Part 15

In a termite colony there is but one king and queen, the royal couple being the true parents of the colony. The state-apartments are situated in the centre of the hive, and are strictly guarded by workers. Both king and queen are wingless, and are of larger size than their subjects. The queen engages in a continual round of maternal duties, the eggs deposited by the sovereign-mother being at once seized by the workers and conveyed to special or "nursery cells," where the young are duly tended and brought up. Once a year, at the beginning of the rainy season, winged termites appear in the hive as developments of certain of the eggs laid by the queen-termite. These latter are winged males and females (Fig. 1, 1), the two sexes being present in equal numbers. Some of these, after shedding their wings, become the founders--kings and queens--of new communities, the privilege of sex being thus associated with the important and self-denying work of perpetuating the species or race in time. Sooner or later--a termite family takes about a year to grow--a veritable exodus of the young winged termites takes place; and just before this emigration movement occurs, a hive may be seen to be stocked with "termites" of all castes and in all stages of development. The workers never exhibit a change of form during their growth; the soldiers begin to differ from the workers in the possession of larger heads and jaws; whilst the young which are destined to become the winged males and females are distinguished by the early possession of the germs of wings which become larger as the skin is successively moulted. Amongst the bees, blind Huber supposed that an ordinary or neuter egg develops into a queen bee if the larva is fed upon a special kind of food--"royal food," as it is called. Although some entomological authorities differ from Huber with regard to the exact means by which the queen bee is reared and specialized from other larvae, yet the opinion thus expressed possesses a large amount of probability. Whatever may be the exact method or causes through or by which the queen bee is developed, Mr. Bates strongly asserts that the differences between the soldiers and worker termites are distinctly marked from the egg. This latter observer maintains that the difference is not due to variations in food or treatment during their early existence, but is fixed and apparent from the beginning of development. This fact is worthy of note, for it argues in favor of the view that if, as is most likely, the differences between the grades of termites may have originally been produced by natural selection or other causes, these differences have now become part and parcel of the constitution of these insects, and are propagated by the ordinary law of heredity. Thus acquired conditions have become in time the natural "way of life" of these animals.

Mr. Bates has also placed on record the noteworthy fact that a species of termites exists in which the members of the soldier class did not differ at all from the workers "except in the fighting instinct." This observation, if it may be used at all in elucidation of the origin of the curious family life of these insects, points not to sudden creation, but to gradual acquirement and modification as having been the method of development of the specialized classes and castes in termite society. Firstly, we may thus regard the beginnings of the further development of a colony to appear in a nest in which workers and soldiers are alike, as stated by Mr. Bates. Then, through the practice of the fighting instinct, we may conceive that natural selection would be competent to adapt the soldiers more perfectly for their duties militant, by developing the head and jaws as offensive weapons. Possibly, were our knowledge of the termites at all complete, we should meet with all stages in the development and specialization of the various grades of society amongst these insects--at least the present state of our knowledge would seem to lead to such a conclusion as being much more feasible than the theory of special or sudden creation of the peculiarities of the race. It is admitted that the termites are in many respects inferior in structure to the bees and wasps, whilst the white ants themselves are the superiors of their own order--that of the _Neuroptera_. That the termites preceded the bees and their neighbors, the common ants, in the order of development of social instincts, is a conclusion supported by the fact that the _Neuroptera_ form the first group of insects which are preserved to us in the "records of the rocks." Fossil _Neuroptera_ occur in the Devonian rocks of North America; the first traces of insects allied to the bees and wasps being geologically more recent, and appearing in the oolitic strata. The occurrence of high social instincts in an ancient group of insects renders the repetition of these instincts in a later and higher group the less remarkable. The observation, however, does not of necessity carry with it any actual or implied connection between the termites and their higher neighbors, although, indeed, the likeness between the social life of the two orders of insects might warrant such a supposition.

[Illustration: FIG. 3. RED, OR HORSE-ANT (_Formica rufa_.) a, male; b, female, winged; c, worker.]

