Chapter III: Ants (1)

WITHIN the last ten or twelve years our information on the habits and intelligence of these insects has been so considerably extended, that in here rendering a condensed epitome of our knowledge in this most interesting branch of comparative psychology, it will be found that the chapter is constituted principally of a statement of observations and experiments which have been conducted during the short period named. The observers to whom we are mainly indebted for this large increase of our knowledge are Messrs. Bates, Belt, Müller, Moggridge, Lincecum, MacCook, and Sir John Lubbock. From the fact that these naturalists conducted their observations in different parts of the world and on widely different species of ants, it is not surprising that their results should present many points of difference; for this only shows, as we might have expected, that different species of ants differ considerably in habits and intelligence. Therefore, in now drawing all these numerous observations to a focus, I shall endeavour to show clearly their points of difference as well as their points of agreement; and in order that the facts to be considered may be arranged in some kind of order, I shall deal with them under the following heads:--Powers of special sense; Sense of direction; Powers of memory; Emotions; Powers of communication; Habits general in sundry species; Habits peculiar to certain species; General intelligence of various species.

_Powers of Special Sense._

Taking first the sense of sight, Sir John Lubbock made a number of experiments on the influence of light coloured by passing through various tints of stained glass, with the following results. The ants which he observed greatly dislike the presence of light within their nests, hurrying about in search of the darkest corners when light is admitted. The experiments showed that the dislike is much greater in the case of some colours than in that of others. Thus under a slip of red glass there were congregated on one occasion 890 ants, under green 544, under yellow 495, and under violet only 5. To our eyes the violet is as opaque as the red, more so than the green, and much more so than the yellow. Yet, as the numbers show, the ants had scarcely any tendency to congregate under it: there were nearly as many under the same area of the uncovered portion of the nest as under that shaded by the violet glass. It is curious that the coloured glasses appear to act on the ants in a graduated series, which corresponds with the order of their influence on a photographic plate. Experiments were therefore made to test whether it might not be the actinic rays that were so particularly distasteful to the ants; but with negative results. Placing violet glass above red produces the same effect as red glass alone. Obviously, therefore, the ants avoid the violet glass because they dislike the rays which it transmits, and do not prefer the other colours because they like the rays which they transmit. Sodium, barium, strontium, and lithium flames were also tried, but not with so much effect as the coloured glass.

It has just been observed that the relative dislike which Sir John Lubbock's ants showed to lights of different colours seems to be determined by the position of the colour in the spectrum--there being a regular gradation of intolerance shown from the red to the violet end. As these ants dislike light, the question suggests itself that the reason of their graduated intolerance to light of different colours may be due to their eyes not being so much affected by the rays of low as by those of high refrangibility. In this connection it would be interesting to ascertain whether ants of the genus _Atta_ show a similarly graduated intolerance to the light in different parts of the spectrum; for both Moggridge and MacCook record of this genus that it not only does not shun the light, but seeks it--coming to the glass sides of their artificial nests to enjoy the light of a lamp. Possibly, therefore, the scale of preference to lights of different colours would be found in this genus to be the reverse of that which Sir John Lubbock has found in the case of the British species.

As regards hearing, Sir John Lubbock found that sounds of various kinds do not produce any effect upon the insects. Tuning-forks and violin notes, shouting, whistling, &c., were all equally inefficient in producing the slightest influence upon the animals; and experiments with sensitive flames, microphone, telephone, &c., failed to yield any evidence of ants emitting sounds inaudible to human ears.

Lastly, as regards the sense of smell, Sir John Lubbock found that on bringing a camel's-hair brush steeped in various strong scents near where ants were passing, "some went on without taking any notice, but others stopped, and evidently perceiving the smell, turned back. Soon, however, they returned, and passed the scented pencil. After doing this two or three times, they generally took no further notice of the scent. This experiment left no doubt on my mind." In other cases the ants were observed to wave about and throw back their antennæ when the scented pencil was brought near.

