Chapter IV: Introduction (1)

My design in this Introduction, is to take a rapid review of the facts collected by several writers relative to the History of Ants. The descriptive part, better known than that which refers to their manners and habits, still presents some doubts which I shall attempt to remove. De Geer, among the ancient, Fabricius and Latreille among the modern naturalists, are those to whom I shall have recourse for their classification.

Systematic authors have placed Ants in the class of insects with four naked wings--with Bees, Wasps, Andrenæ, &c. from which they differ essentially in the composition of their families, where we find the males and females furnished with wings, and the workers without them.

The characters given by M. Latreille, to distinguish them more particularly, are that of having “the peduncle of the abdomen surmounted with a scale, or knotty; the abdomen of the workers and females ejaculating an acid, or armed with a sting; the antennæ filiform, or slightly enlarged at their extremity, bent or fractured in the middle, composed of twelve or thirteen joints; the second conical, of the same length as those that follow; a tongue, spoon-shaped, entire; the upper lip effaced; the palpi filiform unequal, anterior of five, posterior of four joints. The first of these characters furnishes two very distinct families, the one, composed of all those ants that have the peduncle surmounted by a scale, the other, of all those in which it is formed of two knots. The characters of the first family, are--having the antennæ filiform, or pointed at the extremity; no sting; a simple venom-bag; the abdomen more elongated, and composed in the females and workers of five rings.”

The ants of the second family have the antennæ moniliform, and considerably enlarged at their extremity; a sting; the abdomen short, and composed of four rings in females and the workers.

The males have, in general, the antennæ longer, and of thirteen joints; the abdomen is composed of one ring more than in other individuals of their species; they possess neither a sting nor a venom-bag. As we shall treat in this work of none but indigenous ants, all of which find place in this general division, I shall not enter into greater detail relative to their classification.

Let us examine separately all the parts of the body of ants in order to know their external organs. Their head is triangular, oblong, and terminates in a point more or less obtuse; it is thick at the top, thin at the opposite extremity, and terminated by two large teeth, termed mandibles; underneath is the mouth, properly so called. On each side are large reticulated oval eyes; above, we commonly notice three more, very small, and placed so as to form a triangle. In the fore-part of the head are the antennæ, and underneath the lower jaws the palpi.

The mandibles of the females and the workers are of a horny structure, concave, curved, denticulated, moveable, and serve for several purposes: those of the males are very slender, terminate in a point, and are covered with hair. Besides these organs with which the mouth is externally furnished, we also remark an upper lip, slightly projecting, two inferior jaws, very small, which play from right to left, and a lower lip, hidden entirely underneath; we are not yet agreed as to their composition.

Fabricius gives to Ants of all kinds, for their principal character, that of having a mouth destitute of a tongue (_os absque Lingua_); Latreille, on the contrary, grants them one, expressing it under this form (_Langue en cuilleron entière_); “the lower lip,” he says, “is formed of a conical furrow, coriaceous, with an elevated ridge in the middle, and terminated in a point, and of a tongue, or membranous portion, lodged in this furrow, and spoon-shaped.”--I beg leave to add some few observations to those of these great naturalists. When the ants wish to drink, we see proceed from their lower jaws, which are much shorter than the upper, a little conical, fleshy, and yellowish tubercle, which performs the office of a tongue, advancing and retiring alternately; it appears to proceed from what we term the lower lip, which serves as the base, and perhaps a sheath to this tongue, and which is so small, that it is only from analogy with other insects we have given it this name. This lip is capable of advancing conjointly with the two lower jaws, and when the insect wishes to lap, the whole apparatus makes a progressive movement, in such a way, that the tongue, which is very short, has no need of much extension to enable it to accomplish its object. The jaws are elongated, enlarged at their extremity, slightly concave underneath, of a horny substance, and, compared to the mandibles, extremely slender and weak. In the centre, externally, we notice palpi of six rings each, and two more may be also perceived at the base of the tongue; the latter are much smaller and composed only of four rings: we are as yet unacquainted with their use.

The antennæ, as we have before stated, are bent or fractured, situated in the fore-part of the head, more or less near the middle of the forehead; they lie in a small longitudinal furrow, and are composed of twelve or thirteen joints; the first being about half their length. The antennæ of those ants that have a scale upon the fillet of the abdomen are filiform, and are composed of rings of the same size, or terminate slightly in a point. The ants of the second family have the antennæ, on the contrary, enlarged at the extremity; those of the males are setaceous in the first species, more granulated in the latter species, and in all are formed of one ring more than in the workers and females.

The head is connected to the thorax or corslet by a thin, short, and narrow neck, of a fleshy substance, and furnished with muscles, by which all its movements are regulated.

The corslet of the winged individuals is very large comparatively to the head; that of the workers is much narrower; that of the former is convex, entire, composed of several horny pieces, of different forms, retained by proper membranes: the superior is separated from the sternal portion by a furrow, in the middle of which the wings are implanted. The wings are placed in the back part of the corslet, whilst, in other insects of the same kind, they are situated more in front of the body. Another remarkable character respecting their insertion is,--that the corslet has none of those instruments (_Cuillerons_) destined to moderate the movements of the wings, and which are situated at their base in the other hymenopterous insects.[1]

[1] These observations were communicated to me by Professor Jurine, and are a proof of the distinguishing glance of this able naturalist.