The common ants (Fig. 3), the study of which in their native haunts is a matter of no great difficulty, and one which will fully reward the seeking mind, like the termites, possess three grades of individuals. In a single ant's nest more than One female may be found, the ants differing from the bees in this respect; and in the nests of some species of ants there are apparently "soldiers" resembling the military termites in the possession of large heads and well-developed jaws. Very amazing differences are to be perceived amongst the various species of ants. Differences in size are of common occurrence, but naturalists have actually succeeded in classifying ants in a general way, by differences in manner and disposition. We know, for example, that the horse-ant (_Formica rufa_, Fig. 3) has little _individual_ intelligence, but is extremely socialistic, and moves and acts _en masse_ with precision and tact. Another species (_F. fusca_) is timid and retiring. _F. pratensis_ is a revengeful creature, since it "worries" its fallen foes; _F. cinerea_ is bold and audacious; others are termed "thieves" and "cowards"; some are phlegmatic; and to complete the list of failings and traits which are human enough in character, one species is said to present an invariable greediness as its prevailing characteristic. The common ants resemble the termites in the general details of their life. We see in an ant's nest the same restless activity of the workers, the same earnest attention paid to the young and pupae, the same instinct in shielding the young from danger, and much the same general routine of development. Certain rather special, and it may be said extraordinary, habits of ants may, however, demand notice before we attempt a brief survey of their instincts at large. Few readers are unacquainted with the _Aphides_, or plant-lice, those little wingless insects which infest our plants and herbs in myriads in summer. It is a fact now well known to naturalists, and first placed on record by Huber, that between the ants and plant-lice, relations of a very friendly and, as far as the ants are concerned, advantageous character have become established. Ants have been observed to stroke the tips of the bodies of the plant-lice with their antennae, this act causing the plant-lice to exude drops of a clear, sweet fluid, of which the ants are extremely enamoured. The ants would thus appear to habitually "milk" their insect-neighbors, and, as far as observation goes, some ants seem not merely to keep the plant-lice in their nests so as to form a veritable dairy establishment, but also to make provision in the future by securing the eggs of the aphides, and bringing up the young as we rear calves.

[Illustration: FIG 4. APPLE APHIS (_Eriosoma Mali_).]

That the relation between the ants and plant-lice are of very stable kind is proved by the interesting remarks of Mr. Darwin, who "removed all the ants from a group of about a dozen aphides on a dock-plant, and prevented their attendance during several hours." Careful watching showed that the plant-lice after this interval did not excrete the sweet fluid. Mr. Darwin then stroked the plant-lice with a hair, endeavoring thus to imitate the action of the ant's feelers, but not a single plant-louse seemed disposed to emit the secretion. Thereafter a single ant was admitted to their company, the insect, in Mr. Darwin's words, appearing, "by its eager way of running about, to be well aware what a rich flock it had discovered." The ant first stroked one aphis and then another, each insect excreting a drop of the sweet juice "as soon as it felt the antennae;" and "even the quite young aphides behaved in this manner, showing that the action was instinctive, and not the result of experience." If, as Mr. Darwin remarks, it is a convenience for the aphides to have the sweet secretion removed, and that "they do not excrete solely for the food of the ants," the observation does not in any degree lessen the curious nature of the relationship which has become established between the ants and their neighbors, or the interesting features in ant life which have inaugurated and perpetuated the habit.

