BIOLOGY IN HUMAN AFFAIRS 



of the particular insect concerned. Several successful 

 attempts of this sort have been made, such as the introduc- 

 tion of an Australian beetle into California to destroy a 

 scale insect (an aborigine of Australia) which seemed sure, 

 otherwise, to destroy the orange groves, and the use, in 

 New England, of European foes of the gypsy moth. There 

 are special laboratories of the Bureau of Entomology 

 dedicated to this work, where experimentation is now 

 being done on a great variety of foreign species, any one 

 of which may prove to be of the greatest economic value, 

 once the biological problems involved have been worked 

 out. 



It has been estimated that natural forces, including 

 insect enemies, unfavorable seasons, and bacterial diseases, 

 serve — on the average — to prevent about 90 per cent of the 

 damage to agriculture that insects would do if unchecked. 

 But it is the remaining 10 per cent that often makes the 

 difference between the farmer's profit and loss. Thus, 

 economic zoology is really concerned with providing the 

 relatively small amount of artificial aid which is needed to 

 supplement the normal amount of natural control. It is 

 this situation that makes practically effective the measures 

 of protection, which at first sight seem ridiculously inade- 

 quate in the face of the swarming billions of the enemy. 

 It is indeed a narrow margin that exists between victory 

 and defeat in this contest; and some of the experts most 

 competent to judge believe that human welfare, even 

 human existence, will, in the end, depend upon its out- 

 come. Insects will very likely prove to be the most formi- 

 dable contestant with man for the ultimate possession of 

 the earth. As time goes on, all the resources of science will 

 be needed in this strife, just as they are now employed in 

 war between human enemies. Already aeroplanes are being 

 used to spread poisonous dust over large areas of growing 

 crops; poison gas is applied in confined spaces, such as 



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