102 



The Irish Naturalist, 



May, 



That made it possible to play the detective on these six indi- 

 viduals, and I soon found that the hours of all six were very 

 similar, 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 sun- 

 rise- 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 the remaining three were the same. That 

 does not yet tell us all that we want to know, but it tells us 

 something. Not only is it shown that a good many Pipis- 

 trelles are on the wing during the hour before sunrise, but it 

 is also established that these are the same individual Pipis- 

 trelles which left their retreats early after sunset the previous 

 evening, and not, as might be imagined, mere belated indi 

 viduals that had overslept themselves 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 followed the Hairy- 

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

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

 viously 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 



