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shelf. Hague here repeated the same experiment, with exactly the
same result. After this for several days no ants reappeared ; and
during the next three months it was only when fresh and particu-
larly fragrant flowers were put into the vases that a few of the more
daring ants ventured to straggle toward them. Hague concludes his
letter to Mr. Darwin, in which these observations are contained, by
saying ;

VOL. XIX. — 32



i ^rxm - "Brwuy*



498 THE POPULAR SCIENCE MONTHLY.

To turn back these stragglers and keep them out of sight for a number of
days, sometimes for a fortnight, it is sufficient to kill one or two ants on the
trail. . . • The moment the spot is reached an ant turns abruptly and makes
for home, and in a little while there is not an ant visible on the wall.

Many other cases might be quoted to show that ants are able to
communicate information to one another ; but, to save space, I shall
pass on to Sir John Lubbock's direct experiments upon this subject.
Three similar and parallel tapes were stretched from an ant's nest to
three similar glass vessels. In one of the latter Sir John placed
several hundred larva?, in another only two or three larvae, and the third
he left empty. The object of the empty glass was to see whether any
ants might not run along the tapes without any special reference to
the obtaining of larva? ; and this was found not to be the case. Sir
John then put an ant to each of the other two glasses ; they each
took a larva, carried it to the nest, returned for another, and so on.
Each time a larva was taken out of the glass containing only two or
three. Sir John replaced it with another, so that the supply should not
become exhausted. Lastly, every ant (except the two which had first
been put to the larva?), before reaching home with her burden, was
caught and imprisoned till the observation terminated.

The result was, that during forty-seven and a half hours the ants
which had access to the glass containing numerous larvie brought 257
friends to their assistance ; while during an interval of five and a half
hours longer those which visited the glass with only two or three
larv£e brought only 82 friends. This result appears very conclusive as
proving some power of definite communication, not only as to where
food is to be found, but also as to the road which leads to the largest
store. Further experiments, however, proved that these ants are not
able to describe the 2)'''€cise locality where treasure is to be found.
For, having exposed larvse as before and placed an ant upon them, he
Avatched every time that she came out of the nest with friends to assist
her ; but, instead of allowing her to pilot the way, he took her up and
carried her to the larva?, allowing her to return with a larva upon her
own feet. Lender these circumstances the friends, although evidently
coming out with the intention of finding some treasure, were never
able to find it, but wandered about in various directions for a while,
and then returned to the nest. Thus, during two hours, she brought
out altogether in her successive journeys no less than 120 ants, of
which number only five in their unguided wanderings happened by
chance to find the sought-for treasure.

Memory. — The general fact that, whenever an ant finds her way to
a store of food or larva?, she will return to it again and again in a
more or less direct line from her nest, constitutes ample proof that the
ant remembers her way to the store of food. It is of interest to note
that the nature of this insect-memory appears to be identical with that
of memory in general. Thus, a new fact becomes impressed upon ant-



INTELLIGENCE OF ANTS.



