of an ant-hill, it is necessary to select such as have not been
accidentally spoiled, or whose form has not been too much altered by
local circumstances; a slight attention will then suffice to show, that
the habitation of the different species are not all constructed after
the same system. Thus, the hillock raised by the ash-coloured ants will
always present thick walls, fabricated with coarse earth, well-marked
stories, and large chambers, with vaulted ceilings, resting upon a
solid base. We never observe roads or galleries, properly so called,
but large passages, of an oval form, and all around considerable
cavities and extensive embankments of earth. We further notice, that
the little architects observe a certain proportion between the large
arched ceilings and the pillars that are to support them.
The brown, one of the smallest of the ants, is particularly remarkable
for the extreme finish of its work. Its body is of a reddish shining
brown, its head a little deeper, and the antennæ and feet a little
lighter in colour. The abdomen is of an obscure brown, the scale
narrow, of a square form, and slightly scolloped. The body is one line
and two-fifths in length.[3]
[3] See the notes in the Appendix.
This ant, one of the most industrious of its tribe, forms its nest of
stories, four or five lines in height. The partitions are not more
than half a line in thickness, and the substance of which they are
composed is so finely grained, that the inner walls present one smooth,
unbroken surface. These stories are not horizontal: they follow the
slope of the ant-hill, and lie one upon the other to the ground-floor,
which communicates with the subterranean lodges. They are not always,
however, arranged with the same regularity, for these ants do not
follow an invariable plan; it appears, on the contrary, that nature
has allowed them a certain latitude in this respect, and that they
can, according to circumstances, modify them to their wish:--but,
however fantastical their habitations may appear, we always observe
they have been formed by concentrical stories. On examining each
story separately, we observe a number of cavities or halls, lodges
of narrower dimensions, and long galleries, which serve for general
communication. The arched ceilings covering the most spacious places
are supported, either by little columns, slender walls, or by regular
buttresses. We also notice chambers that have but one entrance,
communicating with the lower story, and large open spaces, serving
as a kind of _carrefour_, or cross-road, in which all the streets
terminate. Such is the manner in which the habitations of these ants
are constructed. Upon opening them, we commonly find the apartments,
as well as the large open spaces, filled with adult ants, and always
observe their pupæ collected in the apartments, more or less near the
surface. This, however, seems regulated by the hour of the day, and
the temperature; for in this respect these ants are endowed with
great sensibility, and know the degree of heat best adapted for their
young. The ant-hill contains sometimes more than twenty stories in its
upper portion, and at least as many under the surface of the ground.
By this arrangement the ants are enabled, with the greatest facility,
to regulate the heat. When a too burning sun overheats their upper
apartments, they withdraw with their little ones to the bottom of
the ant-hill. The ground-floor becoming, in its turn, uninhabitable,
during the rainy season, the ants of this species transport what most
interests them to the higher stories, and it is there we find them
more usually assembled with their pupæ and eggs, when the subterranean
apartments are submerged.[4] Having ascertained the internal
arrangement of their habitations, it was still an object of discovery,
how ants, working with a substance so hard, could trace out and finish
works so extremely delicate, with the assistance only of their teeth,
how they could soften the earth, for the purpose of mining, _kneading_,
and building with it, and what cement they employed to unite its
several particles into one mass. Did it depend upon a sort of mucilage
or resin, or some other liquid furnished by the ants themselves,
similar to what the mason-bee employs in building the nest to which it
gives so much solidity? I ought, perhaps, to have analysed the earth
of which these ant-hills are composed, but I was fearful of engaging
in difficulties that did not come within my immediate province, and
therefore kept to the slow but sure method of observation, by which I
hoped to obtain the same result.
[4] De Azara informs us, that during the inundation of the low
districts in South America, when the ant-hills, which are usually
about three feet in height, are completely under water, the ants avail
themselves of an ingenious contrivance, to prevent their being carried
to any distance from their habitation. With this view, and for their
greater security, they collect into a compact mass, and keep firm
hold of each other, previously attaching one of the extremities to
some neighbouring plant, or fixed point of support, leaving the other
end free and floating on the surface of the water, as long as the
inundation (which usually lasts a few days) continues.--T.
I hastened, then, to observe one of these ant-hills, until I should
perceive some change in its form.
The inhabitants of that I had selected kept within during the day,
or only went out by the subterranean galleries, which opened at some
feet distance in the meadow. There were, however, two or three small
openings on the surface of the nest, but I saw none of the labourers
pass out this way, on account of their being too much exposed to the
sun, which these insects greatly dread.
