There can be no doubt of the fact that the particular

species of grain-bearing grass mentioned above is

intentionally planted. In farmer-like manner the

ground upon which it stands is carefully divested of

all other grasses and weeds during the time it is

growing. When it is ripe the grain is taken care of,

the dry stubble cut away and carried off, the paved

area being left unencumbered until the ensuing autumn,

when the same 'ant-rice' reappears within the same

circle, and receives the same agricultural attention

as was bestowed upon the previous crop--and so on year

after year, as I _know_ to be the case, in all

situations when the ant's settlements are protected

from graminivorous animals.

In a second letter Dr. Lincecum, in reply to an inquiry from Mr. Darwin

whether he supposed that the ants plant seeds for the ensuing crop,

says:--

I have not the slightest doubt of it. And my

conclusions have not been arrived at from hasty or

careless observation, nor from seeing the ants do

something that looked a little like it, and then

guessing at the results. I have at all seasons watched

the same ant-cities during the last twelve years, and

I know that what I stated in my former letter is true.

I visited the same cities yesterday, and found the

crop of ant-rice growing finely, and exhibiting also

the signs of high cultivation, and not a blade of any

other kind of grass or weed was to be seen within

twelve inches of the circular row of

ant-rice.--(_Journ. Linn. Soc._, vol. vi. p. 30-1.)

Now, MacCook found the ant-rice growing as described, but only on some

nests. Why it does not grow upon all the nests he does not understand.

So far, then, as his observations go, they confirm those of Dr.

Lincecum; but he does 'not believe that the ants deliberately sow a crop

as Lincecum asserts;' he thinks 'that they have for some reason found it

to their advantage to permit the aristida to grow upon their disks,

while they clear off all other herbage;' but finally concludes 'that

there is nothing unreasonable, nor beyond the probable capacity of the

emmet intellect, in the supposition that the crop is actually sown.

Simply, it is the Scotch verdict--"Not proven."'

The following facts with regard to 'modes of mining' are worth quoting

from MacCook:--

In sinking the galleries the difficulty of carrying is

not great in a moist or tough soil, which permits the

ant to obtain goodly-sized pellets for portage. But

when the soil is light and dry, so that it crumbles

into dust as it is bitten off, the difficulty is

greatly increased. It would be a very tedious task

indeed to take out the diggings grain by grain. This

difficulty the worker overcomes by balling the small

particles against the surface of the gallery, the

under side of the head, or within and against the

mandibles. The fore-feet are used for this purpose,

being pressed against the side face, turned under, and

pushed upward with a motion similar to that of a man

putting his hand upon his mouth. The abdomen is then

swung underneath the body and the apex pressed against

the little heap of grains of dirt massed against the

under side of the mandibles, or between that and the

smooth under surface of the head. Thus the dust is

compressed into a ball which is of sufficient size to

justify deportation.

The same operation is observed in the side-galleries,

where the ants work very frequently upon their sides

or backs, precisely as I have seen colliers do in

Pennsylvania coal-mines.

The following is likewise worth quoting from the same author:--

Seeds are evidently not the only food of our

agriculturals. When the ants at disk No. 2 had broken

through the slight mud-sediment that sealed up their

gate, as described above, they exhibited a peculiar

behaviour. Instead of heading for the roads and

pressing along them, they distributed themselves at

once over the entire disk, radiating from the gate to

all points in the circumference, from which they

penetrated the jungle of grass beyond. In a moment a

large number were returning across the roads, out of

the grass, over the pavement toward the entrance. They

bore in their mandibles objects which I presently

found to be the males and females of white ants

(_Termes flavipes_), which were filling the air,

during and after the rain, in marriage flight. They

had probably swarmed just before the shower. The

agriculturals were under great excitement, and hurried

forth and back at the top of their speed. The number

of ants bearing termites was soon so great that the

vestibule became choked, and a mass of struggling

anthood was piled up around the gate. A stream of

eager insects continually poured out of the door,

pushing their way through the crowd that vainly but

persistently endeavoured to get in with their burdens.

The outcoming ants had the advantage, and succeeded in

jostling through the quivering rosette of antennæ,

legs, heads, and abdomens. Occasionally a worker

gained an entrance by dint of sheer physical force and

perseverance. Again and again would the crowd rush

from all sides upon the gate, only to be pushed back

by the issuing throng. In the meanwhile quite a heap

of termites, a good handful at least, had been

accumulated at one side of the gate, the ants having

evidently dropped them, in despair of entrance, and

hurried off to garner more.

