140 THE BALANCE OF NATURE. 



of the Rocky Moniit;iijis allied to the potato, 

 though much more slirubby ; but, as soon as cul- 

 tivation in its westward development brought the 

 true tuber-bearing plant, with its succulent stem 

 and leaf, within reach of the Colorado beetle, 

 that enterprising insect, struck immediately by 

 its close resemblance to his ancestral food, ob- 

 served to himself, in a thoughtful fashion, "I 

 shouldn't be surprised if I could live upon that 

 new-fangled })lant there quite as well as upon the 

 original solanum." He tried the experiment, and, 

 to the horror of all America, it succeeded admira- 

 bly. Thenceforward the Colorado beetle became 

 a power in the world ; legislatures enacted statutes 

 to his prejudice, and foreign governments watched 

 their ports to prevent his entrance as jealously as 

 if he liad been a friend of humanity with a hun- 

 dredweight of dynamite in a small black port- 

 manteau. 



All nature is one vast network of such contin- 

 uous and ceaseless interactions. Kill off the spar- 

 rows or other small birds, and the grubs, worms, 

 and insects increase enormously. In return, the 

 plants and fruits suffer; there are no gooseberries, 

 no currants, no lettuces, and very few green peas. 

 Drain the fens, and j^ou upset the balance of life 

 for a whole district. With the water go the 

 fishes and water-weeds, the pond-snails and pond- 

 beetles. Where there are no fish there can be no 



