386 Whitaker: The Hatry-Armed Bat. 
with Mr. Armitage, and this time we took care to arm our- 
selves with a good mallet and wood chisel, and with the aid 
of these I soon. cut a hole straight into the den in the main 
trunk, having previously blocked up the exit hole through the 
stump of the side branch. I found, on cutting the retreat open, 
that it commenced, as before stated, with an entrance hole 
some two inches in diameter, running. from the end of the 
broken side stump straight to the centre of the main trunk, a 
distance of about a foot. The trunk itself, at this point, was 
about ten inches in diameter, and in the heartwood was a 
circular hole about four inches in diameter, extending upwards 
from the point where the other hole joined it, for about fourteen 
inches. It also went downwards for a short distance, but the 
bottom part was inclined to be damp. In the upper portion I 
found six bats, which all proved to be female Hairy-Armed 
Bats, a fact which seems to indicate that, as in the case of the 
Noctule, the sexes have a strong inclination to form separate 
colonies during the summer months. 
Another interesting feature about this little colony of 
Leisler’s bats was that it quite lacked the strong and offensive 
odour so characteristic of a Noctules’ den. In fact, the 
absence of this unpleasant smell struck us even before we 
commenced to cut into the hole, and was the first thing which 
led us to suspect that the occupants were Leisler’s, and not 
Noctule bats. 
The average wing expanse of these six Leisler’s bats was 
304 m.m., decidedly less than that of the Noctule, which 
averages about 340 m.m. The colour of the fur, however, 
appears to give by far the most ready method of distinguishing 
between these two species. The Noctule is glossy (almost 
oily-looking) golden brown on the back and only very slightly 
paler and less golden underneath. Leisler’s bat is of a glossy 
clove brown above and paler, with quite a grey tinge, beneath. 
This, however, is a method of identification which can only 
be used when specimens of both species are available for 
comparison. 
It will be found upon a more careful examination, however, 
that the colouration does afford a ready method of distinguishing 
these two species ; and the distinction is one that can easily be 
borne in mind, and used to identify even a single specimen 
which may be obtained when one is in the country, with no 
other specimens or books to refer to, and when general 
impressions as to whether it looked small and darkly 
Naturalist, 
. 
