colubridæ) are Antillean and Neotropical; Ahætulla, (Dendrophidæ) has the same distribution but extends to tropical Africa; Epicrates and Corallus (Pythonidæ) are Neotropical and Antillean; while Chilabothrus from Jamaica and Ungalia from Cuba and Jamaica (both Pythonidæ) are found elsewhere only in Central America and Mexico. There appear to be no Crotalidæ except an introduced species of Craspedocephalus in St. Lucia.
Lizards are more numerous. Ameiva (Teidæ) is found all over America, Gerrhonotus (Zonuridæ) is Neotropical and occurs in Cuba; Gymnophthalmus is South American and Antillean. Of Scincidæ seven genera are noted. Celestus (with 9 species) is peculiar to the Antilles; Camilia (1 species) to Jamaica, Panoplus (1 species) and Embryopus (1 species) to Hayti; Diploglossus is Antillean and South American; while Plestiodon and Mabouya are cosmopolite. Of Geckotidæ there are four genera; Phyllodactylus and Hemidactylus which are cosmopolite; Sphærodactylus which is wholly American; and Cubina found only in Martinique and Brazil. Of Iguanidæ there are six genera; Anolis, which ranges all over America; Polychrus, which is Neotropical; Iguana and Liocephalus which are South American; Tropedurus found in Cuba and Brazil; and Cyclura only known from Jamaica, Cuba, and Central America.
Amphibia.—The genus Trachycephalus, belonging to the Hylidæ or tropical tree-frogs, is almost peculiar to the Antilles; Cuba, Hayti, and Jamaica possessing seven species, while only one is recorded from South America. Other genera are, Peltaphryne (Bufonidæ) from Portorico; Phyllobates (Polypedatidæ) from Cuba; Leiuperus (Ranidæ) from Hayti,—all Neotropical. Of the Urodela, or tailed batrachians, no representative occurs, although they are so characteristic a feature of the Nearctic region.
Fresh-water fish.—The same general remarks apply to these as to the reptiles. Only one peculiar genus is noted—Lebistes, a form of Cyprinodontidæ from Barbadoes; other genera of the same family being, Haplochilus, Rivulus, and Girardinus, widely spread in the Neotropical region; while Gambusia is confined to Central America, Mexico, and the Antilles. Four other families are represented; Siluridæ by Chætostomus, found in Portorico and South America; Chromidæ by the South American Acara; Mugillidæ by the Central American Agonostoma; and Percidæ by the North American Centrarchus, of which a species is recorded from Cuba.
Insects.—The various West Indian islands have not been well explored entomologically; one reason no doubt being, that their comparative poverty renders them little attractive to the professional collector, while the abounding riches of Central and South America lie so near at hand. We can, therefore, hardly tell whether the comparative poverty, or even total absence of some families while others seem fairly represented, is a real phenomenon of distribution, or only dependent on imperfect knowledge. Bearing this in mind, we proceed to give a sketch of what is known of the chief groups of Lepidoptera and Coleoptera.
Lepidoptera.—The Neotropical butterfly-fauna is but poorly represented, the majority of the most remarkable types being entirely wanting; yet there are a few peculiar and very characteristic forms which show great isolation, while the majority of the species are peculiar. Four genera are exclusively or characteristically Antillean,—Calisto belonging to the Satyridæ, with four species, of which one ranges to South Carolina; Clothilda (Nymphalidæ) a fine genus which has 4 Antillean species and 2 in Central America; Lucinia (Nymphalidæ) 2 species, confined to Jamaica and Hayti; and Kricogonia belonging to the Pieridæ, which has 2 West Indian species, while 1 inhabits Mexico and Florida. Genera which show a special relation to Central America are Euptoieta, Eumæus, and Nathalis. Almost all the other genera are South American, the total number recorded in each family as occurring in the West Indian islands, being, 3 of Danaidæ; 1 of Heliconiidæ; 2 of Satyridæ; 18 of Nymphalidæ; 1 of Erycinidæ; 4 of Lycænidæ; 6 of Pieridæ; 1 of Papilionidæ, and 10 of Hesperidæ. The genus Papilio is represented by about 20 species, 2 of which are North American, 4 South American, while the rest form little characteristic groups allied to those of Central America. The most marked feature seems to be the scarcity of Satyridæ and the almost total absence of Erycinidæ, with a great deficiency in characteristic Neotropical forms of Danaidæ and Nymphalidæ.
