184 PLANT LICE. 
Prof. Oestlund during May found these lice on Craetegus 
tomentosa, where they caused the leaves to curl very much, and 
turning dark brown or red in color they became very conspicu- 
ous. 
Aphis maidis Fitch. (The Corn Plant-louse). 
“This species is found on all parts of corn, and becomes very 
destructive in some years, especially if it attaches itself in large 
numbers to the stem which bears the ear, since this is a very vital 
spot as far as the yield is concerned. This species, according to 
the observation of Forbes, winters in the wingless, agamic form, 
in the earth of fields previously infested. In the spring it ap- 
pears to be strictly dependent upon a species of ant, which mines 
along the principal roots of the corn, collects the plant-lice, and 
conveys them into these burrows, and there watches and pro- 
tects them. In a short time after the lice have been transferred 
to the roots of the corn, they mature a winged generation by 
means of which adjacent fields may be stocked. These facts in- 
dicate the inadvisability of planting corn on a field that was in- 
fested by this insect the previous year.” (Comstock). 
Aphis maidi-radicis Forbes. (The Corn Root-louse). 
This root louse, illustrated in Fig. 154, “is a small, soft- 
bodied, greenish-white insect, and will be found adhering to the 
roots of the corn plant, the head attached to the roots by the beak, 
which is inserted in the tissue in order to pump out its food. 
The antennze are composed of seven joints and are rather long, 
reaching to beyond the thorax. The number of joints in the 
antennz and the length will readily separate this species from 
the other form which is found upon the corn roots. Almost 
always this root-louse will be found accompanied by ants, and 
they are quite dependent upon the ants to place them upon suit- 
able roots upon which they can feed, and especially for care over 
winter. It is evident that since they are confined year after year 
to the soil, that rotation of the crop will be useful in avoiding 
their injuries; but it will be most effectual if the corn crop is 
followed by some crop distinctly different, so that it would fail 
to furnish any sustenance for the lice. It hardly seems probable 
that the species has become very much distributed in this state, 
but it would be wise to examine the roots of the corn which 
