Simultaneously, and in a similarly careless way, various animals gained entrance and be came pests, among them innumerable injurious insects. One of the most noticeable of the early invaders of this kind was the Hessian fly. The famous gypsy moth began here with escapes from an entomologist's collection near Boston in 1869. Among higher animals the house-mouse and black rat came across the Atlantic in early days, the brown rat previous to the Revolution, and these have become troublesome and even dangerous everywhere. (See RAT). Later, unwise persons imported the European se sparrow ("English" spar row), about 1851. A few years later the sky lark, European goldfinch and some other birds were introduced, but fortunately have not be come naturalized. Starlings were set free in New York city in •1890, bred abundantly and threaten to become a costly nuisance. Rabbits are common in domestication, but by good fortune have not colonized wild, as has hap pened so disastrously in Australia. Lapp rein deer have been colonized in Alaska to the great advantage of the Eskimos there.
A few years ago the United States govern ment, warned by naturalists, began to realize the danger in further invasions of this kind, and laws were passed requiring inspection of every plant and animal brought into the coun try, to make sure that some new and harmful insect or disease did not come with them; and prohibitions were made against the importa tions of foreign animals, especially certain dreaded ones, as the mungoos. These precau
tions are in the hands of the Department of Agriculture, and have been highly beneficial in their purpose and effect.
It was formerly believed that human in vasions had taken place in prehistoric times on a large scale. Some of the theories, as of ar rival of peoples from Egypt, or India, or Poly nesia, or Japan, were highly fanciful; but more reasonable was the belief that this continent was populated by the invasion, thousands of years ago, of immigrants from Asia by way of Siberia and Alaska. It is not to be denied that something of the sort may have taken place in the very remote past on an extended scale, but there is no direct evidence of it, either then or more recently.
Osborn, 'Age of Mam mals' (New York 1910); Scott, 'History of Land Mammals in the Western Hemisphere' (New York 1913) ; and histories of the economic development of the United States.