499



memory by repetition, and the impression is liable to become effaced
by lapse of time. Sir John Lubbock found it necessary to teach the
insects, by a repetition of several lessons, their way to treasure, if that
way were long or unusual. With regard to the duration of memory
in ants, it does not appear that any direct experiments have been
made ; but the following observation by Mr. Belt on its apparent du-
ration in the leaf-cutting ant may be here stated : In June, 1859, he
found his garden invaded by these ants, and on following up their
paths he found their nest about a hundred yards distant. He poured
down their burrows a pint of diluted carbolic acid. The marauding
parties were at once drawn off from the garden to meet the danger at
home, while in the burrows themselves the greatest confusion pre-
vailed. Next day he found the ants busily engaged in bringing up
the ant-food from the old burrows and carrying it to newly formed
ones a few yards distant. These, however, turned out to be intended
only as temporary repositories ; for in a few days both old and new
burrows were entirely deserted, so that he supposed all the ants to
have died. Subsequently, however, he found that they had migrated
to a new site, about two hundred yards from the old one, and there
established themselves in a new nest. Twelve months later the ants
again invaded his garden, and again he treated them to a strong dose
of carbolic acid. The ants, as on the previous occasion, were at once
withdrawn from his garden, and two days afterward he found " all
the survivors at work on one track that led directly to the old nest of
the year before, where they were busily employed in making new
excavations. ... It was a wholesale and entire migration." Mr. Belt
adds, " I do not doubt that some of the leading minds in this formi-
carium recollected the nest of the year before, and directed the migra-
tion to it." Of course, it is possible that the leaders of the migration
may have simply stumbled on the old burrows by accident, and, find-
ing them already prepared as a nest, forthwith proceeded to transfer
the food and larvoe ; but, as the old and the new burrows were sepa-
rated from one another by so considerable a distance, this supposition
does not seem probable, and the only other one open is that the ants
remembered their former home for a period of twelve months. This
supposition is rendered the more probable from a somewhat analogous
case recorded by Karl Vogt in his " Lectures on Useful and Harmless
Animals." For several successive years ants from a certain nest
used to go through certain inhabited streets to a chemist's shop six
hundred metres distant, in order to obtain access to a vessel filled
with sirup. As it can not be supposed that this vessel was found in
.-uccessive working seasons by as many successive accidents, it can
only be concluded that the ants remembered the sirup-store from
season to season.

Recoonitiox. — I shall now pass on to consider a class of highly
remarkable facts. It has been known since the observations of Huber



500 THE POPULAR SCIEXCE MONTHLY.

that all the ants of the same community recognize one another as
friends, while an ant introduced from another nest, even though it be
an ant of the same species, is known at once to be a foreigner, and is
usually maltreated or put to death. Huber found that, when he re-
moved an ant from a nest and kept it away from its companions for a
period of four months, it was still recognized as a friend, and caressed
by its previous fellow-citizens after the manner in which ants show
friendship, viz., by stroking antennae. Sir John Lubbock, after re-
peating and fully confirming these observations, extended them as
follows :

He first tried prolonging the period of separation beyond four
months, and found that it might be made more than three times as
long without the ants forgetting their absent friend. Thinking that
this fact could only be 'explained, either by all the ants knowing each
other's personal appearance, or by their all having a distinctive smell
peculiar to each nest, or by their all having a sign, like a pass-word,
differing in different nests. Sir John tried sepai-ating some ants from
a nest while still in the condition of larvae, and, when they emerged as
I)erfect insects, transferring them back to the nest from which they
had been taken as larvae. Of course, in this case the ants in the nest
could never have seen those which had been removed, for a larval ant
is as unlike the mature insect as a caterpillar is unlike a butterfly ;
neither can it be supposed that the larvae, thus kept away from the
nest, should retain, when hatched out as perfect insects, any smell be-
longing to their parent nest ; nor, lastly, is it reasonable to imagine
that the animals, while still in the condition of larval grubs, can have
been taught any gesture or sign used as a pass-word by the matured
animals. Yet, although all these possible hypotheses seem to be thus
fully excluded by the conditions of the experiment, the result showed
unequivocally that the ants all recognized their transformed larvae as
native-born members of their community.

Next, therefore, Sir John Lubbock tried dividing a nest into two
parts before the queen ants had become pregnant. Seven months after
the division the queens laid their eggs, and five months later these
eggs had developed into perfect insects. He then transferred some of
these young ants from the division of the nest in which they had been
born to the division in which they had never been, even in the state
of the e^v. Yet these ants also were received as friends, in marked
contrast to the reception accorded to ants from any other nest. It
therefore seems to be blood-relationship that ants are able, in some
way that is as yet wholly inexplicable, to recognize. It ought, how-
ever, to be remembered in this connection that, in an experiment made
by Forel on slave-making ants, it was proved that they almost instan-
taneously recognized their own slaves from other slaves of the same
species — and this after their slaves had been kept away from the nest
for a period of four months.