That ants track one another by scent was long ago mentioned by Huber, and also that they depend on this sense for their power of finding supplies which have been previously found by other ants. Huber proved their power of tracking a path previously pursued by their friends, by drawing his finger across the trail, so obliterating the scent at that point, and observing that when the ants arrived at that point they became confused and ran about in various directions till they again came upon the trail on the other side of the interrupted space, when they proceeded on their way as before. The more numerous and systematic experiments of Sir John Lubbock have fully corroborated Huber's observations, so far as these points are concerned. Thus, to give only one or two of these experiments; in the accompanying woodcut (Fig. 1) A is the nest, B a board, _n_ _f_ _g_ slips of paper, _h_ and _m_ similar slides of glass, on one of which, _h_, there was placed pupæ, while the other, _m_, was left empty. Sir John Lubbock watched two particular (marked) ants proceeding from A to _h_ and back again, carrying the pupæ on _h_ to the nest A. Whenever an ant came out of A upon B he transposed the slips _f_ and _g_. Therefore at the angle below _n_ there was a choice presented to the ant of taking the unscented pathway leading to the full glass _h_, or the scented pathway leading to the empty glass _m_. The two marked ants, knowing their way, always took the right turn at the angle; but the stranger ants, being guided only by scent, for the most part took the wrong turn at the angle, so going to the empty glass _m_. For out of 150 stranger ants only 21 went to _h_, while the remaining 129 went to _m_. Still the fact that all the stranger ants did not follow the erroneous scent-trail to _m_, may be taken to indicate that they are also assisted in finding treasure by the sense of sight, though in a lesser degree. Therefore Sir John Lubbock concludes that in finding treasure 'they are guided in some cases by sight, while in others they track one another by scent.'

As further evidence showing how much more ants depend upon scent than upon sight in finding their way, the following experiment may be quoted. In the accompanying woodcut (Fig. 2) the line marked 1, 2, 3 represents the edge of a paper bridge leading to the nest; A the top of a pencil which is standing perpendicularly upon a board, represented by the general black surface; B the top of the same pencil when moved a distance of a few inches from its first position A. On the top of this pencil were placed some pupæ. Sir John Lubbock, after contriving this arrangement, marked an ant and put it upon the pupæ on the top of the pencil. After she had made two journeys carrying pupæ from the pencil to the nest (the tracks she pursued being represented by the two thick white lines), while she was in the nest he moved the pencil to its position at B. The thin white line represents the course then pursued by the ant in its endeavours to find the pencil, which was shifted only a few inches from A to B. That is, 'the ants on their journey to the shifted object travelled very often backwards and forwards and round the spot where the coveted object first stood. Then they would retrace their steps towards the nest, wander hither and thither from side to side between the nest and the point A, and only after very repeated efforts around the original site of the larvæ reach, as it were, accidentally the object desired at B.' Therefore the ants were clearly not guided by the _sight_ of the pencil.

The same thing is well shown by another form of experiment. 'Some food was placed at the point _a_ (Figs. 3 and 4) on a board measuring 20 inches by 12 inches, and so arranged that the ants in going straight from it to the nest would reach the board at the point _b_, and after passing under the paper tunnel _c_, would proceed between five pairs of wooden bricks, each 3 inches in length and 1-3/4 inches in height. When they got to know their way they went quite straight along the line _d e_ to _a_. The board was then twisted as shown in Fig. 4. 'The bricks and tunnel being arranged exactly in the same direction as before, but the board having been moved, the line _d e_ was now outside them. The change, however, did not at all discompose the ants; but instead of going, as before, through the tunnel and between the rows of bricks to _a_, they walked exactly along the old path to _e_.' Keeping the board steady, but moving the brick pathway to the left-hand corner of the board where the food was next placed (Fig. 5), had the effect of making the ant first go to the old position of the food at _a_, whence it veered to a new position, which we may call _x_. The bricks and food were then moved towards the right-hand corner of the board--_i.e._ over a distance of 8 inches (Fig. 6). The ant now first went to _a_, then to _x_, and not finding the food at either place, set to work to look for it at random, and was only successful after twenty-five minutes' wandering.

And, as evidence how much more dependence they place upon scent in finding their way than upon any other of their faculties, it is desirable to quote yet one further experiment, which is of great interest as showing that when their sense of smell is made to contradict their sense of direction, they follow the former, notwithstanding, as we shall presently see, the wonderful accuracy of the information which is supplied to them by the latter. 'If, when _F. niger_ were carrying off larvæ placed in a cup on a piece of board, I turned the board round so that the side which had been turned towards the nest was away from it, and _vice versâ_, the ants always returned over the same track on the board, and, in consequence, directly away from home. If I moved my board to the other side of my artificial nest, the result was the same. Evidently they followed the road, not the direction.'

There can be little doubt that ants have a sense of taste, as they are so well able to distinguish sugary substances; and it is unquestionable that in their antennæ they possess highly elaborated organs of touch.

