198 ON THE ORIGIN OF SPECIES 



black and not above half the size of their red masters, 

 so that the contrast in their appearance is very great. 

 When the nest is slightly disturbed, the slaves occa- 

 sionally come out, and like their masters are much 

 agitated and defend the nest : when the nest is much 

 disturbed and the larvaB and pupae are exposed, the 

 slaves work energetically with their masters in carrying 

 them away to a place of safety. Hence, it is clear, that 

 the slaves feel quite at home. During the months of 

 June and July, on three successive years, I have watched 

 for many hours several nests in Surrey and Sussex, and 

 never saw a slave either leave or enter a nest. As, 

 during these months, the slaves are very few in number, 

 I thought that they might behave differently when 

 more numerous ; but Mr. Smith informs me that he has 

 watched the nests at various hours during May, J\ ae 

 and August, both in Surrey and Hampshire, aDd has 

 never seen the slaves, though present in large numbers 

 in August, either leave or enter the nest. Hence he 

 considers them as strictly household slaves. The 

 masters, on the other hand, may be constantly seen 

 bringing in materials for the nest, and food of all 

 kinds. During the present year, however, in the 

 month of July, I came across a community with an 

 unusually large stock of slaves, and I observed a few 

 slaves mingled with their masters leaving the nest, and 

 marching along the same road to a tall Scotch fir-tree, 

 twenty -five yards distant, which they ascended to- 

 gether, probably in search of aphides or cocci. Ac- 

 cording to Huber, who had ample opportunities for 

 observation, in Switzerland the slaves 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. 

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