INTELLIGENCE OF ANTS. 501

Under this heading I may also allude to the unquestionable evi-
dence concerning enormous multitudes, or, as we might say, a whole
nation of ants, all recognizing one another as belonging to the same
nationality. No doubt the principle (whatever it may be) on which
the power of recognition depends is the same here as it is in the case
of a single nest ; but, in the cases which I am about to quote, the oper-
ation of this principle is indefinitely and incalculably extended. The
cases to which I allude are those in which new ants' nests spring up as
off-shoots from the older ones, so that a nation of towns, as it were,
o:radually spreads to an immense circumference round an original cen-
ter. Forel describes such a nation of Formica exsecta which comprised
more than two hundred nests, and covered a space of nearly two hun-
dred square metres. Individual ants must here have been numbered
by the million, and yet they all knew each ' other as friends — even
those taken from farthermost nests — while they would admit no for-
eigners within their territory.

A still more remarkable case is recorded by McCook of what be
calls an " ant town." The one he has described occurs in the Alle-
<,diany Mountains of North America, and consists of sixteen or seven-
teen hundred nests, which rise in cones to a height of from two to five
feet. The ground below is riddled in every direction with subter-
ranean passages of communication. The inhabitants are all on the
most friendly terms, so that if any one nest is injured it is repaired by
help from the other nests. Here, also, foreign ants of the same species
were not tolerated ; so that we should have an analogous case if all
the inhabitants of Europe should be directly known to one another
as friends, while an American or an Australian, on setting foot upon
European ground, should be immediately set upon as an enemy.

Emotions. — The pugnacity, valor, and rapacity of ants are too well
and generally kno\\Ti to require the narration of special instances of
their display. With regard to the tenderer emotions, however, there
is among observers a difference of opinion. Sir John Lubbock found
that the species of ants on which he experimented are apparently de-
ficient in feelings both of affection and of sympathy. He tried bury-
ing some specimens of Lasius niger beneath an ant-road ; but none of
the ants traversing the road made any attempt to release their im-
prisoned companions. He repeated the- same experiment, with the
same result, on various other species. Even when the friends in diffi-
culty were actually in sight, it by no means followed that their com-
panions would assist them. On imprisoning some friends! iirOrle Bottle,
the mouth of which was covered with muslin, and some strangers of
the same species (K/iisca) in another bottle similarly protected, and
placing both bottles in the nests, " the ants which were at liberty took
no notice of the bottle containing their imprisoned friends. The
strangers in the other bottle, on the other hand, excited them con-
siderably." For days they crowded round this bottle, endeavoring to



502 THE POPULAR SCIENCE MONTHLY.

gnaw through the muslin by which its mouth was closed. This on the
seventh day they succeeded in doing, when they killed the imprisoned
strangers. " The friends throughout were quite neglected," so that this
experiment, as Sir John observes, seems to show that " in these curious
insects hatred is a stronger passion than affection." This experiment
always gave the same result in the case of this species ; but, when
tried with Formica rufescens, the ants took no notice of cither bottle,
and showed no signs either of affection or hatred ; so that, as Sir John
again observes, " one is almost tempted to surmise that the spirit of
these ants is broken by slavery " — i. e., by the habit of keeping slaves.

But there is no lack of evidence to show, ^:)e;' contra, that the
tenderer emotions have a place in ant-psychology. Even the hard-
hearted species which Sir John Lubbock observed grew sympathetic
toward sick or injured friends. Thus he observed that a specimen
of F". ficsca, which was congenitally destitute of antennsp, and which
had been attacked by an ant of another species, excited the sympathy
of a friend on being placed near her own nest. This friend " examined
the poor sufferer carefully, then picked her up tenderly, and carried
her away into the nest. It would have been difficult for any one who
witnessed this scene to have denied to this ant the possession of
humane feelings." Again, Moggridge has seen one ant carry another
sick and apparently dead ant "down the twig which formed their
path to the surface of the water, and, after dipping it in for a minute,
carry it laboriously up again, and lay it in the sun to dry and re-
cover."

