The Common Bat is in a general sense familiar to everybody, for it may be seen in the evenings flying everywhere, even in the streets of crowded cities. Its British distribution extends from the South of England to Scotland and the Hebrides and westward to Ireland. Its wider range includes Europe and parts of Asia. It is the smallest of the British Bats.
In spite of its small size—the head and body measure little more than an inch and a half—the Common Bat is of robust build, and it has a wing expanse of over eight inches. It has a flat broad head with a blunt muzzle and wide mouth. The short, broad ears are somewhat triangular with blunt tips. The erect, slightly incurved tragus has a rounded tip which does not reach quite to half the height of the ear. There are glandular swellings on the muzzle between the nostril and the small, but rather prominent eye. The tail is little over an inch in length, and the legs also are short. The last joint of the tail is free from the membrane and prehensile, and the Bat makes use of it as a support in crawling up or down. The spur reaches more than halfway to the tail. The narrow wing is attached to the middle of the sole of the foot.
The somewhat silky fur is a reddish-brown on the upper parts, slightly paler beneath. The wing membrane and the ears are blackish.
It is a very active Bat, flying over farmyards and gardens and about houses, frequently uttering its shrill little squeak as it snaps up the flies and small beetles, pouching and eating them without alighting. It continues its flight all through the night, and has a longer period of activity than any other species, for it leaves its hibernaculum in March and does not retire until winter has begun. Even then, a moderately high midday temperature is sufficient to awaken it and bring it out for an hour's hunt. It is this habit that accounts for the letters in the daily papers from City gentlemen who report the presence of a Bat flying along Cornhill or Cheapside early in January.
It is not particular in regard to its sleeping place, and is frequently found under roofs, behind rainwater pipes and gutters, or in any crevices between woodwork and brickwork in buildings. Any regular dormitory acquires a very fetid odour from its use.
The dental formula of the Common Bat is: i 2/3, c 1/1, p 2/2, m 3/3 = 34. Schreber's name of Vespertilio pipistrellus was bestowed in 1774 and is the oldest name; in the British Museum Catalogue it is Pipistrellus pipistrellus, a combination invented by Miller in 1897.
Serotine (Vespertilio serotinus, Schreber).
The Serotine and the Noctule are our two largest Bats, and in the early records they were very much confused. Though similar in size, they may be known apart by the shape of the ear; in the present species oval-triangular with the tips rounded. The fur is also of a darker brown, and there are other points of difference, such as the possession of two additional teeth by the Noctule. But for a few records of its occurrence in Essex, it might be said to be restricted in Britain to that portion of England bounded by the river Thames and the English Channel. A few examples have been taken in Cornwall, and other counties in which it is found are Surrey, Hampshire, Sussex, and Kent. It occurs throughout the Isle of Wight—where it is known as Rattle-mouse—but Kent is its British metropolis, where it is the commonest Bat. It extends through Central and South Europe, from Denmark to the Mediterranean and eastward into Asia.
It has a somewhat swollen face with little hair on the front portion, save for a moustache on the upper lip; but owing to the dark skin of the face the lack of fur is not very noticeable. The dark brown fur of the upper parts is soft and dense; behind the shoulders the hairs have buffy tips. On the underside the fur is somewhat lighter. There is little extension of fur on the wing, except a line of down on the under surface of the forearm. The membrane is attached to the base of the toes. The head and body measure about three inches, and the tail slightly exceeds two inches, the last joint being quite free of the membrane. The expanse of the wings is fourteen and a half inches. There are prominent glandular swellings on the muzzle. The ear is about three-quarters of an inch long; the short tragus—less than half the length of ear—has a straight front border and a curved hind border, with rounded tip. The canines and the inner incisors of the upper jaw are noticeably large and strong. Dental formula: i 2/3, c 1/1, p 1/2, m 3/3 = 32.