CHAPTER XIII 

 INSECTS IN RELATION TO MAN 



A great many insects, eminently successful from their own standpoint, 

 so to speak, nevertheless interfere seriously with the interests of man. 

 On the other hand, many insects are directly or indirectly so useful to 

 man that their services form no small compensation for the damage done 

 by other species. 



Injurious Insects. Insects destroy cultivated plants, infest do- 

 mestic animals, injure food, manufactured articles, etc., and molest or 

 harm man himself. 



The cultivation of a plant in great quantity offers an unusual oppor- 

 tunity for the increase of its insect inhabitants. The number of species 

 affecting one kind of plant to say nothing of the number of individuals- 

 is often great. Thus about 200 species attack Indian corn, 50 of them 

 doing notable injury; 200 affect clover, directly or indirectly; and 400 

 the apple; while the oaks harbor probably 1,000 species. 



The average annual loss through the cotton worm, 1860 to 1874, was 

 $15,000,000, according to Packard; the loss from the Rocky Mountain 

 locust, in 1874, in Iowa, Missouri, Kansas and Nebraska, $40,000,000 

 (Thomas); and the total loss from this pest, 1874 to 1877, $200,000,000. 

 The loss through the chinch bug, in 1864, was $73,000,000 in Illinois 

 alone, as estimated by Riley. The ravages of the Hessian fly, fluted 

 scale, San Jose scale, gypsy moth and cotton boll weevil need only be 

 mentioned. 



At times, an insect has been the source of a national calamity, as was 

 the case for forty years in France, when Phylloxera threatened to ex- 

 terminate the vine. In Africa the migratory locust is an unmitigated 

 evil. 



Probably at least ten per cent, of every crop is lost through the at- 

 tacks of insects, though the loss is often so constant as to escape obser- 

 vation. Regarded as a direct tax of ten cents upon the dollar, however, 

 this loss becomes impressive. Webster says: "It costs the American 

 farmer more to feed his insect foes than it does to educate his children." 

 The average annual damage done by insects to crops in the United States 

 was conservatively estimated by Walsh and Riley to be $300,000,000 



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