Popular Science Monthly/Volume 12/December 1877/Our Six-Footed Rivals I
|OUR SIX-FOOTED RIVALS.|
LET us suppose that, having no previous acquaintance with the subject, we were suddenly informed, on good authority, that there existed in some part of the globe a race of beings who lived in domed habitations, aggregated together so as to form vast and populous cities; that they exercised jurisdiction over the adjoining territory, laid out regular roads, executed tunnels underneath the beds of rivers, stationed guards at the entrance of their towns, carefully removed any offensive matter, maintained a rural police, organized extensive hunting-expeditions, at times even waged war upon neighboring communities, took prisoners and reduced them to a state of slavery; that they not merely stored up provisions with due care, to avoid their decomposition by damp and fermentation, but that they kept cattle, and in some cases even cultivated the soil and gathered in the harvest. We should unquestionably regard these creatures as human beings. who had made no small progress in civilization, and should ascribe their actions to reason. If we were then told that they were not men, and they were in some places formidable enemies to man, and had even by their continued molestations caused certain villages to be forsaken by all human occupants, our interest would perhaps be mixed with some little shade of anxiety lest we were here confronted by a race who, under certain eventualities, might contest our claim to the sovereignty of the globe. But when we learn that these wonderful creatures are insects some few lines in length, our curiosity is cooled; we are apt, if duly guided by dominant prepossessions, to declare that the social organization of these beings is not civilization, but at most quasi-civilization; that their guiding principle is not reason, but "instinct," or quasi-intelligence, or some other of those unmeaning words which are so useful when we wish to shut our eyes to the truth. Yet that ants are really, for good or evil, a power in the earth, and that they seriously interfere with the cultivation and development of some of the most productive regions known, is an established fact. A creature that can lay waste the crops of a province or sack the warehouses of a town has claims upon the notice of the merchant, the political economist, and the statesman, as well as of the naturalist.
Many observers have been struck with the curious mixture of analogies and contrasts presented by the Annulosa and the Vertebrata. These two classes form, beyond any doubt, the two leading subdivisions of the animal kingdom. To them nineteen-twentieths of the population of the dry land, both as regards individuals and species, will be found to belong, and even in the world of waters they are largely represented. At the head of the Vertebrata stands the order of the Primates, culminating in man. At the head of the Annulosa the corresponding place is taken by the Hymenopterous insects. It is very remarkable—as first pointed out, we believe, by Mr. Darwin—that these two groups of animals made their appearance on the earth simultaneously. But along with this analogy we find a contrast. Man stands alone among the Primates as a socially organized being, possessing a civilization. Among the Hymenoptera the lead is undoubtedly taken by the ants, which, like man, have a brain much more highly developed than that of the neighboring inferior groups. But there is no one species of ant which enjoys a preëminence over its congeners anything at all approaching in its nature and extent to man's superiority over the gorilla or the mias. What may be the cause of this contrast we know not. Perhaps it is merely due to the tendency of the Annulosa to branch out into a scarcely numerable host of forms, while the vertebrate structure, less plastic, lends itself more sparingly to variation. Perhaps, on the other hand, lower human or higher ape forms than any now existing have been extirpated, as the traditions of many ancient nations would seem to admit.
