Wars and Slavery in the Animal Kingdom. 75 



wingless queens there were now four of them in the 

 nest. This shows that the ants had reared two new 

 queens from the eggs which had been laid in the fall.^ 

 The mortality prevalent in their colony during summer 

 must have caused this exceptional conduct. On duly 

 considering such facts, it can hardly be found strange 

 that sanguineas try to make up for the deficiency of 

 their numbers by robbing and rearing the pupae of 

 other ants; for the enslaving habit serves them as a 

 secondary means of increasing their colonies. 



The manner, too, in which the sanguineas make 

 their choice between the different castes of alien 

 Formica pupae, confirms the above explanation; for 

 this phenomenon is understood only by referring it to 

 their desire to augment the forces of their colonies. 

 It is evident that the rearing of slave pupae is not 

 governed by a ''blind instinct of education," inducing 

 the ants to transfer all their care to the strange brood ; 

 for they consume the male and female pupae of 

 strangers, or kill the sexual ants as soon as they leave 

 their cocoons, whereas they adopt, at least partly, those 

 pupae of strangers, which will develop into workers. 

 They distinguish, therefore, by olfactory perceptions 

 between their own pupae and those of strangers, and 

 they likewise distinguish between the different castes 

 of the latter. Hence, we are compelled to maintain: 

 the sanguine slavemakers do not rear the worker 

 pupae of strangers, because they are unable to distin- 

 guish them from their own, but because they aim at 

 augmenting the number of their own workers by 



1) The two old queens were still living in the spring of 1900, and 

 laid eggs in spite of their age of almost ten years. One of them died 

 last year (1903), thirteen years old. The surviving queen (fourteen 

 years old) I set at liberty with the rest of the workers in spring, 1904. 



