The habits of the Ants are as remarkable as the habits of the bees. In
their marvellous republics each one has his fixed duties to perform,
of which he acquits himself willingly and without constraint. In
consequence of their habits of foresight and frugality, ease reigns in
the dwellings of these little animals, which become attached to their
nest by a feeling of patriotism. Woe betide him who disturbs them in
their occupations, or destroys their house! Like bees, they form a
regular republic, composed--first, of males; secondly, of females;
thirdly of neuters, or workers. We shall see, further on, the labours
and the part played by each one of these three orders of the republic.
Let us speak first of the species.
Ants are divided into a great number of species, which have been
carefully described by De Geer, Latreille, and Francis Huber, the son
of the celebrated blind man who wrote the history of bees. All these
species have, however, some general traits in common, by which they
may be easily distinguished from all other insects. Ants have a slim
body on long legs. The workers are stouter and smaller than the males;
and these last are smaller than the females. The males have large and
prominent eyes, whilst the eyes of the workers and females are small.
[Illustration: Fig. 359.--Red Ant. Male magnified. (_Myrmica rubra._)]
[Illustration: Fig. 360.--Brazilian Umbrella Ant. (_Atla cephalotes._)]
Ants are provided with antennæ, bent in the form of an elbow, with
which they examine everything they meet, and which seem to assist them
in the communication of their ideas. Two horny, very strong mandibles
serve them at the same time as pincers, tweezers, scissors, pick-axe,
fork, and sword. A thin short neck joins the head to the thorax, to
which, in the case of the males and females, are attached four large
veiny wings. The workers only have no wings. Of the three pairs of
legs, the hind ones are the longest. Each pair is armed with a spur,
and fringed with very short hairs, which serve the purpose of brushes.
The abdomen, large, short, oval, or square, is always most voluminous
in the females.
There are three genera of ants which we shall mention. The _Myrmicæ_
have two knobs to the pedicle, by which the abdomen is attached to the
thorax; the _Poneræ_ only one. In these two genera, the females and
the neuters have a sting, and the larvæ do not spin a cocoon in which
to change into pupa. Lastly, the _Formicæ_--ants properly so
called--have but one knob on the pedicle of the abdomen, as in
_Ponera_; their larvæ spin a silky cocoon. They have no sting, but
they pour into the wounds made by their mandibles an acid liquor, the
pungent smell of which is well known. This liquid is formic acid, a
natural product, which the chemist now-a-days knows how to make
artificially, by the action of dilute sulphuric acid on maize and
other vegetable matters. Their whole body is impregnated with this
acid, and has a strong sour smell. Some people like to chew ants, on
account of their sourish taste. "They also make," says Charles de
Geer, "creams for side-dishes, to which these ants give, they say, the
taste of lemon-juice." We know, in the south of France, people who
have eaten these _crèmes aux fourmis_! _Polyergus_ forms a sub-genus
of _Formica_.
[Illustration: Fig. 361.--Sections of an Ant's Nest.]
In all these species, the workers, or neuters, have the charge of the
building, provisioning, and rearing of the larvæ--in fact, all the
care of the household, and the defence of the nest. Deprived of wings,
they are bound to the soil, and condemned to work. As compensation, to
them belong strength, authority, power: nothing is done but through
them. "Born protectors of an immense family still in the cradle," says
M. Victor Rendu, "by their vigilance, their tenderness, and their
solicitude, without being mothers themselves, they share in the duties
and joy of maternity. Alone, they decide on peace or war; alone, they
take part in combats: head, heart, and arm of the republic, they
ensure its prosperity, watch over its defence, found colonies, and in
their works show themselves great and persevering artists."
The nests of ants (Figs. 361, 362) are known under the name of
ant-hills. They vary very much, both as to their form and the
materials employed in making them--wood and earth are the principal.
That which strikes one at first sight, is the size of these dwellings,
which form a curious contrast to the smallness of their builders. Each
species of ant has an order of architecture peculiar to it. The Red
Ant (_Formica rufa_), one of the commonest in our woods, constructs a
little rounded hillock with all kinds of objects--fragments of wood,
bits of straw, dry leaves, the remains of insects, &c. This hillock,
the base of which is protected by material of greater solidity, is
nothing more than the exterior envelope of the nest, which is carried
underground to a very great depth. Avenues, cleverly contrived, lead
from the summit to the interior. The openings vary in width; and, as
night approaches, are carefully barricaded. They are opened every
morning, except on rainy days, when the doors remain shut, and the
inhabitants confined within.
