1911 Encyclopædia Britannica/Chiroptera
CHIROPTERA (Greek for “hand-wings”), an order of mammals containing the bats, all of which are unique in the class in possessing the power of true flight, and have their fore-limbs specially modified for this purpose.
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| Fig. 1.—Skeleton and Wing-Membranes of the Noctule Bat (Pipistrellus noctula). × 13 | |
| c, Clavicle. h, Humerus. r, Radius. u, Ulna. d1, First digit. d2, d3, d4, d5, Other digits of the fore-limb supporting wm, the wing-membrane. m, m, Metacarpal bones. |
ph1, First phalanx. ph2, Second phalanx. ph3, Third phalanx. am, Antebrachial membrane. f, Femur. t, Tibia. fb, Fibula. c, Calcar supporting im, the inter- femoral membrane. pcl, Post-calcaneal lobe. |
The mammals comprised in this order are at once distinguished by the possession of true wings; this peculiarity being accompanied by other modifications of bodily structure having relation to aerial locomotion. Thus, in direct contrast to all other mammals, in which locomotion is chiefly effected by action from behind, and the hind-limbs consequently greatly preponderate in size over the fore, in the Chiroptera the fore-limbs, being the agents in propelling the body forward during flight, immensely exceed the short and weak hinder extremities. The thorax, giving origin to the great muscles which sustain flight, and containing the proportionately large lungs and heart, is remarkably capacious; and the ribs are flattened and close together; while the shoulder-girdle is greatly developed in comparison with the weak pelvis. The fore-arm (fig. 1) consists of a rudimentary ulna, a long curved radius, and a carpus of six bones supporting a thumb and four elongated fingers, between which, the sides of the body, and the hinder extremities a thin expansion of skin, the wing-membrane, is spread. The knee is directed backwards, owing to the rotation of the hind-limb, outwards by the wing-membrane; an elongated cartilaginous process (the calcar), rarely rudimentary or absent, arising from the inner side of the ankle-joint, is directed inwards, and supports part of the posterior margin of an accessory membrane of flight, extending from the tail or posterior extremity of the body to the hind-limbs, and known as the interfemoral membrane. The penis is pendent; the testes are abdominal or inguinal; the teats, usually two in number, thoracic; the uterus is simple or with more or less long cornua; the placenta discoidal and deciduate; and the smooth cerebral hemispheres do not extend backwards over the cerebellum. The teeth comprise incisors, canines, premolars and molars; and the dental formula never exceeds i. 23, c. 11, p. 33, m. 33; total 38. Despite the forward position of the teats, which is merely an adaptive feature, bats are evidently mammals of low organization, and are most nearly related to the Insectivora.
In consequence of the backward direction of the knee, a bat, when placed on the ground, rests on all fours, having the knees directed upwards, while the foot is rotated forwards and inwards on the ankle. Walking is thus a kind of shuffle; but, notwithstanding a general belief, bats can take wing from the walking posture.
The bones of the skeleton are characterized by their slenderness and the great size of the medullary canals in those of the extremities. The vertebral column is short, and the vertebrae differ but slightly in number and form throughout the group. The general number of dorso-lumbar vertebrae is 17, whereof 12 are dorsal; the cervical vertebrae are broad, but short. Except in fruit-bats (Pteropodidae), the vertebrae, from the third cervical backwards, are devoid of spinous processes. From the first dorsal to the last lumbar the vertebral column forms a single curve, most pronounced in the lumbar region. The bodies of the vertebrae are but slightly movable on each other, and in old individuals become partially welded. The caudal vertebrae are cylindrical bones without processes; their number and length varying in allied species. The development of these vertebrae is correlated with habits, the long tail in the insectivorous species supporting and controlling the position of the interfemoral membrane which aids bats in their doubling motions when in pursuit of insects by acting as a rudder, and assists them in the capture of the larger insects. In the fruit-bats this is not required, and the tail is rudimentary or absent. In all bats the presternum has a prominent keel for the attachment of the great pectoral muscles.
The shape of the skull varies greatly; but post-orbital processes are developed only in some Pteropodidae and a few Nycteridae and Emballonuridae; in Pteropus leucopterus alone does a process from the zygomatic arch meet the post-orbital so as to complete the orbital ring. Zygomatic arches, though slender, are present in all except in some of the species of Phyllostomatidae.
The milk-teeth differ from those of all other mammals in that they are unlike those of the permanent series. They are slender, with pointed recurved cusps, and are soon shed, but exist for a short time with the permanent teeth. In the Rhinolophidae the milk-teeth are absorbed before birth. The permanent teeth exhibit great variety, sometimes even in the same family, as in Phyllostomatidae, whilst in other families, as Rhinolophidae, the resemblance between the dentition of species differing in many respects is remarkable. In all they are provided with well-developed roots, and their crowns are acutely tuberculate, with more or less well-defined W-shaped cusps, in the insectivorous species, or variously hollowed out or longitudinally grooved in the frugivorous kinds.
The shoulder-girdle varies but slightly, the clavicle being long, strong and curved; and the scapula large, oval and triangular, with a long curved coracoid process. The humerus, though long, is scarcely two-thirds the length of the radius; and the rudimentary ulna is welded with the radius. A sesamoid bone exists in the tendon of the triceps muscle. The upper row of the carpus consists of the united scaphoid, lunar and cuneiform bones.
The “hand” has five digits, the first, fourth and fifth of which consist each of a metacarpal and two phalanges; but in the second and third the number of phalanges is different in certain families. The first digit terminates in a claw, most developed in the frugivorous species, in most of which the second digit is also clawed, although in other bats this and the remaining digits are unarmed.
In the weak pelvis the ilia are long and narrow, while in most species the pubes of opposite sides are loosely united in front in males, and widely separated in females; in the Rhinolophidae alone they form a symphysis. Only in the Molossinae is there a well-developed fibula; in the rest this bone is either very slender or cartilaginous and ligamentous in its upper third, or reduced to a small bony process above the heel, or absent. The foot consists of a short tarsus, and of slender, laterally compressed toes, with much-curved claws.
