Bower-birds, _Proceed. Zool. Soc._; _London_, 1840, p. 94;
also _Handbook to the Birds of Australia_ (1865), vol. i.
pp. 444-461. See also Darwin's _Descent of Man_ (1881), pp.
381 and 413-414.
Certain Humming-birds also, according to Gould, decorate their
dwellings with great taste. "They instinctively fasten thereon," he
stated, "beautiful pieces of flat lichen, the larger pieces in the
middle, and the smaller on the part attached to the branch. Now and
then a pretty feather is intertwined or fastened to the outer sides,
the stem being always so placed that the feather stands out beyond the
surface."[94]
[94] Gould, _Introduction to the Trochilidae_, 1861, p. 19.
_Dwellings woven of flexible substances._--In spite of their lack of
skill and the inadequacy of their organs for this kind of work, Fish
are not the most awkward architects. The species which construct nests
for laying in are fairly numerous; the classical case of the
Stickleback is always quoted, but this is not the only animal of its
class to possess the secret of the manufacture of a shelter for its
eggs.
A fish of Java, the Gourami (_Osphronemus olfax_), establishes an
ovoid nest with the leaves of aquatic plants woven together. It makes
its work about the size of a fist, takes no rest until it is
completed, and is able to finish it in five or six days. It is the
male alone who weaves this dwelling; when it is ready a female comes
to lay there, and generally fills it; it may contain from six hundred
to a thousand eggs.
[Illustration: FIG. 25.]
In the sea of Sargasso lives a fish which has received the name of the
_Antennarius marmoratus_. Its flattened and monstrous head gives it a
strange aspect, and it is marbled with brown and yellow. These colours
are those of the tufts of floating seaweed around it, and, thanks to
this arrangement, it can easily hide itself amid them without being
recognised from afar. This animal constructs for its offspring a
fairly safe retreat. The materials which it employs are tufts of
Sargasso so abundant in this portion of the Atlantic. It collects all
the filaments, and unites them solidly by surrounding them with
viscous mucus which it secretes and which hardens. When its work is
sufficiently firm not to be destroyed by the waves it lays its eggs in
it, and the floating nest is abandoned to its fate. The little ones
come out and find within it a sufficient protection for their early
age. These dwellings thus floating on the surface of the sea are
rounded and about the size of a cocoa-nut.
In Guiana and Brazil another species, the _Choestostomus pictus_, is
found, which is equally skilful. With aquatic plants it constructs a
spherical nest and arranges it in the midst of the reeds, level with
the water. At the lower part a hole is left, through which the female
comes to lay. After fertilisation, the couple, as is rarely found
among fish, remain in the neighbourhood of their offspring to assist
them if necessary. This praiseworthy sentiment is often the cause of
their ruin. The inhabitants of the banks speculate on the love of
these fish for their offspring to gain possession of them. It is
sufficient to place a basket near the entrance of the dwelling, which
is then lightly struck. The animal, threatened in its affections,
darts furiously forward with bristling spines and throws itself into
the trap.
It is scarcely necessary to recall the skilful art with which the
Stickleback which inhabits all our streams plaits its nest and remains
sentinel near it. (Fig. 26.) This fish has indeed monopolised our
admiration, and is considered as the most skilful, if not the only
aquatic architect. Yet, besides those which I have already mentioned,
there is one which equals the Stickleback in the skill it displays in
constructing a shelter for its spawn. This is the _Gobius niger_ met
on our coasts, especially in the estuaries of rivers. The male
interlaces and weaves the leaves of algae, etc., and when he has
finished his preparations, he goes to seek females, and leads them one
by one to lay in the retreat he has built. Then he remains in the
neighbourhood until the young come out, ready to throw himself
furiously with his spines on any imprudent intruders.
[Illustration: FIG. 26.]
[Illustration: FIG. 27.]
_Dwellings woven with greater art._--Without doubt the class of Birds
furnishes the most expert artisans in the industry of the woven
dwelling. In our own country we may see them seeking every day to
right and left, carrying a morsel of straw, a pinch of moss, a hair
from a horse's tail, or a tuft of wool caught in a bush. They
intermingle these materials, making the framework of the construction
with the coarser pieces, keeping those that are warmer and more
delicate for the interior. These nests, attached to a fork in a branch
or in a shrub, hidden in the depth of a thicket, are little
masterpieces of skill and patience. To describe every form and every
method would fill a volume. But I cannot pass in silence those which
reveal a science sure of itself, and which are not very inferior to
what man can do in this line. The Lithuanian Titmouse (_AEgithalus
pendulinus_), whose works have been well described by Baldamus, lives
in the marshes in the midst of reeds and willows in Poland, Galicia,
and Hungary. Its nest, which resembles none met in our own country, is
always suspended above the water, two or three metres above the
surface, fixed to a willow branch.[95] All individuals do not exhibit
the same skill in fabricating their dwelling; some are more careful
and clever than others who are less experienced. Some also are obliged
by circumstances to hasten their work. It frequently happens that
Magpies spoil or even altogether destroy with blows of their beaks one
of these pretty nests. The unfortunate couple are obliged to
recommence their task, and if this accident happens two or three times
to the same household, it can easily be imagined that, discouraged and
depressed by the advancing season, they hasten to build a shelter
anyhow, only doing what is indispensable, and neglecting perfection.
