Page:EB1911 - Volume 26.djvu/674

 the sky; and the later assumption of a Jupiter Terminus or Terminalis (cf. the Greek  ) support this view.

 TERMITE, the name applied to a group of insects with four wings which are developed outside the body (a large proportion of the individuals become adult, however, without wings appearing at all). The wings are of nearly one size, of long, narrow form, of paper-like consistence, and in repose are placed flat on the back of the insect so that only one wing shows. After a short time the wings are shed, and only small stumps remain as evidence of the individual being a winged form. The mouth has strong mandibles. Formerly termites were classed as a part of the order Neuroptera, but more recently they have been separated by certain zoologists from the true Neuroptera, and associated with some other forms as an order Corrodentia. By Packard they have been associated with Mallophaga, and called Platyptera. They now constitute with the Embiidæ—a small and obscure family—the order Isoptera, of which about 300 species are known. Termites are more widely known as white ants, but as they are extremely different from true ants, and as they are rarely white, this designation is very deceptive, and should be abandoned.

Termites are found only in warm climates, where they are sometimes very destructive. They are vegetarian, but occasionally eat, or destroy, dry animal matter. The basis of their alimentary regimen is woody matter. Some of them make use of fungi growing in their abodes as food; some cut and store grass; others prepare a peculiar kind of food, which is stored in a tough, dry form, so that it has to be moistened before it can be eaten. Termites are social insects; many of them construct large edifices called termitaria and often spoken of as nests. A termitarium frequently contains an enormous number of individuals forming the society or colony. Termites are totally different in structure and development from all other social insects, but their social existence exhibits numerous analogies with that of the ants and other social Hymenoptera. The most remarkable of these analogies is that the reproduction of the species in each community is confined to a single pair, or to a very limited number of individuals.



The members of one society or colony, however numerous or dissimilar they may be, are the descendants a single pair. The colony is—so far as is known, and on this, as well as on many other points, authentic information is scanty—first started by a pair of winged individuals that cast their wings, secrete themselves in a suitable place, and produce young; the colony, however huge, being subsequently developed by the extreme productivity of the reproductive pair. Very little is known as to how long a colony endures, and, as there is great variety in the social conditions of different kinds of termites, it is probable that there is considerable difference as to the point in question. As a rule a family or colony has only a single termitarium, but there are cases in which a single family has several separate abodes, though usually only one of them is a real home containing reproductive individuals. The social life in termites, as well as in all other social insects, is clearly a development of the family life. It is accompanied by extraordinary modifications of the forms of the individuals constituting the society, and by a great division of labour.

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As regards the forms, or castes, termites differ totally from other social insects; in the latter case there are great differences between the males and females, and the whole of the castes are of the female sex, whereas in termites the males and females are extremely similar, and the castes are in no way correlative with sex. As the termite life is a family life, and as there is normally only a single pair of reproductive individuals in each community, it is easily comprehensible that if anything goes wrong with this pair, the community is at once thrown into a state of complete disorganization. But this misfortune is mitigated by a method which termites have of keeping individuals in an undifferentiated state, and of turning some of them speedily into reproductive individuals, whereby the community is restored to something like a natural condition of activity and growth.

Apart from the forms that are merely juvenile, the following kinds, of adults are normally present in a colony: (1) workers, (2) soldiers, (3) winged individuals ready to leave the nest, (4) king and queen.

(1) The worker termite resembles the young in general appearance, and, like the young, has no trace of wings (fig. 1). The two segments behind the head are more contracted, so that head, thorax and abdomen are more differentiated than they are in the young. The colour too is different, the young being milky-white, whereas the adult worker is variously pigmented according to its species, but is never milky-white. The worker is generally blind, and in only a few species does it possess rudimentary eyes. The species of the group Calolermitides have no workers. In the other species the workers look after the eggs and young, and perform most, if not all, of the industrial work of the community. They are also, in some cases, effective combatants, though quite destitute of any special structures to suit them for this purpose. The sexual organs do not undergo development, but it has been satisfactorily ascertained that both sexes are represented amongst the workers. In certain species the workers seem to be dimorphic, so far as size is concerned, but this point has apparently been only very inadequately considered. Workers form a very large but variable proportion of the members of a community.

(2) The soldier termite is the most extraordinary feature of termite biology It is more varied than any of the other castes, so that most of the species of termites can be best distinguished by their soldiers. The chief feature of the soldier is an extraordinary development of the head, or of the head and mandibles. There are two very distinct kinds of soldiers: (a) the flat-headed or mandibulate soldier, and (b) the nasute or rostrate soldier (fig. 2). In the first kind the head is usually developed out of all proportion to the rest of the body; the mandibles are frequently enormous, and, being in many cases asymmetric, give the appearance of deformity. In the nasute soldier the head is thick or convex, and may be described as unicorn—that is to say, it is prolonged in the middle so as to form a single pointed horn; the mandibles are never largely developed. No species of termite has both mandibulate and nasute soldiers, although the reverse is sometimes still