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POPULAR SCIENCE REVIEW. 
settled and cultivated tract, and the settlement of the territory 
of Nebraska carried cultivation, and with it the potato, into the 
district inhabited by the Doryphora . The insect was not long* 
in taking advantage of the abundant supply of suitable food 
thus offered to it. In fact, we may with some justice assume that 
it found in the cultivated potato a nourishment better adapted 
to its wants than that furnished by the native plant on which 
it had previously fed ; for it seems to have set out almost imme- 
diately in the direction of the more highly cultivated districts, 
and spread eastward with great rapidity. 
In the year 1859 it was still far west, being then at a distance 
of 100 miles west of Onaha city, in Nebraska; but within two 
years (in 1861) it reached the state of Iowa, over which it 
spread completely in about three years, and in 1864 and 1865 
did great mischief to the crops. During these years the beetles 
were also very destructive in the state of Missouri, and in 1864 
and 1865 they crossed the Mississippi and invaded Illinois in 
great force, causing much injury to the potatoes in the north- 
western part of that State. A branch migration northwards 
commenced in 1862, when the beetle made a settlement in 
the south-west corner of Wisconsin ; by 1866 it had spread over 
the whole State. During the next two years it completed its 
occupation of Illinois, and in 1867 passed thence into Indiana 
and the south-west angle of Michigan, where it was very abun- 
dant in 1868. In this year its presence was noted in Pennsyl- 
vania, but it was not until 1871 that the Quaker State was 
fairly invaded by the western beetle. In this year the beetles 
swarmed about Detroit, at the south-eastern angle of Wiscon- 
sin, and great numbers of them are said to have been carried 
down with floating rubbish and on board ship into Lake Erie, 
to be wafted along that sheet of water and landed on the Cana- 
dian shores, and on the shores of New York and Pennsylvania 
at the opposite end of the lake. In 1871 also it was reported 
as doing mischief to the potatoes in Ohio; and in 1873 it had 
crossed Pennsylvania and reached the district of Columbia, near 
Washington, and almost to the shores of the Atlantic near 
Baltimore. In the meantime the northern migration had 
carried the pest through Wisconsin into Minnesota and Dakota ; 
and through Michigan into Canada, where it made its appear- 
ance in 1870. Its transportation into Canada was in part 
effected by means of the shipping on the lakes. In the south 
•also Kentucky and western Virginia were invaded in 1871 and 
1873. 
In the year 1868, when the western potato-beetle had 
reached the centre of Indiana, Mr. B. D. Walsh estimated the 
rate of its advance at about 60 miles a year, and upon this 
foundation predicted that it would reach the Atlantic coast 
