CHIROPTERA 25 



just after sunset and before sunrise. Except when hindered by 

 stormy weather, their appearances are very regular. Amongst 

 the earliest to fly are the inappropriately named Serotine and 

 the Barbastelle, which with the Noctule and Leisler's, may all 

 be seen accompanying swallows and swifts on the wing. The 

 Pipistrelle has been shown to appear in Ireland soon after sunset, 

 and Daubenton's Bat, although seldom noticed, is probably also 

 an early flier. Details regarding the others are wanting. Thus, 

 although nominally creatures of the night, bats normally appear 

 abroad long before the onset of darkness, and do not return 

 home until daylight is far advanced. The times of emergence 

 and retirement are so adjusted to suit the seasons that, as the 

 autumn evenings darken, they awake at a progressively earlier 

 hour, and in the winter, should they fly at all, they often do so in 

 daylight. Apart from this, midday flights, although probably 

 due in some instances to disturbance,^ are so frequent that they 

 can hardly be regarded as extraordinary.^ It seems likely, 

 therefore, that bats can have no inherent objection to light, and 

 many exotic species ^ are regularly active in the daytime, 

 especially those inhabiting shady woods. Again, British bats 

 are often found asleep in summer in positions where they are 

 exposed to moderate or even bright light. 



The diurnal retreats are no less varied than the nightly 

 hunting grounds. But here, again, no fixed rule can be rigidly 

 applied. Most species, besides using the shelter of trees when 

 on the wing, find a safe refuge in their trunks. Houses, too, 

 are resorted to where there are convenient cavities ; and caves, 

 although often so damp that the fur of the bats hibernating in 

 them is wet, are very much appreciated in winter, probably on 

 account of their equable temperature.* Indeed, the occurrence of 

 Horseshoe Bats in any district appears to depend in some degree 

 on the presence of caves, in which many other kinds also con- 



^ See H. W. Newman, Zoologist^ 1859, 6317. 



^ A remarkable instance is related by A. J. Dasent, Field, 7th Sept. 1889, 350. 



^ E.g., amongst others, Nyctalus azoreutn of the Azorean oak woods ; Rhyn- 

 chonycteris naso of Amazonia and Guiana (E. A. Goeldi, Ibis, 1904, 518) ; Laviafrons 

 of Tropical Africa (P. L. Sclater and J. H. Speke, Proc. Zool. Soc. (London), 8th March 

 1864, 99). 



^ Hahn found that for a period of two years' observations the extreme variation of 

 temperature in a bat-cave was from about 51" F. in January to 57° F. in September 

 {op. cit., 140). 



D 



