BIOLOGY FOR HIGH SCHOOLS 
PART I 
ANIMAL BIOLOGY 
CHAPTER I 
THE GRASSHOPPER, AN INTRODUCTION TO THE 
STUDY OF INSECTS 
1. Variety of Animal Life. — There are more than six 
hundred thousand kinds of animals in the world. Of this 
large number nearly four hundred thousand kinds are in¬ 
sects. Insects are so widely distributed, have such a great 
variety of form and color, and are so numerous that the age 
in which man lives is sometimes called the age of insects. 
While insects do not have any representatives that are 
large, compared with dogs or horses, they make up in number 
what they lack in size. 
Man’s greatest competitor for the domination of the earth 
has been not the lions, rattlesnakes, or other large enemies, 
but the hosts of small animals of which the insects form the 
largest class. The building of the Panama Canal was as 
much a triumph over the disease-carrying mosquito as it 
was an engineering feat. Even to-day, many parts of the 
earth are uninhabitable because of mosquitoes. 
The potato beetle, the chinchbug, the scale insects, the 
codling moth, the gypsy moth, the grasshopper, the army 
worm, and many others are taking a heavy toll each year 
from the world’s food crop. The activities of these insects 
make food prices higher and it is in the interest of food con- 
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