But some species of ants seem habitually to show affection and
sympathy even toward healthy companions in distress. Thus Belt
writes of the Eciton humata, that " one day watching a small column
of these ants, I placed a little stone on one of them to secure it. The
next that approached, as soon as it discovered its situation, ran back-
ward in an agitated manner, and soon communicated the intelligence
to the others. They rushed to the rescue," and by their concerted
action effected the release of their companion. Similarly ants of this
species which Belt buried were always dug out by their friends. To
quote one such instance, the ant which first found the buried one

tried to pull her out, but could not. It immediately set off at a great rate,
and I thought it had deserted hef comrade, but it bad only gone for assistance ;
for in a short time about a dozen ants came hurrying up, evidently fully informed
of the circumstances of the case, for they made directly for their imprisoned
comrade and set him free. I do not see bow this could be instinctive. It was
sympathetic help, such as men only among the higher mammalia show. The
excitement and ardor with which they carried on their unflagging exertions for
the rescue of their comrade could not have been greater if they bad been human
beings.

Ford and McCook have also observed displays of sympathy and affec-
tion by other species.



INTELLIGENCE OF ANTS. 503

Nursing. — This may appropriately be considered in connection
\dth the emotions, as it seems to imply something akin to maternal
affection. The eggs will not develop into larvae unless nursed, and
the nursing is effected by licking the surface of the eggs, which under
the influence of this process increase in size, or grow. In about a
fortnight — during which time the workers carry the eggs from higher
to lower levels of the nest, and vice versa, according to the circum-
stances of heat, moisture, etc. — the larvae are hatched out, and require
no less careful nursing than the eggs. The workers feed them by
placing mouths together — the larvae stretching out their heads to re-
ceive the nourishment after the manner of young birds. When fully
grown the larva? spin cocoons, and are then pup», or the " ants' eggs "
of the pheasant-rearers. These require no food, but still need in-
cessant attention with reference to warmth, moisture, and cleanli-
ness. When the time arrives for their emergence as perfect insects,
the workers assist them to get out of their larval cases by biting
through the walls of the latter. When it emerges, the newly-born
ant is inclosed in a thin membrane like a shirt, which has to be
]>ulled off. ""When we see," says Buchner, "how neatly and gently
this is done, and how the young creature is then washed, brushed, and
fed, we are involuntarily reminded of the nursing of human babies."
The young ants are then educated. They are led about the nest and
taught their various domestic duties. Later on they learn to distin-
guish between friends and foes ; and when an ant's nest is attacked
by foreign ants the young ones never join in the fight, but confine
themselves to removing the pupa?. That the knowledge of hei'cditary
enemies is not wholly instinctive is proved by the experiment of Forel,
who put young uneducated ants of three different species into a glass
case with pupae of six other species — all the nine species being natu-
rally hostile to one another. Yet the young ants did not quarrel, but
worked together to tend the pupae. When the latter hatched out, an
artificial colony was formed of a number of naturally hostile species,
all living together like the " happy families " of the showmen.

Keeping Aphides. — It is well and generally known that various
species of ants keep aphides, as men keep milch-cows, to supply a
nutritious secretion. Iluber first observed this fact, and noticed
that the ants collected the eggs of the aphides, and treated them
with as much apparent care as they treated their own. When these
eggs hatch out, the aphides are usually kept and fed by the ants.
Sometimes the stems and branches on which they live are incased
by the ants in clay walls, in which doors are left large enough to
admit the ants, but too small to allow the aphides to escape. The
latter are therefore imprisoned in regular stables. The sweet secre-
tion is yielded to the ants by a process of "milking," which consists
in the ants stroking the aphides with their antennae.

Sir John Lubbock has made an interesting addition to our knowl-



504 THE POPULAR SCIEXCE MONTHLY.

edge respecting the habit in question, as practiced by a certain species
of ant {Lasiusflavtis), which departs in a somewhat remarkable man-
ner from the habit as practiced by other species. He says : " When
my eggs hatched I naturally thought that the aphides belonged to one
of the species usually found on the roots of plants in the nests of
Lasius Jlavus. To my surprise, however, the young creatures made
the best of their way out of the nest, and, indeed, were sometimes
brought out of the nest by the ants themselves." Subsequent obser-
vation showed that these aphides, born from eggs hatched in the ants'
nest, left the nest, or were taken from it, as soon as they were hatched,
in order to live upon a kind of daisy which grew around the nest.
Sir John then made out the whole case to be as follows :

