54 
The life history of none of these forms is completely known, our 
knowledge of the Chaitophorus and the Siphonophora being confined 
to the period of their appearance upon the foliage in summer. The 
root-louse and the corn plant-louse certainly commence their attack 
in spring, and continue, in some of their stages, throughout the 
season, the former infesting likewise several grass-like plants which 
are among the common weeds of corn and sorghum fields, but later 
commonly attacking only sorghum, corn and broom-corn. 
Both of these latter species are continuously attended by certain 
abundant ants which assist in their distribution and protect them 
from their enemies. ‘There is much reason to believe, also, that 
these ants render thém efficient service during the winter by trans- 
porting them to suitable quarters for hibernation, and it is probable 
that they spread them about again in spring and place them upon 
the roots of plants suitable for their food. 
Beyond the fact that the corn plant-louse is obviously much more 
numerous and destructive in fields that have been previously in corn 
or grass, we have at present no clue to preventive or remedial 
measures against these insects; but it is probable that a complete 
knowledge of their life history will enable us to construct a system 
of rotation which will restrain their multiplication, and keep their 
injuries within due bounds. 
By Dr. Thomas, the application of lime fertilizers to the soil is 
recommended for the purpose of preventing injuries by root-lice, but 
apparently more on theoretical than experimental grounds. The 
fact that one of the sorghum fields at Champaign most infested by 
plant-lice, and in which the older roots were thoroughly deadened, 
had been treated to a heavy dressing of superphosphates, indicates 
that this form of fertilizer, at any rate, would have no injurious 
effect upon the plant-lice. There is evident need of careful and 
systematic experiment with respect to the actual value of the appli- 
cation of any substance to the ground for the purpose of controll:ng 
the root-lice, which shall be sufticiently beneficial to the crop to pay 
the expenses of its use. 
