Insects, Their Ways and Means of Living/Chapter V
CHAPTER V
TERMITES
It was the custom, not long ago, to teach the inexperienced that the will can achieve whatever ambition may desire. "Believe that you can, and you can, if only you work hard enough"; this was the subject of many a maxim very encouraging, no doubt, to the young adventurer, but just as likely to lead to a bench in Union Square as to a Fifth Avenue studio or a seat in the Stock Exchange.
Now it is the fashion to give us mental tests and vocational suggestions, and we are admonished that it is no use trying to be one thing if nature bas made us for something else. This is sound advice; the only trouble is the difficulty of being able to detect at an early age the characters that are to distinguish a plumber from a doctor, a cook from an actress, or a financier from an entomologist. Of course, there really are differences between all classes of people from the time they are born, and a fine thing it would be if we could know in our youth just what each one of us is designed to become. In the present chapter we are to learn that certain insects appear to have achieved this very thing.
The termites are social insects; consequently in studying them, we shall be confronted with questions of conduct. Therefore, it will be well at the outset to look somewhat into the subject of morality; not, be assured, to learn any of its irksome precepts, but to discover its biological significance.
Right and wrong, some people think, are general abstractions that exist in the very nature of things. They are, on the contrary, specific attributes that are conditioned by circumstances. An act that is right is one in accord with the nature of the creature performing it; that which is wrong is a contrary act. Hence, what is right for one species of animal may be wrong for another, and the reverse.
Fig. 75. A common species of termite of eastern North America inhabiting dead wood, Reticulitermes flavipes.
A, B, winged forms, C, a soldier. D, workers
The conduct of adult human individuals, according to human standards of right and wrong, we call morals; the similar conduct of other animals is a part of what biologists call behavior. But we unconsciously recognize something in common between morals and behavior when we speak of the acts of a child, which we call his behavior rather than his morals. Behavior, in other words, we regard as involving less of personal responsibility than morality. Hence we say that animals and children behave, but that adult human beings consciously do right or wrong. Yet, the two modes of action accomplish similar results: if the child behaves properly, his actions are right; if the adult has a proper]y developed moral sense, he too does the right thing, or at least he terrains from doing the wrong thing unless misguided by circumstances or by his reasoning.
Animals other than the human, it appears, generally do what is right from their standpoint; but their actions, we say, are instinctive. Some will insist that the terms "right" and "wrong" can have no application to them. Substitute then, if you please, the expression "appropriate or non-appropriate to the animal's way of living." And still, our morality will analyze into the same two elements; our acts are right or wrong according as they are appropriate or non-appropriate to our way of living.
The difference between human actions and those of other animals is not essentially in the acts themselves, but in the methods by which they are brought about. Animals are controlled by instincts, mostly; man is controlled by a conscious feeling that he should do this or that—"conscience," we call it—and his specific actions are the result of his reasoning or teaching as to what is right and what is wrong, excepting, of course, the acts of perverted individuals who lack either a functional conscience or a well-adjusted power of reason, or of individuals in whom the instincts of an earlier way of living are still strong. The general truth is clear, however, that in behavior, as in physiology, there is not just one way of arriving at a common result, and that nature may employ quite different means for determining and activating conduct in her creatures.
Since right and wrong, then, are not abstract properties, but are terms expressing fitness or non-fitness, judged according to circumstances, or an animal's way of living, it is evident that the quality of actions will differ much according to how a species lives. Particularly will there be a difference in the necessary behavior of species that live as individuals and of those that live as groups of individuals. In other words, that which may be right for an individualistic species may be wrong for a communal species; for, with the latter, the group replaces the individual, and relations are now established within the group, or pertaining to the group as a whole, that before applied to the individual, while relations that formerly existed between individuals become now relations between groups.
The majority of animals live as individuals, each wandering here and there, wherever its fancy leads or wherever the food supply attracts it, recognizing no ties or responsibilities to others of its species and contending with its fellows, often in deadly combat, for whatever advantage it can gain. A few animals are communistic or social in their mode of life; notably so are man and certain insects. The best-known examples of social insects are the ants and some of the bees and wasps. The termites, however, constitute another group of social insects of no less interest than the ants and bees, but whose habits have not been so long observed.
Fig. 76. Termite work in a piece of wood. Tunnels following the grain are made by species of Reticulitermes, the common underground termites of the eastern United States
More familiarly to some people, termites are known as "white ants." But since they are not ants, nor always white or even pale in color, we should discard this misleading and unjustifiable appellation and learn to know the termites by the name under which they are universally known to entomologists.
