278 ORIGIN OF SPECIES 



surprise an independent community of F. flava under a stone 

 beneath a nest of the slave-making F. sanguinea; and when 

 I had accidentally disturbed both nests, the little ants at- 

 tacked their big neighbours with surprising courage. Now 

 I was curious to ascertain whether F. sanguinea could dis-. 

 tinguish 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 yel- 

 low ants had crawled away, they took heai/ and carried off 

 the pupae. 



One evening I visited another community of F. sanguinea, 

 and found a number of these ants returning home and enter- 

 ing their nests, carrying the dead bodies of F. fusca (show- 

 ing that it was not a migration) and numerous pupae. I 

 traced a long file of ants burthened 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 motion- 

 less 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. rufes- 

 cens. The latter does not build its own nest, does not deter- 

 mine its own migrations, does not collect food for itself or 

 its young, and cannot even feed itself: it is absolutely depen- 

 dent 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 



