In the warmer regions of the earth’s surface, where their supply of food is constant, the activity of the Bats is not known to have any intermission, but in cold and temperate countries they pass the winter season in a state of torpidity.  The period of this hibernation, as it is called, varies somewhat in the different species, but few of them are to be seen flying about, except when the weather is decidedly mild.  The commonest of all our British species, the Pipistrelle, has a shorter winter sleep than any of its companions, it usually makes its appearance on the wing by the middle of March, and continues active until quite late in the year; in fact Mr. Gould has recorded the fact of his having shot a specimen of it on a warm sunny day just before Christmas.  For the purpose of hibernation the Bats retire to their usual resting-places, but frequently, instead of suspending themselves by their hind feet, as when sleeping, pack themselves away in small parties in holes and crevices, an arrangement which probably furnishes a better protection against the inclemency of the season.

It is probably in the dormitory that the birth of the young bats takes place—­at least, so far as we know, the process is affected in a manner which must preclude active exertions on the part of the mother for some little time.  The best account of the operation with which we are acquainted is that given fifty years ago by Mr. George Daniell, in a paper read before the Zooelogical Society, in which he described the habits of some Noctules kept by him in captivity.  Four out of five died, and the survivor, a female, was observed on 23d June to become very restless, and to continue so for about an hour, although still suspended by the hind limbs in the attitude of repose.  “Suddenly,” to use Mr. Daniell’s words, “she reversed her position, and attached herself by her anterior limbs to a cross wire of the cage, stretching her hind limbs to their utmost extent, curving the tail upwards, and expanding the interfemoral membrane, so as to form a perfect nestlike cavity for the reception of the young ... which was born on its back, perfectly destitute of hair, and blind.  The mother then cleaned it, turning it over in its nest; and afterwards, resuming her usual position, placed the young in the membrane of her wing.  She next cleaned herself, and wrapped up the young one so closely as to prevent any observation of the process of suckling.  At the time of birth the young was larger than a new-born mouse, and its hind legs and claws were remarkably strong and serviceable, enabling it not only to cling to its dam, but also to the deal sides of the cage.  On the 24th the animal took her food in the morning, and appeared very careful of her young, shifting it from side to side to suckle it, and folding it in the membranes of the tail and wings.”  Unfortunately, these interesting observations were cut short by the death of the mother, and the young animal, which was with some difficulty removed from the nipple, survived only eight days, during which it was fed with milk from a sponge, and made but little progress, its eyes being still unopened, and its body almost hairless.