However this may be, the nests which are properly finished have the
form of a purse, twenty centimetres high and twelve broad. (Fig. 27.)
At the side an opening, prolonged by a passage which is generally
horizontal, gives access to the interior. Sometimes another opening is
found without any passage. Every nest in the course of construction
possessed this second entry, but it is usually filled up when the work
is completed. When the bird has resolved to establish its retreat, it
first chooses a hanging branch presenting bifurcations which can be
utilised as a rigid frame on which to weave the lateral walls of the
habitation. It intercrosses wool and goat's hair so as to form two
courses which are afterwards united to each other below, and
constitute the first sketch of the nest, at this moment like a
flat-bottomed basket. This is only the beginning. The whole wall is
reinforced by the addition of new material. The architect piles up
down from the poplar and the willow, and binds it all together with
filaments torn from the bark of trees, so as to make a whole which is
very resistant. Then a couch is formed by heaping up wool and down at
the bottom of the nest.
[95] Baldamus, _Beitraege zur Oologie und Nidologie_, 1853,
pp. 419-445.
The American Baltimore Oriole, also called the Baltimore Bird, is a
distinguished weaver. With strong stalks and hemp or flax, fastened
round two forked twigs corresponding to the proposed width of nest, it
makes a very delicate sort of mat, weaving into it quantities of loose
tow. The form of the nest might be compared to that of a ham; it is
attached by the narrow portion to a small branch, the large part being
below. An opening exists at the lower end of the dwelling, and the
interior is carefully lined with soft substances, well interwoven with
the outward netting, and it is finished with an external layer of
horse-hair, while the whole is protected from sun and rain by a
natural canopy of leaves.
The Rufous-necked Weaver Bird, as described by Brehm, shows itself
equally clever. Its nest is woven with extreme delicacy, and resembles
a long-necked decanter hung up with the opening below. From the bottom
of the decanter a strong band attaches the whole to the branch of a
tree. (Fig. 28.) The Yellow Weaver Bird of Java, as described by
Forbes, constructs very similar retort-shaped nests.[96]
[96] H. O. Forbes, _A Naturalist's Wanderings in the Eastern
Archipelago_, 1885, pp. 56-58.
These birds have no monopoly of these careful dwellings; a
considerable number of genera have carried this industry to the same
degree of perfection.
[Illustration: FIG. 28.]
[Illustration: FIG. 29.]
When animals apply themselves in association to any work, they nearly
always exhibit in it a marked superiority over neighbouring species
among whom the individuals work in isolation. The construction of
dwellings is no exception, and the nests of the Sociable Weaver Birds
of South Africa are the best constructed that can be found. These
birds live together in considerable colonies; the members of an
association are at least two hundred in number, and sometimes rise to
five hundred. The city which they construct is a marvel of industry.
They first make with grass a sloping roof; giving it the form of a
mushroom or an open umbrella, and they place it in such a way that it
is supported by the trunk of a tree and one or two of the branches.
(Fig. 29.) This thatch is prepared with so much care that it is
absolutely impenetrable to water. Beneath this protecting shelter each
couple constructs its private dwelling. All the individual nests have
their openings below, and they are so closely pressed against one
another that on looking at the construction from beneath, the
divisions cannot be seen. One only perceives a surface riddled with
holes like a skimmer; each of these holes is the door of a nest. The
work may endure for several years; as long as there is room beneath
the roof the young form pairs near their cradle; but at last, as the
colony continues to increase, a portion emigrate to found a new town
on another tree in the forest.[97]
[97] An early description of this bird is to be found in W.
Paterson's _Narrative of Four Journeys into the Country of
the Hottentots_, 1789; also in Le Vaillant's _Second Voyage
dans l'interieur de l'Afrique_, 1803, t. iii., p. 322.
[Illustration: FIG. 30.]
The industry of the woven dwelling does not flourish among mammals;
but there is one which excels in it. This is the Dwarf Mouse (_Mus
minutus_), certainly one of the smallest Rodents. It generally lives
amidst reeds and rushes, and it is perhaps this circumstance which has
impelled it to construct an aerial dwelling for its young, not being
able to deposit them on the damp and often flooded soil. This retreat
is not used in every season; its sole object is for bringing forth the
young. It is therefore a genuine nest, not only by the manner in which
it is made, but by the object it is intended to serve. The mouse
chooses in the midst of its usual domain a tuft with leaves more or
less crossed; but not too inextricable, so that there may remain in
the midst an empty space, in the centre of which the work will be
arranged. Great ingenuity is shown in the preliminaries; the mouse
simplifies its task by utilising material within its reach instead of
going afar to collect them with trouble. The little animal examines
the thicket, and on reflection chooses some thirty leaves which appear
suitable. Then, without detaching them, it tears each into seven or
eight threads which are held together by the base, and remain attached
to the reeds. It is a clever idea to avoid losing a natural point of
support. The little bands being thus prepared, they are interlaced and
crossed with much art, the animal comes and goes, placing first one of
them, then another above, taken from a different leaf. It has soon
woven a ball about the size of the fist, and hollowed out the
interior. (Fig. 30.) Delicate materials are not lacking around to make
a soft bed. The mouse gleans and constantly brings in the light down
of the willow, grains with cottony crests, and the petals of flowers.
