THE COLOEADO POTATO-BEETLE. 
151 
insect which, in its original home, seems to confine itself 
strictly to one species of plant, is a fact of considerable zoolo- 
gical interest. 
But this is not the only curious point in the natural history 
of the Colorado potato-beetle. It undoubtedly started on its 
eastward migration from the lower parts of the eastern side of 
the Rocky Mountain range, and probably the direction of its 
movement has been governed to a certain extent by that of the 
prevalent winds. But it is singular not only that the Dory - 
phora is unknown as a potato-eater west of the Rocky Moun- 
tains, but that according to the testimony of the inhabitants of 
the Colorado territory and other elevated parts of the range, 
the beetle is there perfectly true to its original food-plant 
(Solarium rostratum ), even in localities where potatoes are 
cultivated. And this fact becomes still more remarkable when 
we learn that the older States, especially towards the south, are 
inhabited by a species of Doryphora , very nearly allied to the 
potato-beetle, which feeds upon the so-called horse-nettle 
( Solarium carolinense ), and has never yet been known to 
attack the cultivated potato, although grown in its neighbour- 
hood for many years. This beetle, which has received from 
some American writers the euphonious name of the 46 Bogus 
Colorado Potato-bug,” from its having been frequently mistaken 
for the true malefactor, is the Doryphora juncta of Ghermar. It 
agrees closely with the Doryphora 1 0 -lineata in size, form, and 
general character, having the same number of black spots simi- 
larly arranged upon the pro thorax and the same number of 
black stripes upon the wing-cases ; but it may easily be distin- 
guished on close examination by its having the black stripes of 
the elytra margined by an impressed line (stria) containing a 
single row of punctures (fig. 6); by the third and fourth 
stripes, counting from the suture, being united at base and 
apex ; and by the legs being entirely pale, except a small black 
spot on the middle of each thigh in front. The larva also, 
although very similar to that of the potato-beetle in form, is of 
a lighter colour, has the whole of the first body-segment (pro- 
thorax) black, and only a single row of black spots along each 
side of the body. The presence of these two beetles side by 
side in the United States, their close agreement in external 
characters, and their difference in habits, may be expected to 
open a wide field of investigation in connexion with the ques- 
tion of the origin of species. We may obtain some valuable 
data if American entomologists will carefully collect every year 
specimens of Doryphora \0-lineata from various localities, so 
as to compare them, after some time has elapsed, with speci- 
mens of the same species from its original mountain home. 
There is one other matter in connexion with this new foe to 
