200 ON THE ORIGIN OF SPECIES 



ants had crawled away, they took heart and carried 

 off the pupae. 



One evening- I visited another community of F. san- 

 guinea, 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 burthened 

 with booty, for about forty yards, to a very thick clump 

 of heath, whence I saw the last individual of F. san- 

 guinea 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 con- 

 firmation 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 : the masters deter- 

 mine 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 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. 