In due time the pressure upon the vestibule

diminished, the laden workers entered more freely, and

in the end this heap was transferred to the interior.

The rapidity with which the ants were distributed to

all parts of their roads, after the first opening of

the gates, was truly surprising. I was greatly

puzzled, at the first, to know what the cause of such

a rush might be. The whole behaviour was such as to

carry the conviction that they knew accurately what

effect the rain would have, had calculated upon it,

and were acting in accordance with previous

experience. I had no doubt at the time, and have none

now, that the capturing of insects beaten down by the

rain is one of the well-established customs of these

ants. I saw a few other insects taken in, and one

milliped, but chiefly the white ants.

That very afternoon I found in a formicary which I

then opened several large colonies, or parts of one

colony of termites, nested within the limits of the

disk and quite at home. The next day numbers of the

winged white ants were found stored within the

granaries of a large formicary. There is no reason to

doubt that these insects were intended for food, in

accordance with the quite universal habit of the

_Formicariæ_.

A curious habit has been noticed by most observers to occur in many

species of ant, and it is one on which Mr. MacCook has a good deal to

say. The habit in question consists in the ants transporting one another

from place to place. The carrying ant seizes her comrade by the middle,

and hurries along with it held aloft--the ant which is carried remaining

quite motionless with all her legs drawn together. Huber supposed the

process to be one enjoyable to both the insects concerned, and to be

performed by mutual understanding and consent; but MacCook, in common

with most other observers, supposes that it is merely a rough and

primitive way of communicating to fellow-workers the locality where

their services are required. He says:--

Keeping these facts in mind, we have a key to the

solution of the press-gang operations which Lincecum

observed among the agriculturals, and which have been

fully described in other species. In the absence of

any common head or directory, and of all executive

officers, a change of location or any other concerted

movement must be carried forward by the willing

co-operation of individuals. At first sight, the act

of seizing and carrying off workers does not appear

like an appeal to free-will. It is indeed coercive, so

far as the first act goes. But, in point of fact, the

coercion ceases the moment the captive is set down

within the precincts of the new movement. The

carrier-ant has depended upon securing her consent and

co-operation by thus bringing her within the circle of

activity for which her service is sought. As a rule,

no doubt, the deported ant at once yields to the

influence around her, and drops into the current of

fresh enterprise, in which she moves with as entire

freedom and as independently as any other worker. But

she is apparently under no restraint, and if she so

please, may return to her former haunts.

_Certain Ants of Africa._--Livingstone says of certain ants of Africa:--

They have established themselves on the plain where

water stands so long annually as to allow the lotus

and other aqueous plants to come to maturity. When all

the ant-horizon is submerged a foot deep, they manage

to exist by ascending to little houses built of black

tenaceous loam on stalks of grass, and placed higher

than the line of inundation. This must have been the

result of experience, for, if they had waited till the

water actually invaded their terrestrial habitations,

they would not have been able to procure materials for

their aërial quarters, unless they dived down to the

bottom for every mouthful of clay.[42]

_The Tree Ant of India and New South Wales._--These ants are remarkable

from their habit of forming nests only in trees. According to Col.

Sykes' account, the shape of the nest is more or less globular, and

about ten inches in diameter. It is formed entirely of cow-dung, which

the insects collect from the ground beneath, and work into the form of

thin scales. These are then built together in an imbricated manner, like

tiles or slates upon the roof of a house, the upper or outer scale,

however, being one unbroken sheet, which covers the whole nest like a

skull-cap. Below this the scales are placed one upon another in a wavy

or scalloped manner, so that numerous little arched entrances are left,

and yet, owing to the imbricated manner in which the scales are

arranged, the interior of the nest is perfectly protected from rain.

This interior consists of a number of irregular cells, the walls of

which are formed by the same process as the exterior.

In New South Wales there is another species of ant which also frequents

trees, but builds within the stem and branches. In the report of Captain

Cook's expedition its habits are thus described:--'Their habitations are

the insides of the branches of a tree, which they contrive to excavate,

by working out the pith almost to the extremity of the slenderest twig;

the tree at the same time flourishing as if it had no such inmate.' On

breaking one of the branches the ants swarm out in legions. Some of our

native species also have the habit of excavating the interior of trees,

though not on so extensive a scale.

