8o 
MAMMALIA. 
is nearly an hour of twilight, the silver-haired and little brown bats 
begin to fly shortly after eight o’clock, but the present species is 
seldom seen till half an hour later, and those we killed were common- 
ly shot about 9 p. m. As the season advances and the evenings be- 
come shorter, all bats, of course, appear proportionately earlier. On 
the 3d of August I shot Atalapha cinerea at eight o’clock, and on 
the 8th of October at precisely 6 o’clock — three hours earlier than 
the same species was killed during the first part of July. 
In warm evenings it was not to be seen at all, and I have never 
observed it when the temperature was above 1 5 ° C. (59° F.). It was 
most often seen when the thermometer ranged from io° to i2°C. 
( 5 o° to 53.6° F.). Assuming that the species does not leave its 
hiding-place when the temperature is above i 5 ° or i6°C. it might 
be supposed that it would suffer for food if there were several suc- 
cessive warm evenings. But it must be remembered that the coolest 
part of the twenty-four hours is just before daylight, and throughout 
the northern regions inhabited by this species there are few days 
when the temperature does not fall to i 5 °C. in the early morn- 
ing - . Moreover, it is well known that most bats are as active 
just before daylight as in the evening. Hence, if the evenings 
are too warm for its comfort, it would almost always be enabled, 
by the falling temperature, to sally forth at some later hour of the 
night. 
The Hoary Bat occurs about the Red River settlement in British 
America, and Dr. Richardson obtained it at Cumberland House on 
the Saskatchewan, in lat. 54 0 N. * Robert Kennicott procured it 
in the Hudson’s Bay Company’s territory, farther north than any 
other species of bat has been taken. It is a summer resident of 
high latitudes, its southern limit in the east coinciding, apparently, 
with that of the Canadian Fauna. In the west it has been taken 
in Arizona and' New Mexico, but only, so far as I am aware, at 
considerable altitudes. In the fall and early winter isolated indi- 
Fauna Boreali Americana, vol. I, 1829, p. 1. 
