from which it differs in several anatomical characters, and by
the dark violet tint of its wings, brings an improvement to the
formation of the shelter which it makes in wood for its larvæ.
Instead of hollowing a mere retreat to place there all its eggs
indiscriminately, it divides them into compartments, separated by
horizontal partitions. It is the female alone who accomplishes this
task, connected with the function of perpetuating the race. She
chooses an old tree-trunk, a pole, or the post of a fence, exposed to
the sun and already worm-eaten, so that her labor may be lightened.
She first attacks the wood perpendicularly to the surface, then
suddenly turns and directs downward the passage, the diameter of
which is about equal to the size of the insect’s body. The Xylocopa
thus forms a tube about thirty centimetres in length. Quite at the
bottom she places the first egg, leaving beside it a provision
of honey necessary to nourish the larva during its evolution;
she then closes it with a partition. This partition is made with
fragments of the powder of wood glued together with saliva. A first
horizontal ring is applied round the circumference of the tube; then
in the interior of this first ring a second is formed, and so on
continuously, until the central opening, more and more reduced, is at
last entirely closed up. This ceiling forms the floor for the next
chamber, in which the female deposits a new egg, provided, like the
other, with abundant provisions. The same acts are repeated until the
retreat becomes transformed into a series of isolated cells in which
the larvæ can effect their development, and from which they will
emerge either by themselves perforating a thin wall which separates
them from daylight, or by an opening which the careful mother has
left to allow them to attain liberty without trouble.
The second class of habitation, which I have called the woven
dwelling, proceeds at first from the parceling up of substances, then
of objects capable of being entangled like wisps of wood or straw,
then of fine and supple materials which the artisan can work together
in a regular manner, that is to say, by felting or weaving.
There are, first, cases in which the will of the animal does not
intervene, or at least is very slightly manifested. The creature
is found covered and protected by foreign bodies which are often
living beings. Spider-crabs (Maïa), for example, have their carapaces
covered with algæ and hydroids of all sorts. Thus garnished, the
Crustaceans have the advantage of not being recognized from afar when
they go hunting, since beneath this fleece they resemble some rock.
H. Fol has observed at Villefranche-sur-Mer a Maïa so buried beneath
this vegetation that it was impossible at first sight to distinguish
it from the stones around. Under these conditions the animal submits
to a shelter rather than creates it. Yet it is not so passive as one
might at first be led to suppose. When the algæ which flourish on
its back become too long and impede or delay its progress, it tears
them off with its claws and thoroughly cleans itself. The carapace
being quite clean, the animal finds itself too smooth and too easy
to distinguish from surrounding objects; it therefore takes up again
fragments of algæ and replaces them where they do not delay to take
root like cuttings and to flourish anew.
The sponge-crab (Dromia vulgaris) also practices this method of
shelter. It seizes a large sponge and maintains it firmly over its
carapace with the help of the posterior pair of limbs. The sponge
continues to prosper and to spread over the Crustacean who has
adopted it. The two beings do not seem to be definitely fixed to
each other; the contact of a sudden wave will separate them. When
the divorce is effected, the Dromia immediately throws itself on its
cherished covering and replaces it. M. Künckel d’Herculais tells
of one of these curious Crustaceans which delighted the workers
in the laboratory of Concarneau. The need for covering themselves
experienced by these crabs is so strong that in aquariums when their
sponge is taken away they will apply to the back a fragment of wrack
or of anything which comes to hand. A little white cloak with the
arms of Brittany was manufactured for one of these captives, and it
was very amusing to see him put on his overcoat when he had nothing
else wherewith to cover himself.
An Australian bird, the Catheturus Lathami, as described by Gould, is
still in the rudiments, and limits itself to preparing an enormous
pile of leaves. It begins its work some weeks before laying its eggs;
with its claws it pushes behind it all the dead leaves which fall on
the earth and brings them into a heap. The bird throws new material
on the summit until the whole is of suitable height. This detritus
ferments when left to itself, and a gentle heat is developed in the
centre of the edifice. The Catheturus returns to lay near this coarse
shelter; it then takes each egg and buries it in the heap, the larger
end uppermost. It places a new layer above, and quits its labor for
good. Incubation takes place favored by the uniform heat of this
decomposing mass, hatching is produced, and the young emerge from
their primitive nest.