The ant-hill, or _formicarium_, is at first simply a hole hollowed out
in the soil, the entrance to which is masked by the building
materials. But the miners do not cease to hollow out galleries and
chambers, arranged by stories. The earth and rubbish are carried out,
and serve to construct the upper edifice, which rises at the same time
that the excavation grows deeper. It is a labyrinth bored in all
directions. It contains corridors, landings, chambers, and spacious
rooms, which communicate with each other by passages which are often
vertical. All the corridors lead to a large central space, loftier
than the others, and supported by pillars; it is here that the greater
number of the ants congregate. These ant-hills often rise to a height
of fifteen inches above the ground, and descend to an equal depth.
Fig. 362 shows the interior of an ant-hill, drawn from Nature. Outside
it are to be seen some ants occupied in sucking plant-lice.
[Illustration: Fig. 362.--Section of an Ant-hill.]
The group of Mason Ants contains a great number of varieties: the
Ashy-black Ant (_Formica nigra_, Fig. 363), the Brown, the Yellow
(_Formica flava_), the Blood-red, the Russety (_Polyergus rufescens_),
the Black, the Miner (_Formica cunicularia_), the Turf Ant, &c. All
these species employ a mortar, more or less fine, in raising their
hillocks, at the same time that they hollow out their underground
dwellings. The Jet Ant (_Formica fuliginosa_) excavates wood,
hollowing out its labyrinth in the trunk of a tree with consummate
skill. The Red Ant (_Myrmica rubra_) plies, according to
circumstances, the trade of a mason or excavator.
[Illustration: Fig. 363.--Ashy-black Ant (_Formica nigra_). Male, female,
and worker.]
[Illustration: Fig. 364.--Ashy Ant. Male, worker, and female.]
The masons work when they can profit by the rain or by the evening
dew, to make their mortar. They only go out after sunset, or when a
fine rain has wetted their roof. Then they set to work. They roll up
pellets of earth, bring them back in their mandibles, and stick them
on to those places where the building was left unfinished. From all
sides the earth-workers may be seen arriving, laden with materials.
All these are bustling, hurrying, busy, but always in the greatest
order, and with a perfect understanding among themselves. Every part
of the building is going on at the same time. The apartments spring up
one above another, and the edifice visibly rises. The rain, the sun,
and the wind consolidate and harden the building so cunningly
contrived by these industrious workers, who have received from God
alone their marvellous science. With no other tool than their
mandibles, the excavators work their way through the hardest wood.
They bore holes right through it, riddling it completely with numerous
storeys of horizontal galleries. The Yellow Ant raises its little
hillocks in fields, and passes the winter in a burrow or underground
dwelling-place.
Independent of the principal entrances, there exist, in some nests,
masked doors guarded by sentinels. Many species also hollow out
covered galleries, which they only unmask in extreme danger, either to
open an outlet for the besieged, or to turn the enemy who has already
invaded the place. Ant-hills are, in fact, perfect fortresses,
defended by a thousand ingenious contrivances, and guarded by
sentinels always on the _qui vive_.
[Illustration: Fig. 365.--Larva of the Red Ant. (_Myrmica rubra_).]
[Illustration: Fig. 366.--Pupa of the Red Ant (_Myrmica rubra_)
magnified.]
The domestic life of the different species is nearly the same. The
birth and rearing of the little ones, and the duties of the adults, do
not differ perceptibly from each other in the various species of ants.
The females live together in harmony. They lay, without ceasing to
walk about, white eggs of cylindrical form and microscopic dimensions.
The workers pick them up, and carry them to special chambers. In a
fortnight after the laying, the larva (Fig. 365) appears. Its body is
transparent. A head and wings can be made out, but no legs; the mouth
is a retractile nipple, bordered by rudimentary mandibles, into which
the workers disgorge the juices they have elaborated in their
stomachs; and as they lay by no provisions, they are obliged to
gather each day the sugary liquids destined for the food of the larvæ.
From their birth, a troop of nurses is charged with the care of them.