The corslet of the workers is gibbous, divided equally, and composed, according to De Geer, of three pieces; the first--that nearest the head, is thick and round; the second is of less size, extends to the under part of the abdomen, and appears divided in two transversely; the third, much thicker than the second, is truncated and obtuse. We cannot well define the form of the corslet, since it varies according to the species; it has four stigmæ, two of which rest in a slight lateral depression (which seems to divide the corslet), one on each side; the other two are situated near the posterior extremity, to the right and left of the fillet.

The wings, which are four in number, are transparent, large, and sleek; the posterior are shorter than the anterior, their nervures are slightly coloured, and the stigma is yellow or brown. These wings are hooked when the insect flies; they form but one horizontal surface by means of a series of little hooks disposed at their margin.

To each of the three lower parts of the corslet are attached a pair of legs. They are connected by a moveable piece, long and conical, which we may term the hip. The posterior legs are the longest; they are each divided into three principal parts--the thigh, the leg, and the foot or tarsus; the latter is formed of five conical pieces, of unequal length, articulated together, and more or less hairy; the tarsus is terminated by two hooks, between which lies a round substance, which we may regard as the sole of the foot. We remark, at the extremity of the leg, properly so called, a spine or spur, straight, strong, and smooth; that on the anterior feet is slightly curved, and covered with stiff hair, where it is connected to the foot. The first piece of the tarsus, which is opposite the spur, presents a considerable curvature. It is furnished with a fringe-work of strong hair, cut regularly. This constitutes the brush which the insect employs when cleaning its antennæ, head, and corslet; it has also other uses, but to these I shall allude on another occasion.

The vertical scale is heart-shaped, with the point turned downwards. It is traversed at its origin by the abdominal fillet; its form varies, and it furnishes very distinct characters. Latreille remarks that it is provided with two stigmæ, which are situated at its base on the posterior side.

The abdomen or belly of the ant is always larger than the corslet, of an oval form, swoln, and more or less pointed at the posterior extremity. It is composed of demi-rings, which are of a horny substance; the superior are connected with the inferior by means of a flexible membrane, which allows of their separation and approximation at will. It is easy to notice this when the insect has taken a full meal, since each of these horny pieces appears then to be separated from the rest by a little whitish band, which is nothing more than this membrane. The abdomen is composed of four or five rings, the last of which gives passage to the sexual organs and the sting.

Latreille regards the scale as characteristic, which rests on the fillet of the abdomen, and takes the place of a ring, which, without that, would be wanting in the abdomen of these insects. These are his words:--“Naturalists,” he says, “have not considered that this scale or these knots on the peduncle of the abdomen of ants are only the first rings shaped in this way. Several wasps have also the first segment of the abdomen formed like a knot. To decide this point, let us count the number of rings of which the abdomen of ants is composed; we know, and it is a constant rule with respect to insects of this order, that there are seven rings in the abdomen of males, and six in that of females. Let us see if, after taking away the scale and the knots of the peduncle, we shall find this number. We do not:--for the abdomen of the females or workers, which has a scale or single knot in the fore-part, possess but five rings, and that of the males only six. The abdomen of those ants whose peduncle is formed of two knots, will have still one ring less; that is to say, four in some, and five in others.”--We have already remarked, that the workers and females of some species are provided with a sting; this consists of a little short, horny substance, straight and conical, formed of two filaments, and accompanied with two other little pieces, conical, smooth, compressed, one on each side. “There exists,” continues M. Latreille, “the greatest resemblance between the exterior organs of generation in single females and workers; the resemblance indeed is so close, that on the most severe examination we can scarcely perceive any sensible difference.” He regards the workers as impotent females, whose organs have not received their full development. In truth, if we consider the form of their head and their teeth, the number of the joints or articulations in their antennæ, the number of their rings, the presence of the sting, or that of the venom-bag which replaces it, we shall be struck with the similarity existing between these two orders. The workers are much smaller than the females; they also differ in the form of the corslet, in the absence of wings, and in colour. Some of the males are smaller, others larger than the workers of their species; their corslet is shaped like that of the females; the scale or knots are of great similarity in all the individuals of each family: the males are commonly of a blackish hue.

Our knowledge of the manners and habits of ants is extremely limited, consisting only of a small assemblage of detached facts, and of a few assertions, sufficiently vague, which I shall discuss in their proper place. In the list of modern authors who have contributed to the history of ants, we find naturalists of the greatest celebrity.

Leeuwenhoeck is the first who seriously attended to the metamorphoses of ants, and proved that what had been hitherto regarded as their eggs were the real larvæ; indeed from their magnitude this should have been previously known, the eggs of these insects being exceedingly minute.

