belonging to a certain caste of workers having very large heads, for the heads of the other ones would not be large enough. The nest of this species is made in decaying wood, and there is always some worker who thus uses his large head as a stopper, removing it when a fellow-townsman wishes to enter the nest, but presenting its smooth, impenetrable surface, guarded with jaws, to all unauthorised intruders. It is Forel, one of the best ant-observers of to-day, who tells us this, and the ant apparently is _Lasius fuliginosus_, which is a British species, and, according to an account which I have already referred to, does not seem to be always a wood-borer. _Formica sanguinea_, however, does things—or has things done for it—after a more ordinary fashion. Darwin was the witness of a slave-raid on the part of _F. sanguinea_ which was not, in this instance, very successful. He says: “They approached, and were vigorously repulsed by an independent community of the slave-species (_F. fusca_), sometimes as many as three of these ants clinging to the legs of the slave-making _sanguinea_. The latter ruthlessly killed their small opponents, and carried their dead bodies as food to their nest, twenty-nine yards distant; but they were prevented from getting any pupæ to rear as slaves. I then dug up a small parcel of the pupæ of _Formica fusca_ from another nest, and put them down on a bare spot near the place of combat; they were eagerly seized and carried off by the tyrants, who perhaps fancied that, after all, they had been victorious in their late combat.”[52] In his work, _Ants and their Ways_,[53] the Rev. Farren White describes a similar raid which was—or rather which had been, for it was nearly over when he arrived on the scene—wholly successful. Here, however, the oppressed species seems to have made a very poor resistance, though very likely it had been more vigorous in the earlier stages of the raid. “I watched a _fusca_,” says Mr. White, “carrying off a pupa from behind the entrance whence the _sanguineæ_ were issuing forth. Immediately it saw one of the enemy approaching, it dropped its charge and left it to its fate. The _sanguinea_ then gave it a push, and drove it off in double-quick time”; and, again, “I noticed a _sanguinea_ coming up out of the nest with a pupa, and a _fusca_, observing it, went up a fern-frond with the utmost expedition.”[53] Other observations of a similar nature were made, and the conclusion arrived at by Mr. White is “that between the _fuscæ_ and the _sanguineæ_ there is a well-defined and clearly pronounced antagonism. In presence of the _sanguineæ_ the _fuscæ_ were terror-stricken. In fact the depredators had it all their own way, and were able in this instance, at least, to carry out their marvellous instincts without destroying a single life.”[53] It will be seen how ill this accords with the account given by Darwin. My own way of accounting for the discrepancy is that, in the first instance, the little _fuscæ_