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 
larvse. 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 
larvse 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 larva©, 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. 
Another species, 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 
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