Not less remarkable are the “slave-making” instincts of certain species of ants.  It may be safely maintained that the slave-making habit forms a subject of more than ordinary interest not merely to naturalists but to metaphysicians given to speculate on the origin and acquirement of the practices of human existence.  Pierre Huber, son of the famous entomologist, was the first to describe the slave-making instincts in a species (Polyergus rufescens) noted for its predaceous instincts, and subsequent observations have shown that other species participate in these habits. Polyergus is thoroughly dependent on slaves.  Without these bonds-men it is difficult to see how the ants could exist.  Huber tells us that the workers of this species perform no work save that of capturing slaves.  Use and wont, and the habit of depending entirely on their servitors, have produced such changes in the structure of the ants that they are unable to help themselves.  The jaws of these ants are not adapted for work; they are carried by their slaves from an old nest to a new one; and, more extraordinary still, they require to be fed by their slaves, even with plenty of food close at hand.  Out of thirty of these ants placed by Huber in a box, with some of their larvae and pupae, and a store of honey, fifteen died in less than two days of hunger and of sheer inability to help themselves.  When, however, one of their slaves was introduced, 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