Chap. VEX] SLAVE-MAKING INSTINCT. 339 



twenty-five yards distant, which they ascended together, 

 probably in search of aphides or cocci. According to 

 Huber, who had ample opportunities for observation, 

 the slaves in Switzerland habitually work with their 

 masters in making the nest, and they alone open and 

 close the doors in the morning and evening; and, as 

 Huber expressly states, their principal office is to search 

 for aphides. This difference in the usual habits of the 

 masters and slaves in the two countries, probably depends 

 merely on the slaves being captured in greater numbers 

 in Switzerland than in England. 



One day I fortunately witnessed a migration of F. 

 sanguinea from one nest to another, and it was a most 

 interesting spectacle to behold the masters carefully 

 carrying their slaves in their jaws instead of being 

 carried by them, as in the case of F. rufescens. Another 

 day my attention was struck by about a score of the 

 slave-makers haunting the same spot, and evidently not 

 in search of food ; they approached and were vigorously 

 repulsed by an independent community of the slave- 

 species (F. fusca) ; sometimes as many as three of these 

 ants clinging to the legs of the slave-making F. sanguinea. 

 The latter ruthlessly killed their small opponents, and 

 carried their dead bodies as food to their nest, twenty- 

 nine yards distant; but they were prevented from 

 getting any pupae to rear as slaves. I then dug up a 

 small parcel of the pupaa of F. fusca from another nest, 

 and put them down on a bare spot near the place of 

 combat ; they were eagerly seized and carried off by the 

 tyrants, who perhaps fancied that, after all, they had 

 been victorious in their late combat. 



At the same time I laid on the same place a small 

 parcel of the pupae of another species, F. flava, with a 



