Chap. VII. 
SLAVE-MAKING INSTINCT. 
223 
agitation, and one was perclied motionless with its own 
pupa in its mouth on the top of a spray of heath, an 
image of despair, over its ravaged home. 
Such are the facts, though they did not need confirma¬ 
tion by me, in regard to the wonderful instinct of 
making slaves. Let it be observed what a contrast the 
instinctive habits of F. sanguinea present with those of 
the continental F. rufescens. The latter does not build 
its own nest, does not determine its own migrations, 
does not collect food for itself or its young, and cannot 
even feed itself: it is absolutely dependent on its nume¬ 
rous slaves. Formica sanguinea, on the other hand, 
possesses much fewer slaves, and in the early part of 
the summer extremely few: the masters determine 
when and where a new nest shall be formed, and when 
they migrate, the masters carry the slaves. Both in 
Switzerland and England the slaves seem to have the 
exclusive care of the larvae, and the masters alone go 
on slave-making expeditions. In Switzerland the slaves 
and masters work together, making and bringing mate¬ 
rials for the nest: both, but chiefly the slaves, tend, and 
milk as it may be called, their aphides; and thus both 
collect food for the community. In England the masters 
alone usually leave the nest to collect building materials 
and food for themselves, their slaves and larvse. So that 
the masters in this country receive much less service 
from their slaves than they do in Switzerland. 
By what steps the instinct of F. sanguinea originated 
I will not pretend to conjecture. But as ants, which are 
not slave-makers, will, as I have seen, carry off pupae of 
other species, if scattered near their nests, it is possible 
that such pupae originally stored as food might become 
developed; and the foreign ants thus unintentionally 
reared would then follow their proper instincts, and do 
