141 
number of insect pests, none are of much economic importance in 
this state except the Colorado potato-beetle, the wireworms, the 
flea-beetles, and the potato plant-louse. The stalk-borer (Papai- 
pema nitela) is also occasionally injurious to this crop. For a dis- 
cussion of this insect see pages 147-148. 
The Colorado Potato-beetle 
Leptinotarsa lo-lineata Say 
(Doryphora lo-lincata) 
This common and injurious species has doubtless caused greater 
damage to potatoes in Illinois than any other insect, and it is found 
on the vines in destructive numbers every year. It is a western 
species, its original habitat being the Rocky Mountain region. Its 
native food consisted of wild plants closely related to the potato, 
and when potato-culture reached its native prairies it promptly 
availed itself of the increased food supply thus afforded. It began 
its migration eastward, by way of the potato fields, about the year 
i860, reaching Illinois some fifteen years later. Except in the 
Pacific coast region, it is now found generally distributed thruout 
the United States and Canada, wherever the potato is grown. 
Fig. 34. Potato-beetle, Leptinotarsa lO-lincata: a, a. eggs; b, larvae, 
young and full-grown ; c, pupa ; d, adults ; e. wing-cover of 
adult; f, hind leg of adult. Natural size except 
c and /. 
The yellow and black striped beetle (Fig. 34, d, d) passes the 
winter in the ground, and makes its appearance early in spring. It 
feeds at first on the young potato plants if these are at once avail- 
able, or, if not, on some one of its wild food-plants. The sexes soon 