Coleoptera.—Cicindelidæ and Carabidæ are very poorly represented, by a few species of wide-spread groups, and hardly any peculiar genera. No Lucanidæ are recorded. Of Cetoniidæ, Gymnetis only appears to be represented. Buprestidæ seem to be more numerous; 15 genera being recorded, but almost all of wide distribution. One only is peculiar—Tetragonoschoma, found in Hayti; Halecia is the only exclusively South American genus; Chalcophora is widely scattered over the tropical regions but is absent from South America, yet it occurs in the Nearctic region and extends to Jamaica and Guadeloupe. We now come to the Longicorns, the only group of Coleoptera which seems to be well represented, or which has been carefully collected. No less than 40 genera are known from the West Indian islands, and 15 of these are peculiar. Prionidæ are proportionately very numerous, there being 10 genera, 2 of which are widely distributed in both South and North America, 1 is North American, and 1 South American, while the following are peculiar,—Stenodontes (Hayti and Cuba); Dendroblaptus (Cuba); Monodesmus (Cuba and Jamaica); Prosternodes (Cuba); Solenoptera and Elateropsis, the two largest genera found in most of the islands. Of Cerambycidæ there are 16 genera, 2 of which range all over America, 4 are Neotropical, 1 South American only, while the following are confined to the islands,—Merostenus, Pentomacrus, and Eburiola (Jamaica); Bromiades (Cuba); Trichrous, Heterops, and Pœciloderma (Antilles). One genus, Smodicum, is widely spread, having a species in Carolina, 1 in South America, 1 in Hayti, and 1 in West Africa. Of Lamiidæ there are 14 genera, 8 of which are Neotropical, 1 common to Central America and Mexico, 1 to the United States and Cuba, while 2, Proecha and Phidola, are confined to Cuba. Several of the genera are curiously distributed;—Spalacopsis is South American, with 4 species in Cuba and Tropical Africa; Lagocheirus is Neotropical, with a species in Australia; while Leptostilus is characteristic of the Antilles and North America, with a few species in South America, and one in New Zealand. These cases of erratic distribution, so opposed to the general series of phenomena among which they occur, must be held to be sufficiently explained by the great antiquity of these groups and their former wide distribution. They may be supposed to be the remnants of types, now dying out, which were once, like Callichroma, Clytus, and many others, almost universally distributed.
All the peculiar Antillean genera of Cerambycidæ and Lamiidæ are allied to Neotropical forms. The peculiar Prionidæ, however, are mostly allied to Mexican and North American groups, and one, Monodesmus, belongs to a group all the other genera of which inhabit the East Indies and South Africa.
Land-shells.—This subject has already been generally treated under the Region, of which, in this class of animals, the Antilles form so important a part. We must therefore now confine ourselves mainly to the internal distribution of the genera, and to a few remarks on the general bearing of the facts.
The excessive and altogether unexampled productiveness of the West Indian islands in land-shells, may be traced to two main sets of causes. The first and least known, consist of the peculiar influences and conditions which render islands always more productive than continents. Whatever these conditions are, they will be more effective where the islands have been long separated from the mainland, as is here undoubtedly the case. It seems most probable that the great development of land-shells in islands, is due to the absence or deficiency of the vertebrata, which on continents supply a variety of species adapted to prey upon these molluscs. This view is supported by the fact, that in such islands as have been united to a continent at no very distant epoch, and still maintain a continental variety of vertebrata, no such special development of land-shells has taken place. If we compare the Philippine islands with the Sunda group, we find the development of vertebrata and land-molluscs in inverse ratio to each other. The same thing occurs if we compare New Zealand and Tasmania; and we have a still more striking example in the Antillean group itself, continental Trinidad having only 20 genera and 38 species, while the highly insular Jamaica has about 30 genera and more than 500 species.