Swammerdam confirms, by profound researches and admirable descriptions, the observations published by his predecessor:--he notices the several changes ants undergo, and shows the pupa to be the same individual that under the form of larva possessed neither limbs nor any distinct features. He points out the distinction between the males and females, which, he says, are furnished with wings, and remarks, that the common ants are labourers or neuters, as obtains in bees. He also describes some of the domestic occupations in which ants are engaged, and informs us, that the larvæ of some species spin a silken envelope, in which they undergo their transformation, and then gives us excellent descriptions of several species of ants.

Linnæus comes next:--he describes seven species of ants met with in Sweden;--treats of the large conical ant-hills abounding in fir-forests; finds the female ants, as well as the males, furnished with wings; which, he says, they lose a little time after birth, and is of opinion they never return to their original habitation.

Geoffroy adds nothing to the facts brought forward by these excellent naturalists: he falls, on the contrary, into several errors, which, as they have been combated by De Geer, I shall pass over in silence.

This last author (De Geer) informs us, that the young ants cannot extricate themselves from their silken envelope without the assistance of the labourers; and that the larvæ of the shining black ant do not always spin, since we find in their nest pupæ both naked and enclosed. He also observes that the larvæ of certain species pass the winter in that state, and that those of the Yellow Ant are closely invested with hair in the month of April, &c.--Passing from the infant to the adult state of the ant, he notices their amours in the air, believes that the females return to their nest to deposit their eggs, in this respect opposing the opinion of Linnæus, who was, however, better informed on this subject than himself. This justly celebrated naturalist, notwithstanding, gives us more information upon the history of ants than the whole of his predecessors.

Charles Bonnet was in his turn occupied:--he was of opinion that ants are directed in their migrations by the scent. He notices a small family-establishment of these insects on the head of a thistle, of which he gives us an interesting account. Had he, however, opened it, he would have, with admiration, discovered the motive which drew them thither, and would no longer have been astonished at their living there without touching the provision he tendered them. He saw these ants engaged in carrying each other, and describes their proceedings in his usual lively and agreeable manner, although unaware of the purport for which these insects had assembled.

M. Latreille confirms the facts brought forward by other authors. He notices two species of ants destitute of eyes, but does not describe their manners. He also advances some conjectures to which we shall refer hereafter.

It appears from all the observations made to the present day, that we are not agreed as to the fate of the males and females; that we know not why certain larvæ should, others should not, spin; why among some species we should find pupæ both naked and enclosed; that we have not sufficiently attended to the spirit which reigns in the interior of ant-hills, nor to the relation existing between the labouring ants and their females; that we have not discovered whether they possess the means of understanding each other; that we have not sufficiently described the construction of their abode, nor the manner in which they establish it, nor do we know whether these insects do or do not form colonies, &c. The number of questions not yet solved is endless; it is, however, time to fill up some of the numerous sketches which our predecessors have left us upon this subject, and place, if possible, the history of ants on a more solid and secure foundation.

CONTENTS.

CHAP. I.

Page

+The+ Architecture of Ants 1

1. The Architecture of the Fallow Ants 2

2. ---- ---- ---- ---- Mason Ants 16

3. ---- ---- ---- ---- dark Ash-coloured Ants 35

4. ---- ---- ---- ---- Ants that inhabit timber 47

5. ---- ---- ---- ---- Ants that form their residence of
saw-dust, &c. 58

CHAP. II.

+Of+ the Eggs, Larvæ, and Pupæ of Ants 60

CHAP. III.

+Of+ the Fecundation, &c. of Ants 94

1. Of the departure of the Winged Ants _ib._

2. ---- ---- History of the Winged Ants after impregnation 108

3. ---- ---- conduct of the Labourers towards the pregnant
females 127

CHAP. IV.

+Of+ the relation between Ants 142

2. Of the manner in which Ants are guided in their several
excursions 151

3. ---- ---- migrations of the Fallow Ants 157

4. ---- ---- affection of Ants for their companions 168

CHAP. V.

+Of+ the wars of Ants, and some other particulars 178

CHAP. VI.

+Of+ the Relation of Ants with the _Pucerons_ and _Gall
Insects_ 205

1. Of the Antennal Language _ib._

2. ---- ---- intimacy of Ants with the _Pucerons_ 210

3. ---- ---- Relation of Ants with the _Gall Insects_ 219

4. ---- ---- almost human industry of Ants 222

5. ---- ---- resources of the Ants during winter 237

6. ---- ---- eggs of the _Pucerons_ 239

CHAP. VII.

+First+ historical sketch of the Amazon Ants 248

CHAP. VIII.

+Researches+ into the origin of mixed ant-hills 264

CHAP. IX.

+Further+ information on the Amazon Ants 288

CHAP. X.

+The+ Establishment of a mixed Ant-hill, in a glass apparatus 310

CHAP. XI.

+History+ of the Sanguine Ants 329

CHAP. XII.

+Observations+ on those insects that live in Republics 346

+Appendix+ 379

_Pubd. by Longman & Co. Pater Noster Row. May 2nd. 1820._

THE

NATURAL HISTORY

OF

ANTS.