_Sense of Direction._

As evidence of the accuracy and importance of the sense of direction in the Hymenoptera, we must here adduce Sir John Lubbock's highly interesting experiments on ants--leaving his experiments in this connection on bees and wasps to be considered in the next chapter. He first accustomed some ants (_Lasius niger_) to go to and fro to food over a wooden bridge. When they had got quite accustomed to the way, he watched when an ant was upon a bridge which could be rotated, and while she was passing along it, he turned it round, so that end _b_ was at _c_, and _c_ at _b_. 'In most cases the ant immediately turned round also; but even if she went on to _b_ or _c_, as the case might be, as soon as she came to the end of the bridge she turned round.' Next, between the nest and the food he placed a hat-box twelve inches in diameter and seven inches high, cutting two small holes, so that the ants in passing from the nest to the food had to pass in at one hole and out at the other. The box was fixed upon a central pivot, so as to admit of being rotated easily without much friction or disturbance. When the ants had well learnt their way, the box was turned half round as soon as an ant had entered it, 'but in every case the ant turned too, thus retaining her direction.' Lastly, Sir John took a disk of white paper, which he placed in the stead of the hat-box between the nest and the food. When an ant was on the disk making towards the food, he gently drew the disk to the other side of the food, so that the ant was conveyed by the moving surface in the same direction as that in which she was going, but _beyond_ the point to which she intended to go. Under these circumstances 'the ant did not turn round, but went on' to the further edge of the disk, when she seemed 'a good deal surprised at finding where she was.'

These experiments seem to show that the mysterious 'sense of direction,' and consequent faculty of 'homing,' are in ants, at all events, due to a process of registering, and, where desirable, immediately counteracting any change of direction, even when such change is gently made by a wholly closed chamber in which the animal is moving, and not by any muscular movements of the animal itself. And the fact that drawing the moving surface along in the same direction of advance as that which the insect is pursuing does not affect the movements of the latter, seems conclusively to show that the power of registration has reference only to _lateral_ movements of the travelling surface; it has no reference to variations in the _velocity_ of advance along the line in which the animal is progressing.[19]

_Powers of Memory._

Little need here be said to prove that ants display some powers of memory; for many of the observations and experiments already detailed constitute a sufficient demonstration of the statement that they do. Thus, for instance, the general fact that whenever an ant finds her way to a store of food or larvæ, 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 the way to the store. It is of considerable interest, however, to note that the nature of this insect-memory appears to be, as far as it goes, precisely identical with that of memory in general. Thus, a new fact becomes _impressed_ upon their memory by _repetition_, and the impression is liable to become effaced by lapse of time. More evidence on both these features of insect-memory will be adduced when we come to treat of the intelligence of bees; but meanwhile it is enough to refer to the fact that in his experiments on ants, Sir John Lubbock found it necessary to _teach_ the insects by a repetition of several lessons their way to treasure, if that way was long or unusual.

With regard to the _duration_ of memory, it does not appear that any experiments have been made; but the following observation by Mr. Belt on this point in the case of the leaf-cutting ant may here be stated. In June 1859 he found his garden invaded by these ants, and following up their paths he found their nest about a hundred yards distant. He poured down their burrows a pint of common brown carbolic acid, mixed with four buckets of water. The marauding parties were at once drawn off from the garden to meet the danger at home, and the whole formicarium was disorganised, the ants running up and down again in the utmost perplexity. Next day he found them busily employed 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 only intended as temporary repositories; for in a few days both the old and the 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 the garden, and two days afterwards 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 fresh excavations. Many were bringing along pieces of ant-food' from the nest most recently deluged with carbolic acid to that which had been similarly deluged a year before, and from which all the carbolic acid had long ago disappeared. 'Others carried the undeveloped white pupæ and larvæ. It was a wholesale and entire migration;' and the next day the nest down which he had last poured the carbolic acid was entirely deserted. Mr. Belt adds: 'I afterwards found that when much disturbed, and many of the ants destroyed, the survivors migrate to a new locality. I do not doubt that some of the leading minds in this formicarium recollected the nest of the year before, and directed the migration to it.'

Now, I do not insist that the facts necessarily point to this conclusion; for it may have been that the leaders of the migration simply stumbled upon the old and vacant nest by accident, and finding it already prepared as a nest, forthwith proceeded to transfer the food and pupæ to it. Still, as the two nests were separated from one another by so considerable a distance, this hypothesis does not seem probable, and the only other one open to us is that the ants remembered the site of their former home for a period of twelve months. And this conclusion is rendered less improbable from a statement of Karl Vogt in his 'Thierstaaten,' to the effect that for several successive years ants from a certain nest used to go through certain inhabited streets to a chemist's shop 600 mètres distant, in order to obtain access to a vessel filled with syrup. As it cannot be supposed that this vessel was found in successive working seasons by as many successive accidents, it can only be concluded that the ants remembered the syrup store from season to season.

I shall now pass on to consider a class of highly remarkable facts, perhaps the most remarkable of the many remarkable facts connected with ant psychology.