If you split open an old board that has been lying almost anywhere on the ground for some time, or if, when out in the woods, you cut into a dead stump or a log, you are more than likely to find it tunneled all through with small tubular galleries running with the grain of the wood, but everywhere connected crosswise by small openings or short passages. Within the exposed galleries there will be seen numerous small, pale, wingless insects running here and there in an effort to conceal themselves. These insects are termites. They are the miners or the descendants of miners that have excavated the tunnels in which they live. Not all of the galleries in the nest are open runways, many of them being packed solidly with small pellets of refuse.
If the termites confined themselves to useless wood, they would be known only as interesting insects; but since they often extend the[r operations into fence posts, telegraph poles, the woodwork of houses, and even into furniture, they have placed themselves among the destructive insects and have acquired an important place in the pages of economic entomology. Stored papers, books, cloth, and leather are not exempt from their attack. In the United States it not infrequently happens that the flooring or other wooden parts of buildings must be replaced, owing to the unsuspected work of termites; and piled lumber is especially liable to invasion by these insidious insects. But in tropical countries the termites are far more numerous than in temperate regions, and are vastly more destructive than they are with us. Their seclusive habits make the termites a particularly vexatious pest, because they have usually accomplished an irreparable amount of damage before their presence is known or suspected. The economic entomologist studying termites gives most of his attention, therefore, to devising methods of preventing the access of the insects to all wooden structures that they might destroy.
The work of termites and the ways and means that have been contrived to prevent their ravages have been described in many agricultural publications, and the reader whose tastes are purely practical is referred to the latter for information. Here we will look more closely into the lives of the termites themselves to see what lessons we may learn from these creatures that have adopted something of our own way of living.
When a termite nest is broken open, it does not appear that there is much of an organization among the insects
Fig. 77. Reticulitermes flavipes (much enlarged)
A, a mature worker. B, a mature soldier. C, a young termite. D, an immature winged form
hurrying to take refuge in the recesses of the galleries, but neither when a bomb strikes one of out own dwellings is there probably much evidence of order within. The most casual observation of the termites, however, will show something of interest concerning them. In the first place, it is to be seen that not all the members of the colony are alike. Some, usually the greater number, are small, ordinary, soft-bodied, wingless insects with rounded heads and inconspicuous jaws (Figs. 75 D, 77 A). Others, less numerous, have bodies like the first, and are also wingless, but their heads are relatively of enormous size and support a pair of large, strong jaws projecting out in front (Figs. 75 C, 77 B). The individuals of the latter kind are known as soldiers, and the name is not entirely fanciful, since fighting is not necessarily the everyday occupation of one in military service. The others, the small-headed individuals, are called workers, and they earn their title literally, for, even with their small jaws, they do most of the work of excavating the tunnels, and they perform whatever other labors are to be done within the nest.
Both the workers and the soldiers are males and females, but so far as reproductive powers go, they may be called "neuters," since their reproductive organs never mature and they take no part in the replenishment of the colony. In most species of termites the workers and the soldiers are blind, having no eyes or but rudiments of eyes. In a few of the more primitive termite genera, workers are absent, and in the higher genera they may be of two types of structure. The large jaws of the soldiers (Fig. 78 A) are weapons of defense in some species, and the soldiers are said to present themselves at any break in the walls of the nest ready to defend the colony against invasion. In some species, the soldiers have a long tubular horn projecting forward from the face (Fig. 78 B), through which opens the duct of a gland that emits a sticky, semiliquid substance. This glue is discharged upon an attacking enemy, who is generally an ant, and so thoroughly gums him up that he is rendered helpless—a means of combat yet to be adopted in human warfare. The facial gland is developed to such efficiency as a weapon in many species of one termite family that the soldiers of these species have no need of jaws, and their mandibles have become rudimentary. In all cases, the military specialization of the soldiers has rendered them incapable of feeding themselves, and they must depend on the workers for food.
