BIOLOGY IN HUMAN AFFAIRS 



these species. Plant physiologists with the newer knowl- 

 edge of biochemistry have many things still in store 

 for us that will add to the value and beauty of plant 

 products. 



Much of the best effort of science is directed toward the 

 reduction of the loss from insect pests and fungous diseases. 

 Along with the immigrants from across the ocean have 

 come many stowaways that we should have preferred to 

 have had stay at home. When the Hessian troops were hired 

 by King George to fight the colonists, they brought with 

 them straw from Germany to feed their horses. In this 

 straw, it is now supposed with good reason, were some 

 oval-shaped bodies about the size of a flaxseed. When spring 

 came, these inert cocoons took on life and hatched into clear- 

 winged flies whose progeny have done more damage than all 

 the armies that have ever marched on American soil. The 

 Hessian fly is one of the serious pests of wheat that has 

 been held somewhat in check because entomologists, 

 studying its life history, learned that the flies cease to lay 

 eggs after the first frost in the fall. The planting of winter 

 wheat is now timed, as nearly as is possible, so that the 

 plants will not be up until after frost. 



One can not ride far these days without being stopped 

 by inspectors looking for plants that may be carrying an 

 unsuspected foe. The European corn borer, the Japanese 

 beetle, and the Mexican bean beetle are now spreading 

 across the country with a persistence that seems to be im- 

 possible to check, just as in the past the Colorado bettle, 

 whose food was formerly the wild nettle, took to the 

 potato and spread wherever potatoes were grown in this 

 country. The cotton weevil, the pink bollworm, the cod- 

 ling moth, and the chestnut-blight disease have all entered 

 the country without our consent. Most of our serious plant 

 and animal diseases have come with their hosts when the 

 latter were introduced, but some have found other plants 



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