ANTS

external environment, but must also have an intense feeling of coöperation, forbearance and affection towards the other members of its community. In other words, to live in societies, like those of man and the social insects, implies a shifting of proclivities from the egocentric to the sociocentric plane through a remarkable increase in the amplitude and precision of the individual's responses to all the normal environmental stimuli.

Of the four groups of social insects above mentioned, adaptive plasticity attains its richest and boldest expression in the ants. The extraordinary character of these creatures will appear in its proper light if we undertake to compare them on the one hand with the remaining social insects, and on the other hand with man, the paragon of social animals. It is certain that the ants occupy a unique position among all insects on account of their dominance as a group, and this dominance is shown first, in their high degree of variability as exhibited in the great number of their species, subspecies and varieties; second, in their numerical ascendancy in individuals; third, in their wide geographical distribution; fourth, in their remarkable longevity; fifth, in their abandonment of certain over-specialized modes of life from which the other social insects seem not to have been able to emancipate themselves, and sixth, in their manifold relationships with plants and other animals-man included.

Ants are to be found everywhere, from the arctic regions to the tropics, from timberline on the loftiest mountains to the shifting sands of the dunes and seashores, and from the dampest forests to the driest deserts. Not only do they outnumber in individuals all other terrestrial animals, but their colonies even in very circumscribed localities often defy enumeration. Their colonies are, moreover, remarkably stable, somtimes outlasting a generation of men. Such stability, is, of course, due to the longevity of the individual ants, since worker ants are known to live from four to seven and queens from thirteen to fifteen years. In all these respects the other social insects are decidedly inferior. Not only are the colonies of the wasps and bumblebees of rather rare occurrence, but they are merely annual growths. The honeybees, too, are very short-lived, the workers living only a few weeks or months, the queens but a few years. The termites, though perhaps longer-lived than the bees and wasps, are practically confined to very definite localities in the tropics. Only a few of the species have been able to extend their range into temperate regions.

Not only do the ants far outnumber in species all other social insects, but they have either never acquired, or have completely abandoned, certain habits which must seriously handicap the termites, social wasps

and bees in their struggle for existence. The ants neither restrict their diet, like the termites, to comparatively innutritious substances such as cellulose, nor like the bees to a very few substances like the honey and pollen of the evanescent flowers, nor do they build elaborate combs of expensive materials, such as wax. Even paper as a building material has been very generally outgrown and abandoned by the ants. Waxen. and paper cells are not easily altered or repaired, and insects that are wedded to this kind of architecture, not only have to expend much time and energy in collecting and working up their building materials, but they are unable to move themselves or their brood to other localities when the nest is disturbed, when the moisture or temperature become unfavorable or the food supply fails. The custom of depending on a single fertilized queen as the only reproductive center or organ of the colony has also been outgrown by many ants. At least the more dominant and successful species have learned to cherish a number of these fertile individuals in the colony. Finally, the manifold and plastic relationships of ants to plants and other animals are in marked contrast with the circumscribed and highly specialized ethological relationships of the social bees and wasps. The termites undoubtedly resemble the ants most closely in plasticity, but the careful studies of Grassi and Sandias, Sjöstedt, Froggatt, Silvestri, Heath and others, have shown that these insects, too, are highly specialized, or one-sided in their development. This is best seen in their extreme sensitiveness to light, for this practically confines them to a subterranean existence and excludes them from many of the influences afforded by a more varied and illuminated environment.

There can be little doubt that the ants have become dominant through their exquisitely terrestrial habits, a fact which Espinas (1877) was, I believe, one of the first to notice. He says: "Ants owe their superiority to their terrestrial life. This assertion may seem paradoxical, but consider the exceptional advantages afforded by a terrestrial medium to the development of their intellectual faculties, compared with an aërial medium! In the air there are the long flights without obstacles, the vertiginous journeys far from real bodies, the instability, the wandering about, the endless forgetfulness of things and oneself. On the earth, on the contrary, there is not a movement that is not a contact and does not yield precise information, not a journey that fails to leave some reminiscence; and as these journeys are determinate, it is inevitable that a portion of the ground incessantly traversed should be registered, together with its resources and its dangers, in the animal's imagination. Thus there results a closer and much more direct communication with the external world. To employ matter, moreover, is

easier for a terrestrial than an aërial animal. When it is necessary to build, the latter must, like the bee, either secrete the substance of its nest or seek it at a distance, as does the bee when she collects propolis, or the wasp when she gathers material for her paper. The terrestrial animal has its building materials close at hand, and its architecture may be as varied as these materials. Ants, therefore, probably owe their social and industrial superiority to their habitat."

The dominance of ants is clearly indicated by the small number of their enemies. They are preyed upon by comparatively few mammals, birds, reptiles, parasitic insects and other ants. And however much their philoprogenitive instincts may be exploited by their various guests and mess-mates, the adult ants enjoy, in temperate regions at least, a singular immunity. A further indication of dominance is seen in the peculiar and widely distributed defensive modifications of the integument of those animals which are most frequently exposed to the attack of ant colonies. The scales of reptiles, the feathers of birds and the hairs of mammals and caterpillars suggest themselves as such defensive adaptations. At any rate it would be difficult to conceive of structures better suited to the protection of arboreal and terrestrial animals against these ubiquitous insects.