Not less remarkable are the "slave-making" instincts of certain species of ants. It may be safely maintained that the slave-making habit forms a subject of more than ordinary interest not merely to naturalists but to metaphysicians given to speculate on the origin and acquirement of the practices of human existence. Pierre Huber, son of the famous entomologist, was the first to describe the slave-making instincts in a species (_Polyergus rufescens_) noted for its predaceous instincts, and subsequent observations have shown that other species participate in these habits. _Polyergus_ is thoroughly dependent on slaves. Without these bonds-men it is difficult to see how the ants could exist. Huber tells us that the workers of this species perform no work save that of capturing slaves. Use and wont, and the habit of depending entirely on their servitors, have produced such changes in the structure of the ants that they are unable to help themselves. The jaws of these ants are not adapted for work; they are carried by their slaves from an old nest to a new one; and, more extraordinary still, they require to be fed by their slaves, even with plenty of food close at hand. Out of thirty of these ants placed by Huber in a box, with some of their larvae and pupae, and a store of honey, fifteen died in less than two days of hunger and of sheer inability to help themselves. When, however, one of their slaves was introduced, the willing servitor "established order, formed a chamber in the earth, gathered together the larvae, extricated several young ants that were ready to quit the condition of pupae, and preserved the life of the remaining Amazons." It must be noted that there are very varying degrees in the dependence of the ant-masters on their slaves. In the recognition of this graduated scale of relationship and dependence, indeed, will be found the clue to the acquirement of this instinct. The horse-ant (_Formica rufa_) will carry off the larvae and pupae of other ants _for food_, and it sometimes happens that some of these captives, spared by their cannibal neighbors, will grow up in the nest of their captor. A well-known ant, the _Formica sanguinea_, found in the South of England, is however, a true slave-making species, but exhibits no such utter dependence on its servitors as does _Polyergus_. The slave-making habit is not only typically developed in the _Sanguineas_, but the bearing of the captives to their masters indicate a degree of relationship and organization such as could hardly be conceived to exist outside human experience. The _Sanguineas_ make periodical excursions, and, like a powerful predatory clan, carry off the pupae or chrysalides of a neighboring species, _F. fusca_. Thus the children of the latter race are born within the nest of their captors in an enslaved condition. As slaves "born and bred," so to speak, they fall at once into the routine of their duties, assist their masters in the work of the nest, and tend and nurse the young of the family. The slaves, curiously enough in this instance, are black in color, whilst the masters are twice the size of the servitors, and are red in color, and that the slaves are true importations is proved by the fact that males and females of the slave species are never developed within the nest of the masters, but only within those of their own colonies. The slaves in this instance rarely leave the nest, the masters foraging for food, and employing their captives in household work, as it were; whilst, when the work of emigration occurs, the masters carry the slaves in their mouths like household goods and chattels, instead of being carried by them, as in the case of _Polyergus_.

Mr. Darwin gives an interesting account of the different attitudes exhibited by the _Sanguineas_ toward species of ants other than the black race from which their slaves are usually drawn. A few pupae of the yellow ant (_F. flava_), a courageous and pugnacious little species, were placed within the reach of the slave-making _Sanguineas_. A like chance presented with the pupae of their slave race was eagerly seized, and the chrysalides carried off. The pupae of the yellow ants, however, were not merely left untouched, but the slave-makers exhibited every system of terror and alarm at the sight of the chrysalides of their yellow neighbors. Such an instance demonstrates the existence not merely of perception but also of the memory of past experience, probably of not over agreeable kind, of encounters with the yellow ants. When, on the contrary, a nest of the slaves is attacked, the _Sanguineas_ are both bold and wary. Mr. Darwin traced a long file of _Sanguineas_ for forty yards backward to a clump of heath, whence he perceived the last of the invaders marching homeward with a slave pupa in its mouth. Two or three individuals of the attacked and desolate nest were rushing about in wild despair, and "one," adds Mr. Darwin, "was perched motionless, with its own pupa in its mouth, on the top of a spray of heath, an image of despair over its ravaged home." The picture thus drawn is not the less eloquent because its subject is drawn from lower existence; although the pains and sorrows of ant life may not legitimately be judged by the standard of human woe.

The explanation of the slave-making instinct in ants begins with the recognition of the fact that many ants, not slave-makers, store up pupae of other species for food. If we suppose that some of the pupae, originally acquired through a cannibal-like instinct, came to maturity within the nest of their captors, and in virtue of their own inherited instincts engaged in the work of the hive, we may conceive of a rational beginning of the slave-making instinct. If, further, the captors learned to appreciate the labors of their captives, as lightening their own work, the habit of collecting pupae as slaves might succeed and supersede that of collecting them for food. In any case, we should require to postulate on the part of the slave-makers a degree of instinct altogether unusual in insects, or, indeed, in higher animals; but that such instinct is developed in ants other than slave-makers admits of no dispute. The strengthening, through repetition, of a habit useful to the species may thus be credited with the beginning of the practice of slavery amongst ants; whilst special circumstances--such as the number of the slaves as compared with the number of masters--would tend to develop a greater or less degree of dependence of the captors or their servitors.

Huber, for instance, informs us that the _Fusca_-slaves of the _Sanguineas_ of Switzerland work with their masters in building the nest; they close and open the doors of the hive; but their chief office appears to be that of hunting for plant-lice. In England, on the contrary, the slaves are strictly household servants, rarely venturing out of doors. Such differences depend most probably on the fact that a greater number of slaves occur in Swiss than in English nests, and they may therefore be employed in a wider range of duties on the Continent than at home. A fewer number of slaves, a greater aptitude on the part of the slaves for their duties, the inability of the masters to perform the duties of the slaves--each or all of these causes combined would serve to increase the value of the servitors, and at the same time to reduce the independence of the masters.