CHAP. I.

THE ARCHITECTURE OF ANTS.

The first objects which strike the attention in entering upon the study of the history of ants, are the art with which they form their habitations; their variety, and the manner in which they respectively answer the wants of the species who construct them. They are sometimes fabricated with earth, sometimes hewn out in the trunk of the most solid trees, or simply composed of leaves and stalks of plants collected from all quarters. They are of an astonishing size, when compared with their diminutive architects.

I hope, in the course of the present work, to bring the reader to conceive what degree of intelligence we may grant these insects, whose faculties, police, and sagacity, have been, by some authors, as much over-rated as by others not duly appreciated.

The three modes of building, of which I have just spoken, admit of numerous modifications, each species of ant being endowed with some peculiar talent. I shall mention in what they differ, after describing the general outline of their architecture, if we may express, by the same term, the simple and rude work of an insect, and an art brought to perfection by the hands of man.

1. ART OF BUILDING AMONG THE FALLOW ANTS.

The fallow ant is that ant which forms in the woods those hillocks so remarkable for their extent. It admits of easy observation, from its being above the middle size, from its operations being carried on in open day, and from the simplicity of the work in which we find it engaged. It is very common in every part of Europe, and has, therefore, occupied the attention of Linnæus, De Geer, &c., but these learned men, having noticed it under a point of view different from mine, and my plan not permitting me to mention what they say upon this head, I shall, after briefly describing these insects, commence by explaining the construction of their abode, at the same time noticing the very exact police ants of this species observe.

The working fallow ants are from three to four lines in length, and stand high upon their legs. Their head, which is larger than the corslet, is of a pale red or fallow colour at the extremity, and blackish at the top. The mouth is armed with two very strong mandibles, denticulated and hooked at the point, which they generally keep apart, and make use of, not only for attacking their enemies and tearing their prey, but in carrying burthens, and performing the labours and reparations of the ant-hill. The antennæ are black and filiform. The corslet is protuberant, raised anteriorly, compressed and truncated posteriorly, often marked with a black stain above, the rest being of a clear fallow colour. The peduncle of the abdomen is of the same colour, and bears a large scale, which is scolloped and blackish on its superior margin. The abdomen is brown or ash-coloured, slightly invested with hair, globose, composed of five rings, not counting the scale, wanting the sting, but armed with a venom-bag. The feet are brown, and the thighs, at their origin, of a reddish tint. I have described, in the Appendix, two varieties of these ants; one with a black back, another with a back of the same colour as the rest of the corslet. This difference, which scarcely affects the habitudes of these insects, separates, however, those who inhabit the woods from those who live along-side hedges, and in meadows. It is the latter only, that have the corslet stained with black and the scale on its upper margin[1] brown. They both collect, near their habitation, fragments of straw, pieces of wood, little stones, leaves, and all other objects within reach, that may be of service in increasing its height, not neglecting even moths, minute shells, corn, oats, and barley, which doubtless gave rise to their ancient renown. But if this foresight, which we supposed them to possess, has not for its object to preserve them from famine during the winter, a time in which ants eat but little, especially grain, it is not the less worthy of our regard, when we consider its real purport.

[1] _Vide_ the description of the fallow ant, and particularly the note in the Appendix.

That little mound which seems at the first glance only an assemblage of materials confusedly scattered, is, however, an invention as ingenious as simple to carry off the waters from the ant-hill, to defend it from the injuries of the air, and from hostile attacks, and to regulate the heat of the sun, or retain it in the interior. The mass of the different materials of which it is composed, always presents a circular dome, whose base, often covered with earth and pebbles, forms a cone, above which the wooden portion of the building is erected in the form of a sugar loaf. But this is simply the exterior covering of the ant-hill; the most considerable portion is hidden from our sight, descending to a depth of greater or less extent. Avenues constructed very carefully of an irregular funnel shape conduct from the roof to the interior. Their number depends upon the population of the nest and its extent. The entrance to the nest is more or less considerable. We sometimes find a spacious aperture at the top, but more frequently, several apertures of nearly equal size, around which are many narrow passages, symmetrically and circularly disposed, which extend even to the base of their habitation.

These several apertures were necessary to give a free egress to the vast multitude of labourers of which their colony is composed. Not only do they work continually on the outside of their nest, but differing very essentially from other species who willingly remain in the interior sheltered from the sun, they prefer living in the open air, and do not hesitate carrying on, even in our presence, the greater part of their operations.

In the habitations of the yellow ant, the dark ash-coloured ant, the sanguine ant, the brown ant, &c. we never observe the entrances of sufficient width to allow their enemies easy access, or permit the introduction of the rain. They are covered with a dome of earth, closed on all sides, and have no outlet but near the base, which is by a long and tortuous passage that winds to the distance of several feet in the grass. The diminutive size of these apertures, at all times diligently guarded within, prevents the entrance of any insects or reptiles that may happen to arrive there.