This ant-hill, which had a round form, rose in the grass at the border
of a path, and had sustained no injury. I soon perceived that the
freshness of the air and the dew invited the ants to walk over the
surface of their nest; they began making new apertures; several ants
might be seen arriving at the same time, thrusting their head from the
entrances, moving about their antennæ, and at length adventuring forth
to visit the environs.
This brought to my recollection a singular opinion of the ancients.
They believed that ants were occupied in their architectural labours
during the night, when the moon was at its full.[5] This idea was not,
perhaps, without some foundation, and although the moon had doubtless
no kind of influence on their conduct, yet I perceived something true
in the observation.
[5] Aristotle affirmed, that ants worked in the night, when the moon
was at its full; _Hist. Anim._ l. ix. c. 38. Pliny also alludes to
their nocturnal labours. “_Operantur et noctu plena lunâ; eadem
interlunio cessant._” Gould states that they employ each moment by day
and night, almost without intermission, unless hindered by excessive
rains; and the author of a Memoir in the Transactions of the French
Academy, remarks, that the ants, he observed, were so incessantly
occupied during the night, that it seemed as if they never slept!--T.
Having then noticed the movements of these insects during the night,
I found they were almost always abroad and engaged about the dome of
their habitation after sun-set. This was directly the reverse of what I
had observed in the conduct of the fallow ants, who only go out during
the day, and close their doors in the evening. The contrast was still
more remarkable than I had previously supposed, for upon visiting the
brown ants, some days after, during a gentle rain, I saw all their
architectural talents in full play.
As soon as the rain commenced, they left, in great numbers, their
subterranean residence, re-entered it almost immediately, and then
returned, bearing between their teeth pellets of earth, which they
deposited on the roof of their nest. I could not, at first, conceive,
what this was meant for, but at length I saw little walls start up on
all sides with spaces left between them. In several places, columns,
ranged at regular distances, announced halls, lodges, and passages,
which the ants proposed establishing; in one word, it was the _ebauche_
of a new story.
I watched with a considerable degree of interest, the most trifling
movements of my Masons, and found they did not work, after the manner
of wasps and humble-bees, when occupied in constructing a covering
to their nest. The latter sit as it were a-stride (_se mettent pour
ainsi dire à cheval_) the border or margin of this covering, and take
it between their teeth to model and attenuate it according to their
wish. The wax of which it is composed, and the _papier_ which the wasp
employs, moistened by some kind of glue, are admirably adapted for this
purpose; but the earth (often possessing but little tenacity) of which
the ants make use, must be worked up after some other manner.
Each ant, then, carried between its teeth the pellet of earth it had
formed, by scraping with the end of its mandibles, the bottom of its
abode, which I have often witnessed in open day. This little mass of
earth, being composed of particles but just united, could be readily
moulded as the ants wished: thus, when they had applied it to the spot
where it was to rest, they divided, and pressed against it with their
teeth, so as to fill up the little inequalities of their wall. The
antennæ followed all their movements, passing over each particle of
earth as soon as it was placed in its proper position. The whole was
then rendered more compact, by pressing it lightly with the fore-feet.
This work went on remarkably quick. After having traced out the plan
of their masonry, in laying here and there foundations for the pillars
and the partitions they were about to erect, they gave them more relief
by adding fresh materials. It often happened that two little walls,
which were to form a gallery, were raised opposite, and at a slight
distance from each other. When they had attained the height of four or
five lines, the ants busied themselves in covering in the space left
between them by a vaulted ceiling.
Quitting, then, their labours in the upper part of the building, as if
they judged all their partitions of sufficient elevation, they affixed
to the interior and upper part of each wall, fragments of moistened
earth, in an almost horizontal direction, and in such a way, as to form
a ledge which, by extension, would be made to join that coming from the
opposite wall. These ledges were about half a line in thickness; and
the breadth of the galleries was, for the most part, about a quarter
of an inch. Here several vertical partitions were seen to form the
scaffolding of a lodge, which communicated with several corridors, by
apertures formed in the masonry; there, a regularly formed hall, the
vaulted ceiling of which was sustained by numerous pillars; further off
might be recognised the rudiments of one of those _carrefours_ of which
we have before spoken, and in which several avenues terminate. These
parts of the Ant-hill were the most spacious; the ants, however, did
not appear embarrassed in constructing the ceiling to cover them in,
although they were often more than two inches in breadth.
In the upper part of the angles formed by the different walls, they
laid the first foundations of this ceiling, and from the top of each
pillar, as from so many _centres_, a layer of earth, horizontal and
slightly convex, was carried forward to meet the several portions
coming from different points of the large public thoroughfare.