They put them out in the open air during the day. Hardly has the sun
risen, when the ants, placed just under the roof, go to tell those
which are beneath, by touching them with their antennæ, or shaking
them with their mandibles. In a few seconds, all the outlets are
crowded with workers carrying out the larvæ in order to place them on
the top of the ant-hill, that they may be exposed to the beneficent
heat of sun. When the larvæ have remained some time in the same place,
their guardians move them away from the direct action of the solar
rays, and put them in chambers a little way from the top of the hill,
where a milder heat can still reach them. We then see the ants
themselves taking the well-earned luxury of a few minutes' rest,
heaping themselves up together, right in the sun. There is no
observant inhabitant of the country who has not seen the curious
spectacle which we have just mentioned--that is to say, the population
of an ants' nest carrying into the sun the young nurslings, so that
they may experience the action of the solar heat. We recommend the
dweller in towns who is in the country for a day to stretch himself
out near an ant-hill in the warm weather, and witness this spectacle,
one of the most curious in Nature. The care which the working ants
bestow on their young does not consist only in nourishing them and
procuring for them a proper temperature; they have also to keep them
extremely clean. With their palpi they clean them, brush them, distend
their skin, and thus prepare them for the critical trial of their
metamorphosis.
At this moment the larvæ of ants, properly so called, spin themselves
a silky cocoon, of a close tissue and of a grey or yellowish colour;
those of the _Myrmicæ_ and of the _Poneræ_ do not surround themselves
with a silky cocoon before changing into pupæ. These are at first of a
pure white, but they very soon assume a brown colour, which increases
until it becomes dark brown. They possess all the organs of the adult,
enveloped in a membrane so thin that it seems to be iridescent. Fig.
366 represents the pupa of the red ant. They are the cocoons enclosing
the pupæ, which are incorrectly called in the country ants' eggs, and
are given to young pheasants and partridges. The pupæ remain
motionless till the insects emerge, which is accomplished with the
assistance of the workers. These latter tear the covering from the
pupa, and complete its deliverance. They then watch over the
newly-born ant. For some days they feed it, help it to walk, and do
not abandon it till it can dispense with their good offices. These
workers, when provisions fail, or when the ant-hill is threatened with
any great danger, take in their mandibles the eggs, the larvæ, the
pupæ, and sometimes those females and the males which refuse to follow
them. Thus laden, they go their way, to seek for another country they
may call their own. They never forget, in their hurried emigrations,
the infirm or sick workers, which would perish in the house now
abandoned and deserted.
The males and females lately hatched do not enjoy the same liberty as
the young workers. They are confined to the ant-hill, where they are
kept in sight till the day of the general departure. It is towards the
end of the month of August that swarms of winged ants of both sexes
are seen to issue forth. The males come out first, agitating their
iridescent and transparent wings. The females, less numerous, follow
them closely. All of a sudden one sees this troop raise itself at a
given signal, and disappear in the air, where the coupling takes
place. The males perish immediately afterwards. The females
impregnated return to the paternal home, or else found new colonies
with the assistance of a few workers who are their escort. From this
moment they no longer require wings. The workers make haste to cut
them off, or, indeed, which oftenest happens, they themselves tear
them off. With their wings they lose the desire for liberty.
Henceforward, they will quit their retreat no more, the cares of their
approaching maternity now alone occupying them. The working ants
reserve for them subterranean chambers, where they are kept in sight
by the sentinels. At certain hours only are they to be met with in the
upper storeys. When they wish to walk, a company of guards presses
round them on all sides so as to prevent them from advancing too
quickly. There are no sorts of attentions they do not heap upon them
to make them forget their captivity. They caress them, brush them,
lick them, they offer them food continually. On the least appearance
of danger, the workers take possession, first of all, of the pregnant
females, and drag them out by the secret outlets, so as to put in a
place of safety their precious persons, the hope of the community. The
workers' task is immense, for their labours increase in the same
proportion as the population increases. But the division of work and
the good understanding which exists between the members of the
community, allow them to be prepared for anything that may happen, and
to supply all their necessities.
Nothing is more amusing than to observe the shifts ants are put to in
transporting objects of great size. They stumble, they tumble head
over heels, they roll down precipices; but, in spite of all accidents,
return to their task, and always accomplish it. The tranquil
inhabitants of these subterranean republics are bound together by
mutual affection in a devoted fraternity, which makes them ever ready
to assist each other. They all help one another as much as they can.
If an ant is tired, a comrade carries it on its back. Those which are
so absorbed with their work that they have no time to think of their
food, are fed by their companions. When an ant is wounded, the first
one who meets it renders it assistance, and carries it home. Latreille
having torn the antennæ from an ant, saw another approach the poor
wounded one, and pour, with its tongue, a few drops of a yellow liquid
on the bleeding wound.