The other causes favourable to the increase and development of land-shells are of a physical nature. A great extent of limestone-rock is one; and in the larger West Indian islands we have a considerable proportion of the surface consisting of this rock. But perhaps equally or more important, is the character of the land surface, and the texture of the exposed rock itself. A much broken surface, with numerous deep ravines, cutting up the whole country into isolated valleys and ridges, seems very favourable to the specialization of forms in this very sedentary class of animals. Equally favourable is a honeycombed and highly-fissured rock-surface, affording everywhere cracks and crannies for concealment. Now, taking Jamaica as an example of the archipelago, we find all these conditions in a wonderful degree. Over a large part of this island, a yard of level ground can hardly be found; but ridges, precipices, ravines, and rock-bound valleys, succeed each other over the whole country. At least five-sixths of the entire surface is limestone, and under the influence of tropical rains this rock is worn, fissured, and honeycombed, so as to afford ample shelter and concealment for land-shells.
It is probable that the three chief islands, Cuba, Jamaica and Hayti, are nearly equally rich in land-shells; but the last is very much less known, and therefore, perhaps, appears to be much poorer. Cuba has rather more species than Jamaica; but while the former has only 1 peculiar genus (Diplopoma), the latter has 3 (Geomelania, Chittya, and Jamaicea), as well as two others only represented in the other islands by single species. From Hayti, only about one-third as many species are known as from the two former islands. It has no peculiar genera, but it has some forms in common with Cuba and others with Jamaica, which show that those islands have more connection with it, than with each other; just as we found to be the case in birds. Portorico and the Virgin islands have still fewer species than Hayti; and, as many of the genera common to the other three islands are wanting, there is, no doubt, here a real deficiency. In the islands farther south (Barbuda to Martinique) more Antillean genera disappear or become very rare, while some continental forms take their place. The islands from St. Lucia to Trinidad have a still more continental character; the genus Bulimus, so largely developed on the continent, only reaching St. Lucia. The Bahamas contain about 80 species of land-shells, of which 25 are Antillean, the rest peculiar; all the genera being Antillean. The affinity is chiefly with Hayti and Cuba, but closest with the latter island.
In the West Indian islands as a whole, there are 11 peculiar genera; 9 operculate (Geomelania, Chittya, Jamaicea, Licina, Choanopoma, Ctenopoma, Diplopoma, Stoastoma, Lucidella); and 2 inoperculate (Sagda and Stenopus), besides Cyclostomus, which belongs to the Old World and is not found on the American continent. Mr. Bland considers, that many of the Antillean land-shells exhibit decided African and Asiatic, rather than South American affinities. A species of the Asiatic genus Diplommatina has been found in Trinidad, and an Indian species of Ennea occurs in Grenada and St. Thomas; a clear indication that land-shells are liable to be accidentally imported, and to become established in the less productive islands.
Although these islands are so wonderfully rich even now, there is good reason to believe that many species have become extinct since the European occupation of them. When small islands are much cultivated, many of these molluscs which can only live under the shade of forests, are soon extirpated. In St. Croix many species have become extinct at a comparatively recent period, from the burning of forests; and as we know that in all the islands many of the species are excessively local, being often confined to single valleys or ridges, we may be sure that wherever the native forests have disappeared before the hand of man, numbers of land shells have disappeared with them. As some of the smaller islands have been almost denuded of their wood, and in the larger ones extensive tracts have been cleared for sugar cultivation, a very considerable number of species have almost certainly been exterminated.
General Conclusions as to the Past History of the West Indian Islands.—The preceding sketch of the peculiarities of the animal life of these islands, enables us to state, that it represents the remains of an ancient fauna of decided Neotropical type, having on the whole most resemblance to that which now inhabits the Mexican sub-region. The number of peculiar genera in all classes of animals is so great in proportion to those in common with the adjacent mainland, as to lead us to conclude that, subsequent to the original separation from the Mexican area, a very large tract of land existed, calculated to support a rich and varied fauna, and, by the interaction of competing types, give rise to peculiar and specially modified organisms. We have already shown that the outline of the present islands and the depths of the surrounding seas, give indications of the position and extent of this ancient land; which not improbably occupied the space enclosed by uniting Western Cuba with Yucatan, and Jamaica with the Mosquito Coast. This land must have stretched eastward to include Anguilla, and probably northward to include the whole of the Bahamas. At one time it perhaps extended southward so as to unite Hayti with northern Venezuela, while Panama and Costa Pica were sunk beneath the Pacific. At this time the Lesser Antilles had no existence.