Birds are not alone in constructing temporary dwellings in which
to lay their eggs; some fish are equally artistic in this kind of
industry, and even certain reptiles. The alligator of the Mississippi
would not perhaps at first be regarded as a model of maternal
foresight. Yet the female constructs a genuine nest. She seeks a
very inaccessible spot in the midst of brushwood and thickets of
reeds. With her jaw she carries thither boughs which she arranges
on the soil and covers with leaves. She lays her eggs and conceals
them with care beneath vegetable remains. Not yet considering her
work completed, she stays in the neighborhood watching with jealous
eye the thicket which shelters the dear deposit, and never ceases
to mount guard threateningly until the day when her young ones can
follow her into the stream.
A hymenopterous relative of the bees, the Megachile, cuts out in
rose-leaves fragments of appropriate form which it bears away to a
small hole in a tree, an abandoned mouse nest or some similar cavity.
There it rolls them, works them up, and arranges them with much art,
so as to manufacture what resemble thimbles, which it fills with
honey and in which it lays.
The Anthocopa acts in a similar manner, carpeting the holes of which
it takes possession with the delicate petals of the corn poppy.
The retreats of nocturnal birds of prey do not differ in method of
construction from these two kinds of nests. They are holes in trees,
in ruins, in old walls, and are lined with soft and warm material.
These dwellings are related, not to the type of the hollowed cave,
but to that of the habitation manufactured from mingled materials.
They constitute an inferior form in which the pieces are not firmly
bound together, but need support throughout. The cavity is the
support which sustains the real house.
Diurnal birds of prey are the first animals who practice skilfully
the twining of materials. Their nests, which have received the name
of eyries, are not yet masterpieces of architecture, and reveal the
beginning of the industry which is pushed so far by other birds.
Usually situated in wild and inaccessible spots, the young are there
in safety when their parents are away on distant expeditions. The
abrupt summits of cliffs and the tops of the highest forest trees
are the favorite spots chosen by the great birds of prey. The eyrie
generally consists of a mass of dry branches which cross and mutually
support one another, constituting a whole which is fairly resistant.
The abodes of squirrels, though exhibiting more art, are
constructions of the same nature; that is to say, they are formed
of interlaced sticks. This animal builds its home to shelter itself
there in the bad season, to pass the night in, and to rear its young.
Very agile, and not afraid of climbing, it places its domicile near
the tops of our highest forest trees. Rather capricious also, and
desiring change of residence from time to time, it builds several of
them; at least three or four, sometimes more. The materials which it
needs are collected on the earth among fallen dead branches, or are
torn away from the old abandoned nest of a crow or some other bird.
The squirrel first builds a rather hollow floor by intermingling the
fragments of wood which it has brought. In this state its dwelling
resembles a magpie’s nest. But the fastidious little animal wishes
to be better protected and not thus to sleep in the open air. Over
this foundation he raises a conical roof; the sticks which form it
are very skilfully disposed, and so well interlaced that the whole
is impenetrable to rain. The house must still be furnished, and this
is done with Oriental luxury; that is to say, the entire furniture
consists of a carpet, a carpet of very dry moss, which the squirrel
tears from the trunks of trees, and which it piles up so as to have
a soft and warm couch. An entrance situated at the lower part gives
access to the aerial castle; it is usually directed toward the east.
On the opposite side there is another orifice by which the animal can
escape if an enemy should invade the principal entrance. In ordinary
times also it serves to ventilate the chamber by setting up a slight
current of air. The squirrel greatly fears storms and rain, and
during bad weather hastens to take refuge in his dwelling. If the
wind blows in the direction of the openings, the little beast at once
closes them with two stoppers of moss, and keeps well shut in as long
as the storm rages.
The great Anthropoid apes have found nothing better for shelter than
the squirrels’ method. It must, however, be taken into account that
they have much more difficulty in arranging and maintaining much
heavier rooms, and in building up a shelter with larger surface.
The orang-outang, which lives in the virgin forests of the Sunda
Archipelago, does not feel the need of constructing a roof against
the rain. He is content with a floor established in the midst of a
tree, and made of broken and interlaced branches. He piles up on this
support a considerable mass of leaves and moss; for the orang does
not sleep seated like the other great apes, but lies down in the
manner of man, as has often been observed when he is in captivity.