It has been known since the observations of Huber that all the ants of the same nest or community recognise 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 removed an ant from a nest and kept it away from its companions for a period of four months it was still recognised as a friend, and caressed by its previous fellow-citizens after the manner in which ants show friendship, viz., by stroking antennæ. Sir John Lubbock, after repeating and fully confirming these observations, extended them as follows. He first tried keeping the separated ant away from the nest for a still longer period than four months, and found that even after a separation of more than a year the animal was recognised as before. He repeated this experiment a number of times, and always with the same invariable difference between the reception accorded to a foreigner and a native--no matter, apparently, how long the native had been absent.

Considering the enormous number of ants that go to make a nest, it seems astonishing enough that they should be all personally known to one another, and still more astonishing that they should be able to recognise members of their community after so prolonged an absence. Thinking that the facts could only be explained, either by all the ants in the same nest having a peculiar smell, or by all the members of the same community having a particular pass-word or gesture-sign, Sir John Lubbock, with the view of testing this theory, separated some ants from a nest while still in the condition of pupæ, and, when they emerged from that state as perfect insects, transferred them back to the nest from which they had been taken as pupæ. 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 grub is unlike a beetle; neither can it be supposed that a larva, hatched out away from the nest, should retain, when a perfect insect, any smell belonging to its parent nest--more especially as it had been hatched out by ants in another nest;[20] nor, lastly, is it reasonable to imagine that the animal, while still a larval grub, can have been taught any gesture-signal 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 recognised their transformed larvæ as native-born members of their community.

Lastly, Sir John Lubbock tried the experiment of going still further back in the life-history of the ants before separating them from the nest. For in September he divided a nest into two halves, each having a queen. At this season there were neither larvæ nor eggs. The following April both the queens began to lay eggs, and in August--_i.e._ nearly a year after the original partitioning of the nest--he took some of the ants newly hatched from the pupæ in one division, and placed them in the other division, and _vice versâ_. In all cases these ants were received by the members of the other half of the divided nest as friends, although if a stranger were introduced into either half it was invariably killed. Yet the ants which were thus so certainly recognised by their kindred ants as friends had never, even in the state of an egg, been present in that division of the nest before. On this highly remarkable fact Sir John Lubbock says:--

These observations seem to me conclusive as far as
they go, and they are very surprising. In my
experiments of last year, though the results were
similar, still the ants experimented with had been
brought up in the nest, and were only removed after
they had become pupæ. It might therefore be argued
that the ants, having nursed them as larvæ, recognised
them when they came to maturity; and though this would
certainly be in the highest degree improbable, it
could not be said to be impossible. In the present
case, however, the old ants had absolutely never seen
the young ones until the moment when, some days after
arriving at maturity, they were introduced into the
nest; and yet in all ten cases they were undoubtedly
recognised as belonging to the community.

It seems to me, therefore, to be established by these
experiments that the recognition of ants is not
personal and individual; that their harmony is not due
to the fact that each ant is individually acquainted
with every other member of the community.

At the same time, the fact that they recognise their
friends even when intoxicated, and that they know the
young born in their own nest even when they have been
brought out of the chrysalis by strangers, seems to
indicate that the recognition is not effected by means
of any sign or pass-word.

We must, therefore, conclude with reference to this subject that the mode whereby recognition is undoubtedly effected is as yet wholly unintelligible; and I have introduced these facts under the heading of memory only because this heading is not more inappropriate than any other that could be devised for their reception.

It ought here to be added also that the power of thus recognising members of their community is not confined by the limits of blood-relationship, for in an experiment made by Forel it was shown that Amazon ants recognised their own slaves almost instantaneously after an absence of four months.

Under this heading I may also adduce the evidence as to enormous masses, or, as we might say, a whole nation of ants recognising each other as belonging to the same nationality. New nests often spring up as offshoots from the older ones, and thus a nation of towns gradually spreads to an immense circumference around the original centre. Forel describes a colony of _F. exsecta_ which comprised more than two hundred nests, and covered a space of nearly two hundred square mètres. 'All the members of such a colony, even those from the furthermost nest, recognise each other and admit no stranger.'

Similarly, MacCook describes an 'ant town' in the Alleghany Mountains of North America ('Trans. Amer. Entom. Soc.,' Nov. 1877) which was inhabited by _F. exsectoïdes_. It consists of 1,600 to 1,700 nests, which rise in cones to a height of from two to five feet. The ground below is riddled in every direction with subterranean passages of communication. The inhabitants are all on the most friendly terms, so that if any one nest is injured it is repaired by their united forces.

