August 15, worker ants taken from two different nests in the field 
and placed in the same formicary began at once to fight. They kept 
up their contest all night, and several of them were dead in the morn- 
ing. By noon of the following day, however, fighting had ceased 
and the two groups had separated, occupying different parts of the 
enclosure. The larger group had taken possession of a corn plant 
which had been introduced for the use of these ants, and the other 
colony, which established itself near the edge of the formicary, seemed 
timid and cowed, apparently fearing even to feed upon the syrup 
offered them. The dominant group mined actively in the earth about 
the roots of the corn, and appropriated the root-lice introduced into 
the cage, evidently feeling themselves masters of their domain. 
April 24, 1906, a colony of 100 worker ants with 200 larvae of 
various sizes, and eggs of the corn root-aphis, were brought in from 
the field and established in a two-celled glass formicary. After they 
had become thoroly at home, nine worker ants and a few ant larvre — 
strangers to the original colony — a bunch of aphis eggs, and some 
young root-aphids, were introduced into this nest, the original family 
being in the orange or dark cell and the newcomers in the other cell 
of this cage. As soon as the presence of the strangers was detected 
they were attacked by the old colony, which dragged the adults about, 
killing them one by one, ate up their larv?e, ate or pulled to pieces the 
root-lice introduced with them, and crushed the aphis eggs. The root- 
lice and eggs brought in from their own nest they were in the mean- 
time caring for as usual. 
August 7, some eggs of the corn-field ant brought in from the 
field and placed with a colony of workers well established in an artifi- 
cial formicary, were presently found by one of the workers and delib- 
erately crushed, one by one. 
These hostilities of ants to strangers may extend even to those 
of their own sisterhood who have been away from home too long. 
For example, a young worker separated from its formicary mates 
August 21, kept alone, and returned to them twenty-one days later, 
was immediately attacked by them and quickly killed. 
The utility to the ants of this inhospitable savagery — this spirit of 
ferocious clannishness — is doubtless to be found in their social organ- 
ization, and in the necessity under which they live of keeping always 
an active, compact, deeply interested group of workers completely 
devoted to the care and nurture of their helpless young. No young 
of any animal can be more utterly dependent than those of these ants, 
and their feeding and protection must be the constant, consuming care 
of the whole family group. 
The workers are, on the other hand, among the most active and 
enterprising wanderers and foragers among insects, traveling far and 
wide on foot to distances which make it necessary for them to retrace 
their steps carefully, whether by the aid of the sense of sight or by 
antennal senses supposed to resemble what in us is the sense of smell. 
The homing instinct and the nursing instinct are in them so strong as 
