duced, the willing servitor "established order, formed a chamber
in the earth, gathered together the larvae, extricated several young
ants that were ready to quit the condition of pupae, and preserved the
life of the remaining Amazons." It must be noted that there are very
varying degrees in the dependence of the ant-masters on their slaves.
In the recognition of this graduated scale of relationship and
dependence, indeed, will be found the clue to the acquirement of this
instinct. The horse-ant (_Formica rufa_) will carry off the larvae and
pupae of other ants _for food_, and it sometimes happens that some of
these captives, spared by their cannibal neighbors, will grow up in
the nest of their captor. A well-known ant, the _Formica sanguinea_,
found in the South of England, is however, a true slave-making
species, but exhibits no such utter dependence on its servitors as
does _Polyergus_. The slave-making habit is not only typically
developed in the _Sanguineas_, but the bearing of the captives to
their masters indicate a degree of relationship and organization such
as could hardly be conceived to exist outside human experience. The
_Sanguineas_ make periodical excursions, and, like a powerful
predatory clan, carry off the pupae or chrysalides of a neighboring
species, _F. fusca_. Thus the children of the latter race are born
within the nest of their captors in an enslaved condition. As slaves
"born and bred," so to speak, they fall at once into the routine of
their duties, assist their masters in the work of the nest, and tend
and nurse the young of the family. The slaves, curiously enough in
this instance, are black in color, whilst the masters are twice the
size of the servitors, and are red in color, and that the slaves are
true importations is proved by the fact that males and females of the
slave species are never developed within the nest of the masters, but
only within those of their own colonies. The slaves in this instance
rarely leave the nest, the masters foraging for food, and employing
their captives in household work, as it were; whilst, when the work of
emigration occurs, the masters carry the slaves in their mouths like
household goods and chattels, instead of being carried by them, as in
the case of _Polyergus_.

Mr. Darwin gives an interesting account of the different attitudes
exhibited by the _Sanguineas_ toward species of ants other than the
black race from which their slaves are usually drawn. A