38 
(Solenopsis debilis). In five of the six infested hills a single kernel 
of corn had been more or less eaten by the ants. No observations of 
injury to the roots were reported, but the amount of stunted corn in 
this part of the field could scarcely be accounted for except on the sup- 
position that some other injury was being done than this to the kernel 
in the hill. In the worse-infested part of the field thirteen hills were 
examined, eleven of which were infested, and eight of them contained 
kernels which had been more or less eaten by the ants. In five of the 
hills all the kernels had been thus injured, and in the others only one 
kernel to the hill. The ants in these hills were all the common corn- 
field species except in one instance, where only Solenopsis was found. 
In the seven hills selected because of their visible infestation, all the 
kernels were eaten by ants in two, and a single kernel out of two or 
three in each of the others, the ants in all these hills being the common 
corn-field species. Rough estimates of the number of ants to a hill 
ranged from ten workers as a minimum to a maximum of a thousand. 
In one case only were ant larvae present. 
In all these sixty-one hills the corn root-aphis was found but four 
times — twice a single winged female, once a winged female with three 
large and thirty small wingless females, and once four winged females 
with between forty and fifty wingless ones, nearly all of them young. 
There were, in fact, more of the common grass root-louse (Schhoneura 
panic ola) in the field than of the corn root-aphis, some on the roots of 
corn, with ants in charge, and others on smartweed and ragweed roots, 
and also accompanied by ants. 
From these observations we may infer that ants living in the 
meadow-grass in 1902 with grass root-lice in their possession, infested 
the corn the following year ; that they continued in the field through 
1904, when a crop of oats was raised, carrying a small percentage of 
their grass root-lice over on roots of weeds in the field ; and that when 
the ground was planted to corn in 1905 they were still abundant there, 
but with so few root-lice in their possession that they availed them- 
selves of the softened corn kernels in the earth for food, probably 
gnawing away, also, root hairs and the finer roots, as they have been 
seen to do in confinement. 
Effect of a Change of Crop 
The effect of a change of crop — from corn to oats, for example — 
on the ant population of a badly infested field, was illustrated by an 
account in my Thirteenth Report of the disappearance, during the 
latter part of May, of both ants and aphids from an oats field formerly 
in corn. By this time the weeds in the field were practically all dead, 
the oats having reached a height to overshadow and sap them. A 
similar occurrence, more closely observed, is reported by Mr. Kelly in 
a series of notes running from April 21 to June 22, 1906. In a forty- 
acre field of oats fifty nests of the corn-field ant were located and 
marked near two sides of the field, one next a field of corn and the 
other separated from corn by a hedge fence and a road. That this 
