634 The Animal Kingdom 



are represented, including Sorex, Blarina, and Microsorex. Sorex cin- 

 ereus, the masked shrew, is only 80 to 109 mm. long and weighs less 

 than 6 grams. This intensely active mammal is constantly on the search 

 for food to maintain its exceptionally high rate of metabolism. One 

 captive female was observed to eat three and three-tenths times her 

 weight in food in a twenty-four-hour period. No doubt this voracious 

 appetite makes these animals exceptionally valuable as destroyers of 

 noxious insects, small mice, and larvae. 



The Old World, too, has its complement of insectivores, including 

 the hedgehog, the water shrews, tree shrews, elephant shrews, and the 

 golden mole of South Africa. 



Order Dermoptera. — This order includes the flying lemurs, Cyno- 

 cephalus, of the family Cynocephalidae, which are found in the East 

 Indies, southeast Asia, and the Philippines. In appearance these forms 

 resemble the flying squirrels of this country, but they have doglike 

 faces and the flying membrane is more extensive. These nocturnal ani- 

 mals live on fruits and leaves. 



Order Chiroptera.— The only mammals that are able to fly are 

 the bats. The front limb of these interesting mammals has enormously 

 elongated fingers between which is spread the thin leathery skin. This 

 functions as a wing to support the small body in the air. These rapidly 

 flying bats are poorly equipped so far as vision is concerned. To com- 

 pensate for this, they have acute auditory and tactile senses. Thus 

 they find their way about by means of a unique mechanism. They con- 

 tinuously emit supersonic sounds from the mouth ; these sounds bounce 

 against objects and are perceived by the bat. By means of this "radar" 

 apparatus, the bat can fly by its echoes which it emits about thirty times 

 a second. 



Nearly all bats are either insectivorous or frugivorous, but a few 

 of the tropical vampires feed on the blood of other mammals. 



Order Primates. — Structurally the primates are in many ways a 

 very generalized group of animals. The limbs are quite elongate, the 

 hands and feet are somewhat enlarged, and they are provided with five 

 digits having nails. The toe and thumb are usually opposable, thus 

 fitted for grasping and climbing. Most are arboreal in habit and 

 bear but a single young at birth. They are chiefly tropical and sub- 

 tropical in distribution. The chief distinction of this group is their 

 possession of the best developed cerebrum of any animals. 