_Honey-making Ant_ (Myrmecocystus mexicanus).--This ant is found in

Texas and New Mexico. Capt. W. B. Fleeson has observed its habits, and

his observations have been communicated to the Californian Academy of

Sciences, and also, by Mr. Henry Edwards, to Mr. Darwin. The following

are the chief points of interest in Capt. Fleeson's results:--

The community appears to consist of three distinct

kinds of ants, probably of two separate genera, whose

offices in the general order of the nest would seem to

be entirely apart from each other, and who perform the

labour allotted to them without the least encroachment

upon the duties of their fellows. These three kinds

are--

I. Yellow workers; nurses and feeders of II.

II. Yellow honey-makers; sole function to secrete a

kind of honey in their large globose abdomens, on

which the other ants are supposed to feed. They never

quit the nest, and are fed and tended by I.

III. Black workers, guards, and purveyors; surround

the nest as guards or sentinels, in a manner presently

to be described, and also forage for the food required

for I. They are much larger and stronger insects than

either I. or II., and are provided with very

formidable mandibles.

The nest is placed in sandy soil in the neighbourhood of shrubs and

flowers, is a perfect square, and occupies about four or five square

feet of ground, the surface of which is kept almost unbroken. But the

boundaries of the nest are rendered conspicuous by the guard of black

workers (III.), which continuously parade round three of its sides in a

close double line of defence, moving in opposite directions. In the

accompanying diagram this sentry path is represented by the thick black

lines. These always face the same points of the compass, and the

direction in which the sentries march is one column from south-west to

south-east, and the other column from south-east to south-west--each

column, however, moving in regular order round three sides of a square.

The southern side of the encampment is left unguarded; but if any enemy

approaches on this or any other side, a number of the guards leave their

stations, and sally forth to face the foe--raising themselves on their

hind tarsi on meeting the enemy, and moving their large mandibles in

defiance. Spiders, wasps, beetles, and other insects, if they venture

too near the nest, are torn to pieces by the guard in a most merciless

manner, and the dead body of the vanquished is speedily removed from the

neighbourhood of the nest--the guard then marching back to resume their

places in the line of defence, their object in destroying other insects

being the defence of their encampment, and not the obtaining of food.

The object of leaving the southern side of the square encampment open is

as follows. While some of the black workers are engaged on duty as

guard, another and larger division are engaged on duty as purveyors.

These enter and leave the quadrangle by its open or southern side along

the dotted line marked _a_ to the central point _c_. The incoming line

is composed of individuals each bearing a burden of fragments of

flowers or aromatic leaves. These are all deposited in the centre of the

quadrangle _c_. Along the other diagonal _e_ there is a no less

incessantly moving double line of yellow workers (I.), whose office it

is to convey the supplies deposited by the black workers at _c_ to _b_,

which is the gateway of the fortress. It is remarkable that no black ant

is ever seen upon the line _e_, and no yellow one upon the line _a_;

each keeps his own separate station, and follows his own particular duty

with a steadfastness and apparent adherence to discipline that are most

astonishing. The hole at _d_ seems to be a ventilating shaft; it is

never used as a gateway.

[Illustration: Fig. 7.]

Section of the nest reveals, besides galleries, a small chamber about

three feet below the surface, across which is spread, like a spider's

web, a network of squares spun by the insects, the squares being about

1/4 inch across, and the ends of the whole net being fastened to the

earthen walls of the chamber. In each one of the squares, supported by

the web, sits one of the honey-making ants (II.). Here these honey

makers live in perpetual confinement, and receive a constant supply of

flowers, pollen, &c., which is continually being brought them by (I.),

and which, by a process analogous to that performed by the bee, they

convert into honey.

Such is an epitome of the only account that the world has yet received

of the habits and economy of this wonderful insect, whose instincts of

military organization seem to be not less wonderful than those of the

Ecitons, though in this case they are developed with reference to

defence, and not to aggression. It is especially noteworthy that the

black and yellow workers are believed to belong to 'two separate

genera;' for if this is the case, it is the only one I can recall of two

distinct species co-operating for a common end; for even the nearest

parallel which we find supplied in other species of ants maintaining

aphides, is not quite the same thing, seeing that the aphides are merely

passive agents, like Class II., of the honey-making ant, and not

actively co-operating members of the community, like Class I.

_Ecitons._--We have next to consider the habits of the wonderful

'foraging,' or, as it might be more appropriately called, the military

ant of the Amazon. These insects, which belong to several species of the

same genus, have been carefully watched by Belt, Bates, and other

naturalists. The following facts must therefore be accepted as fully

established.