At any rate, while the superiority of the ants as a group to the remaining Hymenoptera, to all other insects, and to the rest of the annulose "sub-kingdom," is undisputed, we are unable to decide which species of ant is elevated above the rest of the Formicide family. Possibly more extended and more systematic observations may settle this interesting question. According to our present knowledge the claims of the agricultural ant, of Western Texas (Myrmica barbata), seem, perhaps, the strongest. This species, which has been carefully studied by Dr. Lincecum, for the space of twelve years, is, save man, the only creature which does not depend for its sustenance on the products of the chase or the spontaneous fruits of the earth. As soon as a colony of these ants has become sufficiently numerous they clear a tract of ground, some four or five feet in width, around their city. In this plot all existing plants are eradicated, all stones and rubbish removed, and a peculiar species of grass is sown, the seeds of which resemble very minute grains of rice. The field—for so we must call it—is carefully tended by the ants, kept free from weeds, and guarded against marauding insects. When mature, the crop is reaped and the seeds are carried into the nest. If they are found to be too damp they are carefully carried out, laid in the sunshine till sufficiently dry, and then housed again. This formation of a plot of cleared land—or, as Dr. Lincecum not very happily terms it, a pavement—is a critical point in the career of a young community. Any older and larger city which may lie within some fifty or sixty paces looks upon the step as a casus belli, and at once marches its armies to the attack. After a combat, which may be prolonged for days, Providence declares in favor of the largest battalions, and the less numerous community is exterminated, fighting literally to the last ant. Where a colony is unmolested it increases rapidly in population, and undertakes to lay out roads: one of these, from two to three inches in width, has been traced to a distance of 100 yards from the city. These ants are not very carnivorous, nor do they damage the crops of neighboring farmers. Persons who intrude upon the "pavement" are bitten with great zeal, but otherwise the species may be regarded as harmless. One creature alone they seem to tolerate on their "pavement"—the so-called small black "erratic" ant—which, as Dr. Lincecum conjectures, may be of some use to them, and which is therefore allowed to build its small cities in their immediate neighborhood. If it becomes too numerous, however, it is got rid of, not by open war, but by a course of systematic and yet apparently unintentional annoyance. The agricultural ants suddenly find that it is necessary to raise their pavement and enlarge the base of their city. In carrying out these alterations they literally bury the nests of their neighbors under heaps of the small pellets of soil thrown up by the prairie earth-worms, and continue this process till the erratic ants in sheer despair remove to a quieter spot.
Concerning the government either of the agricultural ants or of other species, our knowledge is of a very negative character. The queens, or rather mothers, of the city are indeed treated with great attention, but their number is quite indefinite, and, unlike female hive-bees, no jealousy exists between them. How their migrations, their wars, their slave-hunts, are decided on, or even how the guards on duty are appointed, and the visiting parties selected who go round to inspect the works, and who sometimes insist on the destruction and rebuilding of any badly-executed portion, we are utterly ignorant. The outer manifestations of ant-life we have to some extent traced; but its inner springs, its directing and controlling powers, have eluded our observation.
It has been remarked, in the Quarterly Journal of Science, that ants, unlike man, have solved the problem of the practical organization of communism: this is literally true. In a formicary we can detect no trace of private property; the territory, the buildings, the stores, the booty, exist equally for the benefit of all. Every ant has its wants supplied, and each in turn is prepared to work or to fight for the community as zealously as if the benefit of such toil and peril were to accrue to itself alone. If the principle—so common among men—that there is no harm in robbing or defrauding a municipal body, or the nation at large, crops up in an ant-hill at all, it must evidently be stamped out with an old-fashioned promptitude. But, to understand why the ant has succeeded where man has failed, we must turn to certain fundamental distinctions between human and ant society; or, perhaps, speaking more generally, between the associations of vertebrate and those of annulose animals. A human tribe or nation—and, in like manner, e. g., a community of beavers or of rooks—is formed by the aggregation, not of single individuals, but of groups, each consisting of a male, a female, and their offspring. The social unit among vertebrates, therefore, is the family, whether permanent or temporary, and whether monogamous or polygamous. In numberless cases the family exists without combining with other families to form a nation, but we greatly doubt if there exists a single case of a vertebrate nation not formed of and resolvable into families.
Among the Annulosa this is reversed. The family among them scarcely exists at all. Rarely is the union of the male and the female extended beyond the actual intercourse, all provision for the future young devolving upon the latter alone. Among the rare exceptions to this rule, we may mention the burying-beetle, and some of the dung-beetles, both sexes of whom labor conjointly to find and inter the food in which the eggs are to be deposited. Generally speaking, moreover, the young insect never knows—never even sees—its parents, who in most cases have died before it has emerged from the egg. Among non-social insects the earwig and a few other Orthoptera form the chief exceptions. Where a regularly organized society, a nation, or tribe, exists among annulose animals, it is not formed by the coalescence of families to a higher unity. The family, if it can be said to exist at all, is conterminous and identical with the nation. This absence of a something whose claims are felt by all ordinary men to be stronger than those of the state has rendered the successful organization of the "commune" feasible among ants, and among other social Hymenoptera, such as bees, wasps, etc. With them the state has no rival, and absorbs all the energies which in human society the individual devotes to the interests of his family. We thus see that theorists on social reform have been, from their own point of view, logically consistent in attacking the institution of marriage and the whole system of domestic life: they have sought to abolish the great impediment to the commune, and to approximate man to the condition of our six-footed rivals, and to constitute society not as heretofore of molecules, but of atoms.
