Chap. VIII.] SLAVE-MAKING INSTINCT. 339 



Scotch-fir-tree, twenty-five yards distant, which they 

 ascended together, probably in search of aphides or 

 cocci. According to Huber, who had ample opportuni- 

 ties 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 even- 

 ing; 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 -cap- 

 tured in greater numbers in Switzerland than in Eng- 

 land. 



One day I fortunately witnessed a migration of P. 

 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 car- 

 ried by them, as in the case of P. 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. san- 

 guinea. The latter ruthlessly killed their small oppo- 

 nents, and carried their dead bodies as food to their 

 nest, twenty-nine yards distant; but they were prevent- 

 ed from getting any pupae to rear as slaves. I then dug 

 up a small parcel of the pupae 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 



