[Illustration:  SETS OFF AT ONCE ON ITS RETURN.]

After travelling for some hundreds of yards, often for more than half a mile, the formicarium is reached.  It consists of low, wide mounds of brown, clayey-looking earth, above and immediately around which the bushes have been killed by their buds and leaves having been persistently bitten off as they attempted to grow after their first defoliation.  Under high trees in the thick forest the ants do not make their nests, because, I believe, the ventilation of their underground galleries, about which they are very particular, would be interfered with, and perhaps to avoid the drip from the trees.  It is on the outskirts of the forest, or around clearings, or near wide roads that let in the sun, that these formicariums are generally found.  Numerous round tunnels, varying from half an inch to seven or eight inches in diameter, lead down through the mounds of earth; and many more, from some distance around, also lead underneath them.  At some of the holes on the mounds ants will be seen busily at work, bringing up little pellets of earth from below, and casting them down on the ever-increasing mounds, so that its surface is nearly always fresh and new-looking.

Standing near the mounds, one sees from every point of the compass ant-paths leading to them, all thronged with the busy workers carrying their leafy burdens.  As far as the eye can distinguish their tiny forms, troops upon troops of leaves are moving up towards the central point, and disappearing down the numerous tunnelled passages.  The outgoing, empty-handed hosts are partly concealed amongst the bulky burdens of the incomers, and can only be distinguished by looking closely amongst them.  The ceaseless, toiling hosts impress one with their power, and one asks—­What forests can stand before such invaders?  How is it that vegetation is not eaten off the face of the earth?  Surely nowhere but in the tropics, where the recuperative powers of nature are immense and ever active, could such devastation be withstood.

Further acquaintance with the subject will teach the inquirer that, just as many insects are preserved by being distasteful to insectivorous birds, so very many of the forest trees are protected from the ravages of the ants by their leaves either being distasteful to them, or unfitted for the purpose for which they are required, whilst some have special means of defence against their attacks.

These ants do not confine themselves to leaves, but also carry off any vegetable substance that they find suitable for growing the fungus on.  They are very partial to the inside white rind of oranges, and I have also seen them cutting up and carrying off the flowers of certain shrubs, the leaves of which they neglected.  They are very particular about the ventilation of their underground chambers, and have numerous holes leading up to the surface from them.  These they open out or close up, apparently