But it is not enough to show that the failure of communism among mankind and its success among certain Hymenopterous insects are due to the existence and the power of the family in the former case, and to its absence in the latter. We have yet to inquire into the wherefore of so important a distinction. Vertebrate society, where it exists at all, is founded on family life, because every vertebrate animal is sexual, and as such is attracted to some individual of the opposite sex by the strongest instinct of its nature, that of self-preservation alone excepted. Invertebrate society, where it exists in perfection, as among the Hymenoptera, is not formed by a union of families, because the great majority of Hymenopterous individuals (in the social species) are non-sexual, neuter, incapable of any private or domestic attachments, and devoted to the community alone. To attempt, without the existence of such an order, to introduce the social arrangements of the ant—i. e., communism—among mankind is as futile and as irrational as the endeavor to fly without wings: the very primary conditions for success are wanting.
It may not be amiss to examine a little further in the same direction. Among men there is a great diversity both in intellect and in energy. The more highly-endowed individual, if he does not leave his children in a better position, materially speaking, is likely to transmit to them his own personal superiority. In this manner the theoretical equality assumed as one of the bases of communism is in practice annihilated. Among ants nothing of this kind can prevail. The workers and the fighters are sexless. If any individual is superior to its fellows in strength or in intelligence—and we have every reason to believe that such must be the case—it has no posterity to whom its acquisitions could be bequeathed or its personal superiority handed down. Hence the formation of an aristocracy is impossible, and whatever benefit may result from the labors of such an exceptional individual flows to the entire community. In the converse manner the formation of a pariah, a criminal, or a pauper class, is frustrated, and the public is not burdened with useless or dangerous existences.
It is indisputable that this arrangement, joined to the brief term of insect-life, must greatly retard the progress of the ant in civilization. It has been remarked that were human life longer our development in knowledge and in the arts would be much more rapid. Take our present condition: by the time a man has completed his education, general and special—has fully developed his own mental faculties and mastered the position of the subject he has selected—he will be rarely less than five-and-twenty years of age. By the time he is fifty, as a rule, his power of origination begins to decline, and the remainder of his life is spent more in completing and rounding off the work of his younger days than in making fresh inroads into the unknown. Did our full vigor of intellect extend over a century, instead of over a fourth of that duration, we should undoubtedly effect much more. On the other hand, a shortening of our time of activity would have a powerfully retarding effect on the career of discovery and invention. Can we, then, wonder if the short-lived ant and bee sometimes appear to us stationary in their civilization? But this very brevity of the career of each individual acts decidedly in favor of the preservation of social equality. If either ant or man is disposed to rise or to fall, then the shorter the time during which such rise or fall is possible the better will the uniform level of society be preserved. To prevent misunderstanding we must remark that castes with a corresponding difference of duties, and, according to some authorities, with a diversity of honor also, do occur in the ant-hill; but within each caste all are on an exactly equal footing.
If we compare the zoölogical rank of our "six-footed rivals" with our own, we must, from one point of view, concede them a higher position. The more perfectly developed is any animal the more do we find it possessed of an especial organ for the discharge of every function. In like manner it may be contended that, as a species rises in the scale of being, duties once indiscriminately performed by all the species are assigned to distinct individuals. Among the humbler groups of the animal kingdom the whole reproductive task is performed by all members of the species. In other words, hermaphroditism prevails. As we ascend to higher groups the sexes are separated, and the species becomes dimorphous. This arrangement prevails among all vertebrate animals, and among a large majority of annulose species. We find here already, however, one of those contrasts which so often prevail between these two great series of beings. Among vertebrates, and especially in mankind, the function of the female sex seems limited to the nurture—intra-and extrauterine—of the young. Were man immortal and non-reproductive, woman's raison d'être would disappear. Among Annulosa the very reverse holds good; the females are as a rule larger, stronger, and more long-lived, while the task of the male seems limited to the fecundation of the ova. This being once performed, his part is played. Among butterflies, moths, and ants, his death speedily follows, while among spiders he is generally killed and devoured by his better-half. This predominance of the female sex seems to prepare the way for the phenomenon which we recognize among the social Hymenoptera. Here the species become no longer dimorphous, but polymorphous. In other words, in addition to the males and females, whose task is now exclusively confined to the mere function of reproduction, there are, as we have seen, one or more forms of females, sexually abortive, but so developed in other respects as to form the castes of workers and fighters, upon whom the real government of the ant-hill devolves, who provide for its enlargement, well-being, and defense.
