CHAPTER IX 



OUR INSECT FOES RAVAGERS OF 

 CROPS 



OUR very numerous insect foes may be 

 roughly classed under two heads, namely, 

 those insects which when allowed to increase in 

 numbers become the ravagers of crops ; and 

 those insects which are the transmitting agents 

 of disease to man and his flocks. 



Let us first try to realize why certain species 

 of insects have, as the ravagers of crops, become 

 the foes of mankind. But a little careful and 

 discriminate observation is required to bring 

 home the fact that in practically every instance 

 these insects have become the foes of man 

 through his violation of the laws of Nature, 

 either wilfully or in ignorance. While it is very 

 difficult and of rare occurence under absolutely 

 natural conditions for vast swarms of plant- 

 destroying insects to suddenly appear, nothing 

 is easier in the artificial conditions produced by 

 man. The web oi natural life is so wonderfully 

 adjusted that all the species, both plant and 

 animal, making up that environment, are asso- 

 ciated together in such a way that the excessive 

 multiplication of a single species, either plant or 



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