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through the regulation of temperature and humidity, the said enemies 

 could be held in check. 



A far more direct threat to mankind lies, however, in the fact that its 

 perpetuation is dependent upon an incessant supply of food which is 

 ultimately provided by agriculture. It goes without saying that our 

 cultivated plants also furnish a basis for the existence of numerous 

 other forms of life, so that both the crops in the field and the harvest 

 products during storage are incessantly subject to attack by non- 

 human organisms. It is impossible to overemphasize the fact that in 

 this respect the dangers have enormously increased during the past 

 century. Owing to the large increase in population an ever expanding 

 part of the earth's surface has been brought under cultivation ; and 

 as a result the vegetation has taken on a more and more one-sided 

 character. This implies that pestilences, once they get a foothold in 

 some cultivated crop, may spread in a more or less avalanche-like 

 manner, entailing catastrophic consequences for mankind. 



As early as 191 5 the American entomologist, Johnston, declared 

 that the next war would be fought by humans against insects. And, 

 although this prophecy has only partially been fulfilled, nobody who 

 has taken cognizance of L. O. Howard's book, 'The Insect Menace' 

 published in 1931, can avoid the conclusion that it is imperative for 

 humanity's High Command to concentrate more than hitherto on 

 the war against insects. 



Howard, the long-time Head of the U.S. Department of Agric- 

 ulture's Bureau of Entomology, first of all points out that palaeon- 

 tological data leave no doubt that insects have maintained themselves 

 on earth for at least forty million years, and probably much longer, 

 whereas during this epoch many other animal species have disap- 

 peared. In contrast, the human population probably extends over not 

 more than 500,000 years, and hence, geologically speaking, is merely 

 in an experimental stage. Besides, qualified experts estimate the total 

 number of insect species now populating the world at 2-10 million, 

 of which the entomologists have described less than a tenth part. 

 Even though as yet the number of species that has attacked man and 

 his produce on a large scale is relatively small, one shall have to reck- 

 on with the probability that among the still unknown species many 

 potential enemies of mankind may be hidden which at any moment, 



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