AN OCTOBER DIARY. 287 



sense on the part of a butterfly, and have ever since 

 had hopes of equal good-fortune in the case of bats- 

 have had these hopes for twenty years, and still have 

 them. 



Of all our mammals, bats are the most sensitive to 

 cold, and avoid exposure to it with the greatest care ; 

 and yet I find that the little red bat is very late in re- 

 tiring for the season, and reappears with great regular- 

 ity early in February. Their actions at this time indi- 

 cate that considerable food is to be had — that flying 

 insects are abundant. While this bat's ordinary habits 

 do not differ noticeably from those of the other species, 

 it is apparently less sensitive to low temperature, and 

 needs but the least encouragement to arouse from its 

 hibernating sleep. It is also less crepuscular in habit 

 than the others; but I do not know that this fact has 

 any bearing upon tlie irregularity of its hibernation. 



Bats disappear in November or December, immedi- 

 ately after the formation of ice, but do not seem affected 

 by a mere succession of hard frosts. As insect-life is 

 not materially affected by the first few frosts, there does 

 not seem any reason for their withdrawal from active 

 life, and therefore it is not surprising that even up to 

 Christmas bats should be seen flying, at sunset, in con- 

 siderable numbers. When the steady cold of an average 

 winter fairly reaches us, bats hibernate in two ways. If 

 they resort to the ordinary shelter of a hollow tree, or 

 similar locality, that is considerably exposed to the wind, 

 then many individuals cluster together; and contact is 

 mutually beneficial, for the torpor of hibernation is not 

 rapidly, but rather gradually acquired. Such clusters of 



