[99] Tristram, "On the Ornithology of Northern Africa," Isis, 1859-60.
[Ill.u.s.tration: FIG. 31.]
Certain Spiders, while they do not actually sew in the sense that they perforate the leaves they use to build their nest, and draw the thread through them, yet subject the leaves to an operation which cannot well be called anything else but sewing it.[100][100] McCook describes, and gives good ill.u.s.trations of, these nests in various stages of progress, American Spiders, vol i. p. 302.
Modifications of dwellings according to season and climate.--A certain number of facts show that these various industries are not fixed and immutable instincts imposed on the species. Certain Birds change the form of their dwelling according to the climate, or according to the season in which they inhabit it. For example, the Crossbill, Loxia taenioptera (Fig. 32), does not build its nest according to the same rules in Sweden as in France. It builds in every season.
The winter shelter is spherical, constructed with very dry lichens, and it is very large. A very narrow opening, just sufficient for the pa.s.sage of the owner, prevents the external cold from penetrating within. The summer nests are much smaller, in consequence of a reduction in the thickness of the walls. There is no longer need to fear that the cold will come through them, and the animal gives itself no superfluous trouble.
[Ill.u.s.tration: FIG. 32.]
Again, the Baltimore Oriole, which inhabits both the Northern and Southern States of North America, knows very well how to adapt his manner of work to the external circ.u.mstances in which he lives. Thus, in the Southern States the nest is woven of delicate materials united in a rather loose fashion, so that the air can circulate freely and keep the interior fresh; it is lined with no warm substance, and the entrance is turned to the west so that the sun only sends into it the oblique evening rays. In the north, on the contrary, the nest is oriented to the south to profit by all the warm sunshine; the walls are thick, without interstices, and the dwelling is carpeted in the warmest and softest manner. Even in the same region there is great diversity in the style, neatness, and finish of the nests, as well as in the materials used. Skeins of silk and hanks of thread have frequently been found in the Baltimore Bird"s nest, so woven up and entangled that they could not be withdrawn. As such materials could not be obtained before the introduction of Europeans, it is evident that this bird, with the sagacity of a good architect, knows how to select the strongest and best materials for his work. Many other facts might be quoted, but these suffice to show that the species is not animated by an inevitable instinct, but that each individual, skilful no doubt by heredity, can modify the methods transmitted to him by his ancestors, according to his own experience and his own judgment.Built dwellings.--The built dwelling, the expression of the highest civilisation, still remains to be studied. Man has only known how to construct this kind of shelter at a comparatively late period in his evolution; and among animals we do not find it widely spread, much less so, certainly, than the two foregoing methods, especially the first. The difficulty of this work is greater, and it only arrives at considerable development among very sociable species, since the united efforts of a great number of individuals are needed to carry it on.
There are, however, masons who operate separately; but their constructions are rudimentary. The characteristic of all these works is that they are manufactured with some substance to which the animal gives a determined form while it is still soft, and that in drying it preserves this form and acquires solidity. The matter most usually employed is softened and tempered earth--mortar; but there are animals who use with success more delicate bodies. Two examples will suffice to indicate the nature of these exceptions: the labours of Wasps and those of certain Swallows.
[Ill.u.s.tration: FIG. 33.]
Paper nests.--Certain Wasps, by the material of their dwellings, approach the j.a.panese; they build with paper. This paper or cardboard is very strong and supplies a solid support; moreover, being a bad conductor of heat, it contributes to maintain an equable temperature within the nest. The constructions of these insects, though they do not exhibit the geometric arrangement of those of Bees, are not less interesting. The paper which they employ is manufactured on the spot, as the walls of the cells develop. Detritus of every kind enters into its preparation: small fragments of wood, sawdust, etc.; anything is good. These Hymenoptera possess no organ specially adapted to aid them; it is with their saliva that they glue this dust together and make of it a substance very suitable for its purpose. The dwellings often reach considerable size, yet they are always begun by a single female, who does all the work without help until the moment when the first eggs come out; she is thus furnished with workers capable of taking a share in her task. The Vespa sylvestris builds a paper nest of this kind, hanging to the branch of a tree, like a great grey sphere prolonged to a blunt neck. (Fig. 33.) The Hornet"s nest is similar in construction.
Gelatine nests.--These are made by certain Swallows who nest in grottoes or cliffs on the edge of the sea. After having collected from the water a gelatinous substance formed either of the sp.a.w.n of fish or the eggs of Mollusca, they carrythis substance on to a perpendicular wall, and apply it to form an arc of a circle.
This first deposit being dry, they increase it by sticking on to its edge a new deposit. Gradually the dwelling takes on the appearance of a cup and receives the workers" eggs. (Fig. 34.) These dwellings are the famous swallows" nests, so appreciated by the epicures of the extreme East, which are edible in the same way as, for example, caviare.
Constructions built of earth--Solitary masons.--Certain animals, whose dwelling partic.i.p.ates in the nature of a hollow cavern, make additions to it which claim a place among the constructions with which we are now occupied.
[Ill.u.s.tration: FIG. 34.]
[Ill.u.s.tration: FIG. 35.]
The Anthophora parietina is in this group; it is a small bee which lives in liberty in our climate. As its name indicates, it prefers to frequent the walls of old buildings and finds a refuge in the interstices, hollowing out the mortar half disintegrated by time. The entrance to the dwelling is protected by a tube curved towards the bottom, and making an external prominence. (Fig. 35.) The owner comes and goes by this pa.s.sage, and as it is curved towards the earth the interior is protected against a flow of rain, while at the same time the entry is rendered more difficult for Melectes and Anthrax. These insects, in fact, watch the departure of the Anthophora to endeavour to penetrate into their nests and lay their eggs there. The gallery of entry and exit has been built with grains of sand, the debris produced by the insect in working. These grains of sand glued together form, on drying, a very resistant wall.[101]
[101] Latreille, "Observations sur l"abeille parietine (Anthophora parietina),"
Annales du Museum d"Hist. Nat., t. iii., 1804, p. 257.