It remains to be added in connection with this subject that the recognition is not automatically invariable, but when 'ants are removed from a nest in the pupa state, tended by strangers, and then restored, some at least of their relatives are certainly puzzled, and in many cases doubt their claims to consanguinity. I say some, because while strangers under the circumstances would have been immediately attacked, these ants were in every case amicably received by the majority of the colony, and it was sometimes several hours before they came across one who did not recognise them.'

It may also be added that _Lasius flavus_ behaves towards strangers quite differently and much more hospitably than is the case with _L. niger_. The stranger shows no alarm, but, on the contrary, will voluntarily enter the strange nest, and she is there received with kindness; although from the attention she excites, and the numerous communications which take place between her and her new friends, Sir John was 'satisfied that they knew she was not one of themselves. . . . Very different is the behaviour of _L. niger_ under similar circumstances. I tried the same experiment with them. There was no communications with the antennæ, there was no cleaning, but every ant which the stranger approached flew at her like a little tigress. I tried this experiment four times; each stranger was killed and borne off to the nest.'

_Emotions._

The pugnacity, valour, and rapacity of ants are too well and generally known to require the narration of special instances of their display. With regard to the tenderer emotions, however, there is a difference of opinion among observers. Before the researches of Sir John Lubbock it was the prevalent view that these insects display marked signs of affection towards one another, both by caressing movements of their antennæ, and by showing solicitude for friends in distress. Sir John, however, has found that the species of ants on which he has experimented are apparently deficient both in feelings of affection and of sympathy--or, at least, that such feelings are in these species much less strongly developed than the sterner passions.

He tried burying some specimens of _Lasius niger_ beneath an ant-road; but none of the ants traversing the road made any attempt to release their imprisoned companions. He tried the same experiment with the same result on various other species. Even when the friends in difficulty are actually in sight, it by no means follows that their companions will assist them. Of this, he says, he could give almost any number of instances. Thus, when ants are entangled in honey, their companions devote themselves to the honey, and entirely neglect their friends in distress; and when partly drowned, their friends take no notice. When chloroformed or intoxicated their own companions either do not heed them, or else 'seem somewhat puzzled at finding their intoxicated fellow-creatures in such a condition, take them up, and carry them about for a time in a somewhat aimless manner.' Further experiments, however, on a larger scale, went to show that chloroformed ants were treated as dead, _i.e._ removed to the edge of the parade-board and dropped over into the surrounding moat of water; while intoxicated ants were generally carried into the nest, if they were ants belonging to that community; if not, they were thrown overboard. This care shown towards intoxicated friends appears to indicate a dim sense of sympathy towards afflicted individuals; but that this emotion or instinct does not in the case of these species extend to healthy individuals in distress seems to be proved, not only by the experiments of burying already described, but also by the following:--

On Sept. 2, therefore, I put two ants from one of my
nests of _F. fusca_ into a bottle, the end of which
was tied up with muslin as described, and laid it down
close to the nest. In a second bottle I put two ants
from another nest of the same species. The ants which
were at liberty took no notice of the bottle
containing their imprisoned friends. The strangers in
the other bottle, on the contrary, excited them
considerably. The whole day one, two, or more ants
stood sentry, as it were, over the bottle. In the
evening no less than twelve were collected round it, a
larger number than usually came out of the nest at any
one time. The whole of the next two days, in the same
way, there were more or less ants round the bottle
containing the strangers; while, as far as we could
see, no notice whatever was taken of the friends. On
the 9th the ants had eaten through the muslin, and
effected an entrance. We did not chance to be on the
spot at the moment; but as I found two ants lying
dead, one in the bottle and one just outside, I think
there can be no doubt that the strangers were put to
death. The friends throughout were quite neglected.

Sept. 21.--I then repeated the experiment, putting
three ants from another nest in a bottle as before.
The same scene was repeated. The friends were
neglected. On the other hand, some of the ants were
always watching over the bottle containing the
strangers, and biting at the muslin which protected
them. The next morning at 6 A.M. I found five ants
thus occupied. One had caught hold of the leg of one
of the strangers, which had unwarily been allowed to
protrude through the meshes of the muslin. They worked
and watched, though not, as far as I could see, with
any system, till 7.30 in the evening, when they
effected an entrance, and immediately attacked the
strangers.

Sept. 24.--I repeated the same experiment with the
same nest. Again the ants came and sat over the bottle
containing the strangers, while no notice was taken of
the friends.

The next morning again, when I got up, I found five
ants round the bottle containing the strangers, none
near the friends. As in the former case, one of the
ants had seized a stranger by the leg, and was trying
to drag her through the muslin. All day the ants
clustered round the bottle, and bit perseveringly,
though not systematically, at the muslin. The same
thing happened all the following day.