The fallow ants, collected in crowds during the day on their nest, have no fear of being disquieted in the interior, but when, in the evening, they retire to their quarters, no longer perceiving what passes without, how are they screened from the accidents with which they are menaced? or how happens it that the rain does not penetrate their abode, open as it is on every side to its introduction? These questions, simple as they are, do not appear to have engaged the attention of naturalists. Have they not then foreseen the dangers to which these insects would have been exposed, if that wisdom which regulates the universe had not provided for their safety? Struck with these reflections, when I first noticed the fallow ants, I directed my entire attention to this subject, and soon acquired the information I wanted. I remarked that their habitations changed in appearance hourly, and that the diameter of those spacious avenues, where so many ants could freely pass each other during the day, was, as night approached, gradually lessened. The aperture at length totally disappeared, the dome was closed on all sides, and the ants retired to the bottom of their nest.

In further noticing the apertures of these ant-hills, I fully ascertained the nature of the labour of its inhabitants, of which I could not before even guess the purport; for the surface of the nest presented such a constant scene of agitation, and so many insects were occupied in carrying materials in every direction, that the movement offered no other image than that of confusion.

I saw then clearly that they were engaged in stopping up their passages; and for this purpose, they at first brought forward little pieces of wood, which they deposited near the entrance of those avenues they wished to close, they placed them above the aperture, and even sunk them in the stubble; they then went to seek other ligneous fragments which they disposed above the first, but in a different direction, and appeared to choose fragments of less size in proportion as the work advanced. They at length brought in a number of dried leaves, and other materials of an enlarged form, with which they covered the roof. Is not this in miniature the art of our builders when they form the covering of any building? Nature seems every where to have anticipated the inventions of which we boast. This is doubtless one of the most simple.

Our little insects, now in safety in their nest, retire gradually to the interior before the last passages are closed, one or two only remain without, or concealed behind the doors on guard, whilst the rest either take their repose, or engage in different occupations in the most perfect security.

I was impatient to know what took place in the morning upon these ant-hills, and therefore visited them at an early hour. I found them in the same state in which I had left them the preceding evening. A few ants were wandering about on the surface of the nest, some others issued from time to time from under the margin of the little roofs formed at the entrance of the galleries: others afterwards came forth who began removing the wooden bars that blockaded the entrance, in which they readily succeeded. This labour occupied them several hours. The passages were at length free, and the materials with which they had been closed scattered here and there over the ant-hill.

Every day, morning and evening, during the fine weather, I was a witness to similar proceedings. On days of rain, the doors of all the ant-hills remain closed. When the sky is cloudy in the morning, or rain is indicated, the ants, who seem to be aware of it, open but in part their several avenues, and immediately close them when the rain commences. It would appear from this they are not insensible of the motive for which they form these temporary closures.

To have an idea how the straw or stubble roof is formed, let us take a view of the ant-hill at its origin, when it is simply a cavity in the earth. Some of its future inhabitants are seen wandering about in search of materials fit for the exterior work, with which, though rather irregularly, they cover up the entrance; whilst others are employed in mixing the earth, thrown up in hollowing the interior, with fragments of wood and leaves, which are every moment brought in by their fellow-assistants; and this gives a certain consistence to the edifice, which increases in size daily. Our little architects leave here and there cavities where they intend constructing the galleries which are to lead to the exterior, and as they remove in the morning the barriers placed at the entrance of their nest the preceding evening, the passages are kept entire during the whole time of its construction. We soon observe it to become convex; but we should be greatly deceived did we consider it solid. This roof is destined to include many apartments or stories. Having observed the motions of these little masons through a pane of glass which I adjusted against one of their habitations, I am enabled to speak with some degree of certainty upon the manner in which they are constructed.

It is by excavating or mining the under portion of their edifice that they form their spacious halls, low indeed and of heavy construction, yet sufficiently convenient for the use to which they are appropriated, that of receiving at certain hours of the day the larvæ and pupæ.[2]

[2] The terms of _Larva_ and _Pupa_ are employed to designate the intermediate states of existence in the insect, on its passage from the egg to its becoming a perfect animal, endowed with all the powers of its race, the former being commonly known under the appellation of Grub or Caterpillar, the latter of Chrysalis or Aurelia. The ant remains, according to Gould, in the first or larva state of existence nearly a twelvemonth, in the state of pupa about six weeks, and as a perfect insect 16 months. The time, however, they remain as larvæ and pupæ is, no doubt considerably influenced by variations in the temperature, and other causes. M. Reaumur hastened the disclosure of the butterfly by keeping the aurelia or pupa in a warm room, and retarded it by placing it in an ice house. Mr. Kirby once kept one of the aphidivorous flies--the whole term of whose existence, according to this intelligent entomologist, does not, in the summer, exceed at the very utmost six weeks--several months in the state of larva; and, paradoxical as it may seem, by simply neglecting to give it food.--T.

