wearied by my visits, still baffled all my efforts, by making a true
wall of earth behind the _contrevent_. After having for some time
attended to the manners and habits of these insects, I found that we
might accustom them by degrees to suffer the entrance of the light
in their abode; but it was necessary, notwithstanding, to use much
caution. What succeeded with me the best, was that of forming an oblong
opening in the middle of a table, and affixing underneath, a double
frame, glazed on its two longest sides, and opened only at the upper
part, which communicated with this aperture. These frames (fig. 1. Pl.
I.) being furnished with shutters, permitted me, either to observe the
ants, or to favour them in their taste for obscurity. This done, I
scattered all the materials of a nest of Fallow Ants upon the table,
and left them at liberty to arrange them at the bottom of the glazed
box, which they did in such a manner, that it was easy to observe all
their galleries, and the apartments to which they led. I at length
covered over the whole of the materials with a large bell-glass, in
order that I might witness the movements of my prisoners, as well
inside as on the outside, and at the same time guard against their
escape. But when I saw they were accustomed to their fate, and did not
seek to leave their prison, I allowed them free issue from under the
bell-glass, and the liberty of running over the platform upon which it
rested, taking only the precaution of plunging the feet of the table in
vessels filled with water, to arrest the ants in their passage, should
they attempt to escape.
This apparatus, and several others of which the explanation would be
long and tedious, had all the success I wished. I observed, with much
pleasure, that the ants continued to take care of the larvæ, which
proved, that in taking them, in some respects, from the state of
nature, I had not too much disturbed them. This gave me reason to hope,
that I should observe, in its greatest extent, all the care they took
of the rising generation.
I did not, however, always keep to these artificial means. I compared,
as often as possible, the conduct of my prisoners, with that of those
ants inhabiting and ranging about the fields, and as I never remarked
any sensible difference in their manner of acting, I concluded I could
trust the results obtained by means of my glazed apparatus.
Let us now open the shutter which conceals from us the interior of the
ant-hill, and let us see what is passing there.
Here, the pupæ are heaped up by hundreds in their spacious lodges;
there, the larvæ are collected together, and guarded by workers. In one
place, we observe an assemblage of eggs, in another place, some of the
workers seem occupied in following an ant of a larger size than the
rest;--this is the mother, or at least one of the females, for there
are always several in each ant-hill:--she lays as she walks, and the
guardians, by whom she is surrounded, take up her eggs, or seize them
at the very moment of her laying them; they collect them together, and
carry them in little heaps in their mouths.[2] On looking a little
closer, we find that they turn them continually with their tongues; it
even appears, they pass them one after the other between their teeth,
and thus keep them constantly moistened. Such is the first _aperçu_
which my glazed apparatus offered.
[2] The eggs of ants are so remarkably minute, that there would seem
an absolute necessity of their being held together by some glutinous
matter, otherwise, it would render the removal of such small bodies
in the mandibles of ants almost impossible; the mandibles being so
constituted as not to be brought into that close contact necessary for
this operation.--T.
Having directed my close attention to these eggs, I remarked they were
of different sizes, shades, and forms. The smallest were white, opake,
and cylindrical; the largest, transparent, and slightly arched at both
ends; those of a middle size were semi-transparent. In holding them
up to the light, I observed a sort of white oblong cloud; in some, a
transparent point might be remarked at the superior extremity; in
others, a clear zone above and underneath the little cloud. The largest
presented a single opake and whitish point in their interior. There
were some whose whole body was so remarkably clear, as to allow of
my observing very distinctly the rings. In fixing my attention more
closely upon the latter, I observed the egg open, and the larva appear
in its place.
Having compared these eggs with those just laid, I constantly found the
latter of a milky whiteness, completely opake, and smaller by one-half;
so that I had no reason to doubt of the eggs of ants receiving a
very considerable increase in size; that in elongating, they become
transparent, but do not at this time disclose the form of the worm
which is always arched.
To be convinced of the truth of this statement, I viewed these eggs
with the microscope; I also measured them, and having separated them
from each other, found the longest to be those only in which the worms
were disclosed in my presence. If I removed them from the workers,
before they had attained their full length and transparency, they dried
up, and the worms never quitted them.
Is it, then, to the care which the workers take in passing them across
their mouths, that we must attribute the secret of their preservation?
Do these eggs require this humidity, or do they absorb a part of it,
to furnish nourishment to the little worms they contain? It appears
at least highly probable; and the observations of M. Reaumur give
weight to this opinion. I have discovered in his writings, that there
are other eggs, which also increase in size,--as those lodged in the
galls of different trees, which are occasioned by _Cynips_[3], or other
insects of the same kind.