Huber the younger one day took an ant's nest to populate one of those
glass contrivances which he used for making his observations, and
which consisted of a sort of glass bell placed over the nest. Our
naturalist set at liberty one part of the ants, which fixed themselves
at the foot of a neighbouring chestnut tree. The rest were kept during
four months in the apparatus, and at the end of this time Huber moved
the whole into the garden, and a few ants managed to escape. Having
met their old companions, who still lived at the foot of the chestnut
tree, they _recognised_ them. They were seen, in fact, all of them, to
gesticulate, to caress each other mutually with their antennæ, to take
each other by the mandibles, as if to embrace in token of joy, and
they then re-entered together the nest at the foot of the chestnut
tree. Very soon they came in a crowd to look for the other ants under
the bell, and in a few hours our observer's apparatus was completely
evacuated by its prisoners. When an ant has discovered any rich prey,
far from enjoying it alone, like a gourmand, it invites all its
companions to the feast. Community of goods and interests exists
amongst all the members of this model society. It is the practical
realisation of the dream formed by certain philosophers of our day,
who were only able to conceive the idea, the possibility, the project
of such a community of goods and interests, which is among ants a
reality.
How do these insects manage to make themselves understood in such
various ways, asking for help, giving advice, giving invitations? They
must have a language of their own, or else they must communicate their
impressions by the play of their antennæ.
When an ant is hungry, and does not wish to disturb itself from its
work, it tells a foraging ant as it passes, by touching it with its
antennæ; the latter approaches it immediately, and presents it, on the
end of its tongue, some juice it has disgorged for this purpose. The
antennæ, then, are used by the ants for the purpose of making
themselves understood by each other. Dr. Ebrard, who studied these
insects attentively, is of opinion that they use them in the same way
as a blind man does his stick, to feel their way with, for their sight
is not good. The age to which ants live is not well known. It is
believed that the workers live many years.
Ants eat all sorts of things. One sees them eating fresh or decaying
meat, fruits, flowers, particularly everything which is sugary. They
attack living insects, and kill them and suck their blood. Like many
insects, they are very fond of sugary liquids--honey, syrups, pure
sugar, &c. Dupont de Nemours relates in his Memoirs that, to guarantee
his sugar-basin against the invasion of ants, he had found no better
plan than to make it "an island," that is to say, to place it in the
middle of a vessel full of water. He felt sure that he had made the
fortress safe against any attack; but listen to the stratagem made use
of by the besiegers. The ants climbed up the wall to the ceiling,
exactly perpendicularly over the sugar-basin. From there they let
themselves fall into the interior of the place, penetrating thus by
main force, and without injuring any one, into the magazine. As the
ceiling was very high, the draught caused them to deviate from the
straight line, and thus a certain number fell into the fosse of the
citadel, that is to say, into the water in the vessel. Their
companions stationed on the bank made all efforts imaginable to fish
out the drowning ants, but were afraid of taking to the water of such
a large lake. All that they could do was to stretch out their bodies
as far as possible (keeping on the bank the while), to lend a helping
hand to their drowning friends. Nevertheless, the salvage did not
progress much; when the ants, which were getting very uneasy,
conceived a happy thought. A few were seen to run to the ant-hill, and
then to reappear. They brought with them a squad of eight grenadiers,
who threw themselves into the water without any hesitation, and who,
swimming vigorously, seized with their pincers all the drowning ants,
and brought them all on to _terra firma_. Eleven, half-dead, were thus
brought to shore, that is, to the rim of the basin. They would
probably all of them have succumbed, if their companions had not
hastened to lend them assistance. They rolled them in the dust, they
brushed them, they rubbed them, they stretched themselves on their
dying companions to warm them; then they rolled them and rubbed them
again. Four were restored to life. A fifth half recovered, and, still
moving its legs and its antennæ a little, was taken home with all
sorts of precautions. The six others were dead. They were carried into
the ant-hill by their afflicted companions. It seems like a dream to
read such things as this, and yet Dupont de Nemours tells us, "I have
seen it!" Ants are also very fond of a peculiar liquid which the
plant-lice secrete from a pouch in the abdomen. When they have got
possession of a plant-louse, they excite it to secrete this liquid,
but without doing it any harm. They carry the plant-lice into the
ant-hill, or into private stables. There they keep them, give them
their food, and suck them. We have already mentioned these curious
relations which are established between ants and plant-lice.[104] Fig.
367 shows an ant thus occupied. The _Gallinsecta_ also furnish the
ants with sugary liquids.
[104] See the Order Hemiptera, _supra_.--ED.
