al strength, fighting for frontiers, war is not
perennial. After many days of battle and glorious hecatombs, the rival
states would appear to recognise that their respective ambitions are
unattainable. As if by common consent, the armies withdraw within either
side of a frontier, which is accepted by both parties with or without
treaty. This frontier is respected much more perfectly than among men,
bound merely by "scraps of paper." The citizen ants of the two
communities always keep strictly within their borders.

* * * * *

A matter of even greater interest is to note how this war-making
instinct originates among our brothers the insects; to study how it
develops; and to ascertain whether it is fixed or modifiable. Here
Forel's observations and experiments lead to the most remarkable
deductions.

J. H. Fabre, in a famous passage of _Insect Life_,[77] tells us that
"brigandage is the law in the struggle among living beings.... In
nature, murder is universal. Everywhere we encounter a hook, a dagger, a
spear, a tooth, nippers, pincers, a saw, horrible clamps, ..." But he
exaggerates. He has a keen eye for the facts of mutual slaughter and
mutual devouring, but he fails to see the facts of mutual aid and
associated effort. Kropotkin has devoted an admirable book to the study
of phenomena of the latter class, as manifested throughout nature.[78]
Furthermore, the careful observations of Forel show that in ants the
instincts of war and plunder may be modified or overcome by instincts of
a contrary character.

First of all, Forel proves that the war-making instinct is not
fundamental. This instinct does not exist in the early stages of ant
life. Putting together newly hatched ants belonging to three different
species, Forel obtained a mixed ant community whose members lived in
perfect harmony. The only primitive instinct of newly hatched ants is
that for domestic work and the care of larvae. "Not until later do ants
learn to distinguish between friend and foe; not until later do they
realise that they are members of a single ant community on behalf of
which they have to fight."[79]

Forel next presents the fact, even more surprising, that the intensity
of the warrior instinct is directly proportional to the size of the
collectivity. Two ants of enemy species meeting at a distance from their
respective nests or from their own folk, will avoid one another and run
away in opposite directions