Although the brain is of a low type, probably no animals possess so delicate a sense of touch as Chiroptera. In ordinary bats tactile organs exist, not only in the bristles on the sides of the muzzle, but in the sensitive structures forming the wing-membranes and ears, while in many species leaf-like expansions surrounding the nasal apertures or extending backwards behind them are added. These nose-leaves are made up partly of the extended and thickened integument of the nostrils, and partly of the glandular eminences occupying the sides of the muzzle, in which in other bats the sensitive bristles are implanted.
In no mammals are the ears so developed or so variable in form; in most insectivorous species they are longer than the head, while in the long-eared bat their length nearly equals that of the head and body. The form is characteristic in each of the families; in most the “earlet,” or tragus, is large, in some cases extending nearly to the outer margin of the conch; its office appears to be to intensify and prolong the waves of sound by producing undulations in them. In the Rhinolophidae, the only family of insectivorous bats wanting the tragus, the auditory bullae reach their greatest size, and the nasal appendages their highest development. In frugivorous bats the ear is simple and but slightly variable. In all bats the ears are extremely mobile, each independently at will.
The oesophagus is narrow, especially in blood-sucking vampires. The stomach presents two types of structure, corresponding respectively to the two divisions of the order, Megachiroptera and Microchiroptera; in the former the pyloric extremity is, with one exception, elongated and folded upon itself, in the latter simple; an exceptional type is met with in the blood-suckers, where the cardiac extremity is elongated, forming a long appendage. The intestine is comparatively short, varying from one and a half to four times the length of the head and body; longest in the frugivorous, shortest in the insectivorous species. In Rhinopoma and Megaderma a small caecum has been found. The liver is characterized by the great size of the left lateral lobe, which occasionally equals half that of the whole organ; the right and left lateral fissures are usually very deep; in Megachiroptera the spigelian lobe is, with one exception, ill defined or absent, and the caudate is generally large; but in Microchiroptera the former lobe is large, while the caudate is small. The gall-bladder is generally well developed.
In most species the hyoids are simple, consisting of a chain of slender, long, cylindrical bones connecting the basi-hyoid with the skull, while the pharynx is short, and the larynx shallow with feebly developed vocal cords, and guarded by a short pointed epiglottis. In the African epauletted bats, Epomophorus, the pharynx is long and capacious, the aperture of the larynx far removed from the fauces, and, opposite to it, opens a canal, leading from the nasal chambers, and extending along the back of the pharynx; the laryngeal cavity is spacious and its walls are ossified; the hyoids are unconnected, except by muscle with the skull; while the cerato-hyals and epi-hyals are cartilaginous and expanded, entering into the formation of the walls of the pharynx, and (in males of some species) supporting the orifices of a pair of air-sacs communicating with the pharynx (fig. 2).
The extent and shape of the wings generally depend on the form of the bones of the fore-limbs, and on the presence or absence of the tail. The wings consist of an “antebrachial membrane,” which extends from the point of the shoulder along the humerus and more or less of the fore-arm to the base of the thumb, the metacarpal bone of which is partially or wholly included in it; the “wing-membrane” spread out between the elongated fingers, and extending along the sides of the body to the posterior extremities, generally reaching to the feet; and the “interfemoral membrane,” the most variable of all, which is supported between the extremity of the body, the legs and the calcar (fig. 1). The antebrachial and wing membranes are most developed in species fitted only for aerial locomotion which when at rest hang with the body enveloped in the wings;
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Fig. 2.—Head and Neck of Epomophorus franqueti (adult male). From Dobson. The anterior (a.ph.s) and posterior (p.ph.s) pharyngeal sacs are opened from without, the dotted lines indicating the points where they communicate with the pharynx; s, thin membranous partition in middle line between the anterior pharyngeal sacs of opposite sides; s.m, sterno-mastoid muscle separating the anterior from the posterior sac. |
but in the Emballonuridae, and also in the Molossinae, which are the best fitted for terrestrial progression, the antebrachial membrane is reduced to a small size, and not developed along the fore-arm, leaving the thumb quite free, while the wing-membrane is narrow and folded in repose under the forearm. The relative development of the interfemoral membrane has been referred to in connexion with the caudal vertebrae. Its small size in the frugivorous and blood-sucking species, which do not require it, is easily understood. Scent-glands and pouches opening on the surface of the skin are developed in many species, but in most cases more so in males than in females (fig. 3). As rule, bats produce only a single offspring at a birth, which for some time is carried about by the female parent clinging to the fur of her breast; but certain North American bats commonly give birth to three or four young ones at a time, which are carried about in the same manner.
Bats are divisible into two suborders, Megachiroptera and Microchiroptera.
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| Fig. 3.—Frontal Sac and Nose-Leaf in Male and Female Masked Bat (Phyllorhina larvata). From Dobson. |
Megachiroptera.
The first of these comprises the fruit-eating species, which are generally of large size, with the crowns of the cheek-teeth smooth and marked with a longitudinal groove. The bony palate is continued behind the last molar, narrowing slowly backwards; there are three phalanges in the index Fruit-eating bats.finger, the third phalange being terminated generally by a claw; the sides of the ear form a ring at the base; the tail, when present, is inferior to (not contained in) the interfemoral membrane; the pyloric extremity of the stomach is generally much elongated; and the spigelian lobe of the liver is ill-defined or absent, while the caudate is well developed. This group is limited to the tropical and sub-tropical parts of the Eastern Hemisphere.