The other animals of which I have to speak are genuine masons, who prepare their mortar by tempering moistened earth. Every one has seen the Swallow in spring working at its nest in the corner of a window. It usually establishes its dwelling in an angle, so that the three existing walls can be utilised, and to have an enclosed s.p.a.ce there is need only to add the face. It usually gives to this the form of a quarter of a sphere, and begins it by applying earth more or less mixed with chopped hay against the walls which are to support the edifice. At the summit of the construction a hole is left for entry and exit. During the whole of itssojourn in our country the Swallow uses this dwelling, and even returns to it for many years in succession, as long as its work will support the attacks of time.
The faithful return of these birds to their old nest has been many times proved by attaching ribbons to their claws; they have always returned with the distinctive mark.
[Ill.u.s.tration: FIG. 36.]
The Chalicodoma, whose name of Mason Bee indicates the industry it exercises, is a hymenopterous relative to our Bees, long since carefully studied by Reaumur. It does not live in societies like the latter, and exhibits individual initiative and skill as great as the swallows. The females accomplish the work which I am about to describe. The little cells which they build are arranged, to the number of eight or ten together, in the most various places; sometimes on a pebble, sometimes on a branch, or, again, on a stone wall. (Fig. 36.) The insect collects earth as fine as possible, such as the dust of a trodden path, and tempers it with its own saliva. It places side by side these little b.a.l.l.s of mortar and the work soon takes the form of a cupola, to the edge of which it constantly adds new deposits. The sun quickly dries the hole and gives it the necessary consistence. When the cell has acquired sufficient height, the Chalicodoma abandons its occupation of mason, and visits flowers for pollen and nectar wherewith to fill the little chamber. It goes back to the nest, disgorges its supply, and returns to the field, until the little cup of earth is full to the edge. When the dwelling is thus prepared and provisioned, the insect lays an egg there and closes the upper part with a vault, built by successive deposits over the opening, which is more and more narrowed until it is finally shut up. Having completed a chamber, it pa.s.ses on to the next, and so on until it has a.s.sured the fate of all its descendants.
This hymenopterous insect certainly shows in its acts as an artisan an inevitable instinct: hereditary intelligence has become less personal and less spontaneous.
In certain cases, however, the instinct loses its rigidity and automatism. Thus, when a Chalicodoma, at the moment of preparing to accomplish its task, finds an old nest, still capable of repair although dilapidated, it does not hesitate to take possession of it and to silence its a.s.sumed innate instinct of building. It profits by the work already done, and is content to fill up the cracks or to re-establish the masonry where defective; then it provisions the renewed cells with honey, and lays its eggs in them. In certain circ.u.mstances it shows itself still more sparing of trouble, and boldly rebels against the law which seems to be imposed on it bynature. If it feels itself sufficiently strong, the Chalicodoma throws itself on one of its fellows, a peaceful constructor that has almost completed its work; it chases it away, and takes possession of its property to shelter its own eggs. Instead of manufacturing the cell from bottom to top, it has only to complete it. Such acts evidently show the reflection appearing through instinct.
Besides the Swallows, of which I have already spoken, birds offer us several types of skilful construction with tempered earth.
The Flamingo, which lives in marshes, cannot place its eggs on the earth nor in the trunks of trees, which are often absent from its domain. It builds a cone of mud, which dries and becomes very resistant, and it prepares at the summit an excavation open to the air; this is the nest. The female broods by sitting with her legs hanging over the sides of the hillock on which her little family prospers above the waters and the damp soil.
A Perch in the Danube also manufactures a dwelling of dried earth. It gives it the form of an elliptic cupola, and prepares a semicircular opening for entry and exit.
The bird which shows itself the most skilful mason is probably the Oven-Bird (Furnarius rufus) of Brazil and La Plata. Its name is owing to the form of the nest which it constructs for brooding, and which has the appearance of an oven. It is very skilful and knows how to build a dome of clay without scaffolding, which is not altogether easy. Having chosen for the site of its labours a large horizontal branch, it brings to it a number of little clay b.a.l.l.s more or less combined with vegetable debris, works them altogether, and makes a very uniform floor, which is to serve as a platform for the rest of the work. When this is done, and while the foundation is drying, the bird arranges on it a circular border of mortar slightly inclined outwards. This becomes hard; it raises it by a new application, this time inclined inwards. All the other layers which will be placed above this will also be inclined towards the interior of the chamber. As the structure rises, the circle which terminates it above becomes more and more narrow. Soon it is quite small, and the animal, closing it with a little ball of clay, finds itself in possession of a well-made dome. Naturally it prepares an entrance; the form of this is semicircular. But this is not all. In the interior it arranges two part.i.tions: one vertical, the other horizontal, separating off a small chamber. The vertical part.i.tion begins at one of the edges of the door, so that the air from without cannot penetrate directly into the dwelling, which is thus protected against extreme variations of temperature. It is in the compartment thus formed that the femalelays her eggs and broods, after having taken care to carpet it with a thick layer of small herbs.
"In favourable seasons, the Oven-birds begin building in the autumn," Hudson tells us, "and the work is resumed during the winter whenever there is a spell of mild, wet weather. Some of their structures are finished early in winter, others not until spring, everything depending on the weather and the condition of the birds.