Some very striking resemblances between human and ant societies are implied in the fact already mentioned, that animal communities, in order to deserve the name of societies, must have certain fundamental traits in common. Indeed, the resemblances between men and ants are so very conspicuous that they were noted even by aboriginal thinkers. Folk-lore and primitive poetry and philosophy show the ants as an abiding source of similes expressing the fervid activity and coöperation of men. Although these similes have become trite from repetition, the scientific student can hardly free himself from the many anthropomorphisms which they suggest. He is forced to admit that the social and psychical ascendancy of the ants among invertebrates and of the mammals among vertebrates, constitutes a very striking example of convergent development. And the paleontologist may be inclined to admit that this convergence has a deeper significance, that it may have been due, in fact, since ants and mammals seem to make their appearance simultaneously in Mesozoic times, to some peculiar transitory conditions that favored the birth of forms destined to dominance through extraordinary psychical endowment. What these conditions were we have but the slenderest hope of ever knowing. Perhaps they may be conceived as having favored psychical mutations, which are

1

As Forel says: "The ants' most dangerous enemies are other ants, just as man's most dangerous enemies are other men."

more remarkable, but also more obscure than the physical mutations now engrossing the attention of biologists.

Be this as it may, there is certainly a striking parallelism between the development of human and ant societies. Some anthropologists, like Topinard, distinguish in the development of human societies six different types or stages, designated as the hunting, pastoral, agricultural, commercial, industrial and intellectual. The ants show stages. corresponding to the first three of these, as Lubbock has remarked (1894): "Whether there are differences in advancement within the limits of the same species or not, there are certainly considerable differences between the different species, and one may almost fancy that we can trace stages corresponding to the principal steps in the history of human development. I do not now refer to slave-making ants, which represent an abnormal, or perhaps only a temporary state of things, for slavery seems to tend in ants as in men to the degradation of those by whom it is adopted, and it is not impossible that the slave-making species will eventually find themselves unable to compete with those which are more self-dependent, and have reached a higher plane of civilization. But putting these slave-making ants on one side, we find in the different species of ants different conditions of life, curiously answering to the earlier stages of human progress. For instance, some species, such as Formica fusca, live principally on the produce of the chase; for though they feed partially on the honey-dew of aphids, they have not domesticated these insects. These ants probably retain the habits once common to all ants. They resemble the lower races of men, who subsist mainly by hunting. Like them they frequent woods and wilds, live in comparatively small communities, as the instincts of collective action are but little developed among them. They hunt singly, and their battles are single combats, like those of Homeric heroes. Such species as Lasius flavus represent a distinctly higher type of social life; they show more skill in architecture, may literally be said to have domesticated certain species of aphids, and may be compared to the pastoral stage of human progress-to the races which live on the products of their flocks and herds. Their communities are more numerous; they act much more in concert; their battles are not mere single combats, but they know how to act in combination. I am disposed to hazard the conjecture that they will gradually exterminate the mere hunting species, just as savages disappear before more advanced races. Lastly, the agricultural nations may be compared. with the harvesting ants."

2" Science and Faith, or Man as an Animal, and Man as a Member of Society." Translated by T. J. McCormack. Chicago, Open Court Publishing Co., 1899, p. 192 et seq.

Although Lubbock has not been altogether fortunate in the selection of species to illustrate his views, I believe we may adopt his conclusion that among ants "there seem to be three principal types, offering a curious analogy to the three great phases-the hunting, pastoral and agricultural stages-in the history of human development." It is obvious that a further development towards the three remaining stages in human progress-the commercial, industrial and intellectual-is not even foreshadowed in the ants. Nor would this be possible, or indeed conceivable, without conceptual thought and an appreciation of values to which the ants have never attained.

Granting the resemblances above mentioned between ant and human societies, there are nevertheless three far-reaching differences between insect and human organization and development to be constantly borne in mind:

1. Ant societies are societies of females. The males really take no part in the colonial activities, and, in most species, are present in the nest only for the brief period requisite to insure the impregnation of the young queens. The males take no part in building, provisioning or guarding the nest or in feeding the workers or the brood. They are in every sense the sexus sequior. Hence the ants resemble certain mythical human societies like the Amazons, but unlike these, all their activities center in the multiplication and care of the coming generations.

2. In human society, apart from the functions depending on sexual dimorphism, and barring individual differences and deficiencies which can be partially or wholly suppressed, equalized or augmented by an elaborate system of education, all individuals have the same natural endowment. Each normal individual retains its various physiological and psychological needs and powers intact, not necessarily sacrificing any of them for the good of the community. In ants, however, the female individuals, of which the society properly consists, are not all alike but often very different, both in their structure (polymorphism) and in their activities (physiological division of labor). Each member is visibly predestined to certain social activities to the exclusion of others, not as in man through the education of some endowment common to all the members of the society, but through the exigencies of structure, fixed at the time of hatching, i. e., the moment the individual enters on its life as an active member of the community.

3. Owing to this preëstablished structure and the specialized functions which it implies, ants are able to live in a condition of anarchistic socialism, each individual instinctively fulfilling the demands of social life without "guide, overseer or ruler," as Solomon correctly observed,