Vespertilionines are wide-ranging. The bamboo bat (Ty-lonycteris pachypus) and African banana bat (Pipistrellus nanus) are not only the smallest in the subfamily at about 0.1 oz (3 g) in weight, but also two of the tiniest bats in the world. At the opposite end of the spectrum is the subfamily's largest member: the large mouse-eared bat (Myotis myotis) with its nearly 14-in (35-cm) wingspan.
Although a large number of vespertilionines are brown, a few are frosted with silver, yellow, or reddish tips. The hoary bat (Lasiurus cinereus), for example, has a luxuriant pelage highlighted in white. Fur in other species within this subfamily may be golden like that of the yellow bat (Rhogeessa anaeus) of Belize, ginger and white like that of Welwitch's hairy bat (M. welwitschii) of Africa, or vivid orange like that of Myotis formosus of Southeast Asia.
Vespertilionines have some features in common. All lack the fleshy nose ornaments common to so many other bat families. In fact, the family Vespertilionidae is often called "the plain-faced bats." Most of the vespertilionines also have small eyes, although a few, such as the pallid bat (Antrozous pallidus), have noticeably larger eyes. Ear size can be small or large, with many species having tiny, rounded ears smaller than their head while others have enormous ears that extend almost the length of their bodies. The long-eared bat
(Plecotus auritus) has extraordinarily long ears, but it can tuck them so far under the wing (done during the daily sleep and in hibernation) that only the pointed ear cover (tragus) can be seen.
Other distinctive features of vespertilionines—indeed all species within the family Vespertilionidae—are a well developed tragus that reaches up from the base of the ear, and a nearly naked patagium, or flight membrane, that covers the relatively long tail. Vespertilionine tails are commonly half as long as the body.
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