observed in rough weather and in a disturbed sea than during calms; they dart out of the water when pursued by their enemies or frightened by an approaching vessel, but frequently also without any apparent cause, as is also observed in many other fishes; and they rise without regard to the direction of the wind or waves. The fins are kept quietly distended, without any motion, except an occasional vibration caused by the air whenever the surface of the wing is parallel with the current of the wind. Their flight is rapid, greatly exceeding that of a ship going 10 m. an hour, but gradually decreasing in velocity and not extending beyond a distance of 500 ft. Generally it is longer when the fishes fly against, than with or at an angle to, the wind. Any vertical or horizontal deviation from a straight line is not caused at the will of the fish, but by currents of the air; thus they retain a horizontally straight course when flying with or against the wind, but are carried towards the right or left whenever the direction of the wind is at an angle with that of their flight. However, it sometimes happens that the fish during its flight immerses its caudal fin in the water, and by a stroke of its tail turns towards the right or left. In a calm the line of their flight is always also vertically straight or rather parabolic, like the course of a projectile, but it may become undulated in a rough sea, when they are flying against the course of the waves; they then frequently overtop each wave, being carried over it by the pressure of the disturbed air. Flying-fish often fall on board of vessels, but this never happens during a calm or from the lee side, but during a breeze only and from the weather side. In day time they avoid a ship, flying away from it, but during the night when they are unable to see, they frequently fly against the weather board, where they are caught by the current of the air, and carried upwards to a height of 20 ft. above the surface of the water, whilst under ordinary circumstances they keep close to it. All these observations point clearly to the fact that any deflection from a straight course is due to external circumstances, and not to voluntary action on the part of the fish.
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| Fig. 2.—Exocoetus callopterus. |
A little Malacopterygian fish about 4 in. long has recently been discovered in West Africa which has the habits of a fresh-water flying-fish. It has been named Pantodon buchholzi. It has very large pectoral fins with a remarkable muscular process attached to the inner ray. It lives in fresh-water lakes and rivers in the Congo region, and has been caught in its flight above the water in a butterfly-net.
FLYING-FOX, or, more correctly, Fox-Bat. The first name
is applied by Europeans in India to the fruit-eating bats of the
genus Pteropus, which contains more than half the family
(Pteropidae). This genus is confined to the tropical regions of the
Eastern hemisphere and Australia. It comprises numerous
species, a considerable proportion of which occur in the islands
of the Malay Archipelago. The flying-foxes are the largest of
the bats, the kalong of Java (Pteropus edulis) measuring about
a foot in length, and having an expanse of wing-membrane
measuring 5 ft. across. Flying-foxes are gregarious, nocturnal
bats, suspending themselves during the day head-downwards
by thousands from the branches of trees, where with their wings
gathered about them, they bear some resemblance to huge
shrivelled-up leaves or to clusters of some peculiar fruit. In
Batchian, according to Wallace, they suspend themselves chiefly
from the branches of dead trees, where they are easily caught
or knocked down by sticks, the natives carrying them home in
basketfuls. They are then cooked with abundance of spices,
and “are really very good eating, something like hare.” Towards
evening these bats bestir themselves, and fly off in companies
to the village plantations, where they feed on all kinds of fruit,
and so numerous and voracious are they that no garden crop
has much chance of being gathered which is not specially protected
from their attacks. The flying-fox of India (Pteropus
medius) is a smaller species, but is found in great numbers
wherever fruit is to be had in the Indian peninsula.
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| Pigmy African Flying-Squirrel (Idiurus zenkeri). |
FLYING-SQUIRREL, properly the name of such members of the squirrel-group of rodent mammals as have a parachute-like expansion of the skin of the flanks, with attachments to the limbs, by means of which they are able to take long flying-leaps from tree to tree. The parachute is supported by a cartilage attached to the wrist or carpus; in addition to the lateral membrane, there is a narrow one from the cheek along the front of each shoulder to the wrist, and in the larger species a third (interfemoral) connecting the hind-limbs with the base of the long tail. Of the two widely distributed genera, Pteromys includes the larger and Sciuropterus the smaller species. The two differ in certain details of dentition, and in the greater development in the former of the parachute, especially the interfemoral portion, which in the latter is almost absent. In Pteromys the tail is cylindrical and comparatively thin, while in Sciuropterus it is broad, flat and laterally expanded, so as to compensate for the absence of the interfemoral membrane by acting as a supplementary parachute.
In general appearance flying-squirrels resemble ordinary squirrels, although they are even more beautifully coloured. Their habits, food, &c., are also very similar to those of the true squirrels, except that they are more nocturnal, and are therefore less often seen. The Indian flying-squirrel (P. oral) leaps with its parachute extended from the higher branches of a tree, and descends first directly and then more and more obliquely, until the flight, gradually becoming slower, assumes a horizontal direction, and finally terminates in an ascent to the branch or trunk of the tree to which it was directed. The presence of these rodents at night is made known by their screaming cries. Sciuropterus is represented by S. velucella in eastern Europe and northern Asia, and by a second species in North America, but the other species of this genus and all those of Pteromys are Indo-Malayan. A third genus, Eupetaurus, typified by a very large, long-haired, dark-grey species from the mountains to the north-west of Kashmir (Eu. cinereus), differs from all other members of the squirrel-family by its tall-crowned molar teeth. It has a total length of 37 in., of which 22 are taken up by the tail.
In Africa the name of flying-squirrel is applied to the members of a very different family of rodents, the Anomaluridae, which are provided with a parachute. Since, however, this parachute is absent in some members of the family, the most distinctive character is the presence of a double row of spiny scales on the under surface of the tail, which apparently aid in climbing. The flying species are also distinguished from ordinary flying-squirrels by the circumstance that the additional bone serving for the support of the fore part of the flying-membrane rises