It may, we think, be legitimately contended that the development of a distinct working order is a step in advance similar to that taken by the distribution of the sexual functions among two different individuals—that the polymorphic species is higher than the dimorphic, just as the dimorphic is higher than the monomorphic.
Of the development of a neuter order among vertebrate animals, and especially among mankind, we know nothing which can be fairly called a trace. But, in comparing the two civilizations, that of man and that of the ant, we must be struck with the fact that the former has from time to time imitated this peculiar feature. The attempts, however, whether made by the devotion of certain classes to celibacy or by actual emasculation, have been as unsuccessful as the sham elephants of Semiramis. Celibates retaining the sexual appetite, but deprived of its legitimate exercise, have always been a disturbing force in society. On the other hand, emasculation, instead of—as might have been perhaps, a priori, anticipated—increasing the powers of body and mind, enfeebles both. What would be the moral and social effects of the appearance of a neutral form of the human species analogous to the working bee or ant it is impossible to foresee; but we may venture to surmise that they would not be entirely desirable.
It may be suggested that the institution of caste among so many human races is an adumbration of the natural castes existing among social insects, each devoted to some especial function.
The remarkable intelligence of ants has from very early ages made a profound impression on man. Cicero considered them possessed of "mind, reason, and memory." To the present day those who watch the formicary, not in order to defend prepossessions, but to arrive at truth, come to the same conclusion, unpopular though it may be. We sometimes wonder whether ants, like men, consider themselves the sole reasonable beings on the globe, prove their position by sound a priori arguments, and accuse those who take a different view of "skepticism" or "agnosticism."
When it is no longer possible to meet with a flat denial all instances of correct inferences drawn and of happy contrivances adopted by brutes in general and by ants in particular, the writers who still claim reason as the exclusive prerogative of man bring forward a curious objection: they urge that we should likewise collect proofs of animal folly and stupidity, and seem to think that these latter instances would nullify any conclusion that might be drawn from the former. That instances are numerous where some animal fails to draw an inference—very-obvious, in our view—or to adopt some very simple expedient, we do not deny, and that their conduct hence seems strangely checkered, we admit. What, e. g., can seem more inconsistent than the following cases? Sir John Lubbock, to test the intelligence of ants, placed a strip of paper so as to serve as a bridge or ladder for some ants which were carrying their pupæ by a very roundabout way. The slip was, however, purposely left short of its destination by some small fraction of an inch. It would have been very easy for the ants either to have dropped themselves and their burden down this short distance, or to have handed the pupæ to the other ants below, or to have piled up a small amount of earth from below, so as to meet the slip of paper, and thus make the descending road continuous. They adopted, however, none of these expedients, but continued to travel the roundabout way.
On the other hand, Mr. Tennant tells us that Formica smaragdina, in forming its dwellings by cementing together the leaves of growing trees, adopts the following method: A line of ants, standing along the edge of one leaf, seize hold of another, and bring its margin in contact with the one on which they are posted. They then hold both together with their mandibles, while their companions glue them fast with a kind of adhesive paper which they prepare. If the two leaves are so far apart that a single ant cannot reach from one to another, they form chains with their bodies to span over the gap. The same author also informs us that certain Ceylonese ants, when carrying sand or dry earth for the construction of their nests, glue several grains together so as to form a lump as large as they can carry, and thus economize time and labor.
