178 FORESTS AND MANKIND 



The inhabitants of a large sized ant hill may destroy a hundred 

 thousand forest enemies in a good day's hunting. 



Protecting our forests from these harmful organisms is an 

 important phase in man's conquest of the earth. It is part of 

 the battle that man is waging against hostile insect life through- 

 out the world. Some writers believe the fate of all mankind 

 hinges upon his ability to conquer his insect enemies. They 

 believe the world will some day become a battleground between 

 man with his scientific equipment on one hand, and insects 

 with their enormous powers of reproduction on the other. 

 Whether or not that critical time will ever come belongs to the 

 future. But it is a matter of history that many parts of the 

 tropics remained uninhabitable to white men until certain 

 harmful insects were destroyed. And there is no doubt that 

 today foresters in their fight for forest perpetuation are finding 

 it increasingly important to wage warfare against injurious 

 forest insects. 



The question naturally suggests itself. "But why has it sud- 

 denly become necessary for man to protect the forests from 

 insects? What happened when no men were here to protect 

 them?" 



In those days very probably, large areas of timberland were 

 from time to time stripped of forest growth by insects as they 

 rose in sudden waves of invasion. Slowly nature seeded in 

 those areas and the results of the ravages disappeared. Such 

 invasions probably happened whenever conditions became for 

 the time especially favorable to the rapid multiplication of any 

 particular kind of injurious insect. Later their numbers de- 

 creased again because of increased activity on the part of their 

 enemies, or because those favorable conditions ceased to exist. 



