CHAPTER I 

 THE ABUNDANCE OF ANIMAL LIFE 



' Most persons do not realize what an enormous number of 

 animals exist on the earth, and what a variety of habitats 

 they occupy. The forest not only harbors monkeys, 

 squirrels, tree frogs, and other familiar animals which are 

 suited to such a situation, but also supports a host of 

 minute insects, worms, snails, and other things which 

 escape ordinary notice. Many of these are active only at 

 night, on humid days, or on various infrequent occasions. 

 The fields and prairies have a characteristic fauna of 

 prairie-dogs, grasshoppers, antelope, etc. Lakes, ponds, 

 and streams swarm with aquatic animals. Particularly 

 in winter, bodies of water serve as refuges for many animals 

 which may be found elsewhere during warmer seasons. 

 Some animals, such as the mole, the mole-cricket, and the 

 earthworm, pass their whole lives burrowing in the soil, and 

 show structural adaptations which fit them particularly for 

 such a habitat. 



Unsuspected residents may occur in all sorts of situations 

 and in countless numbers. Darwin was once interested 

 in the distribution of animals and plants on the feet of birds. 

 In this connection he tried to ascertain how many living 

 things there were on the muddy shore of a little puddle. 

 From three spoonfuls of mud he raised 537 separate plants. 

 More recently one of the investigators for the United States 

 Department of Agriculture, in studying the food of birds, 

 took a census of all the animal and plant objects in a space 

 two feet square and as deep as a bird might scratch, with 

 the following result: 



Animal Plant 



objects objects 



Forest 112 194 



Meadow.. 1254 3113 



