MAMMALS 



257 



Order 5. Chiroptera. — Bats. Small, flying mammals in which 

 the greatly elongated fore limbs form the supports of the wings. These 

 consist of a paired integumental membrane which extends between the 

 arms and the four lingers and the body, and includes the hind legs and 

 the tail. The knee bends backwards. The portion of the membrane 

 between the hind legs which incloses the tail is called the inter femoral 

 memhrane. The thumb is not included in the wing membrane. The 

 foot has 5 digits; a long spur extends from the heel along the base of 

 the interfemoral membrane. The ear 

 is large and bears an elongated lobe in 

 its concavity called the tragus (Fig. 

 148). In many families, at the end 

 of the snout and surrounding the nos- 

 trils is a series of more or less com- 

 plicated membranes called the nose-leaf 

 (Fig. 148). The mammae are thoracic 

 in position and number i or 2 pairs. 

 The sternum bears a keel. 



The order contains about 900 spe- 

 cies, grouped in 2 suborders, one of 

 which, the Megachiroptera, or the frugivorous flying foxes of India 

 and Australia, is not represented in this country. 



Suborder Microchiroptera. — Bats with a short snout, large ears 

 and multicuspid molar teeth: 16 families and about 600 species, 3 

 families and about 30 species occurring in the United States. Bats 

 are nocturnal animals, which feed mostly on beetles, mosquitoes and 

 other night-flying insects, which they chew before swallowing. Some 

 species are, however, frugivorous and some sanguivorous. The female 

 of most species bears one or two at a birth, which she may carry about 

 with her, clinging to her body until they are old enough to be left in 

 some safe place. Bats spend the day in caves and other dark places, 

 hanging head downward by the hind feet. In the winter they hibernate 

 or migrate. 



Fig. 148. — Head of Microlus cali- 

 fornicus: i, tragus; 2, nose-leaf {from 

 Allen). 



Key to the United States Families of the Microchiroptera 



ai Third finger with 3 phalanges; nose-leaf present; only in the 



extreme south i. Pliylloslomidce. 



ao Third finger with 2 phalanges; nose-leaf absent. 



bi Ear with tragus; all United States bats, with a few excep- 

 tions 2. Vespertilioiiidce. 



be Ear without tragus; in the extreme southwest 3. Molossidce. 