On repeating these experiments with another species
(viz., _Formica rufescens_) the ants took no notice of
either bottle, and showed no sign either of affection
or hatred. 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 the experiments on
_F. fusca_ seem to show that in these curious insects
hatred is a stronger passion than affection.

We must not, however, too readily assent to this general conclusion, that ants as a whole are deficient in the tenderer emotions; for although the case is doubtless so with the species which Sir John examined, it appears to be certainly otherwise with other species, as we shall presently see. But first it may be well to point out that even the hard-hearted species with which Sir John had to do seem not altogether devoid of sympathy with sick or mutilated friends, although they appear to be so towards healthy friends in distress. Thus the care shown to intoxicated friends seems to indicate, if not, as already observed, a dim sense of sympathy, at least an instinct to preserve the life of an ailing citizen for the future benefit of the community. Sir John also quotes some observations of Latreille showing that ants display sympathy with mutilated companions; and, lastly, mentions an instance which he has himself observed of the same thing. A specimen of _F. fusca_ congenitally destitute of antennæ was attacked and injured by an ant of another species. When separated by Sir John, another ant of her own species came by. 'She 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.' Moggridge is also of opinion that the habit of throwing sick and apparently dead ants into the water, is 'in part to be rid of them, and partly, perhaps, with a view to effecting a possible cure; for I have seen one ant carry another 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 recover.'

But that some species of ants display marked signs of what we may call sympathy even towards healthy companions in distress, is proved by the following observation of Mr. Belt. He writes:[21]--

One day, watching a small column of these ants (_i.e._
_Eciton humata_), I placed a little stone on one of
them to secure it. The next that approached, as soon
as it discovered its situation, ran backwards in an
agitated manner, and soon communicated the
intelligence to the others. They rushed to the rescue;
some bit at the stone and tried to move it, others
seized the prisoner by the legs and tugged with such
force that I thought the legs would be pulled off, but
they persevered until they got the captive free. I
next covered one up with a piece of clay, leaving only
the ends of its antennæ projecting. It was soon
discovered by its fellows, which set to work
immediately, and by biting off pieces of the clay soon
liberated it. Another time I found a very few of them
passing along at intervals. I confined one of these
under a piece of clay at a little distance from the
line, with his head projecting. Several ants passed
it, but at last one discovered it and tried to pull it
out, but could not. It immediately set off at a great
rate, and I thought it had deserted its comrade, but
it had 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 soon
set him free. I do not see how this action could be
instinctive. It was sympathetic help, such as man only
among the higher mammalia shows. The excitement and
ardour with which they carried on their unflagging
exertions for the rescue of their comrade could not
have been greater if they had been human beings.

This observation seems unequivocal as proving fellow-feeling and sympathy, so far as we can trace any analogy between the emotions of the higher animals and those of insects. That insects with such highly organised social habits, and depending so greatly on the principles of co-operation, should manifest emotions or instincts of an incipiently altruistic character, is no more than we should antecedently expect on the general principle of survival of the fittest. Our only surprise should be that these emotions, or instincts, should appear to be so feebly developed in some species of ants, and, as we shall subsequently see, also of bees. But it may be worth while in this connection to point out that the valuable observation of Mr. Belt above quoted refers to the species of ant which, as we shall subsequently find, presents the most highly organised instincts of co-operation that are to be met with among ants, and therefore the greatest dependence of the welfare of the individual on that of the community. And the same remark is applicable to our native species, _F. sanguinea_, which the Rev. W. W. F. White has repeatedly seen rescuing buried companions very much in the manner described by Mr. Belt; and he does not appear to be acquainted with Mr. Belt's observations. He figures one case in which he saw three ants co-operating to dig out a buried comrade.[22]

_Powers of Communication._

Huber, Kirby and Spence, Dugardin, Burmeister, Franklin, and other observers have all expressed themselves as more or less strongly of the opinion that members of the same community of ants, and other social Hymenoptera, are able to communicate information to one another by some system of language or signs. The facts, however, on which their opinion rests have not been stated with that degree of caution and detail which the acceptance of the conclusion requires. Thus, Kirby and Spence give only one instance of supposed communication between ants,[23] and even this one is inconclusive, as the facts described admit of being explained by supposing that the ants simply tracked one another by scent; while Huber merely deals in general statements as to 'contact of antennæ,' without narrating any particulars of his observations. Therefore, until within the last few years there was really no sufficient evidence to sustain the general opinion that ants are able to communicate with one another; but the observations which I shall now detail must be regarded as fully substantiating that general opinion by facts as abundant and conclusive as the most critical among us can desire. I shall first narrate in his own words the more important of Sir John Lubbock's experiments in this connection:--

