150 
POPULAR SCIENCE REVIEW. 
offered to them. In the long run probably a balance would be 
arrived at between the contending forces, but in the meantime 
the crops would be seriously affected, and the country would still 
always be liable (like our hop-gardens) to the occasional exces- 
sive multiplication of the destructive insects. Indeed with 
every confidence in the ultimate establishment of a balance of 
power between the western beetle and its enemies, the farmer 
could hardly be expected to look on with equanimity while his 
potato-fields were being ravaged ; and it is not surprising to 
find that the most various methods — some most absurd, others 
more or less judicious — of getting rid of the pest, should have 
been adopted. Of actual remedies— that is to say, means of 
destroying the insect after it has taken possession of the potato- 
plants— the best seem to be the use of sweeping and beating 
nets, or substitutes for the latter, into which the insects are 
beaten by some implement, such as a flat broom, and the dust- 
ing of the plants with a poisonous powder composed of Paris or 
Scheele’s green (arsenite of copper), mixed with from twelve to 
fifteen times its weight of flour or plaster of Paris. It is found 
that the use of this poison does not render the potatoes pro- 
duced by the plants treated with it unfit for food, but it seems 
still to be doubtful whether the potatoes grown afterwards in 
soil upon which it has been employed are not injured in their 
quality, and Mr. Riley strongly recommends that it should be 
used as sparingly as possible. In his opinion, the most valuable 
remedial measures consist in the adoption of certain precautions 
in the selection of sorts for planting, and especially in the 
exercise of great vigilance in the spring of the year, placing 
in the newly-planted fields small heaps of potatoes to which 
the beetles are attracted on emerging from the ground, and 
from which they may easily be gathered every morning, and 
destroying as many as possible of the eggs and young larvae of 
the first brood. By these means it would appear that the 
increase of this new scourge of the potato may at least be 
considerably checked. 
At the same time there is one circumstance in the history of 
the insect which will probably stand in the way of its being 
effectually controlled. In their progress through a civilised 
country the beetles have cast off the simplicity of their western 
ancestors, and having once changed their food-plant, have now 
tried many other articles of diet, and found some of them highly 
congenial to their taste. Besides various Solanacese growing 
•wild, they have been observed feeding on species of Echino- 
spermum , Amaranthus , Helianthus , Cirsium , Sisymbrium , 
Polygonum , Chenopodium , Eupatorium , and Hyoscycimus , 
and on grass, oats, the red currant, and even the cabbage. This 
plasticity of appetite, if it may be so termed, acquired by an 