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Fig. 4.—Head of a Flying-Fox or Fruit-Bat (Pteropus personatus). |
All the members of this suborder are included in the single family Pteropodidae, the first representatives of which are the African epauletted bats, forming the genus Epomophorus. In this the dental formula is i. 22 (or 12), c. 11, p. 23, m. 12. Tail short or absent, when present free from the interfemoral membrane; second finger with a claw; premaxillae united in front. The species are strictly limited to Africa south of the Sahara, and are distinguished by the large and long head, expansible and often folded lips, and the white tufts of hair on the margins of the ears. The males are provided with glandular pouches, situated in the skin of the side of the neck near the point of the shoulder, which are rudimentary or absent in females. In the males they are lined with glandular membrane, from which long coarse yellowish hairs project to form conspicuous epaulet-like tufts on the shoulders. The males often have a pair of air-sacs extending outwards on each side from the pharynx beneath the integument of the neck, in the position shown in fig. 2. These bats appear to live principally on figs, the juicy contents of which their voluminous lips and capacious mouths enable them to swallow without loss. The huge and ugly West African hammer-headed bat, Hypsignathus monstrosus, represents an allied genus distinguished by the absence of shoulder-pouches, and the presence of leaf-like expansions of skin on the front of the muzzle, and of distinct cusps on the outer sides of the cheek-teeth. The great majority of the bats of this group, commonly known as “flying-foxes,” are included in the typical genus Pteropus, of which the dental formula is i. 22, c. 11, p. 33, m. 23. All are of large size, and the absence of a tail, the long pointed muzzle, and the woolly fur covering the neck render their recognition easy. One of the species, P. edulis, inhabiting Java, measures 5 ft. across the fully extended wings, and is the largest member of the order.
The range of the genus extends from Madagascar through the Seychelles to India, Ceylon, Burma, the Malay Archipelago, Japan, New Guinea, Australia and Polynesia. Although two species inhabit the Comoro Islands, scarcely 200 m. from the mainland, not one is found in Africa; while the common Indian species is closely allied to the Madagascar flying-fox. The Malay Archipelago and Australia form the headquarters of these bats, which in some places occur in countless multitudes. The colonies exhale a strong musky odour, and when awake the occupants utter a loud incessant chatter. Wallace’s fruit-bat of Celebes and Macassar has been made the type of a separate genus, as Styloctenium wallacei. In Roussettus (or Cynonycteris) the dentition is as in Pteropus, but the tail is short, and the fur of the nape of the neck not different from that of the back: its distribution accords with that of Pteropus, except that it includes Africa and does not reach farther east than New Ireland. R. aegyptiacus inhabits the chambers of the Great Pyramid and other deserted buildings in Egypt, and is probably the species figured in Egyptian frescoes. Boneia, with two species, from Celebes, differs in having only two upper incisors. Harpyionycteris and Scotonycteris, respectively from the Philippines and West Africa, are represented by a single species each; but of Cynopterus, which is mainly confined to the Indo-Malay countries, there are some half-score different kinds. The dentition is i. 22 or 1, c. 11, p. 33, m. 33, the muzzle is shorter than in Roussettus, with the upper lip grooved in front as in Pteropus, while the tail and fur resemble those of the former genus. These bats are extremely voracious, a specimen of the Indian C. marginatus having eaten a banana twice its own weight in three hours. Among several Austro-Malay genera, such as Ptenochirus and Balionycteris, the tube-nosed bats of the genus Gelasinus (or Harpyia) are remarkable for the conformation of the nostrils (fig. 5). Cephalotes, with one species, ranging from Celebes to the Solomon group, has the dentition i. 11, c. 11, p. 23, m. 23, premaxillae not united in front, nostrils simple, muzzle short, index finger without a claw, tail short. As in Gelasinus, the wing-membrane arises from the middle line of the back, to which it is attached by a longitudinal thin process of skin; the wings are naked, but the back covered with hair. Leipenyx is an allied West African genus with one species.
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Fig. 5.—Head of Papuan Tube-Nosed Bat (Gelasinus major). From G. E. Dobson. |
The foregoing belong to the typical subfamily Pteropodinae, while the remainder represent a second group, Carponycterinae (or Macroglossinae), characterized by having the facial part of the skull produced, the molar teeth narrow, and scarcely raised above the gum, and the tongue exceedingly long, attenuated in the anterior third, and armed with long recurved papillae near the tip. The single representative of the first genus, Notopteris macdonaldi, inhabiting Fiji, New Guinea and the New Hebrides, is distinguished from other bats of this family by the length of its tail, which is nearly as long as the forearm. The dentition is i. 21, c. 11, p. 23, m. 22, while the index finger has no claw, and the wings arise from the spine. Eonycteris, with the dentition i. 22, c. 11, p. 33, m. 23, 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. 22, c. 11, p. 22, m. 33, has a short tail and no index-claws, while Nesonycteris of the Solomons, with the dentition i. 21, c. 11, p. 33, m. 33, 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.
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Fig. 6.—Head of Mitred Horseshoe Bat (Rhino- |
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.
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Fig. 7.—Head of Squirrel Leaf-Bat (Phyllorhina calcarata). |
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. 12, c. 11, p. 23, m. 33, 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.
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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. 12, c. 11, p. 22, or 12, m. 33, 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 to Africa and the Malay Peninsula and Islands, has ossified premaxillae and upper incisors (i. 23, p. 12), and a long tail; but lacks a nose-leaf. As in Megaderma, the frontal bones are deeply hollowed and expanded laterally, the muzzle presents a similar cylindrical form, and the lower jaw also projects; but, instead of a nose-leaf, the face is marked by a deep longitudinal sharp-edged groove extending from the nostrils to the band connecting the base of the large ears; the sides of this depression being margined as far back as the eyes by small horizontal cutaneous appendages. With the exception of N. javanica, the species are limited to Africa.
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| Fig. 9.—The False Vampire (Megaderma gigas). From Dobson. |
According to the classification followed by Dr G. E. Dobson, the extensive family of New World bats known as Phyllostomatidae was widely sundered from the two preceding groups; but in Prof. Max Weber’s system they are placed next one another—an arrangement which has the great advantage of bringing together all the Vampires.bats furnished with nose-leaves. It is indeed probable that the vampires, as the members of the present family may be collectively termed, are the New World representatives of the Old World Rhinolophidae and Nycteridae.
The Phyllostomatidae are characterized by the presence of a nose-leaf, or of lappets on the chin, but the nostrils are not directed upwards. The ethmoturbinal bones of the nasal cavity form simple plates (much as in the two preceding families). The premaxillae are always well developed, with their palatal portions forming a suture and defining the boundaries of distinct palatine foramina (in place of being rudimentary, as in Nycteridae and Rhinolophidae). The large ears have a tragus. The middle finger has three phalanges, and the index one. There is an incomplete fibula. The tail may be either long or short. Generally the dentition is i. 22, c. 11, p. 23, m. 33.
