lOO 



The Irish Naturalist, 



May, 



were visible in the mornings as well as in the evenings, I got 

 one of their sleeping places by watching a group of these 

 Bats in the morning till they went home into the hollow of a 

 decaying ash-tree ; and then, as it proved useless watching 

 in the dim light of late evening to see whether they also went 

 home for the night, I tried pinning a net in the middle of the 

 night (August I2th-i3th, 1900), across the mouth of the 

 sleeping-hole, with the result that about three o'clock in the 

 morning a Hairj^-armed Bat was caught in the act of coming 

 out. That proved beyond question that this largest of Irish 

 Bats passes the night indoors, as it also does the day, flying 

 only in the short intermediate zones of the twilight; during 

 which it whizzes about with wonderful velocity, and does 

 remarkably well for itself in the way of laying in food. 



Of course, the precise time of the Hairy-armed Bat's retire- 

 ment for the night was not ascertained by the midnight net 

 experiment. The morning flight was shown by that experi- 

 ment not to exceed some sixty-five or seventy minutes ; but 

 for the measurement of the evening flight we have still to be 

 pretty largely guided by the fact of the animal's almost in- 

 variable disappearance from view, and of the cessation of its 

 characteristic screeching cries, about an hour and twenty 

 minutes after sunset. On two occasions, however, I was for- 

 tunate enough to see the Bat in the act of going home : on 

 the evening of August 13th, 1900, when (as already recorded 

 in the Irish Naturalist) the retirement took place 81 minutes 

 after sunset, and on that of June 5th, 1901, when it took place 

 82 minutes after sunset. In the earlier instance the Bat 

 observed belonged to a small colony, so the period for which 

 the individual had been on the wing could only be told ap- 

 proximately, but it had certainly not exceeded seventy-five 

 minutes, nor had it been less than seventy-one. The obser- 

 vation of June 5th, 1 90 1, which was not recorded in my 

 former paper, is in this respect more complete, since the Bat 

 which formed the subject of it lived quite alone, and had 

 been timed, the same evening, quitting its retreat four 

 minutes after sunset. It had, therefore, flown for exactly 

 seventy-eight minutes. 



I now come to the Pipistrelle. This is the common Bat 

 which we see everywhere. Systematic zoologists have com- 