In cold, dry weather, and when food is scarce, they do not work at all. The site chosen is a stout horizontal branch, or the top of a post, and they also frequently build on a cornice or the roof of a house; and sometimes, but rarely, on the ground. The material used is mud, with the addition of horse hair or slender fibrous rootlets, which make the structure harder and prevent it from cracking. I have frequently seen a bird engaged in building first pick up a thread or hair, then repair to a puddle, where it was worked into a pellet of mud about the size of a filbert, then carried to the nest. When finished the structure is shaped outwardly like a baker"s oven, only with a deeper and narrower entrance. It is always placed very conspicuously, and with the entrance facing a building, if one be near, or if at a roadside it looks towards the road; the reason for this being, no doubt, that the bird keeps a continuous eye on the movements of people near it while building, and so leaves the nest opened and unfinished on that side until the last, and then the entrance is necessarily formed. When the structure has a.s.sumed the globular form with only a narrow opening, the wall on one side is curved inwards, reaching from the floor to the dome, and at the inner extremity an aperture is left to admit the bird to the interior or second chamber, in which the eggs are laid. A man"s hand fits easily into the first or entrance chamber, but cannot be twisted about so as to reach the eggs in the interior cavity, the entrance being so small and high up. The interior is lined with dry soft gra.s.s, and five white pear-shaped eggs are laid. The oven is a foot or more in diameter, and is sometimes very ma.s.sive, weighing eight or nine pounds, and so strong that, unless loosened by the swaying of the branch, it often remains unharmed for two or three years. A new oven is built every year, and I have more than once seen a second oven built on the top of the first, when this has been placed very advantageously, as on a projection and against a wall."[102]
[102] P. L. Sclater and W. H. Hudson, Argentine Ornithology, 1888, vol. i. pp.
168, 169. See also Burmeister, "Ueber die Eier und Nester einiger brasilianischen Vogel," Cabani"s Journal fur Ornith., 1853, pp. 161-177.Masons working in a.s.sociation.--Ants have already furnished us with numerous proofs of their intelligence and their prodigious industry. So remote from Man from the anatomical point of view, they are of all animals those whose psychic faculties bring them nearest to him. Sociable like him, they have undergone an evolution parallel to his which has placed them at the head of Insects in the same way as he has become superior to all other Mammals. The brain in Ants as in Man has undergone a disproportionate development. Like Man, they possess a language which enables them to combine their efforts, and there is no human industry in which these insects have not arrived at a high degree of perfection. If in certain parts of the earth human societies are superior to those of Ants, in many others the civilisation of Ants is notably superior. No village of Kaffirs can be compared to a palace of the Termites. The cla.s.sifications separate these insects (sometimes called "White Ants") from the Ants, since the latter are Hymenoptera, while the former are ranked among the Neuroptera, but their constructions are almost alike, and may be described together. These small animals, relatively to their size, build on a colossal scale compared to Man; even our most exceptional monuments cannot be placed beside their ordinary buildings. (Fig. 37.) The domes of triturated and plastered clay which cover their nests may rise to a height of five metres; that is to say, to dimensions equal to one thousand times the length of the worker. The Eiffel Tower, the most elevated monument of which human industry can boast, is only one hundred and eighty-seven times the average height of the worker. It is three hundred metres high, but to equal the Termites" audacity, it would have to attain a height of 1,600 metres.
[Ill.u.s.tration: FIG. 37.]
[Ill.u.s.tration: FIG. 38. 1. King before wings are cast off; 2. Worker (neuter); 3.
Queen with abdomen distended with eggs; 4. Soldier (neuter); 5. Young (resembling adults).]
The different species of Termite are not equally industrious. The T. bellicosus seems to have carried the art of construction to the highest point. All the individuals of the species are not alike; there exists a polymorphism which produces creatures of three sorts: 1, the soldiers, recognised by their large heads and long sharp mandibles, moved by powerful muscles; it is their mission to defend the whole colony against its adversaries, and the wounds they can produce, fatal to creatures of their own size, are painful even to man; 2, the workers, who labour as navvies and architects, and take charge of the pupae:they form the great majority of the community; 3, the king and queen. (Fig. 38.) To each nest there is usually only a single fertile and lazy couple. These two personages do absolutely nothing; the soldiers and the workers care for them and bring them food. They have both possessed wings, but these fall off. The queen reigns but does not govern; she lays. The king is simply the husband of the queen. The internal administration of the palace is bound up with the parts played by these three kinds of beings.
[Ill.u.s.tration: FIG. 39.]
The lofty nest, or Termitarium, const.i.tutes a hillock in the form of a cupola. The interior arrangement is very complicated, and at the same time very well adapted to the life of the inhabitants. There are four storeys in all, covered by the general exterior walls. (Fig. 39.) The walls of the dome are very thick; at the base they measure from sixty to eighty centimetres. The clay in drying attains the hardness of brick, and the whole is very coherent. The sentinels of herds of wild cattle choose these tumuli as observatories and do not break them down. The walls of this exterior enceinte are hollowed by galleries of two kinds: some horizontal and giving access from outside to all the storeys; the others mounting spirally in the thickness of the wall to the summit of the dome. When the colony is in full activity, after the construction is completed, these little pa.s.sages have no further use.
They served for the pa.s.sage of the masons when building the cupola; and they could be utilised again if a breach should be made in the wall. At the lower part these galleries in the wall are very wide, and they sink into the earth beneath the palace to a depth of more than 1 metre 50.
These subterranean pa.s.sages (c) are the catacombs of the Termites, and have a very close a.n.a.logy with those of old and populous human cities. Their origin is similar; they are ancient quarries. The insects hollowed them in obtaining the necessary clay for their labours. Later, when the rains come, they serve as drains to carry off the water which might threaten to invade the dwelling.