During the cold of winter the ants sleep at the bottom of their nests,
without taking any food. A small number of species only hold out
through the severe season, by shutting themselves up in the ant-hill
with a number of plant-lice. It is thus that they pass the winter with
a supply of food. We must mention, however, that in warm countries the
ants do not hybernate.
We have just described ant society during the quiet periods, when
peace reigns supreme; but they are not more exempt than other animals
from the necessities and dangers of war. They have a great many
enemies among the population of the woods; they must, then, be
prepared to repel their attacks. They display in that the most
scientific resources of the military art applied to defence.
It is almost needless to say that the sentinels are, at all times,
posted at a reasonable distance from the ant-hill, to observe the
environs. When the fortress is unexpectedly attacked, whether by large
insects, Coleoptera for instance, or by the ants from a neighbouring
nest, these vigilant sentinels immediately fall back and give the
alarm to the camp, not, however, without having boldly confronted the
enemy and opposed to him an honourable resistance. Having re-entered
the nest in all haste, they precipitate themselves into the passages,
tapping with their antennæ all the ants which they meet, and thus
spreading the alarm in the city. Very soon the agitation has become
general, and thousands of combatants sally forth from the citadel,
ready to repel the attack and make the enemy bite the dust.
The possession of a flock of plant-lice is sometimes a subject of
discord, and becomes a _casus belli_ between two neighbouring
ant-hills. But, usually, the war has for its object to make prisoners
in other nests, and to carry off part of the inhabitants as slaves.
This is the origin of _mixed ant-hills_, which, independently of their
natural founders, contain one or two foreign species, helots whom the
conquerors have taken away from their birth-place, to make of them
auxiliaries and slaves. In these mixed ant-hills the species imported
occasionally exceed in number the original population, as it happens
sometimes in those ships which are used in the slave trade, and on
which the slaves are often found in greater numbers than the sailors
composing the crew. The phalanx of ants reduced to a state of slavery
pay all sorts of attentions to their masters. They lick them, brush
them, caress them, carry them on their backs, feed them--good and
faithful servants that they are--and even rear their progeny. The
masters impose on their slaves all sorts of work. They only reserve
for themselves the making of war. From time to time they undertake
expeditions against some neighbouring ants' nest. If they are
conquered and come back without bringing with them any prisoners, the
slaves or auxiliaries are sulky to them, and will not allow them for
some time to enter the nest. If, on the contrary, they return loaded
with booty, they flatter them, give them food, and relieve them of
their prisoners, which they lead away into the interior of the
fortress. The warlike tribes, however, never carry off any other but
the larvæ and nymphs of workers from the ant-hills they plunder. These
young captives get used to their kidnappers: brought up in fear of
their masters, they never think of abandoning them.
[Illustration: Fig. 367.--An Ant milking Aphides or Plant-lice
(magnified).]
[Illustration: Fig. 368.--Russet Ants (_Polyergus rufescens_).]
[Illustration: Fig. 369.--Blood-red Ant (_Formica sanguinea_).]
Two species constitute the warrior tribes which form societies mixed
with the species they reduce to slavery. They are the Russet Ant (Fig.
368) and the Blood-red Ant (Fig. 369). They always attack the nests of
the Ashy-black (_Formica fusca_) and the Miners.
The Russet Ant has mandibles made for war; they appear cut out for
struggling and fighting. The Blood-red Ants are less ferocious; they
work themselves, and make none of those sweeping raids by which the
Russet Ants depopulate the neighbouring ant-hills.
What Peter Huber has done for bees, Francis Huber, his son, has done
for the ants. It is from Francis Huber that we borrow the description
which it remains for us to give of the habits of ants in times of war.
He thus relates one of these expeditions, of which he was a
witness:--"On the 17th of June, 1804," says he, "as I was walking in
the environs of Geneva, between four and five in the afternoon, I saw
at my feet a legion of largish russet ants crossing the road. They
were marching in a body with rapidity, their troop occupied a space of
from eight to ten feet long by three or four inches wide; in a few
minutes they had entirely evacuated the road; they penetrated through
a very thick hedge, and went into a meadow, whither I followed them.
They wound their way along the turf, without straying, and their
column remained always continuous, in spite of the obstacles which
they had to surmount. Very soon they arrived near a nest of ashy-black
ants, the dome of which rose among the grass, at twenty paces from the
hedge. A few ants of this species were at the door of their
habitation. As soon as they descried the army which was approaching,
they threw themselves on those which were at the head of the cohort.
