external environment, but most 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 men and 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 complete 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 artic 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 honey-bees, 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 definitely 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
