59 
Ohio, Kentucky, Minnesota, and Nebraska. It is altogether 
likely that it occurs in larger or smaller numbers throughout the 
whole corn belt. 
INJURY TO CORN. 
The corn root louse is a suctorial insect, taking only fluid 
food through a stiff beak, which it thrusts into the tissues of 
the plant it feeds upon, producing thus no external injury, nor, 
indeed, any local internal effect discoverable by ordinary methods 
of observation. Indications of injury by this insect are conse- 
quentlv all of a general character, affecting the entire plant, and 
do not materiallv differ from those caused by severe drouth, ex¬ 
cept in the fact that they are likely to be unequal in different 
parts of the same field in a way to indicate no connection with 
the amount of retained moisture in the soil. 
A noticeably greater abundance in early spring in the lower 
parts of an infested field seems to be due to the greater abund¬ 
ance there of young weeds on which the corn root aphis feeds at 
first. As soon as the corn starts to grow it may become in¬ 
fested, and even be killed outright before it appears above 
ground. We have, in fact, found the root louse on the plant as 
early as May 9, only four days after the field was planted. 
The dwarfing of the plant, especially in patches here and there, 
with a yellowing or reddening of the leaves— beginning of 
course with the lowest ones — and a general apparent lack of 
thrift and vigor, are sufficient to cause suspicion of injury by 
this louse, a suspicion which will be confirmed in part if numer¬ 
ous burrows of ants are seen in or near the hills of corn. The 
presence of ants in the field may be overlooked after the ground 
has been recently cultivated, but can scarcely escape attention 
shortlv after a rain, when these little insects actively open up 
their burrows, heaping up the little pellets of earth about the 
openings of their nests. 
The appearances described may, nevertheless, be due either to 
the corn root blight—a disease not caused by insects, and hence 
not treated in this report—or to the grass root louse, a species 
likewise attended by ants, but far less injurious to corn than 
the aphis under discussion. If the damage be due to the root 
blight, the root lice themselves will be few or wanting;* and if 
to the grass louse, the fact may readily be ascertained by an 
examination of the roots of the corn. 
The root aphis of the corn is of a bluish green color, slightly 
whitened by a waxy bloom. The form of the body is oval, and 
on the hinder part of the back are two short, slender, but con¬ 
spicuous, tubes, standing erect or projecting slightly backwards, 
which may be seen by the glass to have open ends externally. 
These are called the cornicles of the aphis, or, sometimes, the 
“honey tubes,’’ it having been formerly supposed that they 
were the source of the abundant excretion upon which the ant* 
* See also page 54, b. 
