BATS 



Family Vespertilionidae ^ 



This family includes most of the species of Bats found in 

 North America, north of the Rio Grande. The members of 

 the Vespertilionidse are among the most highly specialized of 

 the entire order and have progressed farther from terrestrial 

 mammals than most of the other families of Bats, with respect 

 to the greatly developed flight mechanism. Only two other 

 families, the Molossidae and the Mystacopid^e, display an equal 

 degree of flight perfection, and even these two families lack the 

 extreme subordination of the ulna seen in the Vespertilionidce. 



Species of the Vespertilionidae are characterized by absence 

 of leaf -like outgrowths on muzzle and lips; separate ears (in 

 most genera), with well-developed tragi which are straight or 

 slightly curved; only two bony phalanges in third finger; 

 absence of sucking disks on sole and thumb ; wide interf emoral 

 membrane; long tail which reaches to edge of interf emoral 

 membrane but never extends much beyond it or becomes free. 



The most diagnostic internal characters are a highly de- 

 veloped double articulation between scapula and humerus; 

 greatly reduced ulna ; shoulder girdle and pelvis unmodified in 

 fundamental details ; teeth normal (insectivorous) ; a con- 

 spicuous emargination at the anterior end of the bony palate. 



The vespertilionids are mainly small to medium-sized Bats 

 and none of them (in North America) attain the size of some 

 of the Phyllostomidas of tropical America. The Vespertilio- 

 nidae are very widely distributed geographically, cosmopolitan 

 in fact, and are found in greatest number of species in the 

 Northern Hemisphere. 



While some of the North American species of the Vesperti- 

 lionidae are social in habit and may be found associated in 

 good-sized colonies, many of the species are found only in small 

 numbers, and in temperate regions the Bat population seldom 

 appears to be very large. Some of the forms are definitely 

 known to be migratory, others are suspected to be so, while 

 still others are found hibernating where winters are severe. 



All of the North American members of the Vespertilionids 

 are strictly insectivorous in diet. 



^ See G. S. Miller, Jr., North American Fauna, No. 13, 1897, for a 

 revision of the Vespertilionidae of North America. Many species have 

 been described, however, since this paper was published. 



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