These halls have a free communication by galleries made in the same manner. If the materials of which the ant-hill is composed were only interlaced, they would fall into a confused heap every time the ants attempted to bring them into regular order. This, however, is obviated by their tempering the earth with rain-water, which afterwards hardening in the sun, so completely and effectually binds together the several substances as to permit the removal of certain fragments from the ant-hill, without any injury to the rest: it, moreover, strongly opposes the introduction of the rain. I never found, even after long and violent rains, the interior of the nest wetted to more than a quarter of an inch from the surface, provided it had not been previously out of repair, or deserted by its inhabitants.

The ants are extremely well sheltered in their chambers, the largest of which is placed nearly in the centre of the building; it is much loftier than the rest, and traversed only by the beams that support the ceiling: it is in this spot that all the galleries terminate, and this forms, for the most part, their usual residence.

As to the under-ground portion, it can only be seen when the ant-hill is placed against a declivity; all the interior may be then readily brought in view, by simply raising up the straw roof. The subterranean residence consists of a range of apartments, excavated in the earth, taking an horizontal direction.

That part of the architecture of fallow ants, which equally obtains with the mason-ants, and of which I shall soon have occasion to speak, I shall not now stop to describe, but pass on immediately to the labours of the latter, which will be found to merit our attention.

2. ARCHITECTURE OF THE MASON-ANTS.

I term those mason-ants, whose nests, on the exterior, have the appearance of hillocks of earth, without admixture of other materials, whilst in the interior they present a series of labyrinths, lodges, vaults, and galleries, constructed with great art.

There are several species of mason-ants. The earth, of which their nest is composed, is more or less compact. That which ants of a certain size, such as the ash-coloured and mining ants employ, appears to be less selected, and forms a less fine paste, than that of which the brown, microscopic, and yellow ants form their abode. It is, however, sufficiently adapted to their use, and to the nature of the edifice they intend erecting.

To form a correct judgment of the interior arrangement or distribution of an ant-hill, it is necessary to select such as have not been accidentally spoiled, or whose form has not been too much altered by local circumstances; a slight attention will then suffice to show, that the habitation of the different species are not all constructed after the same system. Thus, the hillock raised by the ash-coloured ants will always present thick walls, fabricated with coarse earth, well-marked stories, and large chambers, with vaulted ceilings, resting upon a solid base. We never observe roads or galleries, properly so called, but large passages, of an oval form, and all around considerable cavities and extensive embankments of earth. We further notice, that the little architects observe a certain proportion between the large arched ceilings and the pillars that are to support them.

The brown, one of the smallest of the ants, is particularly remarkable for the extreme finish of its work. Its body is of a reddish shining brown, its head a little deeper, and the antennæ and feet a little lighter in colour. The abdomen is of an obscure brown, the scale narrow, of a square form, and slightly scolloped. The body is one line and two-fifths in length.[3]

[3] See the notes in the Appendix.

This ant, one of the most industrious of its tribe, forms its nest of stories, four or five lines in height. The partitions are not more than half a line in thickness, and the substance of which they are composed is so finely grained, that the inner walls present one smooth, unbroken surface. These stories are not horizontal: they follow the slope of the ant-hill, and lie one upon the other to the ground-floor, which communicates with the subterranean lodges. They are not always, however, arranged with the same regularity, for these ants do not follow an invariable plan; it appears, on the contrary, that nature has allowed them a certain latitude in this respect, and that they can, according to circumstances, modify them to their wish:--but, however fantastical their habitations may appear, we always observe they have been formed by concentrical stories. On examining each story separately, we observe a number of cavities or halls, lodges of narrower dimensions, and long galleries, which serve for general communication. The arched ceilings covering the most spacious places are supported, either by little columns, slender walls, or by regular buttresses. We also notice chambers that have but one entrance, communicating with the lower story, and large open spaces, serving as a kind of _carrefour_, or cross-road, in which all the streets terminate. Such is the manner in which the habitations of these ants are constructed. Upon opening them, we commonly find the apartments, as well as the large open spaces, filled with adult ants, and always observe their pupæ collected in the apartments, more or less near the surface. This, however, seems regulated by the hour of the day, and the temperature; for in this respect these ants are endowed with great sensibility, and know the degree of heat best adapted for their young. The ant-hill contains sometimes more than twenty stories in its upper portion, and at least as many under the surface of the ground. By this arrangement the ants are enabled, with the greatest facility, to regulate the heat. When a too burning sun overheats their upper apartments, they withdraw with their little ones to the bottom of the ant-hill. The ground-floor becoming, in its turn, uninhabitable, during the rainy season, the ants of this species transport what most interests them to the higher stories, and it is there we find them more usually assembled with their pupæ and eggs, when the subterranean apartments are submerged.[4] Having ascertained the internal arrangement of their habitations, it was still an object of discovery, how ants, working with a substance so hard, could trace out and finish works so extremely delicate, with the assistance only of their teeth, how they could soften the earth, for the purpose of mining, _kneading_, and building with it, and what cement they employed to unite its several particles into one mass. Did it depend upon a sort of mucilage or resin, or some other liquid furnished by the ants themselves, similar to what the mason-bee employs in building the nest to which it gives so much solidity? I ought, perhaps, to have analysed the earth of which these ant-hills are composed, but I was fearful of engaging in difficulties that did not come within my immediate province, and therefore kept to the slow but sure method of observation, by which I hoped to obtain the same result.