In addition to the soldiers and the workers, there would probably be seen within the termite nest, at cer-
Fig. 78. Two forms of defensive organs of termite soldiers
A, head of soldier of Termopsis, showing the highly developed mandibles (Md), and the great muscles within the head (admd) that close them. B, a soldier of Nasutitermes (from Banks and Snyder); the head has small jaws but is provided with a long snoutlike horn through which is ejected a gummy liquid used for defense
tain seasons of the year, many individuals (Fig. 77 D) that have small wing rudiments on their thoracic segments. As the season advances, the wing pads of these individuals increase in length, until at last they become long, gauzy, fully-developed wings extending much beyond the tip of the body (Figs. 75 A, B, 79). The color of the body also becomes darker, and finally blackish when the insects are mature. Then, on some particular day, the whole winged brood issues from the nest in a great swarm. Since insects are normally winged creatures, it is evident that these flying termites represent the perfect forms of the termite colony—they are, in fact, the sexually mature males and females.
The several forms of individuals in the termite community are known as castes.
An intensive search through the galleries 9f a termite nest might reveal, besides workers, soldiers, and the members of the winged brood in various stages of development, a few individuals of still different kinds. These have heads like the winged forms, but rather larger bodies; some have short wing rudiments (Fig. 80), others have none; and finally there are two individuals, a male and a female, bearing wing stubs from which, evidently, fully-formed wings have been broken off. The male of this last pair is just an ordinary-looking, though dark-bodied termite (Fig. 82 A); but the female is distinguished from all the other members of the colony by the great size of her abdomen (B).
Fig. 79. Adult winged caste of Reticulitermes tibialis, wings shown on one side of the body only. (From Banks and Snyder)
Through the investigations of entomologists it is known that the short-winged, and wingless individuals of this group comprise both males and females that are potentially capable of reproduction, but that in general all the eggs of the colony are actually produced by the large-bodied female, whose consort is the male that has lost his wings. In other words, this fertile female corresponds with the "queen" in a hive of bees; but, unlike the queen bee, the queen termite allows the "king" termite to live with her throughout her life in the community.
It appears, then, that the termite community is a complex society of castes, for we must now add to the worker and soldier castes the two castes of potentially reproductive individuals, and the "royal" or actual producing caste, consisting of the king and the queen. We are thus introduced to a social state quite different from anything known in our own civilization, for, though we may have castes, the distinctions between them are largely matters of polite concession by the less aspiring members of the community. We theoretically claim that we are all born equal. Though we know that this is but a gratifying illusion, our inequalities at least do not go by recognized caste. A termite, however, is literally born into his place in society and eventually has his caste insignia indelibly stamped in the structure of his body. This state of affairs upsets all our ideas and doctrines of the fundamental naturalness and rightness of democracy; and, if it is true that nature not only recognizes castes but creates them, we must look more closely into the affairs of the termite society to see how such things may come about.
Let us go back to the swarm of winged males and females that have issued from the nest. The birds are already feeding upon them, for the termites' powers of flight are at best feeble and uncertain. The winds have scattered them, and in a short time the fluttering horde will be dispersed and probably most of its members will be destroyed one way or another. The object of the swarming, however, is the distribution of the insects, and, if a few survive, that is all that will be necessary for the continuance of the race. When the fluttering insects alight they no longer have need of their wings, and by brushing against objects, or by twisting the body until the tip of the abdomen comes against the wing bases, the encumbering organs are broken off. It may be observed that there is a suture across the base of each wing just to make the breaking easy.
The now wingless termites, being young males and females just come to maturity, naturally pair off; but
Fig. 80. The second form, or short-winged reproductive caste,
of Reticulitermes tibialis. (From Banks and Snyder)
A, male. B, female
not for a companionate marriage, which, it must be confessed, is the popular form of matrimony with most insects. The termites take the vows of lifetime fidelity, or "till death do us part," for with the female termite intensive domesticity and maternity are the ruling passions. To find a home site and there found a colony is her consuming ambition, and, whether the male likes it or not, he must accept her conditions. The female, therefore, searches out a hole or a crevice in a dead tree or a decayed stump, or crawls under a piece of wood lying on the ground, and the male follows. If the site proves suitable, the female begins digging into the wood or into the ground beneath it, using her jaws as excavating tools, perhaps helped a little by the male, and soon a shaft is sunk at the end of which a cavity is hollowed out of sufficient size to accommodate the pair and to serve the purposes of a nest where true matrimony may begin.
