but as time is precious the bat wastes no time in getting to the scene of action. The speed of flight varies considerably, but is usually rapid and straight, though varied with occasional dashes from side to side and sharp oblique dives. These erratic movements are, almost certainly, due to the fact that the bat has become aware of an insect at another level or on a lower plane. Bell thought that they were caused, at any rate when the descent was sudden, by the loss of balance if the bat had caught "some large or intractable insect," and Grabham enlarged on the idea and described the noctule using its thumb to tend asunder the prey it was carrying. If the drop is closely observed it will be seen to be not only direct, but oblique; it is a dive, not a fall.
Noctules frequently chase one another on the wing, squeaking vigorously, and almost the whole time that they are abroad they keep up incessant noise. This sound, a high, shrill squeak, is uttered in the roost before they emerge and after they have returned; Alcock points out that the note may be imitated by striking a halfpenny smartly with a sixpence. Bats are erratic about their appearance in the evening; some nights hundreds are visible, on others hardly one emerges. Doubtless to some extent this irregularity is due to weather conditions, cold, wind, or rain keeping many indoors; but a few go abroad in stormy weather, and at times there are few to be seen on evenings which are apparently suitable.
The noctule has a curious smell, which White and Donovan thought "fetid," but though strong it is not really offensive; it has given rise, so some think, to the name "fox-bat," but that may have originated in the colour of the pelage.
The habits of any creature which comes abroad at night or in the half-light of evening are not easy to observe, but so easily does this bat adapt itself to the restraint of
