COMMON BAT, PIPISTRELLE OR FLITTER-MOUSE 117 



and, on the whole, very regular. Each of them left its retreat 

 every evening during the half-hour after sunset, and returned 

 to it every morning during the hour before sunrise. The time 

 of emergence would, indeed, vary, even for the same individual 

 Bat, from so early as ten minutes to so late as thirty minutes 

 after sunset, and the time of retreat similarly varied from so 

 early as forty to so late as eighteen minutes before sunrise ; 

 but in no instance did a Bat, whose sleeping-place was known, 

 on occasions when I watched for its emergence, fail to come 

 out during the evening twilight, or when I looked for its 

 return in the morning, disappoint my expectation of seeing it 

 go in. After ascertaining this much concerning their habits, 

 I caught three of these animals as they were coming out, and 

 they proved to be Pipistrelles. I have no doubt that the 

 remaining three were the same. That does not tell us all that 

 we want to know, but it tells us something. Not only is it 

 known that a good many Pipistrelles are on the wing during 

 the hour before sunrise, but it is also established that these 

 are the same individual Pipistrelles which left their retreats 

 early after sunset the previous evening, and not, as might be 

 imagined, mere belated individuals that had overslept them- 

 selves before coming out, and were making up for it by 

 breakfasting late. 



" But no amount of mere watching, moonlight or otherwise, 

 would tell whether these animals remained away from their 

 sleeping-places all night, or whether they follow the Hairy- 

 armed Bats' rule of taking a midnight nap. So, on the night 

 of August 1 6th, 1900, I did what I had done four nights 

 previously in the case of the Hairy-armed Bat, and fixed a net 

 at midnight over a hole which a Pipistrelle had quitted the 

 previous evening twenty-eight minutes after sunset. The 

 result was the opposite to what had happened in the case of 

 the Hairy-armed Bat. At 3.45 in the morning no Bat had 

 come out of the hole, and as it now wanted only an hour to 

 sunrise, it was time to remove the net so as to let the Bat in. 

 Of course I kept watch to see that it did go in, and at twenty 

 minutes past four — some twenty-eight minutes before sunrise — 

 I had the gratification of seeing it make its usual return. Now 

 there could be no doubt, in the case of that animal, that it 