This busy crowd of Masons, arriving from all parts with the piece of
mortar they wish to add to the building, the order they observe in
their operations, the harmony which prevails, and the eagerness with
which they avail themselves of the rain to increase the height of their
abode, present to the contemplative observer a scene of considerable
interest.
I sometimes, however, laboured under an apprehension that the building
could not possibly resist its own weight, and that such extensive
ceilings, sustained only by a few pillars, would fall into ruin from
the rain which continually fell upon them;--but I was quickly convinced
of their stability, from observing that the earth, brought by these
insects, adhered at all points, on the slightest contact; and that the
rain, so far from lessening the cohesion of its particles, appeared
even to increase it. Thus, instead of injuring the building, it even
contributed to render it still more secure.
These parcels of moistened earth, which are only held together by
juxtaposition, require a fall of rain to cement them more closely,
and thus varnish over, as it were, those places where the walls and
galleries remain uncovered. All inequalities in the masonry then
disappear. The upper part of these stories, formed of several pieces
brought together, presents but one single layer of compact earth. They
require for their complete consolidation nothing but the heat of the
sun. It sometimes, however, happens that a violent rain will destroy
the apartments, especially should they be but slightly arched; but
under these circumstances the ants reconstruct them with wonderful
patience.
These different labours were carried on at the same time, and were
so closely followed up in the different quarters, that the Ant-hill
received an additional story in the course of seven or eight hours.
All the vaulted ceilings, being formed upon a regular plan, and at
equal distances from one wall to the other, constituted, when finished,
but one single roof. Scarcely had the ants finished this story than
they began constructing another; but they had not time to finish it:
the rain ceasing before the ceiling was fully completed. They still,
however, continued their work for a few hours, taking advantage of
the humidity of the earth; but a keen north wind soon sprung up, and
hastily dried the collected fragments, which, no longer possessing
the same adherence, readily fell into powder. The ants, finding their
efforts ineffectual, were at length discouraged, and abandoned their
employment; but what was my astonishment, when I saw them destroy all
the apartments that were yet uncovered, scattering here and there over
the last story, the materials of which they had been composed! These
facts incontestably prove, that they employ neither gum, nor any kind
of cement to bind together the several substances of their nest, but
in place of this avail themselves of the rain, to work or knead the
earth, leaving the sun and wind to dry and consolidate it.[6] In the
simplicity of these means, I recognised the hand of Nature: however,
I still thought it necessary to make an experiment to be convinced of
the correctness of these results. A few days after, I endeavoured to
excite them to recommence their labours by an artificial shower. With
this view, I took a very strong brush which I plunged in water, and
passing my hand backwards and forwards over the hairs, produced upon
the surface of the Ant-hill a very fine dew. The ants perceiving from
the interior of their dwelling, the humidity of the roof, came out
and passed rapidly over the surface; the sprinkling was continued; the
Masons were deceived. They went to the bottom of the Nest to provide
themselves with little masses of Earth, which they afterwards brought
and deposited on the roof; they then constructed walls and chambers;
in a word, a complete story was erected in the course of a few hours.
This experiment I frequently repeated, and always with the same
success. It is in the Spring more particularly, that the Mason Ants
avail themselves of the rain when they wish to enlarge the boundaries
of their nest. Night even does not arrest their progress. I have often
noticed in the morning stories that had been completely erected during
the night.
[6] I was in the habit of visiting, almost daily, for a month, an
extensive nest of Red Ants, of which a large flat stone formed the
roof.--During my visits for the first three weeks, scarcely a drop of
rain had fallen, and the nest seemed to be considerably injured by
the continual falling in of loose earth, which these little creatures
with amazing industry removed, whenever it happened any of the avenues
were blocked up. No attempt was ever made towards reparation; but
what was my surprise on visiting my little friends, after a two days’
heavy rain, to find, that the repairs were already completed, and that
the upper surface of their habitation presented as smooth a surface
as if a trowel had been passed over it; yet all their work they had
industriously effected by _kneading_ with the rain-water, the loose
earth into a sort of paste. From the nest being situated in the midst
of an extensive heath, where there could be no supply of water, and
from its remaining unrepaired during the dry weather, it amounts to a
full conviction, that Ants employ no other cement than water, in the
construction of their varied habitations.--T.