I took three tapes, each about 2 feet 6 inches long,
and arranged them parallel to one another and about 6
inches apart. An end of each I attached to one of the
nests (_F. niger_), and at the other end I placed a
glass. In the glass at the end of one tape I placed a
considerable number (300 to 600) of larvæ. In the
second I put two or three larvæ only, in the third
none at all. The object of the last was to see whether
many ants would come to the glasses under such
circumstances by mere accident, and I may at once say
that scarcely any did so. I then took two ants, and
placed one of them to the glass with many larvæ, the
other to that with two or three. Each of them took a
larva and carried it to the nest, returning for
another, and so on. After each journey I put another
larva in the glass with only two or three larvæ, to
replace that which had been removed. Now, if several
ants came under the above circumstances as a mere
matter of accident, or accompanying one another by
chance, or if they simply saw the larvæ which were
being brought, and consequently concluded that they
might themselves find a larva in the same place, then
the numbers going to the two glasses ought to be
approximately equal. In each case the number of
journeys made by the ants would be nearly the same;
consequently, if it was a matter of scent, the two
glasses would be in the same position. It would be
impossible for an ant, seeing another in the act of
bringing a larva, to judge for itself whether there
were few or many left behind. On the other hand, if
the strangers were brought, then it would be curious
to see whether more were brought to the glass with
many larvæ than to that which only contained two or
three. I should also mention that every stranger was
imprisoned until the end of the experiment.

The results of these experiments were that during 47-1/2 hours the ants which had access to a glass containing numerous larvæ brought 257 friends to their assistance; while during an interval 5-1/2 hours longer those which visited the glass with only two or three larvæ brought only 82 friends; and, as already mentioned, no single ant came to the glass which contained no larvæ. Now, as all the glasses were exposed to similar conditions, and as the roads to the first two must, in the first instance at all events, have been equally scented by the passage of ants over them, these results look very conclusive as proving some power of definite communication, not only that larvæ are to be found, but even where the largest store is to be met with.

To this interesting account Sir John Lubbock adds,--

One case of apparent communication struck me very
much. I had had an ant (_F. niger_) under observation
one day, during which she was occupied in carrying off
larvæ to her nest. At night I imprisoned her in a
small bottle; in the morning I let her out at 6.15,
when she immediately resumed her occupation. Having to
go to London, I imprisoned her again at 9 o'clock.
When I returned at 4.40 I put her again to the larvæ.
She examined them carefully, and went home without
taking one. At this time no other ants were out of the
nest. In less than a minute she came out again with
eight friends, and the little heap made straight for
the heap of larvæ. When they had gone two-thirds of
the way I again imprisoned the marked ant; the others
hesitated a few minutes, and then with curious
quickness returned home. At 5.15 I put her again to
the larvæ. She again went home _without a larva_, but
after only a few seconds' stay in the nest, came out
with no less than thirteen friends. They all went
towards the larvæ, but when they had got about
two-thirds of the way, although the marked ant had on
the previous day passed over the ground about 150
times, and though she had just gone straight from the
larvæ to the nest, she seemed to have forgotten her
way, and considered; and after she had wandered about
for half an hour, I put her to the larvæ. Now, in this
case, the twenty-one ants must have been brought out
by my marked one, for they came exactly with her, and
there were no other ants out. Moreover, it would seem
that they must have been told, because (which is very
curious in itself) she did not in either case bring a
larva, and consequently it cannot have been the mere
sight of a larva which had induced them to follow her.

Further experiments proved, as we might have expected, that although an ant is able to communicate to her friends in the nest that she has found treasure somewhere outside, she is not able to describe to them its precise locality. Thus, having exposed larvæ and placed an ant upon them as before, Sir John watched every time 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 larvæ, allowing her to return with a larva upon her own feet. Under 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 in her successive journeys altogether no less than 120 ants, of which number only 5 in their unguided wanderings happened to find the sought-for treasure. This result seems to prove, as we might have expected, that the communication is of the nature of some sign amounting to no more than a 'follow me.' Other experiments confirmed this result, and also brought out the fact that 'some species act much more in association than others--_Formica fusca_, for instance, much less than _Lasius niger_.' Thus Sir John Lubbock placed some honey before a marked specimen of the former species; but although she visited and revisited the honey during an entire day, she brought out no friends to share it; and although in her journeys to and from the nest she happened to pass and repass many other individuals, they took no notice of each other.

