^2 The Irish Naturalist, April, 



pretty sure to be found flying if looked for in suitable 

 localities. Below 43° their emergence is not to be calculated 

 on, but it sometimes takes place at lower temperatures, down 

 to 39® It will be noticed that a return of mild weather 

 brings out the Bats immediately, no matter how frosty the 

 previous nights and days may have been. The reason why so 

 few Bats were seen during Februarj^ was that the whole of 

 that month — until the last w^eek, when the}^ re-appeared — was 

 continuously cold. 



The conclusions as to the Hedgehog, however, are strangely 

 in contrast with those as to the Common Bat. There is no 

 evidence that warmth has any effect in waking up the Hedge- 

 hog ; but it is most remarkable how often this animal vShowed 

 itself on cold frosty nights^ not only during the severe spell 

 of November 14th to i6th, when some people might suspect 

 that it had not yet begun to hibernate, but again during the 

 sharp frosts of the latter half of December and of the middle 

 and end of Januar5^ It was almost invariabh' on cold nights 

 that I met the Hedgehog ; the temperature recorded in the 

 table vShows this, but it must be further borne in mind that 

 it would nearly ahvays be several degrees colder on the grass, 

 especially at the late hours at which I used chiefl)^ to meet 

 this eccentric creature going its rounds. Only twice during 

 December, and never in January, were Hedgehogs and Bats 

 seen on the same night, though there were during those two 

 months nineteen nights on which Bats were observed, and 

 thirteen on which Hedgehogs were noticed. A further 

 curious fact is that wdien at last both the Hedgehogs and the 

 Bats retired, the activity of the Frogs really began. 



As a matter of fact the hiber7iation of the Frog seems to be 

 more analogous to that of the Bats than to that of the Hedge- 

 hog, for it is clear that warmth is a principal cause of its 

 interruption. At any temperature above 46° one may meet 

 Frogs moving — as is shown by their emergence at tempera- 

 tures of 46'' and 46^® respectively, on the nights of November 

 i8th, 1901, and January 2nd, 1902. On cold nights, until 

 spawning has begun, one never encounters Rana te^nporaria 

 on the move ; indeed, that animal needs a higher temperature 

 than the Pipistrelle, and at least as high a one as the Long- 

 eared Bat, to induce it to move from its winter retreat. But 



