S HAD E T KR E E INSECTS 
INSECTS 
1. The insects, or the six-legged animals comprising the Class 
Insecta, are the most highly developed of the invertebrate animals. 
They include the smallest of the walking animals, and a greater 
variety of forms than all the rest of the animal kingdom com- 
bined. Man can learn many valuable sociological lessons by a 
careful study of some of these forms. 
2. It has been estimated on good authority that fully ten 
million species will be represented before the insect life of the earth 
is fully explored. New species are being described and named at 
the rate of about 10,000 a year, and the richest collecting grounds 
have hardly been touched. The total number named is rapidly 
approaching a million. 
3. Fortunately but a very small part of these are injurious, 
and many are beneficial. The American insects of special eco- 
nomic importance would hardly reach a thousand, and a tenth of 
these are responsible for the billion dollar loss sustained by the 
United States each year. Even ten of them are responsible for a 
loss each year greater than the total expense for the maintenance 
of the United States Department of Agriculture and all the experi- 
ment stations. 
4. This will give you an idea of the enormous loss that these 
pests are capable of inflicting, and will help you to see the great 
importance of knowing the more important insects that work on 
our shade trees. 
5. To control these pests, you must know their habits, the 
part of the trees attacked, the time when they are the most easily 
killed, the proper remedy to use, and the effect of the remedy upon 
the tree and upon the pest. This knowledge can come only by 
thorough study, hard work, close observation, and practical experi- 
ence. 
6. It would be helpful at this time to consider the structure 
and habits of the different types of insects, but this can be easily 
secured from your text books and general references on the subject. 
CLASSIFICATION 
7. For convenience in studying them, the insects will be classi- 
fied according to the nature of the injury which they inflict upon 
the trees. But to a certain extent this will also classify them ac- 
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