Chap. VII. SLAVE-MAKING INSTINCT. 219 



see no difficulty in natural selection making an occa- 

 sional habit permanent, if of advantage to the species, 

 and if the insect whose nest and stored food are thus 

 feloniously appropriated, be not thus exterminated. 



Slave-making instinct. — This remarkable instinct was 

 first discovered in the Formica (Polyerges) rufescens 

 by Pierre Huber, a better observer even than his cele- 

 brated father. This ant is absolutely dependent on its 

 slaves ; without their aid, the species would certainly 

 become extinct in a single year. The males and fertile 

 females do no work. The workers or sterile females, 

 though most energetic and courageous in capturing 

 slaves, do no other work. They are incapable of 

 making their own nests, or of feeding their own 

 larvae. When the old nest is found inconvenient, and 

 they have to migrate, it is the slaves which determine 

 the migration, and actually carry their masters in their 

 jaws. So utterly helpless are the masters, that when 

 Huber shut up thirty of them without a slave, but with 

 plenty of the food which they like best, and with their 

 larvae and pupae to stimulate them to work, they did 

 nothing; they could not even feed themselves, and 

 many perished of hunger. Huber then introduced a 

 single slave (F. fusca), and she instantly set to work, 

 fed and saved the survivors ; made some cells and 

 tended the larvae, and put all to rights. What can be 

 more extraordinary than these well-ascertained facts? 

 If we had not known of any other slave-making ant, it 

 would have been hopeless to have speculated how so 

 wonderful an instinct could have been perfected. 



Formica sanguinea was likewise first discovered by 

 P. Huber to be a slave-making ant. This species is 

 found in the southern parts of England, and its habits 

 have been attended to by Mr. F. Smith, of the British 



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