152 ORGANIC EVOLUTION — MENTAL 



the slaves differs according to the species which has 

 enslaved them. In the nest of F. sanguinea the com- 

 paratively few captives are kept as household slaves; 

 they never either 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 present to the red colour and 

 much larger size of F. sanguinea. As the slaves are by 

 this species kept strictly indoors, all the outdoor work 

 of foraging, slave-capturing, &c., 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, assigns a much larger 

 share of labour to the slaves, which, as we have already 

 seen, are present in much lai-ger 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 its 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 deter- 

 mine the migration, and, reversing the order of things 

 that obtains in F. sanguinea, carry their masters in their 

 *jaws. Huber shut up thirty masters without a slave, 

 and with abundance of their favourite food, and also 

 with their own larvje and pupae as a stimulus to work ; 

 but they could not feed themselves, and many died of 

 hunger. He then introduced a single slave, and she at 

 once set to work, fed the surviving masters, attended to 

 the larvae, and made some cells. 



" In order to confirm this observation, Lespfes placed 

 a piece of sugar near a nest of slave-makers. If was 

 soon found by one of the slaves, which gorged itself and 

 returned to the nest. Other slaves then came out and 

 did likewise. Then some of the masters came out, and, 

 by pulling the legs of the feeding slaves, reminded 

 them that they were neglecting their duty. The slaves 

 then immediately began to serve their masters with the 

 sugar." — Animal Intelligence, pp. 65-6. 