_Eciton legionis_ moves in enormous armies, and everything that these

insects do is done with the most perfect instinct of military

organization. The army marches in the form of a rather broad and regular

column, hundreds of yards in length. The object of the march is the

capture and plunder of other insects, &c., for food, and as the

well-organised host advances, its devastating legions set all other

terrestrial life at defiance. From the main column there are sent out

smaller lateral columns, the composing individuals of which play the

part of scouts, branching off in various directions, and searching

about with the utmost activity for insects, grubs, &c., over every log,

under every fallen leaf, and in every nook and cranny where there is any

chance of finding prey. When their errand is completed, they return into

the main column. If the prey found is sufficiently small for the scouts

themselves to manage, it is immediately seized, and carried back to the

main column; but if the amount is too large for the scouts to deal with

alone, messengers are sent back to the main column, whence there is

immediately dispatched a detachment large enough to cope with the

requirements. Insects which when killed are too large for single ants to

carry, are torn in pieces, and the pieces conveyed back to the main army

by different individuals. Many insects in trying to escape run up bushes

and shrubs, where they are pursued from branch to branch and twig to

twig by their remorseless enemies, until on arriving at some terminal

ramification they must either submit to immediate capture by their

pursuers, or drop down amid the murderous hosts beneath. As already

stated, all the spoils that are taken by the scouts or by the

detachments sent out in answer to their demands for assistance, are

immediately taken back to the main column. When they arrive there, they

are taken to the rear of that column by two smaller columns of carriers,

which are constantly running, one on either side of the main column,

with the supplies that are constantly pouring in from both sides. Each

of these outside columns is a double line, the ants composing one of the

two lines all running in the same direction as the main army, and the

ants composing the other line all running in the opposite direction. The

former are empty-handed carriers, which having deposited their burdens

in the rear, are again advancing to the van for fresh burdens. Those

composing the other line are all laden with the mangled remains of

insects, pupæ of other ants, &c. On either side of the main column there

are also constantly running up and down a few individuals of smaller

size and lighter colour than the other ants, which seem to play the part

of officers; for they never leave their stations, and while running up

and down the outsides of the column, they every now and again stop to

touch antennæ with some member of the rank and file, as if to give

instructions. When the scouts discover a wasp's nest in a tree, a strong

force is sent out from the main army, the nest is pulled to pieces, and

all the larvæ carried to the rear of the army, while the wasps fly

around defenceless against the invading multitude. Or, if the nest of

any other species of ant is found, a similarly strong force, or perhaps

the whole army is deflected towards it, and with the utmost energy the

innumerable insects set to work to sink shafts and dig mines till the

whole nest is rifled of its contents. In these mining operations the

ants work with an extraordinary display of organized co-operation; for

those low down in the shafts do not lose time by carrying up the earth

which they excavate, but pass on the pellets to those above; and the

ants on the surface, when they receive the pellets, carry them, 'with an

appearance of forethought that quite staggered' Mr. Bates, only just far

enough to ensure that they shall not roll back again into the shaft,

and, after depositing them, immediately hurry back for more. But there

is not a rigid division of labour, although the work 'seems to be

performed by intelligent co-operation amongst a host of eager little

creatures;' for some of them act 'sometimes as carriers of pellets, and

at another as miners, and all shortly afterwards assume the office of

conveyors of the spoil.' Again, as showing the instincts of

co-operation, the following may also be quoted from Bates's account:--

On the following morning no trace of ants could be

found near the place where I had seen them the

preceding day, nor were there signs of insects of any

description in the thicket; but at the distance of

eighty or one hundred yards, I came upon the same

army, engaged evidently on a razzia of a similar kind

to that of the previous evening; but requiring other

resources of their instinct, owing to the nature of

the ground. They were eagerly occupied on the face of

an inclined bank of light earth in excavating mines,

whence, from a depth of eight or ten inches, they were

extracting the bodies of a bulky species of ant of the

genus Formica. It was curious to see them crowding

round the orifices of the mines, some assisting their

comrades to lift out the bodies of the Formicæ, and

others tearing them in pieces, on account of their

weight being too great for a single Eciton; a number

of carriers seizing each a fragment, and carrying it

off down the slope.

