222 THE ORIGIN OF SPECIES 



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 seize 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 san- 

 guinea, 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 mi- 

 grate, the masters carry the slaves. Both in Switzerland and Eng- 

 land 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 mate- 

 rials 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 the nest 

 to collect building materials and food for themselves, their slaves 

 and larvae. So that the masters in this country receive much less 

 service from their slaves than they do in Switzerland. 



By what steps the instinct of F. sanguinea originated I will not 

 pretend to conjecture. But as ants which are not slave-makers will, 

 as I have seen, carry off the pupae of other species, if scattered 

 near their nests, it is possible that such pupae originally stored as 