The obvious objection to these experiments, that an ant observing a friend bringing home food or a pupa might infer, without being told, that by accompanying the friend on the return journey she 'might participate in the good things,' has been partly met by the fact already stated, viz., that there is so very marked a difference in the result if, on experimenting on two ants, one had access to a large treasure and the other only to a small one. But to put this matter beyond question, Sir John Lubbock tried the experiment of pinning down a dead fly, so that the ant which found it was unable, with all her tugging, to move it towards the nest. At length she went back to the nest for assistance, and returned accompanied by seven friends. So great was her excitement, however, that she outran these friends, 'who seemed to have come out reluctantly, as if they had been asleep, and were only half awake;' and they failed to find the fly, slowly meandering about for twenty minutes. After again tugging for a time at the fly, the first ant returned a second time to the nest for assistance, and in less than a minute came out with eight friends. They were even less energetic than the first party, and having lost sight of their guide in the same manner as happened before, they all returned to the nest. Meanwhile several of the first party, which had all the while been meandering about, found the fly, and proceeded to dismember it, carrying the trophy to the nest, and calling out more friends in the ordinary way. This experiment was repeated several times and on different species, always with the same result. Now, as Sir John remarks, 'the two cases (_i.e._ those in which the ant brought out friends to her assistance even when she had no booty to show) surely indicate a distinct power of communication. . . . It is impossible to doubt that the friends were brought out by the first ant; and as she returned empty-handed to the nest, the others cannot have been induced to follow her by merely observing her proceedings. I conclude, therefore, that they possess the power of requesting their friends to come and help them.'

In order to ascertain whether the signs which communicating ants make to one another are made by means of sound, Sir John Lubbock placed near a nest of _Lasius flavus_ six small upright pillars of wood about 1-1/2 inch high, and on one of these he put a drop of honey. 'I then put three ants to the honey, and when each had sufficiently fed, I imprisoned her, and put another; thus always keeping three ants at the honey, but not allowing them to go home. If, then, they could summon their friends by sound, there ought soon to be many ants at the honey.' The result showed that the ants were not able thus to call to one another from a distance.

As additional proof of the general fact that at all events some ants have the power of communicating information to one another, it will be enough here to quote an exceedingly interesting observation of the distinguished geologist Hague. The quotations are taken from his letters written to Mr. Darwin, and published in _Nature_:[24]--

On the mantelshelf of our sitting-room my wife has the
habit of keeping fresh flowers. A vase stands at each
end, and near the middle a small tumbler, usually
filled with violets. Some time ago I noticed a pile of
very small red ants on the wall above the left-hand
vase, passing upward and downward between the
mantelshelf and a small hole near the ceiling, at a
point where a picture nail had been driven. The ants,
when first observed, were not very numerous, but
gradually increased in number, until on some days the
little creatures formed an almost unbroken procession,
issuing from the hole at the nail, descending the
wall, climbing the vase directly below the nail,
satisfying their desire for water or perfume, and then
returning. The other vase and tumbler were not visited
at that time.

As I was just then recovering from a long illness it
happened that I was confined to the house, and spent
my days in the room where the operations of these
insects attracted my attention. Their presence caused
me some annoyance, but I knew of no effective means of
getting rid of them. For several days in succession I
frequently brushed the ants in great numbers from the
wall down to the floor; but as they were not killed
the result was that they soon formed a colony in the
wall at the base of the mantel, ascending thence to
the shelf, so that before long the vase was attacked
from above and below.

One day I observed a number of ants, perhaps thirty or
forty, on the shelf at the foot of the vase. Thinking
to kill them, I struck them lightly with the end of my
finger, killing some and disabling the rest. The
effect of this was immediate and unexpected. As soon
as those ants which were approaching arrived near to
where their fellows lay dead and suffering, they
turned and fled with all possible haste. In half an
hour the wall above the mantelshelf was cleared of
ants.

During the space of an hour or two the colony from
below continued to ascend until reaching the lower
bevelled edge of the shelf, at which point the more
timid individuals, although unable to see the vase,
somehow became aware of trouble, and turned about
without further investigation, while the more daring
advanced hesitatingly just to the upper edge of the
shelf, when, extending their antennæ and stretching
their necks, they seemed to peep cautiously over the
edge until beholding their suffering companions, when
they too turned and followed the others, expressing by
their behaviour great excitement and terror. An hour
or two later, the path or trail leading from the lower
colony to the vase was almost entirely free from ants.

I killed one or two ants on their path, striking them
with my finger, but leaving no visible trace. The
effect of this was that as soon as an ant ascending
towards the shelf reached the spot where one had been
killed, it gave signs immediately of great
disturbance, and returned directly at the highest
possible speed.

A curious and invariable feature of their behaviour
was that when such an ant, returning in fright, met
another approaching, the two would always communicate,
but each would pursue its own way, the second ant
continuing its journey to the spot where the first had
turned about, and then following that example.

For some days after this there were no ants visible on
the wall, either above or below the shelf.