Man often gets his knuckles rapped when he monkeys with the balance of nature. Starlings were introduced into the U. S. to crowd out English sparrows. Now the starlings are a great nuisance in some eastern cities, while the replacement of horses by automobiles hit the sparrows harder than the starlings did. When rabbits were taken into Australia they proliferated enormously for lack of natural enemies. Wholesale slaughter has not suppressed them. Australia also had a distressing experience with the prickly pear but in this case there was a happy ending. The prickly pear story, abstracted from a publication of...