[3] To these insects we are indebted for that valuable article of
commerce, the gall-nut. The _Cynips_ is furnished with a finely-pointed
instrument, with which it wounds the leaves and other parts of the
tree, for the sake of depositing its eggs. The puncture of the leaves,
&c. gives rise to those excrescences termed galls, which not only form
the habitation, for a considerable period, of the infant insect, but
serve it the whole time of its imprisonment for food. On examining the
galls, some will be found to have an opening in them; these are they,
from which the fly has escaped: others, that want this aperture, will
be found to contain the insect, either in its larva, pupa, or imago
state; for it appears these several changes, at least with some of the
species, take place within the body of the gall.--T.
“It ought not,” says this exact and judicious observer, “to be passed
by in silence, that the egg which I found in the gall appeared to
me considerably larger than the eggs of the same species, when they
proceed from the body of the fly, or even when they are taken from the
body of the impregnated or mother-fly, near the time of their being
laid. The whole of those I took from the abdomen of the flies I killed
were remarkably small; it therefore appeared certain, that the egg
would have increased, and indeed had increased, in the gall.”
We are only in the habit of observing eggs surrounded by a covering
incapable of extension; but why is it that those eggs, which nature
has enclosed, in a flexible membrane, do not increase? The envelope
of the egg may, in this instance, be compared to the membrane which
includes the human fœtus, and those of quadrupeds.
Nature has formed the eggs of some other insects in such a manner,
that they are also capable of increase: such are, according to M.
Vallisnieri, the eggs of the _Tenthredo_, which produce those larvæ
that feed upon the rose.[4]
[4] Latreille alludes to this increase in the size of the eggs, both in
these insects, and the _Cynips_.--T.
These remarkable examples authorise me in admitting an increase in
size, in the eggs of ants, as fully proved; although it may not be
exactly under the same circumstances as those of which the philosopher
I have just quoted speaks; but if they are not surrounded with a
liquid, or preserved from the influence of the external air, their
pellicle, moistened every instant by the workers, may preserve a
certain degree of suppleness, and the faculty of extension, according
to the developement of the worm they enclose.
At the end of fifteen days, the little worm is seen to quit the shell:
its body is then perfectly transparent, and presents only a head and
rings, without any rudiment of feet or antennæ. The insect, at this
period, is completely dependant upon the workers.
I have been enabled to observe, through the glasses of my artificial
ant-hill, the great care taken of these little worms, which bear also
the name of Larvæ. They were generally guarded by a body of ants,
who, raised upon their feet, with their abdomen brought between these
members, were prepared to cast their venom upon all intruders, whilst,
here and there, other workers were engaged in clearing the passages, by
removing the materials which were out of place; a great number of their
companions taking at the same time their repose, and appearing to be
fast asleep: but a busy scene occurred at the moment of transporting
their little ones to enjoy the warmth of the sun. When the sun’s rays
fell upon the exterior portion of the nest, the ants, who were then
on the surface, descended with great rapidity to the bottom of the
ant-hill, struck with their antennæ the other ants, ran one after the
other, and jostled their companions, who mounted at the moment under
the bell-glass, and redescended with the same speed, putting in their
turn the whole colony in motion, so that we could observe a swarm of
workers, filling up all the passages; but what proved still more their
intention by these movements, was, the violence with which the workers
sometimes seized, with their mandibles, those who did not appear to
understand them, dragging them forth to the top of the ant-hill, and
immediately leaving them, to go and seek those still remaining with the
young.
As soon as the ants had intimation of the appearance of the Sun, they
occupied themselves with the larvæ and pupæ; they carried them with
all expedition above the ant-hill, where they left them exposed to
the influence of the heat. Their ardour suffered no relaxation; the
female larvæ (which are heavier, and much larger than those of the
other cast) were carried, with some difficulty, through the narrow
passages, leading from the interior to the exterior of the ant-hill,
and placed in the sun, by the side of those of the workers and males.
After remaining there a quarter of an hour, the ants again took them
up, and sheltered them from the direct rays of the sun, by placing them
in chambers, situated under a layer of straw, which did not entirely
intercept the heat.
