~The Colorado Potato-Bug~, (_Doryphora_ 10--_lineata_, Say.)--This insect, which, according to Dr. Walsh, has in the North-West alone damaged the potato crop to the amount of one million seven hundred and fifty thousand dollars, came originally from the Rocky Mountains, where it was found forty-five years ago, feeding on a wild species of potato peculiar to that region, (_Solanum rostratum_, Dunal.) When civilization marched up the Rocky Mountains, and potatoes began to be grown in that region, this highly improved pest acquired the habit of feeding upon the cultivated potato. It went from potato-patch to potato-patch, moving east-ward at the rate of about sixty miles a year, and is now firmly established over all the country extending from Indiana to its old feeding-grounds in the Rocky Mountains. In about twelve years it will have reached the Atlantic coast. There is another very closely allied species, known as the Bogus Colorado potato-bug, (_coryphora juncta_, Germor,) which has existed throughout a great part of the United States from time immemorial. This latter insect, however, feeds almost exclusively on the horse-nettle, (_Solanum carolinense_, Linn.,) and is never known to injure the potato. Both insects are figured, so that one need not be mistaken for the other. Figure 14, _b_, _b_, _b_, gives a view of the larva of the true Colorado potato-bug, in various positions and stages of its existence. Figure 15, _b_, _b_, of that of the bogus Colorado potato-bug. It will be seen at once that the head of the former is black, and the first joint behind the head is pale and edged with black behind only; that there is a double row of black spots along the side of the body; and that the legs are black. In the other larva, (Fig. 15, _b_,) on the contrary, the head is of a pale color, the first joint behind the head is tinged with dusk and edged all round with black; there is but a single row of spots along the side of the body, and the legs are pale. Figure 14, _d_, _d_, exhibits the true Colorado potato-bug; Figure 15, the bogus Colorado potato-bug; each of its natural size. Figure 14, _e_, shows the _left_ wing-case enlarged, and Figure 15, _e_, an enlarged leg of the latter. On a close inspection, it will be perceived that in the former (Fig. 14, _e_) the boundary of each dark stripe on the wing-cases toward the middle is studded with confused and irregular punctures, partly inside and partly outside the edge of the dark stripe; that it is the third and fourth dark stripes, counting from the outside, that are united behind, and that both the knees and feet are black.