Mr. Belt, in his "Naturalist in Nicaragua" (page 27), gives the following account of the manner in which the Ecitons, or foraging 'ants of Central and South America, deal with what may be called engineering difficulties: "I once saw a wide column trying to pass along a crumbling, nearly perpendicular slope. They would have got very slowly over it, and many of them would have fallen, but a number having secured their hold and reaching to each other remained stationary, and over them the main column passed. Another time they were crossing a water-course along a small branch, not thicker than a goose-quill. They widened this natural bridge to three times its width, by a number of ants clinging to it and to each other on each side, over which the column passed three or four deep; whereas, except for this expedient, they would have had to pass over in single file, and treble the time would have been consumed."
Again, in Eciton legionis, according to Mr. Bates, when digging mines to get at another species of ant whose nests they were attacking, the workers were divided into parties, "one set excavating and another set carrying away the grains of earth. When the shafts became rather deep the mining parties had to climb up the sides each time they wished to cast out a pellet of earth, but their work was lightened for them by comrades who stationed themselves at the mouth of the shaft and relieved them of their burdens, carrying the particles, with an appearance of foresight which quite staggered me, a sufficient distance from the edge of the hole to prevent them from rolling in again."
What, then, are we to learn from these somewhat inconsistent cases? Are we to conclude that Sir John Lubbock, Mr. Belt, Mr. Bates, and Mr. Tennant, must be careless and incompetent observers? Assuredly not. Are we to believe that ants are stupid, irrational creatures, and that when they do anything right it must be regarded as an accident or ascribed to that convenient phantom, instinct? Still less: the well-established cases which are on record agree badly with either of these suppositions. The true explanation of the difficulty is that, like all finite intelligences, ants are not equally wise on all occasions. Sometimes they hit upon the best expedient for evading or overcoming an obstacle, but sometimes, under circumstances not more complicated, they fail. This is doubtless the case with man himself. If contemplated by some being endowed with higher reasoning powers, would he not be pronounced a most curiously inconsistent mixture of sagacity and stupidity, now solving problems of no small difficulty, and now standing helpless in presence of others even more simple? That such is in reality the case with man is proved by the history of discoveries, and of their reception. Do we not always say when we hear of any great step, whether in scientific theory or in the practical arts, "How simple, how natural!" Yet, simple and natural as it is, all sorts and conditions of men lived for centuries without opening their eyes to it. To those who, on the score of incidental blunders and stupidities, deny the rationality of' animals, we would hold up the ever-memorable "egg" of Columbus, and exclaim, "What, gentlemen, do you expect the ant to be be more uniformly and consistently intelligent than your erudite selves?"
Concerning the language of ants no small diversity of opinion has prevailed; but among actual observers the general conclusion is that these tiny creatures can impart to each other information of a very definite character, and not merely general signals, such as those of alarm. It has been found that ants fetched by a messenger for some especial purpose seem, when they arrive at the spot, to have some knowledge of the task which is awaiting them, and set about it at once without any preliminary investigation. The cases which we quote elsewhere from Mr. Belt are very conclusive on this point. In order to decide whether ants are really fetched to assist in tasks beyond the strength of any one of their number, Sir John Lubbock instituted a very interesting and decisive experiment. It is well known that if the larvæ of ants are taken out of the nest, the workers never rest till they have fetched them back. Sir John Lubbock took a number of larvæ out of his experimental formicary, and placed them aside in two parcels very unequal in number. Each of these lots was soon discovered by an ant, who at once fell to work to carry the larvæ back to the nest, and was soon joined by others, eager to assist. The observer reasoned thus: If these ants have come to the spot by accident, it is probable that the number who arrive at each lot will be approximately equal. On the other hand, if they are intentionally fetched to assist in removing the larvæ, the number in each case will most likely bear some proportion to the amount of work to be done. The result was, that the large heap of larvæ was visited by about three times as many ants as the small one. Hence the inference is plain that ants can call assistance to any task in which they are engaged, that they can form some estimate of the amount of labor that will be required, and can make their views in some manner known to their companions. The manner in which, when on the march, they are directed by their officers, and the promptitude and precision with which a column is sent out to seize any booty indicated by scouting parties, show likewise a completeness and precision of language very different from anything we observe in quadrupeds and birds.