Such is the external wall within which a busy population swarms. On pa.s.sing to the interior let us first enter the ground-floor. In the centre is found the royal chamber (r). The walls are extremely strong and are supplied with windows for ventilation, and with doors to enable the Termites to render their services. It is necessary to renew the air in this chamber, which constantly contains more than two thousand insects. The openings are large enough for the pa.s.sage of the workers, but the queen cannot pa.s.s through them. She is therefore a prisoner, asimmured as a G.o.ddess in her temple. The chain which holds her is the prodigious development of her abdomen. As a virgin she could enter, when fertilised she cannot henceforth go out. She continuously elaborates eggs; every moment one appears at the orifice of the oviduct. The king remains near her, to give his a.s.sistance when occasion arises; hence he has received the t.i.tle, absolutely justified under the circ.u.mstances, of Father of the People. Around the couple zealous attendants crowd. There are about two thousand of them, workers and soldiers, licking the two royal captives to remove any dust from their hairs, and bringing them food. As soon as the queen lays an egg, one of the workers hastens to take it gently between its jaws; it is the property of the state, and is carefully carried off to the second storey where the state nursery is situated.
The centre of the ground-floor, therefore, is occupied by the royal apartment; around this, and communicating with it by means of numerous entrances, are a number of cells used by the attendants on the queen (s). These little chambers are surrounded by a labyrinth of pa.s.sages. The central room and its dependencies const.i.tute a solid ma.s.s, around which other chambers are grouped. The whole s.p.a.ce between it and the general wall is filled by vast storehouses, divided into many very s.p.a.cious compartments. Within them are piled up the provisions which the Termites harvest every day; they consist especially of gums and the juices of plants, dried and pulverised so as to form a fine powder. Access to this property is given by means of large corridors which cross one another, and conduct to the outside through the horizontal galleries traversing the wall.
Above the whole of this ground-floor rests a thick vault of clay, which forms a strong floor for the first storey (B). This is composed of only a single room; it is put to no use, unless to isolate and support the apartments of the second floor, in the arrangement of which great care is exercised. There are no part.i.tions on this floor, nothing but ma.s.sive columns of clay to support the ceiling. These columns are more than a metre in height. It is a gigantic cathedral in which the lilliputian architects have displayed considerable art. By means of this immense empty chamber a huge reservoir of air is placed in the very centre of the construction; through the galleries in the external wall it is sufficiently renewed for the purposes of respiration without too great a change in temperature.
The second storey rests on the first. To this the eggs are brought, and here the larvae go through their evolution. Part.i.tions of clay divide the s.p.a.ce into a few large halls (a); these are again subdivided, this time not by earth, which isemployed throughout the rest of the building, but by materials of a more delicate kind, which are, moreover, very bad conductors of heat (b). It is a question, in fact, of maintaining these little chambers at an almost constant temperature, favourable for the development of the eggs. The substances utilised for this purpose are fragments of wood and of gum. The Termites glue them together and thus form the walls of these important cells.
The arrangement of the top storey (D) is also disposed with a view of protecting the young who are the future of the city. It const.i.tutes the attic, situated just beneath the cupola, and contains absolutely nothing; it simply serves to interpose beneath the summit of the edifice and the storey below a layer of air, which is a bad conductor of heat. The chamber devoted to the young is thus placed between two gaseous layers, a precaution which, combined with the choice of material, places it in the very best conditions for protection against the alternation of cold at night and torrid heat during the day.
It is difficult to know which to admire most--the audacity and vastness of the labour undertaken by these insects, or the ingenious foresight by which they ensure to their delicate larvae a comfortable youth. There can be no doubt that these animals show themselves very superior to Man, taking into consideration his enormous size compared to theirs, in the art of building. Pillars, cupolas, vaults--nothing is too difficult or too complicated for these small and patient labourers.[103]
[103] The earliest comprehensive account of the Termites and their industries was by Smeathman in the Philosophical Transactions of the Royal Society, vol.
lxxi., 1781, pp. 139-192. Later they were studied by Lespes: "Recherches sur l"organisation et les moeurs du Termite lucifuge," Ann. des Sci. Nat., 4me Serie, t.
v., fasc. 4 and 5, Paris, 1856. For a description of the South American Termitarium see also Bates"s Naturalist on the Amazons (unabridged edition, 1892), pp. 208-214; and for the African Termites of Victoria Nyanza, a chapter in H. Drummond"s Tropical Africa, 1888, pp. 123-158; while Forbes has briefly described them in Java, Naturalist"s Wanderings in the Eastern Archipelago, pp.
73, 74.
The Ants of our own lands do not yield to the Termites in this industry, and their dwellings are models of architecture. As they have been more carefully studied we know more exactly how they work, and the considerable sum of intelligence and initiative which they reveal in the accomplishment of their task. At the foot ofhedges, on the outskirts of woods, they raise their frail monuments. The species are not equally skilful, and such differences as we have found in other industries may also be found here. In a general manner it was soon found that Ants do not, like Bees, obey a rigid instinct which ordains the line of conduct under every circ.u.mstance, and impels each individual to act so that his efforts are naturally combined and harmonised with those of his neighbours in the workshop. One soon perceives when observing an ant-hill that any individual insect follows, when working, a personal idea which it has conceived, and which it realises without troubling itself about the others. Often these latter are executing a quite contradictory plan. It is rather an anarchistic republic. Happily Ants are not obstinate, and when they see the idea of one of them disengaging itself from the labour commenced, they are content to abandon their own less satisfactory idea and to collaborate in the other"s work. They are able, for the rest, to concert plans; the movements of their antennae are a very complicated language containing many expressions, and the worker who desires the acceptance of his own point of view is not sparing in their use.[104] It sometimes happens that his efforts are vain, and that his companions manoeuvre to thwart his schemes. In the presence of such resistance those who are determined to obtain the adoption of their own plans destroy the labours of their opponents; fierce struggles ensue, and here it is the strongest who becomes the architect-general.
