« AnteriorContinuar »
2. About 230 species of Insectivores are recognized, arranged in forty-one genera.
3. The most numerous and all-pervading group of Insectivores is the Shrews (Soricidm), of which upwards of 120 species are known.
4. Many of the families of Insectivores are excessively local in distribution, the Kaguans and Tree-shrews being peculiar to the Oriental Region, the Elephant-shrews and Golden Moles to Africa, the Solenodonts to the Greater Antilles, and the Tenrecs to Madagascar.
Section III.—Distribution Of Bats
(a) Introductory Remarks
The Bats, which constitute the Order Chiroptera, are, after the Rodents, the most numerous of all mammals, upwards of 530 species being already recognized, and many others probably awaiting further researches. As regards their distribution, it must be recollected that their powers of flight, which render them capable of passing over tracts of water that could not be crossed by other small mammals, place them in a somewhat different category from ordinary Mammals. At the same time the mode of their occurrence on the earth's surface presents many interesting features, concerning which a few words should be said. In these remarks, however, we shall be brief, as the Bats are not creatures of general interest, and as a rule are little studied except by the scientific worker.
(b) Chief Points in the Distribution of Bats
The first point to be noticed in the distribution of this extensive Order is, that the members are divisible into two well-marked and easily recognized sections. To the first of these belong the fruit-eating Bats of the family of Pteropodidm, sometimes recognized as a Sub-order under the title "Megachiroptera." This section contains about 110 species, divided into eighteen genera, the whole of which are entirely confined to the tropical and sub-tropical portions of the Eastern Hemisphere, and are quite unknown in the New World. They are spread over the Ethiopian, Oriental, and Australian Regions, the African forms, about five in number, being mostly generically distinct and peculiar to that continent. One of the most remarkable of these is Epomophorus, distinguished for its large lips and capacious mouth, of which eleven or twelve species occur in the Ethiopian tropics. In the Oriental and Australian Regions Epomophorus is replaced by Pteropus, with as many as fifty or sixty species. It is a remarkable fact that Pteropus has never reached the African continent, although two of its species occur in the Comoro Islands, only about 200 miles distant from the African coast.
Passing onwards to the five families of Insectivorous Bats, we find the two first of these, the Rhinolophidm and Nycteridm also absent in the New World, although they are distributed in larger or smaller numbers over most portions of the Old World, including Australia. The fourth family, Vespertilionidm, which is the most numerous group of all, embracing some 200 species and twenty genera, is found in every Region, and seems to pervade nearly the whole of the earth's surface, and to extend far north and south. The common Pipistrelle (Vespertilio pipistrellus), ranges into the high north of Europe; while another species of the same genus (V. magcllanicus) inhabits the cold and desolate shores of the Straits of Magellan.
The Serotine Bat (V. serotinus) is remarkable as the only species of Bat that is known to inhabit both the Old and New Worlds, being found in North America as far south as Guatemala. It also extends over a great part of the Oriental and Ethiopian Regions.
The fourth family of Insectivorous Bats, the EmballonuridiB, easily distinguished by the tail perforating the inter-femoral membrane or being produced far beyond it, has likewise an extensive distribution, as members of the fifteen genera into which it is divided occur in every one of the six Regions. But these Bats are more abundant within the tropics, and are only feebly represented by a few stray forms in the Nearctic and Palsearctic Regions. Of the two Bats known to occur in New Zealand, one (Mystacops) is a member of this family, and is peculiar to New Zealand. This and another Bat (Chalinolobus morio), belonging to the family Vespertilionidm, are the only two indigenous mammals of the New Zealand group, the Rat Mus rrmoriv/m, often attributed to it, being probably a modern introduction.
The last family of Bats, the Phyllostomatidm, or Vampires, are entirely restricted to the Neotropical Region, where they form one of the most characteristic groups of mammals, being very numerous alike in species, genera, and individuals. Of the thirty-six genera, with upwards of eighty species, which belong to this family, the two most remarkable are the purely blood-sucking forms Desmodus and Diphylla, which present an extraordinary modification of their digestive organs, specially adapting them for a diet of blood. These little animals, in fact, are those which have given such a bad reputation to the whole family of Vampires, though it was formerly supposed that the Vampirus spectrum, and other larger forms of tropical America, were likewise sanguinivorous in their habits. But this large Bat is now known, like many other representatives of the same family, to subsist mainly upon fruit, whilst other Vampires feed on a mixed diet of fruit and insects, or on insects only; and others again of the larger forms are said to prey chiefly upon the smaller members of their own order.