The alarm spread at the same instant in the interior of the nest, and
their companions rushed out in crowds from all the subterranean
passages. The russet ants, the body of whose army was only two paces
distant, hastened to arrive at the foot of the nest; the whole troop
precipitated itself forward at the same time, and knocked the
ashy-black ants head over heels, who, after a short but very smart
combat, retired to the extremity of the habitation. The russet ants
clambered up the sides of the hillock, flocked to the summit, and
introduced themselves in great numbers into the first avenues; other
groups worked with their teeth, making a lateral aperture. In this
they succeeded, and the rest of the army penetrated through the breach
into the besieged city. They did not make a long stay there; in three
or four minutes the russet ants came out again in haste, by the same
adits, carrying each one in its mouth a pupa or larva belonging to
the conquered. They again took exactly the same road by which they
had come, and followed each other in a straggling manner; their line
was easily to be distinguished on the grass by the appearance which
this multitude of white cocoons and larvæ, carried by as many
russet-coloured ants, presented. They passed through the hedge a
second time, crossed the road, and then steered their course into a
field of ripe wheat, whither, I regret to say, I was unable to follow
them."[105]
[105] "Recherches sur les Moeurs des Fourmis indigènes," p.
210. Paris, 1810.
Huber adds that, having returned to the pillaged nest to examine it
more closely, he saw some ashy-black workers bringing back to their
home the few larvæ which they had succeeded in saving. Having later
discovered the nest of these Amazons, which is the name he gives to
the warrior ants, he found there many of the ashy-black ants living on
very good terms with their kidnappers.
The Amazons begin their expeditions at the end of June, during the
hottest hours of the day. They come out in long files, eight or ten
abreast, preceded by their scouts. These columns start at a run, in a
straight line, and without feeling their way. They have no chieftain.
The van is re-formed every moment. Those who are in front do not
remain there; at the end of a certain time they go and range
themselves in the rear, and are replaced by those which were behind.
The whole troop is thus in constant communication through its entire
length. Rarely does the expedition divide into two bodies. Arrived
under the walls of the fortress, the column halts and masses itself
into one corps. The assault is made with incredible impetuosity. In
the twinkling of an eye the place is escaladed, taken by storm, and
pillaged, and the ashy-black ants are either put to flight or led away
into captivity. The same ant-hill may be invaded as many as three
times running on the same day; but then the ashy-black ants, on their
guard, have barricaded themselves in, and in that case the aggressors
return home without pillaging them.
[Illustration: Fig. 370.--Mining Ant (_Formica cunicularia_), male,
worker, and female.]
The Mining Ants (Fig. 370) are less timid than the ashy-black; and, as
they defend themselves with more energy, there are frequently deadly
combats, and the field of battle is left covered with heads, legs, and
limbs, scattered about here and there with the dead and wounded. The
miners pursue the pillagers, and snatch their plunder from them. But
they are sometimes driven back vigorously, and the russet ants gain
their lair with the plunder.
The tactics of the Red Ants (_Formica sanguinea_) differ from those of
the russet. They only sally forth in small detachments, which begin by
engaging in skirmishes with the scouts thrown out round the enemy's
ant-hill. Couriers, despatched from time to time to the camp of the
red ants, bring up reinforcements. When the troop feels itself
sufficiently strong, it invades the nest of the ashy-black ants, and
carries off their offspring, which the latter have not had time to
secure. Sometimes, also, the red ants instal themselves in the nest
whose inhabitants they have ejected, and transfer their own population
to it. The motive for this emigration is that the old nest has become
useless, or that it is exposed to some danger. The red ants are not
the only ants which thus desert their birth-place. Many species
abandon it likewise, for analogous motives, and construct elsewhere
another dwelling, to which they transport all the population of the
first nest.
[Illustration: Fig. 371.--Philanthus triangulum.]
[Illustration: Fig. 372.--Mutilla Europæa, male and female.]
When we reflect on the habits of ants, we are forced to admit that
intelligence and reason appear still more in their acts than in those
of bees. The life of ants, as well as that of bees, as far as we are
concerned, is an unintelligible enigma. The acts of animals, in
general, are sometimes an abyss unfathomable to our reason. The
Orientals say, "The last word may be written on man: on the elephant,
never!" Let us add that they should no more say that the elephant will
be an inexhaustible theme, but that the history of the ant will
continue so always.