[104] For a discussion of the methods of communication among Ants, tending to the conclusion that these methods "almost amount to language," see Lubbock"s Ants, Bees, and Wasps, chap. vi. And for a general discussion of language among animals, see Alix, L"esprit de nos Betes, pp. 331-367.
The Formica fusca constructs its nest of plastered earth. The different superimposed storeys have been added one by one to the upper part of the old dwelling when the latter became too small for the growing colony. In opening an ant-hill, they are found to be quite distinct from each other; each is divided by a large number of part.i.tions into vaulted compartments. In the larger ones pillars of earth support the ceiling. The rooms communicate with one another by means of bull"s-eye pa.s.sages formed in the separating walls. The whole is small, proportioned to the size of the works, but excellently arranged.
When, in the council of the republic, it has been resolved to raise a common habitation, the workers operate in a singular manner. All the ants scatter themselves abroad, and with extreme activity take fragments of earth between their mandibles and place them on the summit of the dwelling. After some timethe result of this microscopical work appears. The ancient roof, strengthened by all this material, becomes a thick terrace which the insects first cover very evenly.
The earth, having been brought in grain by grain, is soft and easy to dig. The construction of the new storey begins at first by the hollowing out of a number of trenches. The ants sc.r.a.pe away in places the terrace which they have just made.
They thus diminish the thickness of the layer at the spots where rooms, corridors, etc., are to be formed, and with the material thus obtained they form walls, part.i.tions, and pillars. Soon the entire plan of the new storey may be perceived. It differs essentially from that which Man would adopt; in the latter case the walls would be shown by the hollowing out of the foundations; the work of these Hymenoptera, on the contrary, shows them in relief. These first arrangements made, the six-footed architects have only to complete their constructions by new deposits from without. Gradually the storey reaches a sufficient height. It remains to cover it, and this is not the easiest part of the business. The ceiling is formed of vaults going from one wall to another, or from a wall to a column. When one of these vaults is to be small, some millimetres at the most, the Formica fusca constructs it with the help of two ledges, which are made facing each other on the tops of two part.i.tions. These prominences, formed of materials glued together by saliva, are enlarged by additions to their free edges. They advance to meet each other and soon join; it is wonderful to see each insect, following its individual initiative, profit by every twig or fragment capable of bearing any weight, in order to enlarge the overhanging ledges.
Individual skill and reflection.--This personality in work, which reveals the intelligent effort of each, has certainly its inconveniences for the common work.
Badly-concerted operations may not succeed, and Huber witnessed an accident due to this cause.[105] Two walls facing each other were to be united by an arch.
A foolish worker had begun to form a horizontal ledge on the summit of one of the walls without paying attention to the fact that the other wall was very much higher. By continuing the project the ceiling would have come against the middle of the opposite ceiling instead of resting on its summit. Another ant pa.s.ses, examines affairs with an intelligent air, and evidently considers that this sort of work is absurd. Without consideration for the amour-propre of its unskilful fellow-citizen, it demolishes its work, raises the wall that is too low, and re-makes the construction correctly in the presence of the observer. If this incident reveals inconceivable thoughtlessness in one of the members of this serious republic, it also brings to light the judgment, reflection, and decision of which they are capable, as well as a freedom which cannot be found in the works of instinct.[105] Recherches sur les Moeurs des Fourmis indigenes, pp. 47, 48.
This Formica fusca sometimes finds itself in the presence of other difficulties. It may happen that the hall to be roofed is too large and the arch too considerable to allow of the cohesion of the materials employed. The insects soon become aware of the existence of this embarra.s.sing state of things and remedy it in various ways, either by hastily constructing pillars in the centre of the too large room, or by some other method. Ebrard describes an artifice he has seen employed, which shows to what an extent ants can quickly appreciate and take advantage of the most unforeseen circ.u.mstances.[106] A worker was labouring to cover a large cell; two prominences, parts of opposite walls, were advancing towards each other, but there was still a s.p.a.ce of from twelve to fifteen millimetres between them, and it seemed no longer possible to burden the two sides without risking a general downfall. The little mason was much disturbed. A graminaceous plant was growing near. The ant seemed anxious to take advantage of it, for it went to it and climbed up the stalk. After having examined and devised, it set about curving it in the direction of the edifice. To attain this object, it placed a little ma.s.s of moist earth on the extremity of the leaf, and fixed it there. Under the influence of this weight flexion was produced, but only at the end. This could not satisfy the insect; it became a question of decreasing the resistance at the base. The ant gnawed a little at this spot; the desired result was attained, and the whole length of the leaf became bent over the building in course of construction. To prevent it bending back, and to ensure its remaining adherent to the roof, the worker returned to the plant and placed earth between the sheath and the stalk. This time all difficulties were surmounted, and there was a solid scaffolding to support the materials for the roof.
[106] Ebrard, etudes de Moeurs, Geneve, 1864, p. 3.
Among the Lasius niger the independence of the workers is perhaps still greater; no doubt they do their best to concert their efforts, but they do not succeed so well as if an inevitable instinct impelled them. Notwithstanding the irregularities of the construction, it is possible to recognise in it a whole formed of hollowed, concentric half-spheres; they have been added one after the other to the surface to increase the dwelling. The interval between these clay spheres const.i.tutes a storey, cut up by the part.i.tions which divide it into chambers and communicating galleries; the roofs of the largest halls are supported by numerous pillars. (Fig.
40.)[Ill.u.s.tration: FIG. 40.]
