144 WALTER LOUIS HAHN. 



Both of these common species have been seen in some very- 

 small caves near Mitchell. In one of these, at least, they seem 

 to have wintered, as several were found there on March 26, and 

 a single Pipistrcllus was seen under a ledge of rock just outside 

 the entrance in February. This cave is merely an irregularly 

 spiral sink-hole going down to a depth of forty feet but without 

 any large lateral passages. All parts of it receive daylight on 

 bright days and the temperature certainly falls quite low in cold 

 weather. 



The other caves mentioned vary in size from the two largest 

 known caverns in North America to small caves with not more 

 than half a mile of passages that are large enough to be explored. 

 The entrance to some of them is a vertical shaft, to others it is 

 a horizontal passage going into the side of a hill. 



The conditions prevailing within a cave do not determine a 

 bat's choice of a resting place after it has entered. In Coon 

 Cave, as well as several others that I have visited, there is running 

 water at one point and the air here is usually saturated with mois- 

 ture. In the upper part of the cave, some distance from the en- 

 trance, the atmosphere is always dry and the floor and walls 

 dusty. When I visited this cave, bats were about equally abun- 

 dant in the dry and in the wet parts. In the latter places the 

 moisture had condensed on the animals and drops of water hung 

 from their fur. The arrangement of hairs is such that this mois- 

 ture does not penetrate to the skin unless the animal is rubbed in 

 moving about. 



Usually the animals go far enough into the cave to be in total 

 darkness and a nearly constant temperature, although as men- 

 tioned later (p. 163), they sometimes remain for several weeks 

 where they are reached by both light and cold. Blatchley states 

 that "bats choose as a resting place that part of the roof where 

 small portions have begun to flake, giving a certain degree of 

 roughness, or small crevices, to which they can cling. They can- 

 not attach their claws to a smooth surface, hence from large por- 

 tions of the roof of a room they may be entirely absent." This 

 statement is partly erroneous, for although they cannot attach 

 their claws to a polished surface, the limestone walls and roof of 

 a cave are ordinarily rough enough to furnish adequate support. 