Naturally it would be a very difficult matter to follow the whole course of events in the building of a termite community from one of these newly married pairs, for the termites live in absolute seclusion and any disturbance of their nests breaks up the routine of their lives and frustrates the efforts of the investigator. Many phases, however, of the life and habits of our common eastern United States termites, particularly of species belonging to the genus Reticulitermes, have been discovered and recorded in numerous papers by Dr. T. E. Snyder of the U. S. Bureau of Entomology, and, thanks to Doctor Snyder's work, we are able to give the following account of the life of these termites and the history of the development of a fairly complex community from the progeny of a single pair of insects.
The young married couple live amicably together in conjugal relations within their narrow cell. The male, perhaps, was forced to eject a would-be rival or two, but eventually the mouth of the tunnel is permanently sealed, and from now on the lives of this pair will be completely shut in from the outside world. In due time, a month or six weeks after the mating, the female lays her first eggs, six or a dozen of them, deposited in a mass on the floor of the chamber. About ten days thereafter the eggs hatch, and the new home becomes enlivened with a brood of little termites.
The young termites, though active and able to run about, are not capable of feeding themselves, and the parents are now confronted.with the task of keeping a dozen growing appetites appeased. The feeding formula of the termite nursery calls for predigested wood pulp; but fortunately this does not have to be supplied from outside—the walls of the house furnish an abundance of raw material and the digesting is done in the stomachs of the parents. The pulp needs then only to be regurgitated and handed to the infants. This feature in the termite economy has a double convenience, for not only are the young inexpensively fed, but the gathering of the food automatically enlarges the home to accommodate the increasing need for space of the growing family.
That insects should gnaw tunnels through dead wood is not surprising; but that they should be able to subsist on sawdust is a truly remarkable thing and a dietetic feat that few other animals could perform. Dry wood consists mostly of a substance called cellulose, which, while it is related to the starches and sugars, is a carbohydrate that is entirely indigestible to ordinary animals, though eaten in abundance as a part of all vegetable food. The termites, however, are unusually gifted, not with a special digestive enzyme, but with minute, one-celled, cellulose-digesting protozoan parasites that live in their alimentary canals. It is through the agency of their intestinal inhabitants, then, that the termites are able to live on a diet of dead wood. The young termites receive some of the organisms with the food given them by their parents and are soon able to be wood eaters themselves. Not all termites, however, are known to possess these intestinal protozoa, and, as we shall see, many of them feed on other things than wood.
The termite brood thrives upon its wood-pulp diet, and by December following the spring in which the young were hatched, the members of the new generation begin to attain maturity after having progressed through a series of moltings, as does any other growing insect. But observe, the individuals of this generation, instead of developing into replicas of their parents, have taken on the form of workers and soldiers! However, one should never express surprise when dealing with insects; and for the present we must accept the strange development of the young termites as a matter of fact, and pass on.
Fig. 81. A queen of the third form, or wingless reproductive caste, of Reticulitermes flavipes. (From Banks and Snyder)
During the middle of winter things remain thus in the new family colony. The members of termite species that live in the ground, or that pass from wood into the ground, probably have tunneled deep into the earth for protection from the cold. But in February, the mother termite, now the queen of the brood, responds again to the urge of maternity with some more eggs, probably with a greater number this time than on the first occasion. A month later, or during March, the termitary is once more enlivened with young termites. The king and the queen are now, however, relieved of the routine of nursery duties by the workers of the first brood. The latter take over the feeding and care of their new brothers and sisters, and also do all the excavation work involved in the enlarging of the home.
In the spring the termites ascend to the surface of the ground beneath a board or log, or at the base of a stump, and reoccupy their former habitation. As the galleries are extended, the family moves along, slowly migrating thus to uneaten parts of the wood and leaving the old tunnels behind them mostly packed with excreted wood-pulp and earth.
When June comes again, the young family may consist of several dozen individuals; but all, except the king and queen, are soldiers and workers, the latter much outnumbering the former. During the second year, the queen lays a still greater number of eggs and probably produces them at more frequent intervals. With the increase in the activity of her ovaries, her abdomen enlarges and she takes on a matronly appearance, attaining a length fully twice that of her virgin figure and a girth in proportion. The king, however, remains faithful to his spouse; and he, too, may fatten up a little, sufficiently to give him some distinction amongst his multiplying subjects. The termite king is truly a king, in the modern way, for he has renounced all authority and responsibility and leads a care-free life, observing only the decorums of polite society and adhering to the traditions of a gentleman; but he also achieves the highest distinction of democracy, for he is literally the father of his country.