These ants, as Huber has shown, are highly accomplished in the art of constructing a cupola. When they wish to increase their nest by a new layer, they take advantage of the first wet day, the rain serving to agglutinate and unite the materials. They operate in almost the same way as the Formica fusca, though exhibiting more skill and resource as architects; they know better how to calculate beforehand the number of pillars required in a hall of a determined size. As soon as the rain has given the signal for work, they spread themselves abroad and prepare a very thick terrace on the external surface of the dwelling which has become too small. They carry to it small b.a.l.l.s of earth ground very fine by their jaws, and then lightly piled up so as to pulverise afresh; these are then spread over the construction with the anterior legs. Then, by hollowing out, the ants trace the plan of the new storey, leaving the walls, part.i.tions, and columns in relief.
After having raised these parts to a sufficient height, all work together to cover them with a general ceiling, each ant applying itself to one small corner of the work.
The vaulting is executed by the method already described; horizontal ledges, slanting from the summit of pillar or wall, are formed to meet one another. The insects are intelligent enough to begin their labour at the spots best fitted to give strong support to the overhanging materials, as for instance, at the angle of two walls. There is so much activity among the workers, and they are so anxious to take advantage of the damp, that the storey is sometimes completely finished in seven or eight hours. If the rain suddenly stops in the course of the work, they abandon operations, to complete them as soon as another shower falls.
I have already had occasion to speak of the covered pa.s.sages and Aphis-pens built by Ants outside their dwellings. Besides these constructions, they also make roads in the fields, tearing up the gra.s.s and hollowing out the earth so as to form a beaten path free from the lilliputian bushes in which there would be danger of becoming entangled, on returning to the nest laden with various and often embarra.s.sing burdens.
Nor are Ants by any means alone in exhibiting the results of individual skill and reflection. It will, however, be sufficient to mention only one other example, that furnished by Spiders. McCook, in his great work, after elaborately describing and carefully ill.u.s.trating the skill exhibited in individual cases by Spiders in their aerial labours, considers himself justified in concluding as follows:--"The manner inwhich the ends of the radii which terminate upon the herb are wrapped roundabout and braced by the notched zone; the manner in which the wide non-viscid scaffold lines are woven in order to give vantage ground from which to place the close-lying and permanent viscid spirals, upon which the usefulness of the orb depends--all these, to mention no other points, seem to indicate a very delicate perception of those modes (shall I also say principles?) of construction which are continually recognised in the art of the builder, the architect, and the engineer."[107]
[107] American Spiders, vol. i. p. 228.
Dwellings built of hard materials united by mortar.--Among mammals few animals have become so skilful in the art of building houses as the insects we have just been considering. There are, however, two who equal if they do not surpa.s.s them--the Musk-rat and its relative, the Beaver.
The Musk-rats of Canada live in colonies on the banks of streams or deep lakes, and construct dwellings which are very well arranged. In their methods we find combined the woven shelter with the house of built earth. Their cabins are established over the highest level of the water and look like little domes. In building them the animals begin by placing reeds in the earth; these they interlace and weave so as to form a sort of vertical mat. They plaster it externally with a layer of mud, which is mixed by means of the paws and smoothed by the tail. At the upper part of the hut the reeds are not pressed together or covered with earth, so that the air may be renewed in the interior. A dwelling of this kind, intended to house six or eight individuals who have combined to build it, may measure up to 65 centimetres in diameter. There is no door directly opening on to the ground. A subterranean gallery starts from the floor and opens out beneath the water. It presents secondary branches, some horizontal, through which the animal goes in search of roots for food, while others descend vertically to pits specially reserved for the disposal of ordure.
But it is, above all, the Beaver (Castor fiber) who exhibits the highest qualities as an engineer and mason. This industrious and sagacious Rodent is well adapted to inconvenience the partisans of instinct as an ent.i.ty, apart from intelligence, which renders animals similar to machines and impels them to effect a.s.sociated acts, without themselves being able to understand them, and with a fatality and determination from which they can under no circ.u.mstance escape.Beavers now only live in Canada. A few individuals may, however, still be found on the banks of the lower Rhone, in Camargue, and on a few other European rivers. Several centuries ago they existed in the neighbourhood of Paris in considerable numbers. The Bievre gained its name from the old French word for Beaver, and its resemblance to the English name, as well as to the German (Biber), is striking. In the sixteenth century, according to Bishop Magnus of Upsala, the Beaver was still common on the banks of the Rhine, the Danube, and on the sh.o.r.es of the Black Sea, and in the North it still exercised great art in its constructions. In the twelfth century it was found in Scotland and Wales. If we go back to ancient times, we find that Herodotus mentions that the Budini who lived in the neighbourhood of the Black Sea used the skins of the Beavers, which abounded there, on the borders of their garments; and in the time of Pliny the Beaver was so common there that he speaks of it as the Pontic Beaver. Fossil remains of the Beaver have also been found throughout Europe in conjunction with those of the Mammoth and other extinct animals.
But the civilisation of the Beaver has perished in the presence of Man"s civilisation, or rather of his persecution. In regions where it is tracked and disturbed by Man the Beaver lives in couples, and is content to hollow out a burrow like the Otter"s, instead of showing its consummate art. It merely vegetates, fleeing from enemies who are too strong for it, and depriving itself of a dangerous comfort. But when the security of solitude permits these animals to unite in societies, and to possess, without too much fear, a pond or a stream, they then exhibit all their industry.
They build very well arranged dwellings, although at first sight they look like mere piles of twigs, branches, and logs, heaped in disorder on a small dome of mud. At the edge of a pond each raises his own lodge, and there is no work by the colony in common. If, however, there is a question of inhabiting the bank of a shallow stream, certain preliminary works become necessary. The rodents establish a dam, so that they may possess a large sheet of water which may be of fair depth, and above all constant, not at the mercy of the rise and fall of the stream. A sudden and excessive flood is the one danger likely to prove fatal to these d.y.k.es; but even our own constructions are threatened under such circ.u.mstances.
