Chap. Yffl.] SLAVE-MAKING INSTINCT. 341 



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 confir- 

 mation 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, pos- 

 sesses 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 Switzer- 

 land 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. 



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 food might 

 become developed ; and the foreign ants thus uninten- 