These Ecitons have no fixed nest themselves, but live, as it were, on a

perpetual campaign. At night, however, they call a halt and pitch a

camp. For this purpose they usually select a piece of broken ground, in

the interstices of which they temporarily store their plunder. In the

morning the army is again on the march, and before an hour or two has

passed not a single ant is to be seen where the countless multitudes had

previously covered the ground.

Another and larger species of Eciton (_E. humata_) hunts sometimes in

dense armies, and sometimes in columns, according to the kind of prey of

which they are in search. When in columns they are seeking for the nests

of a certain species of ant which have their young in holes of rotten

logs. These Ecitons when seeking for these nests hunt about, like those

just described, in columns, which branch off in various directions. When

a fallen log is reached, the column spreads over it, searching through

all the holes and cracks. Mr. Belt says of them:--

The workers are of various sizes, and the smallest are

here of use, for they squeeze themselves into the

narrowest holes, and search out their prey in the

furthest ramifications of the nests. When a nest of

the _Hypoclinea_ is attacked, the ants rush out,

carrying the larvæ and pupæ in their jaws, but are

immediately despoiled of them by the Ecitons, which

are running about in every direction with great

swiftness. Whenever they come across a _Hypoclinea_

carrying a larva or pupa, they take it from it so

quickly, that I could never ascertain exactly how it

was done.

As soon as an Eciton gets hold of its prey, it rushes

off back along the advancing column, which is composed

of two sets, one hurrying forward, the other returning

laden with their booty, but all and always in the

greatest haste and apparent hurry. About the nest

which they are harrying, all appears in confusion,

Ecitons running here and there and everywhere in the

greatest haste and disorder; but the result of all

this apparent confusion is that scarcely a single

_Hypoclinea_ gets away with a pupa or larva. I never

saw the Ecitons injure the Hypoclineas themselves,

they were always contented with despoiling them of

their young.

The columns of this species 'are composed almost entirely of workers of

different sizes;' but, as in the species previously mentioned, 'at

intervals of two or three yards there are larger and lighter coloured

individuals that often stop, and sometimes run a little backward,

stopping and touching some of the ants with their antennæ,' and looking

'like officers giving orders and directing the march of the column.'

Concerning the other habits of this species, the same author writes:--

The eyes in the Ecitons are very small, in some of the

species imperfect, and in others entirely absent; in

this they differ greatly from the _Pseudomyrma_ ants,

which hunt singly and which have the eyes greatly

developed. The imperfection of eyesight in the Ecitons

is an advantage to the community, and to their

particular mode of hunting. It keeps them together,

and prevents individual ants from starting off alone

after objects that, if their eyesight was better, they

might discover at a distance; the Ecitons and most

other ants follow each other by scent, and, I believe,

they can communicate the presence of danger, of booty,

or other intelligence, to a distance by the different

intensity or qualities of the odours given off. I one

day saw a column of _Eciton hamata_ running along the

foot of a nearly perpendicular tramway cutting, the

side of which was about six feet high. At one point I

noticed a sort of assembly of about a dozen

individuals that appeared in consultation. Suddenly

one ant left the conclave, and ran with great speed up

the perpendicular face of the cutting without

stopping. It was followed by others, which, however,

did not keep straight on like the first, but ran a

short way, then returned, then again followed a little

further than the first time. They were evidently

scenting the trail of the pioneer, and making it

permanently recognisable. These ants followed the

exact line taken by the first one, although it was far

out of sight. Wherever it had made a slight _détour_

they did so likewise. I scraped with my knife a small

portion of the clay on the trail, and the ants were

completely at fault for a time which way to go. Those

ascending and those descending stopped at the scraped

portion, and made short circuits until they hit the

scented trail again, when all their hesitation

vanished, and they ran up and down it with the

greatest confidence. On gaining the top of the

cutting, the ants entered some brushwood suitable for

hunting. In a very short space of time the information

was communicated to the ants below, and a dense column

rushed up to search for their prey. The Ecitons are

singular amongst the ants in this respect, that they

have no fixed habitations, but move on from one place

to another, as they exhaust the hunting grounds around

them. I think _Eciton hamata_ does not stay more than

four or five days in one place. I have sometimes come

across the migratory columns; they may easily be

known. Here and there one of the light-coloured

officers moves backwards and forwards directing the

columns. Such a column is of enormous length, and

contains many thousands if not millions of

individuals. I have sometimes followed them up for two

or three hundred yards without getting to the end.