The workers, after having fulfilled the duties imposed upon them in
regard to the larvæ, did not forget themselves; they sought, in their
turn, to stretch themselves in the sun, lay upon each other in heaps,
and seemed to enjoy some repose, but it was of no long duration. I
observed a great number constantly employed on the surface of the
ant-hill, and others engaged in carrying back the larvæ, in proportion
as the sun declined. The moment of nourishing them being at length
arrived, each ant approached a larva, and offered it food. “The larvæ
of ants,” observes M. Latreille, “resemble, when they quit the egg,
little white worms, destitute of feet, thick, short, and in form almost
conical; their body is composed of twelve rings; the anterior part is
slender and curved. We remark at the head two little horny pieces or
hooks, too distant from each other to be regarded as true teeth; under
these hooks we observe four little points or _cils_, two on each side,
and a _mamelon_, or tubercular process, almost cylindrical, soft, and
retractile, by which the larva receives its food.”[5]
[5] What a world of wonders is there not opened to our view, in the
transformations the insect tribe undergo, from the period of their
birth, to the full and complete development of their several organs.
Unless well assured of the fact, how could we imagine the feeble
helpless worm just described would ever become the industrious,
enterprising ant, furnished with organs of motion and of flight.
How devoid of probability would appear the statement, did we not
possess evidence to the contrary, that the magnificent butterfly we
see hovering from flower to flower, ever drew its origin from the
creeping caterpillar. But these changes, surprising as they are, are
yet equalled by other circumstances connected with the metamorphoses of
insects, for with these changes in appearance, the animal alters its
habits and mode of life. The butterfly in its first or larva state of
existence eats voraciously, and in a manner greatly disproportioned to
its size, devouring twice its weight of leaves in a day; in its second
or pupa state, this inordinate appetite ceases, and all its active
powers are suspended; in its third, imago, or perfect state, no longer
bound to the spot that gave it birth, it takes a wider range, cleaves
the regions of the air, and sips the nectar of flowers. That beautiful
silver-winged insect (_Libellula_) now crossing our path, passed the
first part of its existence as a water insect, and that little creature
(_Ephemera_) we see sporting in the sun-beam, whose existence as a
winged insect is limited only to a few hours, and seemingly with no
other view than that of continuing its kind, has also passed the first
period of its life in the same element. The common gnat, that so much
annoys us in our evening walks, was originally an inhabitant of some
stagnant pool. The beetle that flits along at even-tide, lay in a
worm-like state for a considerable period, locked up in the caverned
chambers of the earth, and--but why proceed, when the whole insect
tribe, generally speaking, undergo such developements.--T.
The ants do not prepare for their larvæ _provisions de bouche_, as
happens with several species of bees and other insects, which provide
before-hand for the wants of their little ones; they give them every
day the nourishment best suited to their condition; the instinct of the
larvæ is sufficiently developed, to enable them to demand and receive
their repast, in the same way as the young of birds receive it from
their parents. When hungry, they erect their body, and search with
their mouth that of the workers, who are appointed to nourish them. The
ant then separates its mandibles, and allows them to take from its very
mouth the fluids they seek.
I know not if these fluids undergo any change in the body of the
workers, but I am far from believing it to be the case, since I have
often seen the ants offer them nourishment, almost immediately after
they had themselves taken it; perhaps honey and sugar dissolved in
water. I presume, however, that the regimen is proportioned to the
age and sex of each individual, that the aliment is more substantial
the nearer the time of their metamorphosis, and that more is given
to the larvæ of females than to those of the workers and males; but
the questions which have reference to the quality and quantity of
these aliments are of difficult solution: however, as it is of some
importance to ascertain if the nourishment which the larva takes
has any influence upon the development of the sexes in the females
of ants, as obtains in bees, I purpose making some experiments by
nourishing myself the larvæ of different species. Let us at present
follow the workers in the last care they bestow upon the larvæ; it is
not sufficient to lay them in the sun and give them food; it is still
necessary to keep them remarkably clean. These insects, therefore, who
in point of tenderness to the young committed to their charge, do not
yield to any of the females of the larger animals, pass their tongue
and mandibles continually over their bodies, and thus render them
perfectly white.[6] The ants have also another occupation; that of
extricating them from their cuticle, which becomes distended and soft
at the period of their transformation.
[6] As these insects evince so much attachment to the charge committed
to their care, I was desirous of ascertaining if they would show
equal concern for the offspring of another species. For this purpose,
I visited a nest inhabited by the little black ant, where there
were only larvæ, and removed a few to a nest occupied by the yellow
ant, containing only pupæ. Here they lay for a time unnoticed. At
length, one or two of the ants took them up, with the intention of
carrying them away, when another, who appeared stationed as centinel,
ran violently against and overthrew them, thus occasioning them to
relinquish their hold: this part of the nest was at length deserted,
the larvæ were left where first deposited, and the centinel retired.