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| Fig. 10.—Head of Blainville’s Vampire (Mormops blainvillei). From Dobson. |
All the bats of this family may be readily recognized by the presence of a well-developed third phalange in the middle finger, associated either with a distinct nose-leaf, or with central upper incisors, or with both. Unlike the Rhinolophidae, their eyes are generally large and the tragus is well developed, maintaining almost the same form throughout the species, however much the other parts of the body may vary. Their fur is of a dull colour, and the face and back are often marked with white streaks. A few species, probably all those with the tail and interfemoral membrane well developed, feed principally on insects, while the greater number of the species of the groups Vampyreae and Glossophageae appear to live on a mixed diet of insects and fruits, and the Desmodonteae, of which two species are known, are true blood-suckers, and have their teeth and intestinal tract specially modified in accordance with their habits. The group is practically limited to the tropical and subtropical parts of Central and South America, although one species of Otopterus reaches California. In the first subfamily, Mormopsinae (Lobostominae), the nostrils open by simple apertures at the extremity of the muzzle in front, not margined by a distinct nose-leaf; while, in compensation, the chin is furnished with expanded leaf-like appendages. The tail is short. It includes two genera. In Chilonycteris the crown of the head is moderately elevated above the face-line, and the basi-cranial axis is almost in the same plane as the facial, while in Mormops (fig. 10) the crown of the head is greatly elevated above the face-line, and the basi-cranial axis is nearly at right angles to the facial; i. 22, p. 23, in both genera. As regards the species of Chilonycteris, the most striking feature is the occurrence of a rufous and a dark brown phase in each. In some the two phases are very marked, but in others they are connected by intermediate shades. Here may be mentioned the two species of tropical American hare-lipped bats, forming the genus Noctilio, which presents characters common to this and the following family, to which latter it is often referred. The typical N. leporinus is a bat of curious aspect, with strangely folded lips, erect skin-processes on the chin, and enormous feet and claws. The two middle incisors are close together, and so large as to conceal the small outer ones, while in the lower jaw there are but two small incisors; the premolars numbering 12. These bats live near the coast, and feed on small crabs and fishes.
Most of the remaining members of the family are included in the subfamily Phyllostomatinae, characterized by the presence of a distinct nose-leaf and the warty chin. The clitoris is imperforate, whereas it is perforated in the Mormopsinae. The incisors are generally 22 (occasionally 21), and the molars well developed. The subfamily is divided into a number of groups or sections. The first of them, the Vampyreae, is characterized as follows: Muzzle long and narrow in front, the distance between the eyes generally less than (rarely equal to) that from the eye to the extremity of the muzzle; nose-leaf horseshoe-shaped in front, lanceolate behind; interfemoral membrane well developed; tail generally distinct, rarely absent; inner margin of the lips not fringed; i. 22 or 21, p. 22 or 23; molars with W-shaped cusps, usually well developed.
Nearly all the Vampyreae appear to be insectivorous, so that the term cannot be considered indicative of habits; but a few, if not all, probably supplement their insect diet with fruit. Vampyrus spectrum (the largest bat in the New World) is said to be wholly frugivorous, and Otopterus waterhousei appears to prey occasionally on smaller bats. The genera may be arranged in two subgroups according as the tail is produced to the margin of the interfemoral membrane or perforates it to appear on its upper surface. In the first division are included three genera, Lonchorhina, Otopterus (or Macrotus) and Dolichophyllum (or Macrophyllum), the first represented by L. aurita, characterized by an extraordinary long nose-leaf, and peculiarly large ears and tragus. In the second subsection are included Vampyrus, Chrotopterus, Tonatia (Lophostoma) Micronycteris, Glyphonycteris, Trachyops, Phylloderma, Phyllostoma, Anthorhina (Tylostoma), Mimon, Hemiderma (Carollia) and Rhinophylla; all, with the exception of the last, distinguished chiefly by the form of the skull and the presence or absence of the second lower premolar. Phyllostoma hastatum, next in point of size to Vampyrus spectrum, is a well-known species in South America; P. elongatum (fig. 11) differs in its smaller size and larger nose-leaf. Hemiderma brevicauda, a small species, closely resembles Glossophaga soricina, and forms a connecting link between this and the next group. Rhinophylla pumilio is the smallest species of the family; further distinguished by the absence of a tail, the narrowness of its molars, which do not form W-shaped cusps, and the small size of the last upper molar, characters connecting it and the group with the Stenodermateae. Both in Hemiderma and Rhinophylla the zygomatic arch is incomplete.
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| Fig. 11.—Head of Lesser Javelin Vampire (Phyllostoma elongatura). |
The next subsection, Glossophageae, presents the following distinctive features: Muzzle long and narrow; tongue long and extensible, attenuated towards the tip, and beset with long filiform recurved papillae; lower lip with a wide groove above, and in front margined by small warts; nose-leaf small; tail short or none; i. 22, p. 23 or 33 or 22, m. 33 or 23 or 22; teeth narrow; molars with narrow W-shaped cusps, sometimes indistinct or absent; lower incisors small or deciduous. The species included in this group represent some ten genera, distinguished principally by differences in the form and number of the teeth, and the presence or absence of the zygomatic, arch of the skull. In Glossophaga and Phyllonycteris the upper incisors form a continuous row between the canines. In Monophyllus and Leptonycteris (Ischnoglossa) they are separated into pairs by a narrow interval in front; while in Lonchoglossa, Glossonycteris and Choeronycteris they are widely separated and placed in pairs near the canines. In the first four of these genera the lower incisors are present (at least to a certain age), in the last three they are deciduous even in youth. The zygomatic arch is wanting in Phyllonycteris, Glossonycteris and Choeronycteris. The typical species is Glossophaga soricina, which, as already mentioned, closely resembles Hemiderma brevicauda, both in form and dentition. Its long brush-tipped tongue (which it possesses in common with other species of the group) is used to lick out the pulpy contents of fruits having hard rinds. The food of the species of this group appears to consist of both fruit and insects, and the long tongue may be used for extracting the latter from the deep corollas of flowers. Other genera are Lonchophylla, Rhithronycteris, Hylonycteris and Lychonycteris, each with a single species (in 1904).
