bstance of the leaf, and goes
under ground to assume the pupa state. It passes through all its stages
in about a month, and there are two or three broods of them in the
course of the same season. This is emphatically the greatest insect pest
that the potato-grower has to contend with in Pennsylvania. It abounds
throughout most of the Northern, Middle, and Western States. Large
fields of potatoes can any summer be seen in the Middle States much
injured by this minute insect, every leaf apparently completely riddled
with minute round holes, and the stalks and leaves appearing yellow and
seared. Plaster frequently and bountifully applied is sure to prevent
the attacks of this insect, or to disperse it after it has commenced
operations.

~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