They make their temporary habitations in hollow trees,

and sometimes underneath large fallen trunks that

offer suitable hollows. A nest that I came across in

the latter situation was open at one side. The ants

were clustered together in a dense mass, like a great

swarm of bees, hanging from the roof but reaching to

the ground below. Their innumerable long legs looked

like brown threads binding together the mass, which

must have been at least a cubic yard in bulk, and

contained hundreds of thousands of individuals,

although many columns were outside, some bringing in

the pupæ of ants, others the legs and dissected bodies

of various insects. I was surprised to see in this

living nest tubular passages leading down to the

centre of the mass, kept open just as if it had been

formed of inorganic materials. Down these holes the

ants who were bringing in booty passed with their

prey. I thrust a long stick down to the centre of the

cluster, and brought out clinging to it many ants

holding larvæ and pupæ, which probably were kept warm

by the crowding together of the ants. Besides the

common dark-coloured workers and light-coloured

officers, I saw here many still larger individuals

with enormous jaws. These they go about holding wide

open in a threatening manner.

It was this ant which, as previously stated, showed sympathy and

fellow-feeling with companions in difficulties.

The habits of _E. drepanophora_ are closely similar to those of the

species already described; and, indeed, except in matters of detail,

all the species of Ecitons have much the same habits. Mr. Bates records

an interesting observation which he made on one of the moving columns of

this species. He says: 'When I interfered with the column or abstracted

an individual from it, news of the disturbance was quickly communicated

to a distance of several yards to the rear, and the column at that point

commenced retreating.' The main column is in this species narrower,

viz., 'from four to six deep,' but extends to a great length, viz., half

a mile or more. It was this species of Eciton that the same naturalist

describes as enjoying periods of leisure and recreation in the 'sunny

nooks of the forest.'

Next we have to consider _E. prædator_, of which the same observer

writes:--

This is a small dark reddish species, very similar to

the common red stinging ant of England. It differs

from all other Ecitons in its habit of hunting, not in

columns, but in dense phalanxes consisting of myriads

of individuals, and was first met with at Ega, where

it is very common. Nothing in insect movements is more

striking than the rapid march of these large and

compact bodies. Wherever they pass, all the rest of

the animal world is thrown into a state of alarm. They

stream along the ground and climb to the summits of

all the lower trees, searching every leaf to its apex,

and whenever they encounter a mass of decaying

vegetable matter, where booty is plentiful, they

concentrate, like other Ecitons, all their forces upon

it, the dense phalanx of shining and quickly-moving

bodies, as it spreads over the surface, looking like a

flood of dark red liquid. They soon penetrate every

part of the confused heap, and then, gathering

together again in marching order, onward they move.

All soft-bodied and inactive insects fall an easy prey

to them, and, like other Ecitons, they tear their

victims in pieces for facility of carriage. A phalanx

of this species, when passing over a tract of smooth

ground, occupies a space of from four to six square

yards; on examining the ants closely they are seen to

move, not all together in one straightforward

direction, but in variously spreading contiguous

columns, now separating a little from the general

mass, now reuniting with it. The margins of the

phalanx spread out at times like a cloud of

skirmishers from the flanks of an army. I was never

able to find the hive of this species.

Lastly, there are two species of Eciton totally blind, and their habits

differ from those of the species which we have hitherto considered.

Bates writes of them:--

The armies of _E. vastator_ and _E. erratica_ move, as

far as I could learn, wholly under covered roads, the

ants constructing them gradually but rapidly as they

advance. The column of foragers pushes forward step by

step, under the protection of these covered passages,

through the thickets, and on reaching a rotting log,

or other promising hunting-ground, pour into the

crevices in search of booty. I have traced their

arcades, occasionally, for a distance of one or two

hundred yards; the grains of earth are taken from the

soil over which the column is passing, and are fitted

together without cement. It is this last-mentioned

feature that distinguishes them from the similar

covered roads made by termites, who use their

glutinous saliva to cement the grains together. The

blind Ecitons, working in numbers, build up

simultaneously the sides of their convex arcades, and

contrive, in a surprising manner, to approximate them

and fit in the key-stones without letting the loose

uncemented structure fall to pieces. There was a very

clear division of labour between the two classes of

neuters in these blind species. The large-headed

class, although not possessing monstrously lengthened

jaws like the worker-majors in _E. hamata_ and _E.

drepanophora_, are rigidly defined in structure from

the small-headed class, and act as soldiers, defending

the working community (like soldier termites) against

all comers. Whenever I made a breach in one of their

covered ways, all the ants underneath were set in

commotion, but the worker-minors remained behind to

repair the damage, whilst the large-heads issued forth

in a most menacing manner, rearing their heads and

snapping their jaws with an expression of the fiercest

rage and defiance.