The ants, not content with giving additional elevation to their
abode, hollow out, in the earth, apartments still more spacious;
the materials thus obtained, are, as before stated, employed in the
exterior construction. The art of these insects, therefore, consists
in their executing, at the same time, two contrary operations, the one
of mining, the other of building, making the former subservient to the
latter; and what is still as singular, the same talent is manifested in
these excavations, as in that portion of the building above ground. The
humidity which penetrates to the bottom of their nest, is doubtless of
great assistance to them in these labours.[7]
[7] It may not be uninteresting after this account of the labours of
the Mason-Ants, to give a sketch of the manner in which the Termites,
or what have been termed by travellers, White Ants, so abundant in
Africa, construct their dwelling. Compared with the Architects, their
habitations are of an astonishing magnitude; they frequently exceed
twelve feet in height, and are so firmly cemented as to bear the
pressure of several men at the same time. It often happens that, whilst
a herd of wild cattle are quietly grazing below, one of their body is
stationed on them as sentinel, to give timely notice of approaching
danger. The Termites begin constructing their habitations, by raising,
at little distances from each other, several turrets of compact clay in
the shape of sugar-loaves: upon these they erect others; those in the
centre run to the greatest height: they afterwards cover in the spaces
between them, and then take down the sides of all the inner turrets,
leaving only the upper portion to form the cupola or dome, making use
of the clay they thus procure, in the formation of the several chambers
intended for magazines, nurseries, &c. The nurseries are entirely
composed of wooden materials, enclosed in chambers of clay, usually
half an inch in width, ranged around, and as close as possible to the
royal apartment. The royal chamber, which, with the rest, are arched
over, occupies as nearly as possible the centre of the building, and
is on a level with the surface of the ground; it is at first only an
inch in length, but increases in size with that of the Queen, until it
extends to six or more inches. In this chamber the King and Queen are
retained close captives; it is impossible they can ever quit it; the
entrance only allowing of the passing and repassing of the Soldiers and
Labourers (the Queen, in the last stage of her pregnancy, is 1000 times
the weight of the King, and equal in bulk to about 20,000 Labourers,
although, on her first appearance as a winged insect, she equalled only
in bulk about 30 Labourers,--her abdomen increases from half an inch
to three inches in length, and she lays, according to Smeathman, as
many as 80,000 eggs in the course of 24 hours: hence the necessity for
the numerous attendants by whom she is continually surrounded.) In an
Ant-Hill of such extensive size, and where there is such an infinity
of chambers to accommodate its numerous inhabitants, there must be of
necessity a vast number of subterraneous and winding passages. These
passages, which conduct to the upper parts of the dome, are carried in
a spiral manner round the building, for the Labourers find it extremely
difficult to ascend in a less circuitous direction. Very frequently,
however, to shorten the distance to the upper nurseries, where they
have to take the eggs, they project an arch of about ten inches in
length, and half an inch in breadth, grooved or worked into steps, on
its upper surface to allow of a more easy passage. When these insects
quit their nest on any expedition, they construct covered galleries of
clay which sometimes run to a considerable distance, and under this
they continue their extensive and highly dreaded depredations.--T.
3. ARCHITECTURE OF THE DARK ASH-COLOURED ANTS.
These Ants, which are fully described in the Appendix, are
distinguished, according to Latreille, by their having the body, head,
and abdomen, of a shining dark ash-colour, the base of the antennæ and
the feet reddish, the scale large and nearly triangular, and three
small _ocelli_ or simple eyes.
The Ash-coloured Ants build in a manner very different from the Brown
Ants. We have already seen from the description of their dwelling,
that, in comparison to the latter, it is exceedingly simple and heavy
in its construction. This simplicity, however, was better adapted to
my object,--that of examining, if possible, how many ants could concur
in the execution of the same design, and how far they appeared to
understand each other in the general progress of their labour;--that of
discovering also, if they acted in concert, or independently of each
other; of their own accord, or from some general impulse. I do not
flatter myself that I have solved these important questions, but the
facts I am about to adduce, will, at least, serve to elucidate this
subject.
When the Ash-coloured Ants seem desirous to give greater elevation to
their dwelling, they commence, by placing over the roof a thick layer
of earth, which they bring from the interior. It is here they trace
_en creux et en relief_, the plan of a new story; they, at first, form
here and there little dykes more or less close to each other, and of a
breadth proportioned to the use for which they are designed: they give
them nearly equal depth, for the most part equalling their breadth: the
masses of earth left between them, serve afterwards, for the foundation
of the inner walls. Having removed all the useless earth from the
bottom of each chamber, and reduced to their proper thickness the
foundation of the walls, the architects have nothing more to do, than
to increase the height of their building, and cover over with a ceiling
the several apartments.
After witnessing the manner in which these ant-hills are constructed, I
was aware that the best and only mode of attaining a correct knowledge
of their organization, was that of following individually the conduct
of the Labourers engaged in erecting them. My journals are filled with
observations of this nature. I extract a few that seem to possess some
interest. I shall at present describe the operations of a single ant
that I observed sufficiently long to satisfy my curiosity.