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Fig. 12.—Head of Long-tongued Vampire (Choeronycteris mexicana), |
The third group, Stenodermateae, presents the following characteristics:—Muzzle very short and generally broad in front, the distance between the eyes nearly always exceeding (rarely equalling) the distance from the eye to the extremity of the muzzle; nose-leaf short, horseshoe-shaped in front, lanceolate behind (except in Brachyphylla and Centurio); interfemoral membrane concave behind; tail none; inner margin of the lips fringed with conical papillae; i. 22 or 21, p. 22, m. 33 or 23 or 22; cheek-teeth broad (except in Sturnira), molars with concave or flat crowns margined externally by raised cutting-edges. Although the Stenodermateae are generally easily distinguished from the Vampyreae by the shortness and breadth of the muzzle and the form of the cheek-teeth, certain species of the latter resemble the former in external appearance, agreeing almost absolutely in the form of the nose-leaf, the ears and the tragus, and the warts on the chin. These resemblances show that, while the form of the teeth and jaws has become modified to suit the food, the external characters have remained much the same, and indicate the common origin of the two sections. The food of these bats appears to be wholly or in great part fruit. The species are divided into some eleven genera, mostly distinguished by the form of the skull and teeth. Artibeus includes the frugivorous A. perspicillatus. Stenoderma achradophilum, found in Jamaica and Cuba, with the last, from which it is scarcely distinguishable externally except by its much smaller size, differs in the absence of the horizontal plate of the premaxillae on the palate. Sturnira lilium, while agreeing with these in the form of the nose-leaf and ears, differs from all the species of the family in its longitudinally-grooved molars, which resemble those of the Pteropodidae more closely than those of any other bats; and the presence of tufts of long differently-coloured hairs over glands in the sides of the neck is another character in common with that group. Centurio senex (fig. 13) is the type of a small genus distinguished from Stenoderma and other genera of this group by the absence of a distinct nose-leaf. Some naturalists make this genus the type of a distinct subgroup, Centurioneae. Up to 1904 the genera, exclusive of Centurio, included in the Stenodermateae were Artibeus (with several sub-genera), Vampyrops (also with subgenera), Mesophylla, Chiroderma, Stenoderma (with 3 subgenera), Ectophylla, Ametrida (with 2 sub-genera), Pygoderma, Sturnira and Brachyphylla.
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Fig. 13.—Head of Masked Vampire (Centurio senex). |
The third subfamily, Desmodontieae, is represented only by the blood-sucking bats, and distinguished by having i. 12, of which the upper pair are cutting, the rudimentary molars, the very short interfemoral membrane, and the blood-sucking habit. They are further characterized as follows: Muzzle short and conical; nose-leaf distinct; p. 23, m. 11 or 00; upper incisors occupying the whole space between the canines; premolars narrow, with sharp-edged longitudinal crowns; molars rudimentary or absent; stomach elongated, and intestiniform. There are two genera, Desmodus, without calcar or molars, and Diphylla, with a short calcar and a single rudimentary molar on each side—restricted to Central and South America. Desmodus rufus, the commoner species, is a little larger than the noctule bat, and abundant in certain parts of South America, where it is troublesome owing to its attacks upon domestic animals, sucking their blood and leaving them weakened from repeated bleedings. (See Vampire.)
The fourth family of bats, unlike any of the three previous ones, has a cosmopolitan distribution. These free-tailed bats, as they are conveniently called, constituting the family Emballonuridae, present the following distinctive features. TheFree-tailed bats. nostrils are of normal form and without a nose-leaf. The premaxillae have their palatal portion imperfectly developed, and united by a slender process with the maxillae. The ears are large, with a small tragus. The middle finger has two phalanges, and the index generally a single one. The fibula is incomplete. The tail is generally short, and always partly free from the interfemoral membrane. There is generally only a single pair of upper incisors, separated by gaps from the canines, and from one another in the middle line.
The distinctive feature of these bats is the free tail-tip, which pierces the interfemoral membrane to appear on its upper surface, and may project beyond its margin. As a rule, these bats may also be recognized by the peculiar form of the muzzle, which is obliquely truncated, the nostrils projecting more or less in front beyond the lower lip, by the first phalange of the middle finger being folded in repose forwards on the upper surface of the metacarpal bone, and by the upper incisors. Although cosmopolitan, these bats rarely extend north or south of the thirtieth parallels of latitude.
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Fig. 14.—Ear of Emballonura raffrayana. |
The family may be divided into two subfamilies, of which the Emballonurinae is characterized by the incomplete premaxillae, the presence of only one phalange in the index finger, and the short tail. The dental formula is generally i. 13 (sometimes 23 or 12), c. 11, p. 23, m. 33. This subfamily may be further subdivided into subgroups or sections of which the first, Embalionurae, is characterized by the slender tail perforating the interfemoral membrane, so as to appear on its upper surface; the legs long, with a slender fibula; the incisors weak; and the premolars 22. The typical genus Emballonura presents the following features: i. 23, extremity of the muzzle more or less produced beyond the lower lip, forehead flat. The genus contains several species, inhabiting islands from Madagascar through the Malay Archipelago and Siam to the Navigator Islands. Coleura, with i. 13, the extremity of the muzzle broad, and the forehead concave, has two species from East Africa and the Seychelles. Rhynchonycteris is distinguished from Coleura by the produced extremity of the muzzle. The single species, R. naso, from Central and South America, is common in the vicinity of streams, where it is usually found during the day resting on the vertical faces of rocks, or on trunks of trees growing over water; it escapes notice owing to the greyish colour of the fur of the body and of small tufts on the antebrachial membrane counterfeiting the weathered surfaces of rocks and bark. As evening approaches it appears on the wing, flying close to the water. Saccopteryx has i. 13 and the antibrachial membrane with a pouch opening on its upper surface; it contains several species from Central and South America. This sac is developed only in the male and in the female is rudimentary. In adult males a valvular longitudinal opening occupies the upper surface of the membrane leading into a small pouch, the interior of which is lined with a glandular membrane secreting an unctuous reddish substance with a strong ammoniacal odour. Allied genera are the tropical American Peropteryx and the Brazilian Cormura. The various species of tomb-bats (Taphozous) inhabit the tropical and subtropical parts of all the eastern hemisphere except Polynesia, and are distinguished by the cartilaginous premaxillaries, the deciduous pair of upper incisors, and the presence of only two pairs of lower incisors. Most of the species have a glandular sac (fig. 15) between the angles of the lower jaw, more developed in males than in females, in some species absent in the latter. An open throat-sac is wanting in T. melanopogon, but about its position are the openings of small pores, the secretion from which probably causes the hairs to grow long, forming the black beard found in many males. The three tropical American white bats, Diclidurus, with i. 13, c. 11, p. 32, m. 33, resemble Taphozous in the form of the head and ears, but, besides other characters, differ from all other bats in possessing a pouch, opening off the centre of the interior surface of the interfemoral membrane; the extremity of the tail enters this, and perforates its base.
