Fig. 240.—Fragment of Termitarium of Termes angustatus, S. Africa, showing fungus chambers and orifices of communication.
These nurseries rest on the clay-like framework of the nest, but are not attached thereto; they in no way support it, or one another, indeed they have the appearance of being constantly added to on their upper margins and constantly eaten away on their under parts. Fig. 240 represents the appearance of the upper boundary of a nursery taken from a nest of Termes angustatus. The small white bodies, mentioned above, have disappeared: the mycelium of the fungus, though not shown in the figure, is still visible on the specimen from which it was drawn, and gives rise to a whitish, glaucous appearance.
In various parts of the world nests formed on trees by Termites are to be seen; these tree nests are, it would appear, in some cases only parts of a community, and are connected with the main body by galleries. In other cases nests are formed in various positions of advantage; Messrs. Hubbard and Hagen have given us an account[[304]] of some of these—probably the work of Eutermes ripperti—as seen in Jamaica. They describe the nests as spherical or conical masses, looking externally as if composed of loamy earth; they are placed on trees, fences, or walls; they vary in size from that of a man's fist to that of a hogshead; they appear to be composed of finely comminuted wood fastened together by saliva. These nests are formed on the same principle as those of the wasps that make nests hanging to trees and bushes, as they consist of an external protecting envelope covering a comb-like mass in the interior. At the bottom of the nest there is a covered gallery leading to the earth, where the main nest appears to be situate; galleries also are constructed so as to lead to the tops of trees and other places, in such a manner that the Termite can still keep up its peculiarity of working and travelling in tunnels and yet roam over a large area; the activity of these Termites continues day and night. In each nest there is a queen, who lays eggs that are removed by the worker Termites to the bottom of the nest. The young are fed on a prepared food, consisting apparently of comminuted vegetable matter, of which considerable masses are laid in store. Some of the nests are rich in containing many pounds' weight of this material, while others are apparently quite destitute of it. There is a soldier form and at least two kinds of workers. Some species of true ant frequently shares the nest of these white ants, but on what terms the two kinds of Insects live together is not stated.
Termite Ravages.—In countries whose climate is favourable to their constitutions certain kinds of Termites become of great importance to our own species. Owing to their taste for woody matter and to their habit of working in concealment, it is no uncommon thing for it to be discovered that Termites have obtained access to a building and have practically destroyed the wooden materials used in its construction; all the interior of the wood being eaten away and only a thin outer shell left intact. A Termite, T. tenuis, was introduced—in what manner is not certainly known[[305]]—to the Island of St. Helena, and committed such extensive ravages there that Jamestown, the capital, was practically destroyed and new buildings had to be erected. Other such cases are on record. Destructive species can sometimes be destroyed by placing in the nests a portion of arsenicated food. This is eaten by some individuals, who perish in consequence; and their dead bodies being consumed by their comrades, the colony becomes checked if not exterminated.
The number of described species of Termitidae does not much exceed 100, but this is certainly only a small portion of those existing, the total of which may probably reach 1000 species.
Termitidae are classed by some naturalists with the Orthoptera, and they have a great deal in common with some of the cursorial division of that Order, more particularly Forficulidae and Blattidae; but they differ from Orthoptera in the nature and form of the wings. They are also classed by some, with a few other forms, as a separate Order of Pseudo-Neuroptera called Corrodentia, but this is not a very satisfactory course, as the Termitidae do not agree closely with the forms associated with them, while the aggregate so formed is far from being very distinct from other forms of Neuroptera. On the whole the best plan appears to be to treat the Termitidae as forming a distinct family of the Order Neuroptera, or to make it a distinct Order, as proposed by Grassi. Packard now associates Termites in an Order with the biting-lice, and calls it Platyptera.
Fossil Termites.—Termitidae were very abundant in Tertiary times, and the genera appear to have been then much the same as at present. In Mesozoic strata the remains of true Termitidae apparently exist in the Lias in Europe, but farther back than this the family has not been satisfactorily traced. It was formerly supposed that Termitidae existed in the Carboniferous strata, but this appears to be very doubtful; and the fossil remains of that epoch, which were presumed to be those of Termites, are now referred by Scudder and others to the Neuropteroid division of the Order Palaeodictyoptera, an Order which is formed entirely of Palaeozoic fossil remains.
CHAPTER XVII
NEUROPTERA CONTINUED—PSOCIDAE (BOOK-LICE AND DEATH-WATCHES)—THE FIRST FAMILY OF AMPHIBIOUS NEUROPTERA (PERLIDAE, STONE-FLIES).
Fam. IV. Psocidae—Book-Lice, Death-Watches.