CHAPTER XV 
IMPORTANCE AND CHARACTERISTICS OF INSECTS 
Way Insects ArE ImMporRTANT 
Damage Done. — There are about us on every hand — 
on the ground and on plants, in the air and in the water — 
numberless insects that are usually thought unworthy of 
serious notice. But our food supply often depends upon 
the presence or absence of some species of these tiny creatures. 
Practically all plants cultivated by farmers and gardeners 
are subject to insect attack. The potato beetle, chinchbug, 
Hessian fly, and grasshopper are familiar crop pests. The 
total damage to vegetation each year in the United States from 
insects has been estimated at $700,000,000 to $800,000,000. 
It is often necessary for us to combat these foes of vege- 
tation, and to do this intelligently requires a knowledge of 
their nature and habits. We should therefore consider it 
worth while to learn something about this branch of the 
animal kingdom. 
Their Numbers.— The number and variety of insects 
is enormous. More than 300,000 species have already been 
named by specialists. No one person could ever become 
acquainted with all of these. If he studied ten new species 
every day, and worked 300 days a year, it would take him 
too years to go over all of them just once. But it is esti- 
mated that these 300,000 include only a fifth or possibly 
only a tenth of those living through the world. About 95 
per cent of all the species of animals are insects. Moreover, 
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