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 few pupae of the yellow ant (F. flava), a courageous and pugnacious little species, were placed within the reach of the slave-making Sanguineas.  A like chance presented with the pupae of their slave race was eagerly seized, and the chrysalides carried off.  The pupae of the yellow ants, however, were not merely left untouched, but the slave-makers exhibited every system of terror and alarm at the sight of the chrysalides of their yellow neighbors.  Such an instance demonstrates the existence not merely of perception but also of the memory of past experience, probably of not over agreeable kind, of encounters with the yellow ants.  When, on the contrary, a nest of the slaves is attacked, the Sanguineas are both bold and wary.  Mr. Darwin traced a long file of Sanguineas for forty yards backward to a clump of heath, whence he perceived the last of the invaders marching homeward with a slave pupa in its mouth.  Two or three individuals of the attacked and desolate nest were rushing about in wild despair, and “one,” adds Mr. Darwin, “was perched motionless, with its own pupa in its mouth, on the top of a spray of heath, an image of despair over its ravaged home.”  The picture thus drawn is not the less eloquent because its subject is drawn from lower existence; although the pains and sorrows of ant life may not legitimately be judged by the standard of human woe.

The explanation of the slave-making instinct in ants begins with the recognition of the fact that many ants, not slave-makers, store up pupae of other species for food.  If we suppose that some of the pupae, originally acquired through a cannibal-like instinct, came to maturity within the nest of their captors, and in virtue of their own inherited instincts engaged in the work of the hive, we may conceive of a rational beginning of the slave-making instinct.  If, further, the captors learned to appreciate the labors of their captives, as lightening their own work, the habit of collecting pupae as slaves might succeed and supersede