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Fig. 15.—Heads of Tomb-Bat (Taphozous longimanus), showing relative |
The second subfamily of the Emballonuridae, Rhinopomatinae, is represented only by the genus Rhinopoma, with several species ranging from Egypt through Arabia to India, Burma and Sumatra. The premaxillae (fig. 16) are complete; the index finger has two phalanges; the tail is very long and mouselike; and the dental formula i. 12, c. 11, p. 12, m. 23. Dr G. E. Dobson has remarked that these mouse-tailed bats might be elevated to the rank of a family, for it is difficult to determine their affinities, a kind of cross relationship attaching them to the Nycteridae on the one hand and to the Emballonuridae on the other. These bats, distinguished from all other Microchiroptera by the presence of two phalanges in the index finger and the long and slender tail projecting far beyond the narrow interfemoral membrane, inhabit the subterranean tombs in Egypt and deserted buildings generally from north-east Africa to Burma and Sumatra.
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Fig. 16.—Skull of Mouse-tailed Bat |
The last group, according to the system adopted by Prof. Max Weber, is that of the Vespertilionidae, which includes such typical bats as the pipistrelle, the noctule, and the long-eared species. By Mr G.S. Miller[1] the first section of theTypical bats. family—Natalinae—is regarded as of family rank, while the last section, or Molossinae, is included by Dr G. E. Dobson in the Emballonuridae, from the typical forms of which its members differ widely in tail-structure. In this extended sense the family, which has a cosmopolitan distribution, may be defined as follows:—The nostrils are normal and without a nose-leaf. The ethmoturbinal bones of the nasal chamber are involuted. The palatine processes of the premaxillae do not form a suture. The ear is mostly large, with a tragus. The middle finger (except in Thyroptera) has two phalanges. The fibula is usually rudimentary. The tail is long and does not perforate the interfemoral membrane. The incisors are generally 23 or 12, but may be reduced to 11 in the Molossinae.
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| Fig. 17.—Head of Chilonatalus micropus. ×2. (From Dobson.) |
In the first subfamily, Natalinae, which is exclusively tropical American, the other upper incisors are separated from one another and from the canines; palatine processes of the premaxillae are at least partially developed; and the dental formula is i. 23, c. 11, p. 2 or 33, m. 33. In general appearance these bats recall the more typical Vespertilionidae, although the form of the muzzle is suggestive of the Mormopsinae among the Phyllostomatidae. Again, while the form of the skull is vespertilione, the relation of the vomer to the front end of the premaxillae is of the phyllostomine type. The molars and incisors are likewise vespertilione, whereas the premolars are as distinctly phyllostomine. Finally, while the third, or middle, finger normally has two phalanges, as in typical Vespertilionidae, the second of these is elongated and in Thyroptera divided into two, as in Phyllostomatidae.
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Fig. 18.—Suctorial Disks in Thyroptera tricolor, a, side, and b, concave surface, of thumb disk; |
The first two genera, Furipterus and Amorphochilus, each have a single species, the latter being distinguished from the former by the wide separation of the nostrils and the backward prolongation of the palate. In both the crown of the head is elevated, the thumb and first phalange of the middle finger are very short, and the premolars are 23. The same elevation of the crown characterizes the genera Natalus and Chilonatalus (fig. 17), in which the premolars are 33: in general appearance these bats are very like the Old World vespertilionine genus Cerivoula, except for the short triangular tragus. Lastly, Thyroptera includes two species distinguished by an additional phalange in the middle finger and by accessory clinging-organs attached to the extremities. In Thyroptera tricolor, i. 23, p. 33, from Brazil, these have the appearance of small, circular, stalked, hollow disks (fig. 18), resembling miniature sucking-cups of cuttle-fishes, and are attached to the inferior surfaces of the thumbs and the soles of the feet. By their aid the bat is able to maintain its hold when creeping over smooth vertical surfaces.
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Fig. 19.—Head of Scotophilus |
The second or typical subfamily, Vespertilioninae, includes all the remaining members of the family with the exception of the aberrant Molossinae. The upper incisors are in proximity to the canines; the premaxillae widely separated; the ears medium or large; the dental formula is i. 23 (or 13), c. 11, p. 33 ( 23, 22, or 12), m. 33; and the fibula very small and imperfect. All the members of this large cosmopolitan group are closely allied, and differ chiefly by external characters. They may be divided into subgroups. In the first of these, the Plecoteae, of which the long-eared bat (Plecotus auritus) is the type, the crown of the head is but slightly raised above the face-line, the upper incisors are close to the canines, and the nostrils are margined behind by grooves an the upper surface of the muzzle, or by rudimentary nose-leaves; the ears being generally very large and united. Of the six genera, Plecotus, with i. 23, p. 23, has three species:—one the long-eared European bat referred to above; P. macrotis, restricted to North America, is distinguished by the great size of the glandular prominences of the sides of the muzzle, which meet in the centre above and behind the nostrils; the third species being also American. The second, Barbastella, with i. 23, p. 22, distinguished by its dentition and by the outer margin of the ear being carried forwards above the mouth and in front of the eye, includes the European barbastelle bat, B. barbastellus, and B. darjelingensis from the Himalaya. Otonycteris, i. 13, pm., 12, connecting this group with the Vespertilioneae, is represented by O. hemprichii, from North Africa and the Himalaya, and an Arabian species. The next two genera are distinguished by the presence of a rudimentary nose-leaf: Nyctophilus, i. 13, p. 12, with three species from Australasia; and Antrozous, i. 12, p. 12, distinguished from all the other members of the subfamily by having but two lower incisors, and from other Plecoteae by the separate ears; the two species inhabit California. The sixth genus, Euderma, is also represented by a Californian species.