When the Beavers, tempted by abundance of willows and poplars, of which they eat the bark and utilise the wood in construction, have chosen a site, and have decided to establish a village on the edge of the water, there are several labours to be successively accomplished. Their first desire is to be in possession of alarge number of felled trunks of trees. To obtain them they scatter themselves in the forest bordering the stream and attack saplings of from twenty to thirty centimetres in diameter. They are equipped for this purpose. With their powerful incisors, worked by strong jaws, they can soon gnaw through a tree of this size.
But they are capable of attacking trees, even more than 100 cc. in circ.u.mference and some forty metres in height, with great skill and adaptability; "no better work could be accomplished by a most highly-finished steel cutting tool, wielded by a muscular human arm" (Martin). They operate seated on their hind quarters, and they make their incision in the wood with a feather edge. It was once supposed that they always take care so to direct their wood-cutting task that the tree may fall on the water-side, but this is by no means the case, and appears to be simply due, as Martin points out, to the fact that trees by the water-side usually slope towards the water. The austerity of labour alternates, it may be added, with the pleasures of the table. From time to time the Beavers remove the bark of the fallen trees, of which they are very fond, and feed on it.
Mr. Lewis H. Morgan studied the American Beaver with great care and thoroughness, more especially on the south-west sh.o.r.e of Lake Superior; he devotes fifty pages to the dams, and it is worth while to quote his preliminary remarks regarding them. "The dam is the princ.i.p.al structure of the beaver. It is also the most important of his erections as it is the most extensive, and because its production and preservation could only be accomplished by patient and long-continued labour. In point of time, also, it precedes the lodge, since the floor of the latter and the entrances to its chamber are constructed with reference to the level of the water in the pond. The object of the dam is the formation of an artificial pond, the princ.i.p.al use of which is the refuge it affords to them when a.s.sailed, and the water-connection it gives to their lodges and to their burrows in the banks. Hence, as the level of the pond must, in all cases, rise from one to two feet above these entrances for the protection of the animal from pursuit and capture, the surface-level of the pond must, to a greater or less extent, be subject to their immediate control. As the dam is not an absolute necessity to the beaver for the maintenance of his life, his normal habitation being rather natural ponds and rivers, and burrows in their banks, it is, in itself considered, a remarkable fact that he should have voluntarily transferred himself, by means of dams and ponds of his own construction, from a natural to an artificial mode of life.
"Some of these dams are so extensive as to forbid the supposition that they were the exclusive work of a single pair, or of a single family of beavers; but it does not follow, as has very generally been supposed, that several families, or a colony,unite for the joint construction of a dam. After careful examination of some hundreds of these structures, and of the lodges and burrows attached to many of them, I am altogether satisfied that the larger dams were not the joint-product of the labour of large numbers of beavers working together, and brought thus to immediate completion; but, on the contrary, that they arose from small beginnings, and were built upon year after year, until they finally reached that size which exhausted the capabilities of the location; after which they were maintained for centuries, at the ascertained standard, by constant repairs. So far as my observations have enabled me to form an opinion, I think they were usually, if not invariably, commenced by a single pair, or a single family of beavers; and that when, in the course of time, by the gradual increase of the dam, the pond had become sufficiently enlarged to accommodate more families than one, other families took up their residence upon it, and afterwards contributed by their labour to its maintenance. There is no satisfactory evidence that the American beavers either live or work in colonies; and if some such cases have been observed, it will either be found to be an exception to the general rule, or in consequence of the sudden destruction of a work upon the maintenance of which a number of families were at the time depending.
"The great age of the larger dams is shown by their size, by the large amount of solid materials they contain, and by the destruction of the primitive forest within the area of the ponds; and also by the extent of the beaver-meadows along the margins of the streams where dams are maintained, and by the hummocks formed upon them by and through the annual growth and decay of vegetation in separate hills. These meadows were undoubtedly covered with trees adapted to a wet soil when the dams were constructed. It must have required long periods of time to destroy every vestige of the ancient forest by the increased saturation of the earth, accompanied with occasional overflows from the streams. The evidence from these and other sources tends to show that these dams have existed in the same places for hundreds and thousands of years, and that they have been maintained by a system of continuous repairs.
"At the place selected for the construction of a dam, the ground is usually firm and often stony, and when across the channel of a flowing stream, a hard rather than a soft bottom is preferred. Such places are necessarily unfavourable for the insertion of stakes in the ground, if such were, in fact, their practice in building dams. The theory upon which beaver-dams are constructed is perfectly simple, and involves no such necessity. Soft earth, intermixed with vegetable fibre, is used to form an embankment, with sticks, brush, and poles embedded withinthese materials to bind them together, and to impart to them the requisite solidity to resist the effects both of pressure and of saturation. Small sticks and brush are used, in the first instance, with mud and earth and stones for down-weight.
Consequently these dams are extremely rude at their commencement, and they do not attain their remarkably artistic appearance until after they have been raised to a considerable height, and have been maintained, by a system of annual repairs, for a number of years."[108]
[108] L. H. Morgan, The American Beaver and his Works, Philadelphia, 1868, pp.
82-86.
There are two different kinds of beaver-dams, although they are both constructed on the same principle. One, the stick-dam, consists of interlaced stick and pole work below, with an embankment of earth raised with the same material upon the upper or water face. This is usually found in brooks or large streams with ill-defined banks. The other, the solid-bank dam, is not so common nor so interesting, and is usually found on those parts of the same stream where the banks are well defined, the channel deep, and the current uniform. In this kind the earth and mud entirely buries the sticks and poles, giving the whole a solid appearance. In the first kind the surplus water percolates through the dam along its entire length, while in the second it is discharged through a single opening in the crest formed for that purpose.
