368 READINGS IN BIOLOGICAL SCIENCE 



all tied together in a circle of mutual dependence and should one factor 

 get out of balance, someone will have to pay for it. 



MAN AND NATURE * 



R . T . YOUNG 



An ardent French entomologist in Medford, Mass., was one day eagerly 

 inspecting some caterpillars which he had reared from eggs brought by him 

 from Europe, when some of them, growing tired of his society, made their 

 escape and went on their way rejoicing. This was in 1869. From 1890- 1900 

 Massachusetts spent about $1,000,000 to fight the gypsy moth. At this time 

 the pest being partly under control the efforts were relaxed, with the in- 

 evitable increase of the pest, and its further spread over a large part of New 

 England and into Canada. 



In 1850 caterpillars were devouring the trees of the eastern United States. 

 But in England there was a merry, if not melodious little sparrow, who was 

 supposed to enjoy nothing so much as a meal of luscious juicy caterpillars, 

 and so what was more natural than to bring sparrows from the old world 

 to enjoy the rich feasts of caterpillars provided by the new? Today he has 

 spread over all of the United States and much of Canada, and is emulating 

 the example of his fellow countrymen by driving before him many of the 

 native inhabitants and inheriting their patrimony. 



Inhabiting the wheat fields of the greater part of the United States is a 

 little fly known as the Hessian fly, about an eighth of an inch long, which 

 lays its eggs on the leaves of the wheat, and whose larvae as they hatch crawl 

 down the stem, burrow into it, and kill the plant. This fly is supposed to 

 have come to America as an unintentional ally of King George with his 

 Hessian soldiers; hence its name. Another immigrant which came to us in 

 Revolutionary days was the brown rat. 



This rat first crossed the Russian frontier of Asia in 1727 in such numbers 

 that it soon overran Europe, whence it came to America. With the rat came 

 its parasite, the deadly Trichina, while more recently the yet more deadly 

 bacillus of the bubonic plague has become established in California, brought 

 in by rats from oriental ports. What a pity we cannot return to Europe with 

 our compliments all of the undesirables, four-legged, as well as two-legged 

 and winged ones as well! 



To kill a hawk is, in the minds of most of us, a laudable act for are not all 

 hawks "hen hawks," the inveterate enemies of the poultry men? So at least 

 thought the farmers in the Humboldt valley in Nevada, which in 1907 was 

 visited by a plague of mice, which ate up everything in sight, gnawing the 

 bark from fruit trees, burrowing in the alfalfa fields and destroying the 



* From Biology in America by R. T. Young, copyright 1922 by Chapman and 

 Grimes, Boston. 



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