[4] De Azara informs us, that during the inundation of the low districts in South America, when the ant-hills, which are usually about three feet in height, are completely under water, the ants avail themselves of an ingenious contrivance, to prevent their being carried to any distance from their habitation. With this view, and for their greater security, they collect into a compact mass, and keep firm hold of each other, previously attaching one of the extremities to some neighbouring plant, or fixed point of support, leaving the other end free and floating on the surface of the water, as long as the inundation (which usually lasts a few days) continues.--T.

I hastened, then, to observe one of these ant-hills, until I should perceive some change in its form.

The inhabitants of that I had selected kept within during the day, or only went out by the subterranean galleries, which opened at some feet distance in the meadow. There were, however, two or three small openings on the surface of the nest, but I saw none of the labourers pass out this way, on account of their being too much exposed to the sun, which these insects greatly dread.

This ant-hill, which had a round form, rose in the grass at the border of a path, and had sustained no injury. I soon perceived that the freshness of the air and the dew invited the ants to walk over the surface of their nest; they began making new apertures; several ants might be seen arriving at the same time, thrusting their head from the entrances, moving about their antennæ, and at length adventuring forth to visit the environs.

This brought to my recollection a singular opinion of the ancients. They believed that ants were occupied in their architectural labours during the night, when the moon was at its full.[5] This idea was not, perhaps, without some foundation, and although the moon had doubtless no kind of influence on their conduct, yet I perceived something true in the observation.

[5] Aristotle affirmed, that ants worked in the night, when the moon was at its full; _Hist. Anim._ l. ix. c. 38. Pliny also alludes to their nocturnal labours. “_Operantur et noctu plena lunâ; eadem interlunio cessant._” Gould states that they employ each moment by day and night, almost without intermission, unless hindered by excessive rains; and the author of a Memoir in the Transactions of the French Academy, remarks, that the ants, he observed, were so incessantly occupied during the night, that it seemed as if they never slept!--T.

Having then noticed the movements of these insects during the night, I found they were almost always abroad and engaged about the dome of their habitation after sun-set. This was directly the reverse of what I had observed in the conduct of the fallow ants, who only go out during the day, and close their doors in the evening. The contrast was still more remarkable than I had previously supposed, for upon visiting the brown ants, some days after, during a gentle rain, I saw all their architectural talents in full play.

As soon as the rain commenced, they left, in great numbers, their subterranean residence, re-entered it almost immediately, and then returned, bearing between their teeth pellets of earth, which they deposited on the roof of their nest. I could not, at first, conceive, what this was meant for, but at length I saw little walls start up on all sides with spaces left between them. In several places, columns, ranged at regular distances, announced halls, lodges, and passages, which the ants proposed establishing; in one word, it was the _ebauche_ of a new story.

I watched with a considerable degree of interest, the most trifling movements of my Masons, and found they did not work, after the manner of wasps and humble-bees, when occupied in constructing a covering to their nest. The latter sit as it were a-stride (_se mettent pour ainsi dire à cheval_) the border or margin of this covering, and take it between their teeth to model and attenuate it according to their wish. The wax of which it is composed, and the _papier_ which the wasp employs, moistened by some kind of glue, are admirably adapted for this purpose; but the earth (often possessing but little tenacity) of which the ants make use, must be worked up after some other manner.

Each ant, then, carried between its teeth the pellet of earth it had formed, by scraping with the end of its mandibles, the bottom of its abode, which I have often witnessed in open day. This little mass of earth, being composed of particles but just united, could be readily moulded as the ants wished: thus, when they had applied it to the spot where it was to rest, they divided, and pressed against it with their teeth, so as to fill up the little inequalities of their wall. The antennæ followed all their movements, passing over each particle of earth as soon as it was placed in its proper position. The whole was then rendered more compact, by pressing it lightly with the fore-feet. This work went on remarkably quick. After having traced out the plan of their masonry, in laying here and there foundations for the pillars and the partitions they were about to erect, they gave them more relief by adding fresh materials. It often happened that two little walls, which were to form a gallery, were raised opposite, and at a slight distance from each other. When they had attained the height of four or five lines, the ants busied themselves in covering in the space left between them by a vaulted ceiling.

Quitting, then, their labours in the upper part of the building, as if they judged all their partitions of sufficient elevation, they affixed to the interior and upper part of each wall, fragments of moistened earth, in an almost horizontal direction, and in such a way, as to form a ledge which, by extension, would be made to join that coming from the opposite wall. These ledges were about half a line in thickness; and the breadth of the galleries was, for the most part, about a quarter of an inch. Here several vertical partitions were seen to form the scaffolding of a lodge, which communicated with several corridors, by apertures formed in the masonry; there, a regularly formed hall, the vaulted ceiling of which was sustained by numerous pillars; further off might be recognised the rudiments of one of those _carrefours_ of which we have before spoken, and in which several avenues terminate. These parts of the Ant-hill were the most spacious; the ants, however, did not appear embarrassed in constructing the ceiling to cover them in, although they were often more than two inches in breadth.