This is all carefully fitted, and when the edifice is completed the
female retires into it to bring forth her young, which are there well
sheltered against the dangers without, and the caprices of storms and
floods. The nest is made with as much delicacy as that of any bird,
and no other mammal except Man is capable of executing such weaver's
work.
_The art of sewing among birds._--There are birds which have succeeded
in solving a remarkable difficulty. Sewing seems so ingenious an art
that it must be reserved for the human species alone. Yet the Tailor
Bird, the _Orthotomus longicauda_, and other species possess the
elements of it. They place their nests in a large leaf which they
prepare to this end. With their beaks they pierce two rows of holes
along the two edges of the leaf; they then pass a stout thread from
one side to the other alternately. With this leaf, at first flat, they
form a horn in which they weave their nest with cotton or hair. (Fig.
31.) These labours of weaving and sewing are preceded by the spinning
of the thread. The bird makes it itself by twisting in its beak
spiders' webs, bits of cotton, and little ends of wool. Sykes found
that the threads used for sewing were knotted at the ends.[98] It is
impossible not to admire animals who have skilfully triumphed over all
the obstacles met with in the course of these complicated
operations.[99]
[98] _Catalogue of Birds, etc._, p. 16.
[99] Tristram, "On the Ornithology of Northern Africa," _Isis_, 1859-60.
[Illustration: 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 illustrations 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 passage 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.
[Illustration: 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 circumstances 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.
[Illustration: FIG. 33.]
_Paper nests._--Certain Wasps, by the material of their dwellings,
approach the Japanese; 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 spawn of fish or
the eggs of Mollusca, they carry this 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 participates in the nature of a hollow cavern, make
additions to it which claim a place among the constructions with which
we are now occupied.
[Illustration: FIG. 34.]
[Illustration: 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 passage, 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 space 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 its sojourn 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.
[Illustration: 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 balls 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 passes on to the next, and so on until it has assured 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 assumed 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 circumstances it shows itself still more sparing of trouble,
and boldly rebels against the law which seems to be imposed on it by
nature. 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 balls 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 partitions: one
vertical, the other horizontal, separating off a small chamber. The
vertical partition 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 female lays 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 assumed 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 grass, and five white pear-shaped eggs are laid. The oven is a
foot or more in diameter, and is sometimes very massive, 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 Voegel," _Cabani's Journal fuer Ornith._,
1853, pp. 161-177.
_Masons working in association._--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 classifications 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.
[Illustration: FIG. 37.]
[Illustration: 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.
[Illustration: FIG. 39.]
The lofty nest, or Termitarium, constitutes 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 passages have no further
use. They served for the passage 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 passages (_c_) are the catacombs of the Termites,
and have a very close analogy 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
passing 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 passage of the
workers, but the queen cannot pass through them. She is therefore a
prisoner, as immured as a goddess 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 assistance when
occasion arises; hence he has received the title, absolutely justified
under the circumstances, 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
passages. The central room and its dependencies constitute a solid
mass, around which other chambers are grouped. The whole space between
it and the general wall is filled by vast storehouses, divided into
many very spacious 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 partitions on this floor,
nothing but massive 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. Partitions of clay
divide the space into a few large halls (_a_); these are again
subdivided, this time not by earth, which is employed 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 constitutes
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 of hedges, 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 circumstance, 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
partitions 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 passages 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 time the 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 scrape 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,
partitions, 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 partitions. 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 passes, 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 embarrassing 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 circumstances.[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 space 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 mass 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
constitutes a storey, cut up by the partitions which divide it into
chambers and communicating galleries; the roofs of the largest halls
are supported by numerous pillars. (Fig. 40.)
[Illustration: 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 balls 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, partitions, 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 passages and
Aphis-pens built by Ants outside their dwellings. Besides these
constructions, they also make roads in the fields, tearing up the
grass 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
embarrassing 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
illustrating the skill exhibited in individual cases by Spiders in
their aerial labours, considers himself justified in concluding as
follows:--"The manner in which 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 surpass 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 entity, apart from intelligence, which renders animals
similar to machines and impels them to effect associated acts, without
themselves being able to understand them, and with a fatality and
determination from which they can under no circumstance 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
shores 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 dykes; but even our own constructions
are threatened under such circumstances.
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 a large 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 circumference 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 shore 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
principal 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
principal use of which is the refuge it affords to them when assailed,
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 within
these 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 dyke. 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 mass 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 dyke, 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 passage
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 partition,
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 classical account of the Beaver,
written nearly two hundred years ago, and free from the many
exaggerations and superstitions 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 surpassed, or even indeed yet attained.