At this time not a single ant was within view. In about five minutes
a little troop sallied forth, and, as if acting under some general
impulse, carried off their unwelcome visitors to one of their
underground apartments. Visiting this nest from day to day, I never
afterwards saw these larvæ, and therefore, conclude they had been set
apart, where, from neglect, they had perished. Had the larvæ been
brought up in common with those of their own family, I must have
known it; for, as I before said, the nest contained pupæ only. In an
after-visit to this nest, I reversed the experiment, by carrying away
some of the pupæ, and placing them in the nest from which I had before
taken the larvæ. This done, a similar scene took place. The pupæ were
at first regarded with indifference. Some of the inhabitants then
attempted a removal, to which there was, for a time, strong opposition.
In a few minutes, however, they were carried off to the subterranean
chambers. In these experiments, there was this slight difference: in
the former instance, the ants retired, as it would seem, to deliberate;
in the latter, they remained the whole time within sight, a little
distance from the pupæ. Had the larvæ or pupæ been suffered to remain
where first placed, this would have greatly embarrassed the ants in
their daily operations, this being the spot where they were in the
habit of bringing their young to enjoy the sun’s warmth. But why they
should take them under-ground, in preference to carrying and depositing
them beyond the nest, is a question I can only answer by supposing
they there conveyed them to insure their certain destruction, and thus
prevent further molestation.--T.
Previous to changing this skin, the larvæ spin themselves a silken
covering or cocoon, (as is the case with many other insects,) in which
in the form of pupæ, they prepare to undergo their last metamorphosis.
This cocoon is of a cylindrical form, elongated, of a pale yellow
colour, and very smooth and close in its texture. A remarkable
circumstance for which no cause has been yet assigned is, that there
are ants whose larvæ never spin; but this exception only holds with
those species that possess a sting and two knots on the peduncle of the
abdomen. Thus, there are some larvæ which undergo their change in a
silken envelope, and others which become pupæ, without lying under the
necessity of spinning or weaving one.[7]
[7] Among the spinning larvæ, there are some whose web is marked with
a black point at one of the extremities, which has been taken for the
remains of the skin of the pupæ, which they reject in their preceding
state; but as I have found the cocoons, thus stained, before the larvæ
they contained had undergone their metamorphosis, this supposition
falls to the ground. I am fully convinced it is nothing more than the
residue of the aliment, which these insects discharge a little time
before their change.--A.
Gould is of our Author’s opinion; but Sir Edward King, who published
a memoir on ants in an early number of the Philosophical Transactions
conjectures, that it is a secretion cast out by the larva in its
transformation.--T.
The larvæ of some ants pass the winter heaped up in the lowermost floor
of their dwelling. I have found, at this period, very small larvæ in
the nests inhabited by the Yellow Ant, the Field Ant, and some other
species, but none, in those of the Fallow, Ash-coloured, and Mining
Ants. Those that are to pass the winter in this state are covered
with hair, which is not the case in summer; affording another proof
of that Providence at which naturalists are struck at every step. We
do not find the larvæ of males and females but in the spring; their
transformation takes place in the beginning of summer.
The insect, in the state of pupa, has acquired the figure it will
always preserve; nothing seems wanting but strength and a little more
consistence: it is also as large as it will ever be; all its members
are distinct, one single pellicle envelopes them. The ant, under
this form, continues to move for some moments after its quitting the
state of larva, but it soon becomes immoveable: it afterwards changes
gradually in colour, passing from a fine white to a pale yellow;
then becoming red, and in several species, brown, almost verging to
black. The rudiments of wings may at this time be seen in those which
are destined to fly. The pupæ have still many attentions to receive
from the workers; the greater part are enclosed in a tissue spun by
themselves before their metamorphosis; but they cannot, like other
insects, liberate themselves from this covering by effecting an opening
in it with their teeth. They have scarcely the power of moving; their
covering is of too compact a texture, and formed of too strong a silk,
to allow of their tearing it without the assistance of the workers.
But how do these indefatigable attendants ascertain the proper moment
for this process?--If they possessed the faculty of hearing, we might
imagine they knew the fit time, from some noise produced in the
interior of the prison by the insects whose developement has commenced;
but there is no indication favouring this opinion; it is probable they
have a knowledge of it from some slight movements that take place
within, which they ascertain through the medium of their antennæ; for
these organs are endowed with a sensibility, of which it would be
difficult to form a just idea: whatever it be, they are never deceived.