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| Fig. 20.—Head of Cerivoula hardwickei. (From Dobson.) |
The second group Vespertilioneae, with about thirteen genera, includes the great majority of the species; and a large number of these may be classed under Vespertilio, which is divisible into subgenera, differing from one another in the number of premolars, and often ranked as separate genera. One group is represented by V. (Histiolus) magellanicus, a species remarkable for its extreme southern range, its relatives being also South American. A second group, with p. 12, includes the British serotine, V. (Eptesicus) serotinus, of Europe and northern Asia, and represented in North America by the closely allied V. (E.) fuscus. In the typical group, which includes the Old World V. murinus, one species, V. borealis, ranges to the Arctic circle. The European noctule, V. (Pierygistes) noctula, and Leisler’s bat, V. (P.) leisleri, represent another group; and the common pipistrelle, V. (Pipistrellus) pipistrellus, yet another, with p. 22. The only other group that need be mentioned is one represented by the North American V. (Lasionycteris) noctivagans, with p. 23. The African Läephotes, the Chinese Ia, and the Papuan Philetor are allied genera, each with a single species. Chalinolobus and Glauconycteris have the same general dental character as Vespertilio, but are distinguished by the presence of a lobe projecting from the lower lip near the gape; the former, with p. 22, is represented by five Australasian species, one of which extends into New Zealand; while the latter, with p. 12, is African. The species of Glauconycteris are noticeable for their peculiarly thin membranes traversed by distinct reticulations and parallel lines. Scotophilus, with i. 13, p. 12, includes several species, restricted to the tropical and subtropical regions of the eastern hemisphere, though widely distributed within these limits. These bats, though approaching certain species of Vespertilio in many points, are distinguished by the single (in place of two) pair of unicuspidate upper incisors separated by a wide space and placed close to the canines, by the small transverse first lower premolar crushed in between the canine and second premolar, and, generally, by their conical, nearly naked, muzzles and thick leathery membranes. S. temmincki is the commonest bat in India, and appears often before the sun has touched the horizon. S. gigas, from equatorial Africa, is the largest species. Nycticejus, with the same dental formula as Scotophilus, is distinguished, by the first lower premolar not being crushed in between the adjoining teeth, and the comparatively greater size of the last upper molar. It includes only the North American N. humeralis (crepuscularis), a bat scarcely larger than the pipistrelle. The hairy-membraned bats of the genus Lasiurus (Atalapha), with i. 13, p. 22 or 12, are also limited to the New World, and generally characterized by the interfemoral membrane being more or less covered with hair and by the peculiar form of the tragus, which is expanded above and abruptly curved inwards. In those species which have two upper premolars the first is extremely small and internal to the tooth-row. The genus, which is divided into Lasiurus proper and Dasypterus, is further characterized by the presence of four teats in the female, and by the general production of three or four offspring at a birth. Rhogëessa and Tomopeas are allied tropical American types. Murina, with the subgenus Harpiocephalus, has i. 23, p. 22, and includes several small bats distinguished by the prominent tube-like nostrils and hairy interfemoral membrane. M. suilla, from Java, the Malay and neighbouring islands, is a well-known species, and the closely allied M. hilgendorfi is from Japan. The remaining species are from the Himalaya, Tibet and Ceylon; and apparently restricted to the hill-tracts of the countries in which they are found. Next to Vespertilio the genus Myotis (divisible into several subgenera), with i. 23, p. 33, includes the largest number of species, and has rather a wider geographical distribution in both hemispheres, one species being recorded from the Navigator Islands. The species may be recognized by the peculiar character of the pairs of upper incisors on each side, the cusps of which diverge from each other, by the large number of premolars, of which the second upper is always small, and by the oval elongated ear and narrow tragus. The British M. bechsteini and M. nattereri are examples of this group. Cerivoula (Kerivoula), which also has p. 33, is distinguished by the parallel upper incisors and the large second upper premolar. There are numerous African and Indo-Malayan species, of which C. picta, from India and Indo-Malay, is characterized by its brilliant orange fur, and membranes variegated with orange and black. The genus includes delicately formed insectivorous, tropical, forest-haunting bats, whose colouring approximates them to the ripe bananas among which they often pass the daytime.
Another subgroup, Minioptereae, is represented solely by the genus Miniopterus, with i. 23, p. 23. The incisors are separated from one another in front and from the canines; the first phalange of the middle finger is very short, the crown of the head elevated, and the tail long. The genus is represented by some half-dozen Old World species, among which the typical M. schreibersi ranges from Europe, southern Asia, and Africa to Japan and Australasia.
