attacked their big neighbours with surprising
courage. Now I was curious to ascertain whether F. sanguinea could
distinguish the pupae of F. fusca, which they habitually make into
slaves, from those of the little and furious F. flava, which they rarely
capture, and it was evident that they did at once distinguish them:
for we have seen that they eagerly and instantly seized the pupae of F.
fusca, whereas they were much terrified when they came across the pupae,
or even the earth from the nest of F. flava, and quickly ran away; but
in about a quarter of an hour, shortly after all the little yellow ants
had crawled away, they took heart and carried off the pupae.

One evening I visited another community of F. sanguinea, and found a
number of these ants entering their nest, carrying the dead bodies of F.
fusca (showing that it was not a migration) and numerous pupae. I traced
the returning file burthened with booty, for about forty yards, to
a very thick clump of heath, whence I saw the last individual of F.
sanguinea emerge, carrying a pupa; but I was not able to find the
desolated nest in the thick heath. The nest, however, must have been
close at hand, for two or three individuals of F. fusca were rushing
about in the greatest agitation, and one was perched motionless with its
own pupa in its mouth on the top of a spray of heath over its ravaged
home.

Such are the facts, though they did not need confirmation by me, in
regard to the wonderful instinct of making slaves. Let it be observed
what a contrast the instinctive habits of F. sanguinea present with
those of the F. rufescens. The latter does not build its own nest, does
not determine its own migrations, does not collect food for itself or
its young, and cannot even feed itself: it is absolutely dependent on
its numerous slaves. Formica sanguinea, on the other hand, possesses
much fewer slaves, and in the early part of the summer extremely few.
The masters determine when and where a new nest shall be formed, and
when they migrate, the masters carry the slaves. Both in Switzerland and
England the slaves seem to have the exclusive care of the larvae, and
the masters alone go on slave-making expeditions. In Switzerland the
slaves and masters work together, making and bringing materials for the
nest: both, but chiefly the slaves, tend, and milk as it may be called,
their aphides; and thus both collect food for the community. In England
the masters alone usually leave