When he feels the cold he is ingenious enough to cover himself with
the leaves of his couch.
In Upper and Lower Guinea the chimpanzee (Troglodytes niger) also
establishes his dwelling on trees. He first makes choice of a large
horizontal branch, which constitutes a sufficient floor for the agile
animal. Above this branch he bends the neighboring boughs, crosses
them, and interlaces them so as to obtain a sort of framework. When
this preliminary labor is accomplished, he collects dead wood or
breaks up branches and adds them to the first. Before commencing he
had taken care when choosing the site that the whole was so arranged
that a fork was within reach to sustain the roof. He thus constructs
a very sufficient shelter.
The Troglodytes calvus, a relative of the preceding, inhabiting
the same regions, as described by Du Chaillu, shows still more
skill in raising his roof. A tree is always chosen for support. He
breaks off boughs and fastens them by one end to the trunk, by the
other to a large branch. To fix all these pieces he employs very
strong creepers, which grow in abundance in his forests. Above this
framework, which indicates remarkable ingenuity, the animal piles
up large leaves, forming in layers well pressed down and quite
impenetrable to the rain. The whole has the appearance of an open
parasol. The ape sits on a branch beneath his handiwork, supporting
himself against the trunk with one arm. He has thus an excellent
shelter against the midday sun as well as against tropical showers.
There exists in Australia a bird with very curious customs. This is
the satin bower-bird. The art displayed in this bird’s constructions
is not less interesting than the sociability he gives evidence of,
and his desire to have for his hours of leisure a shelter adorned
to his taste. The bowers which he constructs, and which present on
a small scale the appearance of the arbors in our old gardens, are
places for reunion and for warbling and courtship, in which the birds
stay during the day, when no anxiety leads them to disperse. They
are not, properly speaking, nests built for the purpose of rearing
young; for at the epoch of love each couple separates and constructs
a special retreat in the neighborhood of the bower. These shelters
are always situated in the most retired parts of the forest, and
are placed on the earth at the foot of trees. Several couples work
together to raise the edifice, the males performing the chief part
of the work. At first they establish a slightly convex floor, made
with interlaced sticks, intended to keep the place sheltered from the
moisture of the soil. The arbor rises in the centre of this first
platform. Boughs vertically arranged are interlaced at the base
with those of the floor. The birds arrange them in two rows facing
each other; they then curve together the upper extremities of these
sticks, and fix them so as to obtain a vault. All the prominences
in the materials employed are turned toward the outside, so that
the interior of the room may be smooth and the birds may not catch
their plumage in it. This done, the little architects, to embellish
their retreat, transport to it a number of conspicuous objects, such
as very white stones from a neighboring stream, shells, the bright
feathers of the paroquet, whatever comes to their beak. All these
treasures are arranged on the earth, before the two entries to the
bower, so as to form on each side a carpet, which is not smooth, but
the varied colors of which rejoice the eye. The prettiest treasures
are fixed into the wall of the hut. These objects are intended solely
for the delight of these feathered artists. They are very careful
also only to collect pieces which have been whitened and dried by the
sun.
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.”
In spite of their lack of skill and the inadequacy of their organs,
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.
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 can not 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 (Ægithalus 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
with in England, is always suspended above the water, two or three
metres above the surface, fixed to a willow branch. 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. 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 possesses 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 utilized as a rigid frame on
which to weave the lateral walls of the habitation. It intercrosses
wool and goats’ hair so as to form two courses which are afterward
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.
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. The yellow weaver bird of Java, as described by
Forbes, constructs very similar retort-shaped nests.
These birds have no monopoly of these careful dwellings; a
considerable number of genera have carried this industry to the same
degree of perfection.
When animals apply themselves in association to any work, they nearly
always exhibit in it a marked superiority over neighboring 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. 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 can not 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.
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
amid 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
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.
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. These labors 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. It is impossible not to admire animals
who have skilfully triumphed over all the obstacles met with in the
course of these complicated operations.
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 can
not well be called anything else but sewing it.
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 gray
sphere prolonged to a blunt neck. The hornet’s nest is similar in
construction.
Gelatine nests 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. 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.
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.