CHAPTER XI 



THEIR RELATION TO THE FARMER AND 

 FRUIT-GROWER 



IT was emphasized in another connection that insect 

 species that are naturally abundant are so because 

 they have made good their position and relative num- 

 ber as against all their checks, and so long as natural 

 conditions prevail they will maintain that abundance 

 with such slight seasonal variations as may be caused 

 by temporary favorable or unfavorable conditions. 



When civilized man enters the field, serious changes 

 in environment are produced and these changes are 

 produced faster than the insect and other life can adapt 

 itself to them. In a decade a wilderness is transformed 

 to a farm or an orchard, and the balance which it has 

 required centuries to establish is rudely upset. Those 

 species so nicely adjusted to their surroundings as to 

 barely maintain themselves under normal conditions 

 may be completely crowded out by the destruction of 

 some one factor that permitted survival, and, on the 

 other hand, conditions may be changed to favor such a 

 species, so as to permit it to increase out of all propor- 

 tion to its past history. 



The Colorado or zo-lined potato beetle, universally 

 known as the "potato bug," Doryphora io-!meata, was 

 not always the pest that it is at present. When first 

 discovered in the foot-hills of the Rocky Mountains it 

 was accounted rather a rare species, that barely main- 

 tained itself on the scattered indigenous solanaceous 

 plants. But when civilization brought in the cultivated 

 potato, the species that had been so rare that it had 



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