The best-known genera of the Fossores, or Fossorial Hymenoptera, are
_Philanthus_ (Fig. 371), which feeds its larvæ on bees, having first
numbed them by its sting; _Pompilus_ and _Sphex_, which attack
spiders; and _Mutilla_ (Fig. 372), whose females resemble ants, being
variegated with red and yellow, the males, being provided with wings
and smaller in size, and black. The _Mutillæ_ are parasitical on
solitary bees, their larvæ devouring their larvæ.
[Illustration: Fig. 373.--A species of Pimpla.]
[Illustration: Fig. 374.--A species of Ophion.]
Other Hymenoptera lay their eggs under the skin of certain insects,
especially when these are in the larva or caterpillar state, thus
rendering service to agriculture by destroying a great number of
noxious insects. In lieu of a sting they have an auger, intended to
pierce the skin of their victims. It is thus that the _Ichneumons_
introduce their eggs under the skin of caterpillars. The _Pimplas_
(Fig. 373), which belongs to this group, have a very long ovipositor,
which, with its two appendages, constitute three lancets, and enable
them to get at the larvæ in their retreats. The _Ophions_ (Fig. 374)
have a sickle-shaped abdomen. They lay their eggs on the skin of
caterpillars, which they attack with the short cutting auger with
which they are provided.
[Illustration: Fig. 375.--Gall insect (_Cynips quercusfolii_).]
[Illustration: Fig. 376.--Oak Galls, produced by _Cynips quercusfolii_.]
[Illustration: Fig. 377.--Interior of a Gall.]
The _Cynips_, or Gall-insects, are small black or tawny Hymenoptera,
the females of which have an auger, rolled up spirally and hidden in a
fissure of the abdomen, with which they prick the young shoots of
plants. A peculiar liquid which they pour into the hole round the egg
they have laid, causes an excrescence to grow, which is called a
"gall." The larva is developed in the centre of this gall, and
transformed into a pupa; and afterwards into a perfect insect, which
makes its exit by a hole in the wall of its prison. Fig. 375
represents the Cynips of the oak tree (_Cynips quercusfolii_), and
Figs. 376 and 377 the galls it produces. The galls of the rose are
hairy, and are sometimes called "Robin's Cushion." The gall-nut, rich
in tannin, which is used in the manufacture of ink, is the produce of
a foreign Cynips, which lives on an oak found in the East. Apples of
Sodom, which travellers bring back from the shores of the Dead Sea,
are large galls[106] full of dry dust and larvæ.
[106] Made by _Cynips insana_.--ED.
The _Urocerata_ and the _Tenthredinetæ_ form two tribes of insects,
of which the first are of great size, have a cylindrical body, the
abdomen being attached to the thorax in its whole breadth, without any
pedicle.
[Illustration: Fig. 378.--Sirex gigas.]
The insects of the genus _Sirex_ (Fig. 378), belonging to the former
of these, lay their eggs in living wood, and their larvæ live for many
years in the interior. They are to be met with in great numbers in
forests of pine trees, and, according to Latreille, show themselves
sometimes in such great numbers as to become an object of terror. The
female of the Giant Sirex (_Sirex gigas_) possesses a long rectilinear
auger. The mandibles of the larvæ are of great strength, and are even
capable of perforating lead. This fact has been observed many times.
In 1857 Marshal Vaillant presented to the Académie des Sciences some
packets of cartridges containing balls which had been pierced through
by the larvæ of the Sirex during the sojourn of the French troops in
the Crimea. Some of these insects were still shut up in the gallery
which they had hollowed out in the metal. M. Dumeril (and this was one
of the last works of that venerable and learned naturalist) wrote a
Report on this subject, in which were recorded many analogous
instances. He quoted, as an example, that M. le Marquis de Brême, in
1844, showed to the Société Zoologique many cartridges in which the
balls had been perforated by the insects to a depth of about a
quarter of an inch. These cartridges came from the arsenal of Turin.
They had been placed in barrels made of larch wood, the inside of
which had been attacked by the insects. It was discovered that it was
after having left the wood that they had gnawed through the envelopes
of the cartridges, and at last into the balls themselves. In 1833
Audouin presented to the Société Entomologique de France a plate of
lead, from the roof of a building, on which this naturalist supposed
that the larvæ of a _Callidium_[107] had made deep sinuosities, as
they do in wood. Before this, parts of the leaden roofs at La Rochelle
had been noticed not only gnawed, but pierced from one side to the
other, by the larvæ of _Bostrichus capucinus_.[108] In 1844 M.
