Page:EB1911 - Volume 06.djvu/258

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242
CHIROPTERA

as the forearm. The dentition is i. 2/1, c. 1/1, p. 2/3, m. 2/2, while the index finger has no claw, and the wings arise from the spine. Eonycteris, with the dentition i. 2/2, c. 1/1, p. 3/3, m. 2/3, is also represented by a single species, E. spelaea, from Tenasserim, Burma, and the Malay Peninsula and Islands, which has somewhat the appearance of a Roussettus, but the absence of a claw in the index finger and the presence of the characteristic tongue and teeth at once distinguish it. Carponycteris (Macroglossus) and Melonycteris, the former with several and the latter with a single species, are closely allied Indo-Malay and Papuan genera, the index finger in both having a claw, but the number of the teeth being the same as in Eonycteris. C. minimus is the smallest known species of the suborder, much smaller than the serotine bat of Europe, with the fore-arm scarcely longer than that of the long-eared bat. It is nearly as common in certain parts of Burma as Cynopterus marginatus, and extends eastwards through the Malay Archipelago as far as New Ireland, where it is associated with Melonycteris melanops, distinguished by its larger size and the total absence of the tail. An allied small Carpopycteris inhabits India. Trygenycteris (Megaloglossus) woermanni, of West Africa, is the only member of the group occurring west of the Himalaya. Callinycteris of Celebes, with the dentition i. 2/2, c. 1/1, p. 2/2, m. 3/3, has a short tail and no index-claws, while Nesonycteris of the Solomons, with the dentition i. 2/1, c. 1/1, p. 3/3, m. 3/3, differs by the absence of the tail.

Microchiroptera.

The second and larger suborder, the Microchiroptera, includes all the insectivorous species, the majority of which are of relatively small size as compared with the Megachiroptera. In these bats, with a few specialized exceptions, the crowns of theInsect-eating bats. cheek-teeth are surmounted by sharp cusps, divided by transverse grooves. In the skull the bony palate narrows abruptly and is not continued backwards laterally behind the last molar; there is one rudimentary phalange (rarely two or none) in the index finger, which is never terminated by a claw; the outer and inner sides of the ear commence interiorly from separate points of origin; the tail, when present, is contained in the interfemoral membrane, or appears on its upper surface; the stomach, except in the blood-sucking group, is simple; and the spigelian lobe of the liver large, and the caudate generally small.

The bats included in this suborder are so numerous in genera (to say nothing of species) that only some of the more important types can be mentioned.

Brief references have already been made to the manner in which in many or most of these bats the tail aids in the capture of prey. From the observations of C. Oldham, it appears that these bats, when walking, carry the tail downwards and forwards, so that the membrane connecting this organ with the hind-legs forms a kind of pouch or bag. If a large insect be encountered the bat seizes it with a snatch, and slightly spreading its folded wings and pressing them on the ground in order to steady itself, brings its feet forwards so as to increase the capacity of the tail-pouch, into which, by bending its neck and thrusting its head beneath the body, it pushes the insect. Although the latter, especially if large, will often struggle violently, when once in the pouch it but rarely escapes, from which it is subsequently extracted and devoured. It is assumed that the same method of capture is employed when on the wing; and a naturalist who has observed the long-eared bat picking moths off willows states that the bat always hovers when taking off the moth, and bends up the tail so as to form a receptacle for the insect as it drops.

EB1911 Chiroptera Fig. 6.jpg
Fig. 6.—Head of Mitred Horseshoe Bat
(Rhinolophus mitratus). From Dobson.

In the Rhinolophidae, Horse-shoe and Leaf-nosed bats of the Old World, the nose-leaf is developed and surrounds the nasal apertures, which are situated in a depression on the upper surface of the muzzle so as to look upwards; the ears are large and generally separate, without trace of a tragus or earlet; the premaxillae are rudimentary, suspended from the nasal cartilages, and support a single pair of small incisors; the molars have acute W-shaped cusps; the skull is large, and the nasal bones which support the nose-leaf much expanded vertically and laterally. In females a pair of teat-like appendages are found in front of the pubis; and the long tail extends to the margin of the interfemoral membrane. The middle finger has two phalanges, but the index is rudimentary. The fibula is rudimentary.

The Rhinolophidae are the most highly organized of insectivorous bats, in which the osseous and cutaneous systems reach the fullest development. Compared with theirs, the bones of the extremities and the wings of other bats appear coarsely formed, and their teeth seem less perfectly fitted to crush the hard bodies of insects. The complicated nasal appendages reach their highest development, and the differences in their form afford characters in the discrimination of the species, which resemble one another closely in dentition and the colour of the fur.

