34 INTERRELATIONS OF PLANTS AND ANIMALS 



Damage done by insects. These trees have 

 been killed by boring insects. 



oak trees alone. Everywhere animals are engaged in taking their 

 nourishment from plants, and millions of dollars of damage is done 



every year to gardens, 

 fruits, and cereal crops 

 by insects. 



All Animals depend on 

 Green Plants. — But in- 

 sects in their turn are the 

 food of birds ; cats and 

 dogs may kill birds ; lions 

 or tigers live on still larger 

 defenseless animals as deer 

 or cattle. And finally 

 comes man, who eats the 

 bodies of both plants and 

 animals. But if we reduce 

 this search after food to its final limit, we see that green plants 

 provide all the food for animals. For the lion or tiger eats the 

 deer which feeds upon grass or green shoots of young trees, or 

 the cat eats the bird that lives on weed seeds. Green plants 

 supply the food of the world. Later by experiment we will prove 

 this. 



Homes and Shelter. — After a field trip no one can escape the 

 knowledge that plants often give animals a home. The grass 

 shelters millions of grasshoppers and countless hordes of other small 

 insects which can be obtained by sweeping through the grass with 

 an insect net. Some insects build their homes in the trees or 

 bushes on which they feed, while others tunnel through the wood, 

 making homes there. Spiders build webs on plants, often using 

 the leaves for shelter. Birds nest in trees, and many other wild 

 animals use the forest as their home. Man has come to use all 

 kinds of plant products to aid him in making his home, wood and 

 various fibers being the most important of these. 



What do Animals do for Plants ? — So far it has seemed that 

 green plants benefit animals and receive nothing in return. We 

 will later see that plants and animals together form a balance of life 

 on the earth and that one is necessary for the other. Certain 



