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 returning home and entering their nests, carrying the dead bodies of F.fusca (showing that it was not a migration) and numerous pupae.

I traced a long file of ants burdened with booty, for about forty yards back, 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, an image of despair 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 continental 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.