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| Fig. 21.—Head of Mastiff-bat (Molossus glaucinus). (From Dobson.) |
Fig. 22.—Head of Nyctinomops macrotis. (From Dobson.) |
The last subfamily is that of the Molossinae, included by Dobson in the family Emballonuridae. In this group the premaxillae are in contact or but very slightly separated; the ears are large, with the tragus small; the dental formula is i. 11 (12 or 13), c. 11, p. 12 (22), m. 33; and the fibula is strongly developed. In their blunt muzzles and many other features these bats undoubtedly resemble the Emballonuridae, from the typical members of which they differ by the production of the thick tail far beyond the margin of the interfemoral membrane. They are further characterized by their broad and stout feet, in which the first, and in most cases also the fifth, toe is thicker than the rest, and furnished with long bent hairs; and by the presence of callosities at the base of the thumbs, and a single pair of large upper incisors occupying the centre of the space between the canines. The feet are free from the wing-membrane, which folds up under the fore-arm and legs; the interfemoral membrane is retractile, being movable backwards and forwards along the tail; this power of varying its superficial extent confers on these bats great dexterity in changing the direction of flight. All are able to walk or crawl well, and spend much of their time on trees. The genus Chiromeles, with i. 11, c. 11, p. 12, m. 33, the first hind-toe much larger than and separate from the others, and the widely sundered ears, is represented by C. torquata, a large bat of peculiar aspect, inhabiting the Indo-Malay countries. This species is nearly naked, a collar only of thinly spread hairs half surrounding the neck, and is remarkable for its enormous throat-sac and nursing-pouches. The former consists of a semicircular fold of skin forming a pouch round the neck beneath, concealing the orifices of subcutaneous pectoral glands which discharge an oily fluid of offensive smell. The nursing-pouch is formed on each side by an extension of a fold of skin from the side of the body to the inferior surfaces of the humerus and femur. In the anterior part of this pouch the teat is placed. The typical genus Molossus (fig. 21) includes the mastiff-bats, characterized by the dental formula i. 11 or 12, p. 12 or 22; and by the upper incisors being close together in front. The genus is restricted to the tropical and subtropical regions of the New World. M. obscurus, a small species common in tropical America, inhabits the hollow trunks of palms and other trees and the roofs of houses. The males and females live apart (as is the case in most if not all bats). In West Africa the mastiff-bats are represented by Eomops, with one species; while Nyctinomops includes a number of tropical American species more nearly related to the next genus, in which some of them (fig. 22) were formerly included. The widely spread Nyctinomus, with i. 13 or 12, p. 22 or 12, and the upper incisors separate in front, includes numerous species inhabiting the tropical and subtropical parts of both hemispheres. The lips of the bats of this genus are even more expansible than in Molossus, in many of the species (fig. 22) showing vertical wrinkles. N. toeniotis (or cestonii), one of the largest species, alone extends into Europe, as far north as Switzerland. N. johorensis, from the Malay Peninsula, is remarkable for the extraordinary form of its ears. N. brasiliensis is common in tropical America, and extends as far north as California.
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| Fig. 23.—Thumb and leg and foot of New Zealand bat (Mystacops tuberculatus), enlarged. (From Dobson.) |
Here may be conveniently noticed two very rare and aberrant bats, Myzopoda (or Myxopoda) aurita of Madagascar, and Mystacops (or Mystacina) tuberculatas of New Zealand, the latter of which is believed to be well-nigh, if not entirely, exterminated. Their systematic position and Myzopoda and Mystacops.affinities are somewhat uncertain; but in the opinion of O. Thomas[2] the former should typify a separate family, Myzopodidae, in which the latter may also find a place. From all other bats Myzopoda is distinguished by the presence of a peculiar mushroom-shaped organ at the base of the large ear, and by the union of the tragus with the latter, on the inner base of which it forms a small projection. There are three phalanges in the middle finger; and the whole inferior surface of the thumb supports a large sessile horseshoe-shaped adhesive pad, with the circular margin directed forwards and notched along its edge, while a smaller pad occupies part of the sole of the hind-foot. Mr Thomas regards this bat as related on the one hand to the subfamily Mormopsinae of the Phyllostomatidae, and on the other to the Natalinae among the Vespertilionidae; both these groups being regarded by him as of family rank.
Mystacops resembles Myzopoda in having three phalanges to the middle finger, but differs in that the tail perforates the interfemoral membrane to appear on its upper surface in the manner characteristic of the Emballonuridae. The greater part of the wing-membrane is exceedingly thin, but a narrow portion along the fore-arm, the sides of the body, and the legs, is thick and leathery, and beneath this thickened portion the wings are folded. Other peculiarities of structure are found in the form of the claws of the thumbs and toes, each of which has a small heel projecting from its concave surface near the base, also in the sole of the foot and inferior surface of the leg, as shown in fig. 23. The plantar surface, including the toes, is covered with soft and very lax, deeply wrinkled skin, and each toe is marked by a central longitudinal groove with short grooves at right angles to it. The lax wrinkled integument is continued along the inferior flattened surface of the ankle and leg. These peculiarities appear to be related to climbing habits in the species.
Extinct Bats.
Palaeontology tells us nothing with regard to the origin of the Chiroptera, all the known fossil species, some of which date back to the Oligocene, being more or less closely allied to existing types, and therefore of comparatively little interest. The origin of the order from primitive insectivorous mammals must have taken place at least as early as the Lower Eocene. It is, however, noteworthy that several of the earlier extinct species appear to be related to the Rhinolophidae, which is the most generalized family of the order. Remains of Pteropodidae belonging to existing genera occur in the caves of tropical countries in the eastern hemisphere; and the skeleton of an extinct generic type, Archaeopteropus, has been obtained from the Miocene lignite of Italy, which indicates a form to a certain extent transitional in character between typical fruit-bats and the insectivorous bats. The tail, for instance, which in most modern fruit-bats is rudimentary, with only three or four vertebrae, in the fossil has eight complete vertebrae; while the teeth of the extinct form are distinctly cusped. Whether, however, the tail is longer than in the existing Notopteris of Fiji and New Guinea, or whether the molars are more distinctly cusped than is the case with the Solomon Island Pteropus (Pteralopex), is not stated. Still, the fact that the Miocene fruit-bat does show certain signs of approximation to the insectivorous (and more generalized) section of the order is of interest. Of the Oligocene forms, Pseudorhinolophus of Europe is apparently a member of the Rhinolophidae; but the affinities of Alastor and Vespertiliavus, which are likewise European, are more doubtful, although the latter may be related to Taphozous. The North American Vespertilio (Vesperugo) anemophilus and the European V. aquensis and V. parisiensis are, on the other hand, members of the Vespertilionidae, the last being apparently allied to the serotine (V. serotinus).
Authorities.—The above article is based to some extent on the article in the 9th edition of this work by G. E. Dobson, whose British Museum “Catalogue” is, however, now obsolete. Professor H. Winge’s “Jordfundae og nulevende Flagermus (Chiroptera),” published in E. Mus. Lundi (Copenhagen, 1892), contains much valuable information; and for Pteropodidae Dr P. Matschie’s Megachiroptera (Berlin, 1899), should be consulted. For the rest the student must refer to namerous papers by G. M. Allen, K. Andersen, F. A. Jentink, G. S. Miller, T. S. Palmer, A. G. Rehn, O. Thomas and others, in various English and American zoological serials, all of which are quoted in the volumes of the Zoological Record. (R. L.*)