Desmarest reported the erosion and perforation of sheets of lead by a
species of _Bostrichus_ and by _Callidium_. In 1843 M. Du Boys
presented to the Société d'Agriculture of Limoges some stereotyped
plates--composed, as is well-known, of a very hard alloy, formed of
antimony and lead--which had been pierced and riddled with holes by
two specimens of a _Bostrichus_. The holes were a seventh of an inch
in diameter by two inches in depth. The stereotypes were thus
perforated, although they had been wrapped up in many folds of paper
and cardboard. As the printing served for a work called "Les Fastes
Militaires de la France," one may say that the brave soldiers received
from an insect more wounds than their enemies had ever given them.
[107] A coleopterous insect.--ED.
[108] Also a beetle.--ED.
To prove that these insects have really the power to perforate metals
as others perforate and pass through woody matter, the entomologist of
Limoges made the following experiments. He placed in a leaden box, the
sides of which were thin, a living specimen of the Fire-coloured
Lepture of Geoffroy (_Callidium sanguineum_), a Coleopteron which is
commonly found in houses in France in winter, its larvæ being
developed in great numbers in firewood. Above this box he fitted on
another, also containing a specimen of this insect, which he shut in
with a third box. A few days afterwards he separated the boxes. The
middle one had been pierced through, and the two insects were found
together, the one which was below having made a hole through which it
might introduce itself into the middle box. M. Du Boys made a chemical
experiment which enabled him to establish beyond a doubt that the
insect which had gnawed the metal had not made it serve as its food.
The dried body of one of these insects was analysed. After having
immersed it in nitric acid it was completely burnt, and there could
not be found in the ashes acted upon by the nitric acid the least
trace of lead. This experiment proves that these insects had for their
object only to escape from the galleries in which they were
accidentally deposited in their larva state, and that it was not until
they had undergone their complete transformation that they endeavoured
to gain their liberty. Observations of the same kind were multiplied
after the Report of M. Dumeril. The Académie des Sciences received, in
the month of June, 1861, two Memoirs--one from M. Heriot, captain of
artillery, the other from M. Bouteille, curator of the Museum of
Natural History of Grenoble--containing many new observations on the
perforation by insects of leaden balls contained in cartridges
prepared for war. M. Milne-Edwards read to the Académie des Sciences a
short Report on these works.
The insect which had produced the perforations observed in the balls
sent to the Crimea in 1857, and which M. Dumeril particularly studied,
was the _Sirex juvencus_, and had been taken from France in the wood
forming the boxes which contained the cartridges. In the other case of
which we are speaking, that is to say, of the cartridges which were
sent in 1861 to the Académie by Captain Heriot and by M. Bouteille,
the perforations had been produced by other species. M. Milne-Edwards,
who found the insect that had caused this strange damage, had no
trouble in recognising it as the _Sirex gigas_, which, in its larva
state, lives in the interior of old trees or pieces of wood, and
which, after it has gone through all its metamorphoses, comes out of
its retreat to reproduce its kind. To clear themselves a passage, they
cut away with their mandibles the ligneous substances or other hard
bodies they meet with on their road. It was in pursuing this object
that the insects, imprisoned accidentally in the packets of cartridges
when they were yet only in the larva state, must have attacked the
leaden balls, as also the paper and the other matters which they met
with on their road, and which opposed their passage. M. Bouteille
proves, in his Memoir, that M. Dumeril has committed an error in
saying that the perforating organ employed by the _Sirex_ to attack
the leaden balls in the cartridges in the Crimea was the auger
situated at the extremity of the abdomen of the female, and intended
for cutting into that part of the wood where it is to lay its eggs. M.
Bouteille has established, in fact, that they were not only the
females which attacked the cartridges, but that the males, which have
no auger, had occasioned the same damage.
The _Tenthredinetæ_ are called "Saw-Flies," because the females are
furnished with a double auger, notched like a saw, with which they cut
into the branches in which they lay their eggs. The larvæ of these
insects have a striking resemblance to the caterpillars of
Lepidoptera. They can only be distinguished from them by a great
globular head, not hollowed out, and by their abdominal legs, in
general to the number of more than ten. They are called false
caterpillars (Fig. 379). Most of them, when touched, erect themselves
and move about in a threatening manner. They spin a silken cocoon
before changing into pupæ. The _Lophyrus pini_, which devours the
leaves of pine trees, belongs to this family.
[Illustration: Fig. 379.--Larva of a Saw-Fly. (_Tenthredo_).]
[Illustration: Fig. 380.--Lophyrus pini.]