_Annornia arcens._--This is the so-called 'driver' or 'marching' ant of

West Africa, which in habits and intelligence closely resembles the

military ants of the other hemisphere. I shall therefore not wait again

to describe these habits in detail. Like the Ecitons, the marching ants

of Africa have no fixed nest, but make temporary halts in the shade of

hollow trees, overhanging rocks, &c. They march in large armies, and,

like the Ecitons, always in the form of a long close column; but in this

case the relative position of the carriers of spoil and larvæ is

reversed, for while these occupy the middle place the soldiers and

officers march on either side. These have large heads armed with

powerful jaws, and never take part in carrying; their function is to

maintain order, act as scouts, and attack prey. The habits of these ants

resemble most closely those of the blind Ecitons in that they very

frequently, and indeed generally, build covered ways; they do so

apparently in order to protect themselves from the heat of the African

sun. Their line of march is therefore marked by a continuous arch or

tunnel, which is always being constructed by the van of the column. The

structure is made of earth moulded together by saliva, and is very

quickly built. But it is only built in places where the line of march is

exposed to the sunlight; at night, or in the shadow of trees or long

grass, it is not made. If their camp is flooded by a tropical rainstorm,

the ants congregate in a close mass, with the younger ants in the

centre; they thus form a floating island.

It is remarkable that ants of different hemispheres should manifest so

close a similarity with respect to all these wonderful habits. The

Chasseur ants of Trinidad, and, according to Madame Merian, the ants of

visitation of Cayenne, also display habits of the same kind.

_General Intelligence of Various Species._

Many of the foregoing facts display an astonishing degree of

intelligence as obtaining among ants; for I think that however much

latitude we may be inclined to allow to 'blind instinct' in the way of

imitating actions elsewhere due to conscious purpose, some at least of

these foregoing facts can only be fairly reconciled with the view that

the insects know what they are doing and why they are doing it. But as I

am myself well aware of the difficulty that arises in all such cases of

drawing the line between purposeless instinct and purposive

intelligence, I have thought it desirable to reserve for this concluding

division of the present chapter several isolated facts which have been

observed among sundry species of ants, and which do not seem to admit

of being reasonably comprised under the category of instinctive action,

if by the latter we mean action pursued without knowledge of the

relation between the means adopted and the ends attained.

It will be remembered that our test of instinctive as distinguished from

truly intelligent action is simply whether all individuals of a species

perform similar adaptive movements under the stimulus supplied by

similar and habitual circumstances, or whether they manifest individual

and peculiar adaptive movements to meet the exigencies of novel and

peculiar circumstances. The importance of this distinction may be

rendered manifest by the following illustrations.

[Illustration: Fig. 8.]

We have already seen that the ants which Sir John Lubbock observed

display many and complex instincts, which together might seem to justify

us in anticipating that animals which present such wonderful instincts

must also present sufficient general intelligence to meet simple though

novel exigencies by such simple adaptations as the unfamiliar

circumstances require. Yet experiments which he made in this connection

seem to show that such is not the case, but that these ants, with all

their wealth of instinctive endowments, are utterly destitute of

intelligent resources; they have abundance of common and detailed

knowledge (supposing the adaptations to be made consciously) how to act

under certain complex though familiar circumstances, but appear quite

unable to originate any adaptive action to obviate even the simplest

conceivable difficulty, if this is of a kind which they have not been

previously accustomed to meet. Thus, on a horizontal rod B supported in

a saucer of water S, and therefore inaccessible to the ants from

beneath, he placed some larvæ A. On the nest N he then placed a block of

wood C D, constructed so that the portion D should touch the larvæ at

A. When the ants had made a number of journeys over C D A and back

again, he raised the block C D so that there was an interval 3/10 of an

inch between the end of the block D and the larvæ at A.

The ants kept on coming, and tried hard to reach down

from D to A, which was only just out of their

reach. . . . After a while they all gave up their

efforts and went away, losing their prize in spite of

most earnest efforts, because it did not occur to them

to drop 3/10 of an inch. At the moment when the

separation was made there were fifteen ants on the

larvæ. These could, of course, have returned if one had

stood still and allowed the others to get on its back.