The only large island of whose geology we have any detailed account, is Jamaica; and taking this as a type of what will probably be found in Cuba and Hayti, we must place the continental period as having occurred after the close of the Miocene, or during some part of the Pliocene epoch, since a large portion of the surface of the former island consists of beds of marine limestone from 2,000 to 3,000 thick, believed to be of Pliocene age. After some time, the land between Hayti and South America subsided, and still later that between Central America and Cuba with Jamaica; but a large tract of land remained insulated, and no doubt supported a very much richer and more varied fauna than now. We have evidence of this in extinct Mammalia of large size, belonging to the peculiar South American family of the chinchillas, which have been found in caves in the small islands of Anguilla, and which, from the character of the land-shells associated with them, are believed to be of Pliocene or Post-pliocene age. This discovery is most interesting, and gives promise of very valuable results from the exploration of the numerous caverns that undoubtedly exist in the abundant limestone strata of the larger islands. This extensive Antillean land, after long continuing undivided, was at length broken up by subsidence into several islands; but as this alone would not account for the almost complete annihilation of the mammalian fauna, it seems probable that the subsidence was continued much farther, so as greatly to reduce the size and increase the number of the islands. This is indicated, by the extensive alluvial plains in Cuba and Hayti, and to a less extent in Jamaica; and by elevated beds of Post-pliocene marls in the latter island.
The series of changes now suggested, will account for all the main features of the Antillean fauna in its relations to that of the American continent. There remains the affinity with Madagascar, indicated by Solenodon, and a few cases of African and Asiatic affinity in insects and land-shells; but these are far too scanty to call for any attempt at special explanation. Such cases of remote affinity and discontinuous distribution, occur in all the regions, and in almost every group of animals; and we look upon them almost all, as cases of survival, under favourable conditions, of once wide-spread groups. If no wild species of the genus Equus were now to be found, except in South Africa (where they are still most abundant), and in South Temperate America, where their fossil remains show us they did exist not very long ago, what a strong fact it would have appeared for the advocates of continental extensions! Yet it would have been due to no former union of the great southern continents, but to the former extensive range of the family or the genus to which the two isolated remnants belonged. And if such an explanation will apply to the higher vertebrata, it is still more likely to be applicable to similar cases occurring among insects or mollusca, the genera of which we have every reason to believe to be usually much older than those of vertebrates. It is in these classes that examples of widely scattered allied species most frequently occur; and the facility with which they are diffused under favourable conditions, renders any other explanation than that here given altogether superfluous.
The Solenodon is a member of an order of Mammalia of low type (Insectivora) once very extensive and wide-spread, but which has begun to die out, and which has left a number of curious and isolated forms thinly scattered over three-fourths of the globe. The occurrence, therefore, of an isolated remnant of this order in the Antilles is not in itself remarkable; and the fact that the remainder of the family to which the Antillean species belong has found a refuge in Madagascar, where it has developed into several distinct types, does not afford the least shred of argument on which to found a supposed independent land connection between these two sets of islands.
Summary of the Past History of the Neotropical Region.
We have already discussed this subject, both in our account of extinct animals, and in various parts of the present chapter. It is therefore only necessary here, briefly to review and summarise the conclusions we have arrived at.
The whole character of Neotropical zoology, whether as regards its deficiencies or its specialities, points to a long continuance of isolation from the rest of the world, with a few very distant periods of union with the northern continent. The latest important separation took place by the submergence of parts of Nicaragua and Honduras, and this separation probably continued throughout much of the Miocene and Pliocene periods; but some time previous to the coming on of the glacial epoch, the union between the two continents took place which has continued to our day. Earlier submergences of the isthmus of Panama probably occurred, isolating Costa Rica and Veragua, which then may have had a greater extension, and have thus been able to develope their rich and peculiar fauna.
The isthmus of Tehuantepec, at the south of Mexico, may, probably, also have been submerged; thus isolating Guatemala and Yucatan, and leading to the specialization of some of the peculiar forms that now characterise those countries and Mexico.
The West Indian Islands have been long isolated and have varied much in extent. Originally, they probably formed part of Central America, and may have been united with Yucatan and Honduras in one extensive tropical land. But their separation from the continent took place at a remote period, and they have since been broken up into numerous islands, which have probably undergone much submergence in recent times. This has led to that poverty of the higher forms of life, combined with the remarkable speciality, which now characterises them; while their fauna still preserves a sufficient resemblance to that of Central America to indicate its origin.
