We found a fourth kind, which are perfectly harmless, and almost exactly resemble the white ants of the East Indies:  The architecture of these is still more curious than that of the others.  They have houses of two sorts; one is suspended on the branches of trees, and the other erected upon the ground:  Those upon the trees are about three or four times as big as a man’s head, and are built of a brittle substance, which seems to consist of small part of vegetables kneaded together with a glutinous matter, which their bodies probably supply.  Upon breaking this crust, innumerable cells, swarming with inhabitants, appear in a great variety of winding directions, all communicating with each other, and with several apertures that lead to other nests upon the same tree; they have also one large avenue, of covered way, leading to the ground, and carried on under it to the other nest or house that is constructed there.  This house is generally at the root of a tree, but not of that upon which their other dwellings are constructed:  It is formed like an irregularly sided cone, and sometimes is more than six feet high, and nearly as much in diameter.  Some are smaller, and these are generally flat-sided, and very much resemble in figure the stones which are seen in many parts of England, and supposed to be the remains of druidical antiquity.  The outside of these is of well-tempered clay, about two inches thick; and within are the cells, which have no opening outwards, but communicate only with the subterranean way to the houses on the tree, and to the tree near which they are constructed, where they ascend up the root, and so up the trunk and branches, under covered ways of the same kind as those by which they descended from their other dwellings.  To these structures on the ground they probably retire in the winter, or rainy seasons, as they are proof against any wet that can fall, which those in the tree, though generally constructed under some overhanging branch, from the nature and thinness of their crust or wall, cannot be.[89]

[Footnote 89:  There are upwards of twenty species of ants known, which differ from one another in several respects, but more especially in the materials and construction of their habitations.  Some employ earth, others the leaves and bark of trees, and others again prefer straw; whilst another species, as is mentioned above, occupy the central parts of trees.  Their manners too are very different, though all, in various degrees, no doubt, manifest very remarkable instinctive wisdom, and, if the expression be allowable, even acquired knowledge.  The reader who is desirous of minute and most instructive information on the subject of these sagacious animals, will do well to consult the Edinburgh Review, vol. xx. page 143, &c. where an account is given of Mr Huber’s observations and experiments respecting them.  A single extract from the Review may prove interesting to the reader who has not the convenience of referring to the volume.