326 
WISCONSIN STATE AGRICULTURAL SOCIETY. 
THE COLORADO POTATO BUG. 
(Doryphora 10 -lineata, Saj.) 
[From the American Entomologist.] 
BY CHARLES V. RILEY. 
Up to the autumn of 1865, it was generally supposed by 
Economic Entomologists, that this destructive insect had exist¬ 
ed from time immemorial in the northwestern states, feeding 
upon some worthless weed or other; and that of late years, 
from some unexplained cause, it had all of a sudden taken to 
attacking the potato plant. In October, 1865, the senior editor 
of this journal published a paper, showing that originally its 
exclusive home was in the Rocky Mountains, where it had 
been known to exist for at least forty-five years, feeding upon 
a wild species of potato peculiar to that region {Solarium ros- 
tratum , Dunal); that when civilization march up to the Rocky 
Mountains and potatoes began to be grown in that region, it 
gradually acquired the habit of feeding upon the cultivated 
potato; that in 1859, spreading eastward from potato patch to 
potato patch, it had reached a point one hundred miles to the 
west of Omaha city, in Nebraska; that in 1861 it invaded 
Iowa, gradually in the next three or four years spreading east¬ 
ward over that state; that in 1861 and 1865 it crossed the 
Mississippi, invading Illinois on the western borders of that 
state, from the eastern borders of north Missouri and Iowa, 
upon at least five different points on a line of two hundred 
miles; and that in all probability it would in future years 
“travel onwards to the Atlantic, establishing a permanent col¬ 
ony wherever it goes, and pushing eastward at the rate of 
about fifty miles a year.” A remarkable peculiarity in the east¬ 
ern progress of this insect was subsequently pointed out by the 
same writer in 1866, namely, that “ in marching through Illi 