Another year rolls by, bringing more eggs, more workers, more soldiers. And now, perhaps, other forms appear in the maturing broods. These are marked at a certain stage of their development by the possession of short wing stubs or pads on the back of the normally wing-bearing segments. With succeeding molts the wing pads become larger and larger, until they finally develop, in most of these individuals, into long wings like those of the king and the queen when they first flew out from the parent colony. At last, then, the new family is to have its first swarm; and when the fully-winged members are all ready for the event and the proper kind of day arrives, the workers open a few exits from the galleries, and the winged ones are off. We already know their history, for they will only do what their parents did before them and what their ancestors have done for millions of generations. Let us go back to the galleries.
A few of the individuals that developed winged pads are fated to disappointment, for their wings never grow to a functional size and they are thereby prevented from joining the swarm. Their reproductive organs and their instincts, however, attain maturity, and these short-winged individuals, therefore, become males and females capable of procreation. They differ from the fully-winged sexual forms in a few respects other than the length of the wings, and they constitute a true caste of the termite community, that of the short-winged males and females (Fig. 80). The members of this caste mature along with the others, and, Doctor Snyder tells us, many of them, regardless of their handicap, actually leave the nest at the time the long-winged caste is swarming; as if in them, too, the instinct for flight is felt, though the organs for accomplishing it are unable to play their part. Just what becomes of these unfortunates is a mystery, for Doctor Snyder says that after the swarming none of them is to be found in the nest. It may be that some of them pair and found new colonies after the manner of the winged forms, but the facts concerning their history are not known. It is at least true that colonies are sometimes found which have no true royal pair, but in which the propagating individuals are members of this short-winged reproductive caste.
Finally, there are also found in the termite colonies certain wingless individuals that otherwise resemble the winged forms, and which, as the latter, are functionally capable of reproduction when mature. These individuals constitute a third reproductive caste—the wingless males and females. Little is known of the members of this caste, but it is surmised that they may leave the nests by subterranean passages and found new colonies of their own.
Just how long the primary queen of a colony can keep on laying eggs is not known, but in the course of years she normally comes to the end of her resources, and before that time she may be injured or killed through some accident. Her death in any case, however, does not mean the end of the colony, for the king may provide for the continuance of his race, and at the same time console himself in his bereavement, by the adoption of a whole harem of young short-winged females. But if he too should be lost, then the workers give the succession to one or more pairs of the second- or third-caste reproductive forms, to whom they grant the royal prerogatives. The progeny of any of the fertile castes will include the caste of the parents and all castes below them. In other words, only winged forms can produce the whole series of castes; short-winged parents can not produce long-winged offspring; and wingless parents can not produce winged
Fig. 82. The usual king (A) and queen (B), or winged reproductive caste after having lost the wings (fig. 79), of Reticulitermes flavipes. (From Banks and Snyder)
offspring of any form; but both short-winged and wingless parents can produce soldiers and workers. It appears, therefore, that each imperfect fertile insect lacks something in its constitution that is necessary for the production of a complete termite individual.
The production of constitutionally different castes from the eggs of a single pair of parents would be a highly disconcerting event if it happened anywhere else than in a termite colony, where it is the regular thing. But the fact of its being regular with termites makes it none the less disconcerting to entomologists, for it seems to defy the very laws of heredity.
There can be no doubt of the utility of a caste system where the members of each caste know their places and their duties, and where nobody ever thinks of starting a social revolution. But we should like to know how such a system was ever established, and how individuals of a family are not only born different but are made to admit it and to act accordingly.
These are abstruse questions, and entomologists are divided in opinion as to the proper answers. Some have maintained that the termite castes are not distinguished when the various individuals are young, but are produced later by differences in the feeding—in other words, it is claimed the castes are made to order by the termites themselves. One particular objection to this view is that no one has succeeded in finding out what the miraculous pabulum may be, and no one has been able to bring about a structural change in any termite by controlling its diet. On the other hand, it has been shown that in some species there are actual differences in the young at the rime of hatching, and such observations establish the fact that insects from eggs laid by one female can, at least, give rise to offspring of two or more forms, beside those of sex, and that potential differences are determined in the eggs. It is most probable that in these forms no structural differences could be discovered at an early embryonic period, and hence it may be that, where differences are not perceptible at the time of hatching, the period of differentiation has only been delayed to a later stage of growth. It is possible that a solution to the problem of the termite castes will be found when a study of the eggs themselves has been made.