EB1911 Chiroptera Fig. 7.jpg
Fig. 7.—Head of Squirrel Leaf-Bat (Phyllorhina calcarata).
From Dobson.

In the first subfamily, Rhinolophinae, the first toe has two, and the other toes three phalanges each; and the ilio-pectineal spine is not connected by bone with the antero-inferior surface of the ilium. In the horseshoe bats, Rhinolophus, the dentition is i. 1/2, c. 1/1, p. 2/3, m. 3/3, the nose-leaf has a central process behind and between the nasal orifices, with the posterior extremity lanceolate, and the antitragus large. Among the numerous forms R. luctus is the largest, and inhabits elevated hill-tracts in India and Malaysia; R. hipposiderus of Europe, extending into south England and Ireland, is one of the smallest; and R. ferrum-equinum represents the average size of the species, which are mainly distinguished from one another by the form of the nose-leaf. The last-named species extends from England to Japan, and southward to the Cape of Good Hope, but is represented by a number of local races. When sleeping, the horseshoe bats, at least in some instances, suspend themselves head downwards, with the wings wrapped round the body after the manner of fruit bats. The posture of ordinary bats is quite different, and while the lesser horseshoe (R. hipposiderus) alights from the air in an inverted position, other bats, on first coming to rest, do so with the head upwards, and then reverse their position.

EB1911 Chiroptera Fig. 8.jpg
Fig. 8.—Head of Persian Leaf-Bat. (Triaenops persicus). From Dobson.

In the second subfamily, Hippo-siderinae (formerly called Phyllorhinae), the toes are equal and include two phalanges each, while the ilio-pectineal spine is united by a bony isthmus with a process derived from the antero-inferior surface of the ilium. Hipposiderus, Clöeotis, Rhinonycteris, Triaenops, Anthops and Coelops represent this subfamily. Hipposiderus (Phyllorhina), with many species, ranging over Asia, Africa and Australasia, and the dental formula i. 1/2, c. 1/1, p. 2/2, or 1/2, m. 3/3, differs from Rhinolophus in the form of the nose-leaf, which is not lanceolate behind (fig. 6), and is unprovided with a central process covering the nostrils; the largest species, H. armiger, appears to be the most northerly, having been taken at Amoy in China, and in the Himalaya at an elevation of 5500 ft. Many are provided with a frontal sac behind the nose-leaf, rudimentary in females (see fig. 7), which can be everted at pleasure; the sides of this sac secrete a waxy substance, and its extremity supports a tuft of straight hairs. Rhinonycteris, represented by R. aurantia from Australia, and Triaenops. by T. persicus from Persia and other species from Africa and Madagascar, are closely allied genera. Triaenops (fig. 8) is characterized by the remarkable form of its nasal appendages and ears, and the presence of a bony projection from the upper extremity of the second phalange of the fourth finger. Coelops (C. Frithi), from the Bengal Sanderbans, Java and Siam is distinguished by the peculiar form of its nose-leaf and the length of the metacarpal bone of the index finger, as well as by the shortness of the calcar and interfemoral membrane. Clöeotis is represented by a single East African species, and Anthops by one from the Solomon Islands characterized by the nose-leaf covering the whole front of the face.

The next family, Nycteridae, which is also Old World, is a small one, nearly allied to the last, in which it is included by Prof. Max Weber as a subfamily under the name of Myadermatinae. It differs by the presence of a small tragus inFalse vampires. the ears, which are united at their bases; and by the nasal chamber not being inflated. The premaxillae are either small and separated in front, or rudimentary; and the first phalange of the middle finger when in repose is laid back on the metacarpus. There are only pectoral teats.

Of the two genera, Megaderma, as represented by the five species of false vampires, is distinguished by the absence of ossified premaxillae and upper incisors (i. 0/2, p. (2 or 1)/2), the cylindrical narrow muzzle surmounted by an erect nose-leaf the base of which conceals the nasal orifices, the immense joined ears with large bifid tragus, and the great extent of the interfemoral membrane, in the base of which the short tail is concealed. M. gigas (fig. 9), from central Queensland, is the largest species of the genus, and of the suborder. M. lyra, common in India (fore-arm 2.7 in.), has been caught in the act of sucking the blood, while flying, from a small bat which it afterwards devoured. The range of the genus includes Africa, the Indo-Malay countries and Australasia. Nycteris, which is common