30 INTRODUCTION 



Pipistrelle probably fly whenever the weather is mild throughout 

 the winter. An evening temperature of 40^ to 43° Fahrenheit is 

 probably required to keep the latter at home, the corresponding 

 figure for the Long-eared being one or two degrees higher. On 

 the other hand, it is probably the temperature of midday that 

 influences Leisler's Bat in its winter flights. Most authorities 

 are agreed that bats fly more frequently in the early than in the 

 later months of winter, by which time probably most insect life 

 has been killed by frost. In the equable temperature of 

 churches and caverns they are active although they may not 

 venture outside, and the delicate Horseshoes probably snatch 

 irregular meals on the cave-haunting moths and spiders which 

 share their winter quarters. 



North American naturalists have proved that bats perform 

 regular migrations, but it is not clear that they do so to avoid 

 hibernation. Of six species found in Manitoba, according to 

 Mr Ernest Thompson Seton,^ "all are migratory and yet 

 hibernate," and the seasonal journeys of at least three of them, 

 the Red, the Hoary, and the Silver-haired, are on a scale 

 comparable with those of birds. The second of these has 

 even been known to cross from the American continent to 

 the Bermudas, a distance of over six hundred miles. The 

 regular passage of these bats over the Atlantic was invested 

 with special interest in view of an old record of the occurrence 

 of one of them in the Orkneys. Unfortunately this turns out 

 to be an example of a Hawaiian species,^ which cannot possibly 

 have reached this side of the Atlantic unassisted. 



Occasionally bats are reported from lighthouses as if 

 they were migrating,^ but it is regrettable that for Europe 

 there is on this point not much definite information, although 

 it is more than a century since Spallanzani wrote that in 

 Italy most bats are migrants.* More recently Bell accepted 

 Blasius' belief in the migration of the Northern Bat,^ based on 



^ Life Histories of Northern Anitnals, ii., 1909, 1161. 



- Nycteris { = Lasiurus) semota. 



^ R. M. Barrington, The Migration of Birds, 284 : R. H. Porter, London, 1900, 

 gives records from Fastnet, Rockabill, Blackrock (Mayo) and Tearaght, on the west, 

 and from Lucifer Shoals and Arklow South on the east coast of Ireland. 



* Rapports de Pair avec les etres organises, ii., 179, edition Jean Senebier, Geneva, 

 1807. ^ Vesper tilio nilssoni. 



