Family VESPERTILIONIDAE 



69 



place with the little brown bat. The little brown bat can be 

 distinguished from Keen's hat by smaller ears, which do not 

 reach beyond the nose when laid forward, and by tragi, fig. 51a, 

 that are each less than 6.5 mm. long. It differs from the gray 

 bat by having forearms that are each less than 42 mm. long. It 



Fig. 52. — Little brown bat. 



differs from the Indiana bat by having a bronzy sheen on the 

 back, and from the southeastern bat by its buffy rather than 

 nearly white under parts. 



The little brown bat differs from the eastern pipistrel by its 

 brown rather than yellow color and from the evening bat by its 

 lighter brown color. It also has less blunt tragi than either of 

 these species. 



Life History. — The little brown bat is present in Illinois 

 throughout the year. During the warm months it congregates 

 in large numbers in attics and steeples; during cold weather it 

 hibernates in suitable caves and mines in even larger numbers. 

 In these hibernating chambers, where the temperature is con- 

 stantly cool but above freezing, individuals of this species may 

 hang with their heads down, singly or in clusters of 20 to 100 

 or more, or they may wedge their bodies into cracks. Here they 

 become dormant and in a state of deep hibernation ; they may 

 not fly or feed until spring, when they break up into smaller 