The great continent of South America, as far as we can judge from the remarkable characteristics of its fauna and the vast depths of the oceans east and west of it, has not during Tertiary, and probably not even during Secondary times, been united with any other continent, except through the intervention of North America. During some part of the Secondary epoch it probably received the ancestral forms of its Edentates and Rodents, at a time when these were among the highest types of Mammalia on the globe. It appears to have remained long isolated, and to have already greatly developed these groups of animals, before it received, in early Tertiary times, the ancestors of its marmosets and monkeys, and, perhaps also, some of its peculiar forms of Carnivora. Later, it received its Camelidæ, peccaries, mastodons, and large Carnivora; and later still, just before the Glacial epoch, its deer, tapir, opossums, antelopes, and horses, the two latter having since become extinct. All this time its surface was undergoing important physical changes. What its earlier condition was we cannot conjecture, but there are clear indications that it has been broken up into at least three large masses, and probably a number of smaller ones; and these have no doubt undergone successive elevations and subsidences, so as at one time to reduce their area and separate them still more widely from each other, and at another period to unite them into continental masses. The richness and varied development of the old fauna of South America, as still existing, proves, however, that the country has always maintained an extensive area; and there is reason to believe that the last great change has been a long continued and steady increase of its surface, resulting in the formation of the vast alluvial plains of the Amazon, Orinoko, and La Plata, and thus greatly favouring the production of that wealth of specific forms, which distinguishes South America above all other parts of our globe.
The southern temperate portion of the continent, has probably had a considerable southward extension in late Tertiary times; and this, as well as the comparatively recent elevation of the Andes, has given rise to some degree of intermixture of two distinct faunas, with that proper to South Temperate America itself. The most important of these, is the considerable Australian element that appears in the insects, and even in the reptiles and fresh-water fishes, of South Temperate America. These may be traced to several causes. Icebergs and icefloes, and even solid fields of ice, may, during the Glacial epoch, have afforded many opportunities for the passage of the more cold-enduring groups; while the greater extension of southern lands and islands during the warm periods—which there is reason to believe prevailed in the southern as well as in the northern regions in Miocene times—would afford facilities for the passage of the reptiles and insects of more temperate zones. That no actual land-connection occurred, is proved by the total absence of interchange of the mammals or land-birds of the two countries, no less than by the very fragmentary nature of the resemblances that do exist. The northern element consists almost wholly of insects; and is evidently due to the migration of arctic and north temperate forms along the ridges and plateaus of the Andes; and most likely occurred when these organisms were driven southward at successive cold or Glacial periods.
A curious parallel exists between the past history and actual zoological condition of South America and Africa. In both we see a very ancient land-area extending into the South Temperate zone, isolated at a very early period, and developing only a low grade of Mammalian life; chiefly Edentates and Rodents on the one, Lemurs and Insectivora in the other. Later we find an irruption into both of higher forms, including Quadrumana, which soon acquired a large and special development in the tropical portions of each country. Still later we have an irruption into both of northern forms, which spread widely over the two regions, and having become extinct in the land from whence they came, have been long held to be the original denizens of their adopted country. Such are the various forms of antelopes, the giraffe, the elephant, rhinoceros, and lion in Africa; while in America we have deer and peccaries, the tapir, opossums, and the puma.
On the whole, we cannot but consider that the broad outlines of the zoological history of the Neotropical region can be traced with some degree of certainty; but, owing to the absence of information as to the most important of the geological periods—the Miocene and Eocene—we have no clue to the character of its early fauna, or to the land connections with other countries, which may possibly have occurred in early Tertiary times.
- ↑ Messrs. Sclater and Salvin, and Professor Newton, divide the Neotropical Region into six sub-regions, of which our "Brazilian sub-region" comprises three—the "Brazilian," the "Amazonian," and the "Columbian;" but, after due consideration, it does not seem advisable to adopt this subdivision in a general work which treats of all the classes of terrestrial animals. (See p. 27.)
- ↑ Mr. Salvin, who has critically examined the ornithological fauna of these islands, has kindly corrected my MS. List of the Birds, his valuable paper in the Transactions of the Zoological Society not having been published in time for me to make use of it.
- ↑ This name will be used for the whole island of St. Domingo, as being both shorter and more euphonious, and avoiding all confusion with Dominica, one of the Lesser Antilles. It is also better known than "Hispaniola," which is perhaps the most correct name.