8 
always takes place, which can not fail to affect the tubers when it has 
oecurred practically without intermittence for periods of from twenty 
to forty years. 
FOOD PLANTS. 
A wild species of Solanum (vostratum, and perhaps also cornutum) 
is an original food plant of this potato beetle, and the latter is proba- 
bly incapable of developing for any number of generations on plants 
other than those of the potato or mghtshade family (Solanacez). 
The genus Solanum is preferred, and the potato, because of its greater 
succulence and less acrid taste, is now chosen in preference to plants 
that grow wild. Still, the insect is nearly always found where its 
wild food plants grow, particularly where poisons or repellents are 
used in near-by gardens. It feeds on practically all solanaceous 
plants, including eggplant, tomato, tobacco, ground cherry (Physa- 
lis), thorn apple, and Jamestown weed (Datura), henbane (Hyoscya- 
mus), belladonna, petunia, and pepper. The last is not often at- 
tacked, nor are the other plants of different genera from the potato, 
under ordinary circumstances. Occasionally, when none of these 
are to be had, the insect will feed on certain weeds and garden plants, 
among which are cabbage, thistle, and mullein. 
It was long ago ascertained that the tender-leaved varieties of 
potato are most affected, while other kinds, with less tender foliage, 
such as Peach Blow and Early Rose, are comparatively immune, more 
particularly when growing in the same field with the preferred 
variety. Even eggplant seems to be preferred to certain varieties of 
potato, and is consequently damaged at times, and tomatoes are sub- 
ject to injury when the foliage of potato is not available. 
GENERATIONS. 
The normal number of generations of the Colorado potato beetle 
is evidently two. In fact Tower” has observed that this number 
in both temperate and tropical latitudes is a remarkably constant 
generic character. In the course of his investigations he has not 
been able to get the present species to breed more than twice in 
a season without a period of hibernation or estivation. Person- 
ally the writer has never observed more than two generations in 
the District of Columbia. Years ago, however, Riley made the 
positive statement that this species is three-brooded in Missouri,’ and 
Lugger has made the same statement in regard to its development in 
Minnesota. Dr. J. B. Smith claims two generations in New Jersey, 
a Loe. cit., p. 243. 
6 First Annual Report State Entomologist Missouri, 1869, p. 107. 
[Cir. 87] 