We may conclude, therefore, that the structural differences between the termite castes are probably innate, and that they arise from differences in the constitutional elements of the germ cells that direct the subsequent development of the embryos in the eggs and of the young after hatching.
Still, however, there remain questions as to the nature of the force that controls termite behavior. Why do the termites remain together in a community instead of scattering, each to live its own life as do most other insects? Why do the workers accept their lot and perform all the menial duties assigned to them? Why do the soldiers expose themselves to danger as defenders of the nests? Structure can account for the things it is impossible for an animal to do, but if can not explain positive behavior where seemingly the animal makes a choice between many lines of possible action open to it.
In the community of the cells that make up the body of an animal, as we learned in Chapter IV, organization and control are brought about either through the nerves, which transmit an activating or inhibiting force to each cell from a central controlling station, or through chemical substances thrown into the blood. In the insect community, however, there is nothing corresponding to either of these regulating influences; nor is there a law-making individual or group of individuals as in human societies, nor a police force to execute the orders if any were issued. If would seem that there must be some inscrutable power that maintains law and order in the termite galleries. Are we, then, to admit that there is a "spirit of the nest," an "âme collective," as Maeterlinck would have us believe—some pervading force that unites the individuals and guides the destinies of the colony as a whole? No, scientists can not accept any such idea as that, because it assumes that nature's resources are no greater than those of man's imagination. Nature is always natural, and her ways and means of accomplishing anything, when once discovered, never invoke things that the human mind can not grasp, except in their ultimate analysis into first principles. Those who have faith in the consistency of nature endeavor to push a little farther into the great unknown knowable.
There are a few things known about the termites that help to explain some of the apparent mysteries concerning them. For example, the members of a colony are forever licking or nibbling at one another; the workers appear to be always cleaning the queen, and they are assiduous in stroking the young. These labial attentions, or lip affections, moreover, are not unrewarded, for it appears that each member of the colony exudes some substance through its skin that is highly agreeable to the other members. Furthermore, the termites all feed one another with food material ejected from the alimentary canal, sometimes from one end, sometimes from the other. Each individual, therefore, is a triple source of nourishment to his fellows—he has to offer exudates from the skin, crop food from the mouth, and intestinal food from the anus—and this mutual exchange of food appears to form the basis for much of the attachment that exists among the members of the colony. It accounts for the maternal affections, the care of the queen and the young by the workers, the brotherly love between the workers and the soldiers. The golden rule of the termite colony is "feed others as you would be fed by them."
The termites, therefore, are social creatures because, for physical reasons, no individual could live and be happy away from his fellows. The same might be said of us, though, of course, we like to believe that our social instincts have not a purely physical basis. Be that as it may, we must recognize that any kind of social tie is but one of various possible means by which the benefits of community life are insured to the members of the community.
The custom of food exchange in the termite colonies can not be held to account by any means for all the things that termites do. Where other explanations fail, we have always to fall back on "instinct." A true instinct is a response bred in the nervous system; and the behavior of termites, as of all other insects, is largely brought
Fig. 83. A fore wing of a termite, Kalotermes approximatus, showing the humeral suture (hs) where the wing breaks off when it is discarded
about by automatic reflexes that come into action when external and internal conditions are right for their production. The physical qualities of the nervous system that make certain reactions automatic and inevitable are inherited; they are transmitted from parent to offspring, and bring about all those features of the animal's behavior that are repeated from generation to generation and which are not to be attributed to the individual's response to environmental changes.
The termites have an ancient lineage, for though no traces of their family have been round in the earlier records, there can be no doubt that the ancestors of the termites were closely related to those of the roaches; and the roach family, as we have seen in Chapter III, may be reckoned among the very oldest of winged insects. In human society it means a great deal to belong to an "old family," at least to the members of that family; but in biology generally it is the newer forms, the upstarts of more recent times, that attain the highest degree of organization; and most of the social insects—the ants, the bees, and the wasps—belong to families of comparatively recent origin. It is refreshing, therefore, to find the belief in aristocracy vindicated by the ancient and honorable line of descent represented by the roaches and flowering in the termites.
One particular piece of evidence of the roach ancestry of the termites is furnished by the wings. With most termites the wings (Fig. 83) are not well developed, and
Fig. 84. Wings of Mastotermes, the hind wing with a basal expansion similar to that of the hind wing of a roach (fig. 53), suggesting a relationship between termites and roaches
their muscles are partly degenerate. In some forms, however, the wings (Fig. 84) are distinctly of the roach type of structure (Fig. 53), and these forms are undoubtedly more closely representative of the ancestral termites than are the species with the usual termite wing structure.