In the upper part of the angles formed by the different walls, they laid the first foundations of this ceiling, and from the top of each pillar, as from so many _centres_, a layer of earth, horizontal and slightly convex, was carried forward to meet the several portions coming from different points of the large public thoroughfare.

This busy crowd of Masons, arriving from all parts with the piece of mortar they wish to add to the building, the order they observe in their operations, the harmony which prevails, and the eagerness with which they avail themselves of the rain to increase the height of their abode, present to the contemplative observer a scene of considerable interest.

I sometimes, however, laboured under an apprehension that the building could not possibly resist its own weight, and that such extensive ceilings, sustained only by a few pillars, would fall into ruin from the rain which continually fell upon them;--but I was quickly convinced of their stability, from observing that the earth, brought by these insects, adhered at all points, on the slightest contact; and that the rain, so far from lessening the cohesion of its particles, appeared even to increase it. Thus, instead of injuring the building, it even contributed to render it still more secure.

These parcels of moistened earth, which are only held together by juxtaposition, require a fall of rain to cement them more closely, and thus varnish over, as it were, those places where the walls and galleries remain uncovered. All inequalities in the masonry then disappear. The upper part of these stories, formed of several pieces brought together, presents but one single layer of compact earth. They require for their complete consolidation nothing but the heat of the sun. It sometimes, however, happens that a violent rain will destroy the apartments, especially should they be but slightly arched; but under these circumstances the ants reconstruct them with wonderful patience.

These different labours were carried on at the same time, and were so closely followed up in the different quarters, that the Ant-hill received an additional story in the course of seven or eight hours. All the vaulted ceilings, being formed upon a regular plan, and at equal distances from one wall to the other, constituted, when finished, but one single roof. Scarcely had the ants finished this story than they began constructing another; but they had not time to finish it: the rain ceasing before the ceiling was fully completed. They still, however, continued their work for a few hours, taking advantage of the humidity of the earth; but a keen north wind soon sprung up, and hastily dried the collected fragments, which, no longer possessing the same adherence, readily fell into powder. The ants, finding their efforts ineffectual, were at length discouraged, and abandoned their employment; but what was my astonishment, when I saw them destroy all the apartments that were yet uncovered, scattering here and there over the last story, the materials of which they had been composed! These facts incontestably prove, that they employ neither gum, nor any kind of cement to bind together the several substances of their nest, but in place of this avail themselves of the rain, to work or knead the earth, leaving the sun and wind to dry and consolidate it.[6] In the simplicity of these means, I recognised the hand of Nature: however, I still thought it necessary to make an experiment to be convinced of the correctness of these results. A few days after, I endeavoured to excite them to recommence their labours by an artificial shower. With this view, I took a very strong brush which I plunged in water, and passing my hand backwards and forwards over the hairs, produced upon the surface of the Ant-hill a very fine dew. The ants perceiving from the interior of their dwelling, the humidity of the roof, came out and passed rapidly over the surface; the sprinkling was continued; the Masons were deceived. They went to the bottom of the Nest to provide themselves with little masses of Earth, which they afterwards brought and deposited on the roof; they then constructed walls and chambers; in a word, a complete story was erected in the course of a few hours. This experiment I frequently repeated, and always with the same success. It is in the Spring more particularly, that the Mason Ants avail themselves of the rain when they wish to enlarge the boundaries of their nest. Night even does not arrest their progress. I have often noticed in the morning stories that had been completely erected during the night.

[6] I was in the habit of visiting, almost daily, for a month, an extensive nest of Red Ants, of which a large flat stone formed the roof.--During my visits for the first three weeks, scarcely a drop of rain had fallen, and the nest seemed to be considerably injured by the continual falling in of loose earth, which these little creatures with amazing industry removed, whenever it happened any of the avenues were blocked up. No attempt was ever made towards reparation; but what was my surprise on visiting my little friends, after a two days’ heavy rain, to find, that the repairs were already completed, and that the upper surface of their habitation presented as smooth a surface as if a trowel had been passed over it; yet all their work they had industriously effected by _kneading_ with the rain-water, the loose earth into a sort of paste. From the nest being situated in the midst of an extensive heath, where there could be no supply of water, and from its remaining unrepaired during the dry weather, it amounts to a full conviction, that Ants employ no other cement than water, in the construction of their varied habitations.--T.

The ants, not content with giving additional elevation to their abode, hollow out, in the earth, apartments still more spacious; the materials thus obtained, are, as before stated, employed in the exterior construction. The art of these insects, therefore, consists in their executing, at the same time, two contrary operations, the one of mining, the other of building, making the former subservient to the latter; and what is still as singular, the same talent is manifested in these excavations, as in that portion of the building above ground. The humidity which penetrates to the bottom of their nest, is doubtless of great assistance to them in these labours.[7]