The materials being prepared in the manner I have previously described, the animals make ready to establish their d.y.k.e. They intermix their materials--driftwood, green willows, birch, poplars, etc.--in the bed of the river, with mud and stones, so making a solid bank, capable of resisting a great force of water; sometimes the trees will shoot up forming a hedge. The dam has a thickness of from three to four metres at the base, and about sixty centimetres at the upper part. The wall facing up-stream is sloping, that directed down-stream is vertical; this is the best arrangement for supporting the pressure of the ma.s.s of water which is thus expended on an inclined surface. In certain cases Beavers carry hydraulic science still further. If the course of the water is not very rapid, they generally make an almost straight d.y.k.e, perpendicular to the two banks, as this is then sufficient; but if the current is strong, they curve it so that the convexity is turned up-stream. In this way it is much better fitted to resist. Thus they do not always act in the same way, but arrange their actions so as to adapt them to the conditions of the environment.The embankment being completed, the animals construct their lodges.
Fragments of wood, deprived of the bark, are arranged and united by clay or mud which the Beavers take from the riverside, transport, mix, and work with their fore-paws. During a single night they can collect as much mud at their houses as amounts to some thousands of their small handfuls. They thus plaster their houses with mud every autumn; in the winter this freezes as hard as a stone and protects them from enemies. These cabins form domes from three to four metres in diameter at the base, and from two to two and a half metres in height. The floor is on a level with the surface of the artificial pond. A pa.s.sage sinks in the earth and opens about one and a half metres below the level of the water, so that it cannot be closed up by ice during the severe winters of these regions.
Within, near the entry, the beavers form, with the aid of a part.i.tion, a special compartment to serve as a storehouse, and they there pile up enormous heaps of nenuphar roots as provisions for the days when ice and snow will prevent them from barking the young trunks.
A dwelling of this kind may last for three or four years, and the animal here tranquilly enjoys the fruits of its industry, as long as man fails to discover the retreat; for the beaver can escape by swimming from all carnivorous animals excepting, perhaps, the Otter. During floods the level of the water nearly reaches the hut; if the inundation is prolonged and the animal runs the risk of being asphyxiated beneath his dome, it breaks through the upper part with its teeth and escapes. When the water returns to its bed the beaver comes back, makes the necessary repairs, and resumes the usual peaceful course of its life.[109]
[109] The Beaver has been fully studied by Lewis H. Morgan, The American Beaver, 1868. See also Horace T. Martin"s recent work, Castorologia, or the History and Traditions of the Canadian Beaver, 1892; in an appendix to this work will be found Samuel Hearne"s cla.s.sical account of the Beaver, written nearly two hundred years ago, and free from the many exaggerations and superst.i.tions which have grown up around this animal.
We have thus seen, from a shapeless hole to these complex dwellings, every possible stage; we have found among animals the rudiments of the different human habitations, certain animals, indeed, having arrived at a degree of civilisation which Man himself in some countries has not yet surpa.s.sed, or even indeed yet attained.CHAPTER VII.
THE DEFENCE AND SANITATION OF DWELLINGS.
GENERAL PRECAUTIONS AGAINST POSSIBLE DANGER--SEPARATION OF FEMALES WHILE BROODING--HYGIENIC MEASURES OF BEES--PRUDENCE OF BEES--FORTIFICATIONS OF BEES--PRECAUTIONS AGAINST INQUISITIVENESS--LIGHTING UP THE NESTS.
The building of comfortable dwellings is not the last stage reached by the industry of animals. There are among them some who show genuine skill in rendering them healthy and defending them against invasions from without.
General precautions against possible danger.--Some animals show, even during the construction of the nest, extreme prudence in preventing its site from being discovered. Several authors refer to the stratagem of the Magpie, who begins several nests at the same time; but only one is intended to receive the brood, and that only is completed. The aim of the others is merely to distract attention. It is around these latter that the bird shows ostentatious activity, while it works at the real nest only for a few hours during the day, in the morning and evening.
The Crane takes equally ingenious precautions in order that its constant presence at the same spot may not arouse suspicion. It never comes or goes flying, but always on foot, concealing itself along tufts of reeds. De Homeyer even reports that the female at the time of laying covers her wings and back with mud.
When dried this gives the animal a red tone, which causes it to be confused with neighbouring objects; this is intentional mimicry.
The Linnet (Fig. 41) again, wrongly accused of wanting judgment, is well aware that a pile of excrement at the foot of a tree announces a nest in the branches. It is careful to suppress this revealing sign, and every day takes it away in its beak to disperse it afar.
[Ill.u.s.tration: FIG. 41.]
Birds will sometimes take the trouble to remove the eggs or the nest altogether, when the latter has been discovered, in order to avoid further risks of danger. The American Sparrow Hawk has been observed to do this, and the following incident is quoted by Bendire, from MacFarlane"s Ma.n.u.script Notes on Birds Nesting inBritish America, concerning the Pigeon Hawk (Falco columbarius):--"On May 25, 1864, a trusty Indian in my employ found a nest placed in a thick branch of a pine tree at a height of about six feet from the ground. It was rather loosely constructed of a few dry sticks and a small quant.i.ty of coa.r.s.e hay; it then contained two eggs; both parents were seen, fired at, and missed. On the 31st he revisited the nest, which still held but two eggs, and again missed the birds.
Several days later he made another visit thereto, and, to his surprise, the eggs and parents had disappeared. His first impression was that some other person had taken them; but after looking carefully around he perceived both birds at a short distance, and this led him to inst.i.tute a search which soon resulted in finding that the eggs must have been removed by the parent birds to the face of a muddy bank at least forty yards distant from the original nest. A few decayed leaves had been placed under them, but nothing else in the way of lining. A third egg had been added in the interim. There can hardly be any doubt of the truth of the foregoing facts."[110]