BAT, one of a group (order Cheiroptera) of small mammals adapted to life in the air by the possession of wings formed of a membrane stretched between the greatly prolonged bones of the arm and hand. The general organiza tion of bats allies them to the Insectivora. The bones of the spine, hinder limbs and tail are of a normal character; the chest is much enlarged to admit of the increased size of the lungs and heart, necessary to the relatively violent exer tion necessary to flight, the breast bone is keeled as in birds, and the muscles of the fore limbs are much enlarged. The fore limbs them selves consist of the normal number and ar rangement of bones, but all are greatly elon gated, especially those of the fingers, which are so lengthened out as often to be equal to the total length of the spine. The thumb, however, is comparatively small, stands at right angles to the other bones, and terminates in a strong claw of great service in clinging to supports. The whole extent of the arm and hand in the bats is enclosed within a membrane which con sists of leathery skin more or less furry upon the outside, which stretches between the fin gers, arm bones and body, forming an exten sible membrane or parachute, and constituting an effective instrument of flight. In some bats a sitnilar membrane (which is only an extension of the skin and is of double thiclmess) stretches from the heel of each hind foot, where it is supported by a bony spur, to the tip of the tail, but in many bats the tail is free from any such membrane. The tail is very variable in length, but is never prehensile nor bushy. The hinder limbs of bats are peculiar in being twisted in such a way that the kttee bends back ward, making wa&ing very difficult.
The menaWanous wings of the bat are not only an organ of flight, enabling it to perform feats in the air probably not exceeded by any bird or insect, but are also a means of inform ing the creature as to its surroundings. Bats are mainly nocturnal and their eyes, though highly organized, are very small, embedded in fur and comparatively useless in the dark, yet no animal seems more thoroughly wide awake and able to talce care of itself, even in almost complete darlcness, than this one, which habi tually lives in gloomy caves and seeks its food only after daylight has departed. The ability which it displays in catching its prey by ex traordinary agility in pursuit, and in avoiding obstacles as it darts about among the trees, seem to be due largely to an extreme sensitive ness in the wings. These are not only supplied with a great number of blood vessels and nerves, but their surfaces abound in minute sense-organs, each the terminus of a nerve fibrilla., This armature has evidently arisen as an added means of information, giving the animal a sense of touc.h more exquisite than we know of elsewhere in the animal kingdom. The well-known experiments of the Italian Spal lanzani toward •the end of the 18th century, which have been verified by more recent in vestigations, rnake it plain that bats depend very largely upon these sense organs in their wings to guide them in their &vious flight through the darlaiess. It was found that bats whose eyes were sealed up with varnish, or even completely destroyed, made their way with apparent ease not only through dark rooms but in places where strings had been stretched across the path in various directions, and other obstacles had to be avoided. These blinded bats never collided with such obstruc tions, but seemed able to approach a wall at ease, alight upon a perch, or even find a stnall cavity without apparently searching for it.
For a similar purpose of information many bats are furnished with extraordinary mem branous appendages upon the nostrils and ears, which give to some of them the most grotesque appearance. In the large frwit-eating fox headed bats of the East Indies, whic.h are more nearly diurnal than any others, the ears are of no great size, and the nose is defended only by long hairs about the nostrils and eyelids, but in all the smaller, insect-eating, nocturnal bats, there arise upon the nostrils leaf-like ap pendages, sometimes very large and complicated which resemble the leathery substance of the wings and in such species, the ears are often several times larger in area than all the rest of the face. These great ears must not only col
lect sounds far too faint for us to hear, but their membranes are as nervous and sensitive as those of the wings, probably. being able to feel degrees of density in the air entirely perceptible to most other creatures.
Bats are divisible into two groups or sub orders, the Megacheiroptera, and the Microchei roptera. The first group. contains the fruit ealing bats whose large size, reddish fur and fox-hke head have given them the name of fly ing foxes (q.v.). Their chief distinguishing feature, however, is the fact that the molar teeth are not tubercular but are marked with a longitudinal furrow. They live mainly upon fruit and are confined to the tropics of the Old World, and are all included in a single family, Pteropodidce. The Microcheiroptero have molars with sharp cusps adapted to cut ting and crushing the insects upon which they mainly subsist. This group includes all of the ordinary bats, of which those most familiar in North America and Europe belong to the large and typical family Vespertilionidce, of which nearly '200 species are named. Among the most numerous and widespread of the North Ameri can bats are the large hoary bat (Lasiusus cinereus) of the Northeastern States; but it keeps to the woods and is not often seen; it migrates to the southern States in winter. It is about 5.50 inches long. Another common bat of the woods is the smaller silver-haired (Lasionycterus noctivagans). 1The red bat (length 4.40 inches) is numerous in the Alle ghanian region, inhabiting caves in great com panies; but the acommonp bat of the whole country east of the Rockies is the little, glossy, brown familiar of our homes and gardens, as well as of the woods, which remains with us the year round, hibernating during cold weather in the hollow trees, caves and crevices about buildings, where they make their home, and whence they emerge at night, to seek their prey about our farmyards and gardens. As the in sects caught are mainly mosquitoes and similar pests, and as they do no harm, they should be encouraged, rather than feared and persecuted. ((Awake at the most,* says Cram, gsome four out of every 24 hours of their drowsy little lives, they never make any nests or even at tempt to fix over the crannies where they hide, and where the little bats are born. These helpless little things are not left at home at the mercy of foraging rats and mice. When the old bat flits off into the twilight, the youngsters often go with her, clinging about her neck. .. . At times, she deposits them on the branch of a tree, where they hang, sheltered by the leaves.* The lower Mississippi Valley has a yellow ish bat, called obig-eared* (Corynorhinus macrotis) which differs from the others in that its great ears are joined together by their bases in front.
For a systematic account of the bats of the world consult Dobson, (Catalo e of Chirop tera in the British Museum) 1878), and his er subsequent papers, mention in Flower's 'Mammalia) (1891). For North American forms consult Allen, H., (Bats of North America) (Smithsonian Institution, Washing ton 1893). For habits, etc., consult the writings of Harlan, Audubon, Baird, Godman, Mearns, E. A., Herrick, C. L., Miller, G. S., and especially Merriarn, C. H., (Mammals of the Adirondacks) (Linnman Society New York 1893) ; Stone and Cram, (American Animals) (1902); Goose, (A Naturalist's Sojourn in Jamaica) (1851). See also FOX-BAT ; FRUIT-BAT ; LEAF-NOSED BATS ; VAMPIRE, and similar titles.
Besides bugs (see BED-BUG) certain very strangely modified wing less flies are in rare cases found living on bats in Africa and the East Indies. They are some what spider-like, with a narrow eyeless head, though four ocelli are present in some species, which rests on the back of the thorax, while the legs are large, long, and sprawling, ending in large claws. They are only a line or' two in length. The larva is, like that of the sheep tick (q.v.) and horse-fly (Hippobosea), very peculiar, the maggot being probably nourished in the dilated oviduct of the fly, then attaining its full growth, when it is expelled in the shape of a broad, short puparium, the skin being hardened by the excretion of chitin.