CHAPTER XI. 



PRINCIPLES OF ECONOMIC ENTOMOLOGY. 



While it cannot be assinned that we have at present a 

 complete knowledge of those underlying principles which 

 are to be recognized in the prevention or control of insect 

 ravages, enough has been done to make an attempt at a 

 brief statement of such principles in order. Many of these 

 principles have been stated in greater or less detail in the 

 writings of different entomologists but no comprehensive 

 statement has been attempted — especially since the marked 

 advances of the past quarter-century. Applied entomology 

 today is a totally different structure than that which 

 existed twenty or even ten years ago. In many respects it 

 is getting nearer to the fundamental laws of biology, and 

 there is a more general appreciation that its successful appli- 

 cation involves thorough acquaintance with biological prin- 

 ciples. In the broadest sense economic entomology involves 

 a recognition of the relation existing between insects and 

 other organisms, but finally, the relation they bear to the 

 human species. 



RELATION OF INSECTS TO OTHER ORGANISMS. 



Considering the great multiplicity of insect forms, their 

 world-wide distribution in almost every condition open to 

 the su])port of life, it is not strange they occupy a most 

 important relation to other organisms. This relation may be 

 serviceable or inimical, directly or indirectly from the 

 stand-point of any particular organism, and may indeed 

 differ totally at different times or under different conditions. 

 From the stand-point of any particular species it is detri- 

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