But as to the nature of this language, which Mr. Belt rightly calls "wonderful," we are as yet very much in the dark. Sounds audible to our ears they scarcely can be said to emit. Their principal organs of speech are doubtless the antennæ: with these, when seeking to communicate intelligence, they touch each other in a variety of ways. There can be no doubt that, with organs so flexible and so sensitive, an interchange not merely of emotions but of ideas must be easy.
But there is another channel of communication which deserves to be carefully investigated. We know that the language of vertebrates, or at least of their higher sections, turns on the production or recognition of sounds. What if the language of social insects should be found to depend, in part at least, on the production and recognition of odors? We have already full proof that their sense of smell is developed to a degree of acuteness and delicacy which utterly passes our conceptions of possibility, and to which the scent of the keenest hound presents but a very faint approximation. Collectors of Lepidoptera are well aware that if a virgin female moth of certain species is inclosed in a box, males of the same species will make their appearance from distances which may be relatively pronounced prodigious. As soon, however, as the decoy has been fecundated, this attraction ceases. This is only one among the many phenomena which testify to the wonderful olfactory powers of insects. So much, then, for the recognition of odors. Nor is their production among insects a matter open to doubt. Scents, distinctly perceptible even to our duller organs, are given off by many. The pleasant odor of the musk-beetle, and the offensive smells of the ladybirds, the common ground-beetles, the oil-beetles, the Spanish fly, and the "devil's coach horse"—hence technically named Gœrius olens—are known to every tyro in entomology. The next question is, Are these odors at all under the control of the insect, and capable of being produced, suppressed, or modified at will? We have noticed many instances where the odors of insects became more intense under the influence of anger or alarm. A peculiarly pungent odor is said to issue from a beehive if the inmates are becoming excited.
The possibility of a scent-language among insects must therefore be conceded. Mr. Belt thinks that the Ecitons mark out a track which is to be followed by their comrades by imparting to it some peculiar odor. He says: "At one point I noticed a sort of assembly of about a dozen individuals that appeared in consultation. Suddenly one ant left the conclave, and ran with great speed up the perpendicular face of the cutting without stopping. It was followed by others, which, however, did not keep straight on like the first, but ran a short way, then returned, and then again followed a little farther than the first time. They were evidently scenting the trail of the pioneer, and making it permanently recognizable. These ants followed the exact line taken by the first one, though it was far out of sight. Wherever it had made a slight détour, they did so likewise. I scraped with my knife a small portion of the clay on the trail, and the ants were completely at fault for a time which way to go. Those ascending and those descending stopped at the scraped portion, and made short circuits until they hit the scented trail again, when all their hesitation vanished, and they ran up and down it with the greatest confidence."
That among groups like the Ecitons, in which the sense of sight is imperfect, or even totally wanting, enhanced delicacy of scent and touch must be required in compensation, may be taken as self-evident. With the language of ants, and especially with a possible scent-language, is connected the faculty by means of which denizens of the same city recognize each other under circumstances of great difficulty. In the battles which take place between two nations of the same species, how, save by scent, do the tiny warriors distinguish friend from foe? We are told by some older observers that if an ant is taken from the nest, and restored after the lapse of several months, it is at once received by its companions and caressed, while a stranger ant introduced at the same time is rejected, and generally killed. To a great extent this has been confirmed by recent investigators. The returned exile was not indeed caressed, but was quietly allowed to enter the nest, while a stranger was at once greeted with hostile demonstrations. It has been maintained that this power of recognition is destroyed by water, and that ants will treat a comrade as an enemy if he has received a drenching. This, however, is evidently a mistake. To prevent rain from penetrating into the nests of the agricultural ant, the guards block up the doorways with their bodies, and are often drowned at their posts. But their companions are not thereby prevented from recognizing them, as they try to bring the dead bodies to life.—Quarterly Journal of Science.
- It is very remarkable that among the Termites, which, though improperly called "white ants," belong to a different order of insects, neuters exist. These, however, do not appear to be imperfectly developed females. It would thus seem that among insects social organization necessitates a class of sexless individuals.
- "Mens, ratio, et memoria."