Here are apliides, not living in the ants' nests, but outside, on the leaf-stalks
of plants. The eggs are laid early in October on the food-plant of the insect.
They are of no direct use to the ants, yet they are not left where they are laid,
where they would be exposed to the severity of the weather, and to innumerable
dangers, but are brought into their nests by the ants, and tended by thera with
the utmost care througli the long winter months until the following March, when
the young ones are brought out and again placed on the young shoots of the
daisy. This seems to me a most remarkable case of prudence. Our ants may
not perhaps lay up food for the winter, but they do more, for they keep during
six months the eggs which will enable them to procure food during tlie following
winter.

As a supplement to this interesting observation, I may here append
the following, which is due to Herr Nottebohm, who communicated it
to Professor Bilchner : This gentleman had a weeping-ash which was
covered by millions of aphides. To save the tree, he one day in March
cleaned and washed every branch and spray before the buds had burst,
so removing all the aphides. There was no sign of the latter till the
beginning of June, when he was surprised one fine sunny morning to
see a number of ants running quickly up and down the trunk of the
tree, each carrying up a single aphis to deposit it on the leaves, when
it hurried back to fetch another. " After some weeks the evil was as
great as ever. ... I had destroyed one colony, but the ants replanted
it by bringing new colonists from distant trees and setting them on
the young leaves."

Aphides are not the only insects which are utilized by ants as cows.
Gall-insects and cocci are kept in just the same way ; but McCook ob-
served that, where aphides and cocci are kept by the same ants, they
are kept in separate chambers, or stalls. Caterpillars of the genus
Lyccena have also been observed to be kept by ants for the sake of a
sweet secretion which they supply.

Slavery. — The habit or instinct of keeping slaves obtains at least
among three species of ant. It was first observed by P. Huber in
Formica riifescens, which enslaves the species F. fusca, the members
«f which are appropriately colored black. The slave-making ants



INTELLIGENCE OF ANTS. 505

attack a nest of F.fusca in a body ; there is a great fight Vith much
slaughter, and, if victorious, the slave-makers carry off the pupaj of
the vanquished nest in order to hatch them out as slaves. When these
pupa? hatch out, the young slaves begin their life of work, and seem
to regard their masters' home as their own, for they never attempt to
escape, and they fight in defense of the nest should it be attacked.
The work that devolves upon the slaves differs according to the species
which has enslaved them. In the nests of F. sanguinea the compara-
tively few captives are kept exclusively as household slaves, all the
out-door work of foraging, slave-capturing, etc., being performed by
the masters ; and when for any reason a nest has to migrate, the mas-
ters carry their slaves in their jaws. On the other hand, F. rufescens
assigns a much larger share of work to the slaves, which they capture
in much larger numbers to take it. In this species the masters do no
work whatsoever, unless the capturing of slaves be regarded as such.
Therefore the whole community is entirely dependent upon its slaves ;
the masters are not able to make their own nests, to feed their own
larva?, or even to feed themselves ; they die of starvation in the midst
of favorite food if a slave should not be present to hand it in proper
form. In order to confirm this observation (originally due to Iluber)
Lespes placed a piece of moistened sugar near a nest of these slave-
makers. It was soon found by one of the slaves, which gorged itself
and returned. Other slaves then came out and did likewise. Some of
the masters next came out, and by pulling the legs of the feeding slaves
reminded them that they were neglecting their duty. The slaves then
immediately began to serve their masters to the sugar. Had they not
done so, there is no doubt they would have been punished, for the mas-
ters bite the slaves when displeased with them. Forel and Darwin
have also confirmed these observations of Huber. Indeed, the struct-
ure of the mouth in F. I'ufescens is such as to render self-feeding diffl-
cult, if not physically impossible. Its long and narrow jaws, admira-
bly adapted to 'pierce the head of an enemy, do not admit of being



Online LibraryD. S. (David Samuel) MargoliouthThe Popular science monthly (Volume 19) → online text (page 62 of 110)