58 
IMPORTANT AND FAMILIAR INSECTS 
wings. Some insects are parasitic and lead dependent lives. 
Insects feeding on plants which we wish to eat are called 
harmful. Others, like the honey-bees and silkworms, which 
make products that we use, are beneficial. Insects such as 
ticks and lice, that injure our domestic animals, are harmful. 
Then there are the beautifully colored moths and butterflies 
whose larvae never become numerous enough to do much 
damage; we say that they are beneficial because we get 
pleasure from their beauty. 
The whole question of what is beneficial or harmful depends 
on the relation of the insect to man. Insects living on an 
uninhabited island could not be thus classified. In the 
earlier stages of our civilization, many insects now regarded 
as harmful were not so classified, because man had not learned 
to use the plants upon which they fed. The important 
relation which insects bear to disease has, in recent years, 
caused us to classify several insects as harmful which were 
not so considered earlier. 
Insects, like man, are constantly undergoing a struggle 
to escape their enemies and to secure food and a place to 
live. It is interesting in this biological study to try to 
view ourselves in the same unprejudiced way in which we 
study the lower animals; it helps us to understand 
ourselves, and to go forth better equipped to wage our 
contest and win our fight. 
QUESTIONS 
Explain the difference between beneficial and injurious insects. 
Which are some of our most beneficial insects? How do they help 
us? 
How did they help to save the orange industry of California? 
How do fruit growers spray their trees? Why? 
What can you do to prevent harmful insects from spreading? 
Describe the habits of ants and compare with honey-bees. 
Name the common flies. What are their food habits ? 
Compare the life history of fly and mosquito. 