Our termites and those of other temperate regions constitute the mere fringes of termite civilization. The termites are particularly insects of warm climates, and it is in the tropics that they find their most congenial environment and attain the full expression of their possibilities.
In the tropics the characteristic termites are not those that inhabit dead wood, but species that construct definite and permanent nests, some placed beneath the ground, others reared above the surface, and still others built against the trunks or branches of trees. Different species employ different building materials in the construction of their nests. Some use particles of earth, sand grains, or clay; others use earth mixed with saliva; still others make use of the partly digested wood pulp ejected from their bodies; and some use mixed materials. Certain kinds of tropical termites, moreover, have foraging habits.
Fig. 85. Vertical section of an underground nest of an African termite, Termes badius. (From Hegh, after Fuller)
The large central chamber is the principal "fungus garden"; in the wall at the left is the royal chamber (rc); tunnels lead from the main part of the nest to smaller chambers containing fungus, and to the small mounds at the surface
Great armies of workers of these species leave the nests, even in broad daylight, and march in wide columns guarded by the soldiers to the foraging grounds, where they gather bits of leaves, dead stems, or lichens, and return laden with provender for home consumption.
The underground nests (Fig. 85) consist chiefly of a cavity in the earth, perhaps two by three feet in diameter and a foot beneath the surface, walled with a thick cement lining; but from this chamber there may extend tunnels upward to the surface, or horizontally to other smaller chambers located at a distance from the central one. The termites that live in these nests subsist principally upon home-grown food, and it is in the great vaulted central chamber that they raise the staple article of their diet. The cavity is filled almost entirely with a porous, spongy mass of living fungus. The fungi as we ordinarily see them are the toadstools and mushrooms, but these fungus forms are merely the fruiting bodies sent up from a part of the plant concealed beneath the ground or in the dead wood; and this hidden part has the form of a network of fine, branching threads, called a mycelium. The mycelium lives on decaying wood, and it is the mycelial part of the fungus that the termites cultivate. They feed on small spore-bearing stalks that sprout from the threads of the mycelium. The substratum of the termite fungus beds is generally made of pellets of partly digested wood pulp.
The nests that termites erect above the ground include the most remarkable architectural structures produced by insects. They are found in South America, Australia, and particularly in Africa. In size they vary from mere turrets a few inches high to great edifices six, twelve, or even twenty feet in altitude. Some are simple mounds (Fig. 86 A), or mere hillocks; others have the form of towers, obelisks, and pyramids (B); still others look like fantastic cathedrals with buttressed walls and tapering spires (Fig. 87); while lastly, the strangest of all resemble huge toadstools with thick cylindrical stalks and broad-brimmed caps (Fig. 86 C). Many of the termites that build mound nests are also fungus-growing species, and one chamber or several chambers in the nest are given over to the fungus culture.
Termite nests built in trees are usually outlying retreats of colonies that live in the ground, for such nests (Fig. 86 D) are connected with an underground nest by covered runways extending down the trunk of the tree.
The queens of nearly all the termites that lire in permanent nests attain an enormous size by the growth of the abdomen, the body becoming thus so huge that the royal
Fig. 86. Four common types of above-ground nests made by tropical termites
A, type of small mound nest, varying from a few inches to several feet in height. B, type of a large tower or steeple nest, reaching a height of 9 or 10 feet. C, a mushroom-shaped nest, made by certain African termites, from 3 to 16 inches high. D, a tree nest, showing the covered runway going down to the ground
Fig. 87. Type of pinnacled nest made by species of African termites, sometimes reaching a height of twenty feet or more
From a study of the termites we may draw a few lessons for ourselves. In the first place, we see that the social form of life is only one of the ways of living; but that, wherever it is adopted, it involves an interdependence of individuals upon one another. The social or community way of living is best promoted by a division of labor among groups of individuals, allowing each to specialize and thereby to attain proficiency in his particular kind of work. The means by which the termites have achieved the benefits of social life are not the same as those adopted by the ants or social bees, and they have little in common with the principles of our own social organization. All of which goes to show that in the social world, as in the physical world, the end alone justifies the means, so far as nature is concerned. Justice to the individual is a human concept; we strive to equalize the benefits and hardships of the social form of life, and in so far as we achieve this aim our civilization differs from that of the insects.