This increase of the value of the slaves as active factors in the ant community might at length proceed to such extremes as we see exemplified in the _Polyergus_, already referred to--a race which has become literally unable to feed itself, and to discharge the simplest duties of ant existence, and whose actual life is entirely spent in marauding expeditions on the nests of its neighbors.

The subject of the general intelligence of ants, and of their ability to adapt themselves to awkward and unusual circumstances, may be briefly touched upon by way of conclusion.

Between the reason and intelligence of higher animals and the "instinct" of ants there is unquestionably a great gulf fixed. I make this statement unhesitatingly, notwithstanding that I should no more willingly attempt to define "instinct" than to give an exact definition of "insanity." In the latter case one may make the definition so limited as practically to exclude all save one class of cases, or so wide as to include even the judge on the bench. In the case of instinct, the rigid definition of one authority might cause us to regard it as the exclusive property of lower forms and as having no relationship whatever with the mental powers of higher beings; or, on the other hand, as being but a modified form of, or in some respects identical with, these very powers. We know too little respecting the so-called "automatic" powers and ways, even of higher animals, to dogmatize regarding the acts of lower animals, but we may safely assume that one apparent ground or distinction between instinct and reason may be found in the common incompetence of instinct to move out of the beaten track of existence, and in the adaptation of reason, through the teachings of experience, to new and unwonted circumstances. Let Dr. Carpenter speak as an authority on such a subject. "The whole nervous system of invertebrated animals, then, may be regarded as ministering entirely to _automatic_ action; and its highest development, as in the class of insects, is coincident with the highest manifestations of the 'instinctive' powers, which, when carefully examined, are found to consist entirely in movements of the excito-motor and sensori-motor kinds. (The terms '_excito-motor_' and '_sensori-motor_' are applied to nervous actions resulting in movements of varying kinds, and produced by impressions made on nervous centres, but without any necessary emotion, reason, or consciousness.) When we attentively consider the habits of these animals, we find that their actions, though evidently adapted to the attainment of certain ends, are very far from evincing a _designed_ adaptation on the part of the beings that perform them.... For, in the first place, these actions are invariably performed in the same manner by all the individuals of a species, when the conditions are the same; and thus are obviously to be attributed rather to a uniform impulse than to a free choice, the most remarkable example of this being furnished by the economy of bees, wasps, and other 'social' insects, in which every individual of the community performs its appropriated part with the exactitude and method of a perfect machine. The very perfection of the adaptation, again, is often of itself a sufficient evidence of the unreasoning character of the beings which perform the work; for if we attribute it to their own intelligence, we must admit that this intelligence frequently equals, if it does not surpass, that of the most accomplished Human Reasoner."

Appealing to the most recent observations on ants, we may find evidence of the truth of Dr. Carpenter's statements, whilst at the same time we may also detect instances of the development of higher powers which are hardly to be classed as "automatic," and which, in certain species (as in the _Ecitons_, charmingly described by Mr. Belt in "The Naturalist in Nicaragua"), may be said to be elevated above the common instincts of the race. Dr. Henry Maudsley has also well summed up the relationship of the acts of these insects to the acts of higher forms, and to new adaptations when he says: "I do not say that the ant and the bee are entirely destitute of any power of adaptation to new experiences in their lives--that they are, in fact, purely organized machines, acting always with unvarying regularity; it would appear, indeed, from close observation, that these creatures do sometimes discover in their actions traces of a sensibility to strange experiences, and of corresponding adaptations of movements. We cannot, moreover, conceive how the remarkable instincts which they manifest can have been acquired originally, except by virtue of some such power. But the power in them now is evidently of a rudimentary kind, and must remain so while they have not those higher nerve-centres in which the sensations are combined into ideas, and perceptions of the relations of things are acquired. Granting, however, that the bee or ant has these traces of adaptive action, it must be allowed that they are truly rudiments of functions, which in the supreme nerve-centres we designate as reason and volition. Such a confession might be a trouble to a metaphysical physiologist, who would thereupon find it necessary to place a metaphysical entity behind the so-called instincts of the bee, but can be no trouble to the inductive physiologist--he simply recognizes an illustration of a physiological diffusion of properties, and of the physical conditions of primitive volition, and traces in the evolution of mind and its organs, as in the evolution of other functions and their organs, a progressive specialization and increasing complexity."