25 
young weeds in the field on which the root-hce are dependent for food 
until the corn begins to grow may thus be so thoroly destroyed as to 
result in the starvation of the insects. Fortunately the labor of this 
treatment of the field will usually be more than repaid by an improve- 
ment of the corn crop independent of all protection against aphis in- 
jury, this being practically the preparation for corn especially recom- 
mended by our best teachers of high-grade agriculture and practiced 
by some of our most successful corn farmers. 
It should be clearly understood, however, that this measure will 
not destroy all the root-aphids in the field. In a few cases ants' nests 
will go so deep that a part of their contents will be undisturbed by the 
plow, and will thus remain as centers of infestation from which the 
ants and aphids spread later to reoccupy the field. Furthermore, the 
corn-field ant, even under these difficult and discouraging conditions, 
will sometimes search out and bring together again at least a part of 
the scattered contents of its burrows. 
The outcome of several carefully conducted experiments with this 
cultivation method of preventing the root-louse injury, is given in 
Bulletin 104 of the Illinois Agricultural Experiment Station, pp. 102- 
123, and also in the Twenty-fourth Report of the Illinois State En- 
tomologist, pp. 8-29. 
3. The maintenance and increase of the fertility of the soil. The 
richer the ground and the more thrifty the crop the less, other things 
being equal, will be the injury to plants by the root-louse. We have 
no present evidence that these insects thrive any the less or multiply 
any less rapidly on the thrifty corn plant than on one poorly nour- 
ished, but there is, of course, no doubt that the plant itself suflFers 
most under insect attack when it has least surplus of vigor and sap 
to spare. In this respect also, the corn root-aphis helps to enforce 
the teachings of a better agriculture, increasing the penalty of a poor 
management by still further diminishing the yield of a deteriorating 
soil. 
4. Finally, the use of repellents on the seed as described in this 
paper. This is still an experimental measure, and evidently can not 
be commonly relied upon until we know more of its general and 
average results. It seems to me desirable, however, that a consider- 
able plot should be planted each favorable year in each suitable field, 
with seed treated by one or the other of the odoriferous repellents here 
discussed, or, still better, perhaps, by one of the strongest-smelling 
fertihzers, to be applied by means of a fertilizer dropper; and that the 
consequences of this treatment should be carefully studied by a com- 
parison of the product of this plot with that of adjacent parts of the 
field. By a favorable year- is meant one in which the spring is of a 
fairly average character — a little drier than normal, perhaps — and in 
which, consequently, the seed is likely to grow quickly and the plant to 
get a good and early start. By a suitable field is meant one in corn 
for a year or more preceding, and in which nests of the corn-field ant 
are turned out in plowing at the rate of some fifty or sixty to the mile 
