228 THE PRINCIPLES OF HEREDITY 



members of the species, the power of making useful mental 

 acquirements is correspondingly great. It reaches a 

 remarkable development even among insects some species ot 

 which live together in great communities. Young ants, for 

 example, are tended with anxious care. It is said that they 

 are led about the nest by older individuals and taught their 

 duties. They are said to be playful. 1 Most significant of all 

 is the fact that some species have the habit of capturing 

 slaves belonging to other species. These they take as pupae, 

 never as adult ants. " When the pupae hatch out in the 

 nests of their captors, the young slaves begin their life of 

 work, and seem to regard their masters' home as their own ; 

 for they never attempt to escape, and they fight no less 

 keenly than their masters in defence of the nest. F. sanguined 

 content themselves with fewer slaves than F. rufescens : 

 and the work that devolves upon the slaves differs according 

 to the species which has enslaved them. In the nest of P. 

 sanguinea the comparatively few captives are kept as house- 

 hold slaves ; they never enter or leave the nest, and so are 

 never seen unless the nest is opened. They are then very 

 conspicuous from the contrast which their black colour and 

 small size presents to the red colour and the much larger size 

 of F. sanguinea. As the slaves are by this species kept 

 strictly indoors, all the outdoor work of foraging, slave- 

 capturing, etc. is performed by the masters ; and when, for 

 any reason, a nest has to migrate, the masters carry their 

 slaves in their jaws. F. rufescens, on the other hand, assign a 

 much larger share of the labour to the slaves, which, as we 

 have already seen, are present in much larger numbers to 

 take it. In this species the males and fertile females do no 

 work of any kind ; and the workers, or sterile females, though 

 most energetic in capturing slaves, do no other kind of work. 

 Therefore the whole community is absolutely dependent upon 

 the slaves. The masters are not able to make their own nests 

 or to feed their own larvae. When they migrate, it is the 

 slaves that determine the migration, and, reversing the order 

 of things that obtains in F. sanguinea, carry the masters in 

 their jaws. Huber shut up thirty masters without a slave 

 and with abundance of their favourite food, and also with 

 their own larvae and pupae for a stimulus to work ; but they 

 could not feed themselves and many died of hunger. He 

 then introduced a single slave and she set to work at once, 

 fed the surviving masters, attended to the larvae and made 

 some cells. 



1 Huber, confirmed by Fabre, Lesfourmis de la Suisse, 1874. 