This, however, did not occur to them; nor did they

think of letting themselves drop from the bottom of the

paper (P) on to the nest. Two or three, indeed, fell

down, I have no doubt by accident; but the remainder

wandered about, until at length most of them got into

the water.

In another experiment he interposed a light straw bridge on the way

between the nest and the larvæ, and when the ants had well learnt the

way, he drew the bridge a short distance towards the nest, so that a

small chasm was made in the road. The ants tried hard and ineffectually

to reach across it, but it did not occur to them to _push_ the straw

into its original position.

The following experiment is still more illustrative of the absence of

intelligence, because the adjustive action required would not demand the

exercise of such high powers of imagination and abstraction as would

have been required for the moving forwards of the paper drawbridge.

To test their intelligence I made the following

experiments: I suspended some honey over a nest of

_Lasius flavus_ at a height of about 1/2 an inch, and

accessible only by a paper bridge more than 10 feet

long. Under the glass I then placed a small heap of

earth. The ants soon swarmed over the earth on to the

glass, and began feeding on the honey. I then removed

a little of the earth, so that there was an interval

of about 1/3 of an inch between the glass and the

earth; but though the distance was so small, they

would not jump down, but preferred to go round by the

long bridge. They tried in vain to stretch up from the

earth to the glass, which, however, was just out of

their reach, though they could touch it with their

antennæ; but it did not occur to them to heap the

earth up a little, though if they had moved only half

a dozen particles of earth they would have secured for

themselves direct access to the food. This, however,

never occurred to them. At length they gave up all

attempts to reach up to the glass, and went round by

the paper bridge. I left the arrangement for several

weeks, but they continued to go round by the long

paper bridge.

Another and somewhat similar experiment consisted in placing an upright

stick A, supporting at an angle another stick B, which nearly but not

quite touched the ground at C. At the end of the stick B there were

placed some larvæ in a horizontal glass cell at D. Into this cell were

also placed a number of ants along with the larvæ. The drop from D to C

was only 1/2 an inch; 'still, though the ants reached over and showed a

great anxiety to take this short cut home, they none of them faced the

leap, but all went round by the sticks, a distance of nearly 7 feet.'

Sir John then reduced the interruption to 2/5 of an inch, so that the

ants could even touch the glass cell with their antennæ; yet all day

long the ants continued to go the long way round rather than face the

drop. Next, therefore, he took still longer sticks and tapes, and

arranged them as before, only horizontally instead of vertically. He

also placed some fine earth under the glass cell containing the larvæ.

The ants as before continued to go the long way round (16 feet), though

the drop could not have hurt either themselves or the larvæ, and though

even this drop might have been obviated by heaping up the fine earth

into a little mound 1/8 of an inch high, so as to touch the glass cell.

It is desirable, however, here to state that all species of ants do not

show this aversion to allowing themselves to drop through short

distances; for Moggridge describes the harvesting ants of Europe as

seeming rather to enjoy acrobatic performances of this kind; and the

same fact is recorded by Belt of the leaf-cutting ants of the Amazons.

Dr. Bastian, in his work on 'Brain as an Organ of Mind,' suggests that

the 'seeming lack of intelligence betrayed by our English ants, from

their disinclination to take a small leap, may be due simply to their

defective sight' (pp. 241-2). But even this consideration does not

extenuate the stupidity of the ants which failed to heap up the fine

earth to reach the glass cell which they were able to touch with their

antennæ.

That the species of ants on which Sir John Lubbock experimented were

not, however, quite destitute of intelligence is proved by the result of

the following experiment:--

I put some provisions in a shallow box with a glass

top and a single hole in one side; I then put some

specimens of _Lasius niger_ to the food, and soon a

stream of ants was at work busily carrying supplies

off to the nest. When they had got to know their way

thoroughly, and from thirty to forty were so occupied,

I poured some fine mould in front of the hole, so as

to cover it to a depth of about 1/2 an inch. I then

took out the ants which were actually in the box. As

soon as the ants had recovered from the shock of this

unexpected proceeding on my part, they began to run

all round and about the box, looking for some other

place of entrance. Finding none, however, they began

digging down into the earth just over the hole,

carrying off the grains of earth one by one and

depositing them without any order all round at a

distance of from 1/2 to 6 inches, until they had

excavated down to the doorway, when they again began

carrying off the food as before.

This experiment was several times repeated on _L. niger_ and on _L.

flavus_, always with the same result.

Thus, then, we may conclude that the reasoning power of these ants,

although shown by the first experiments to be almost _nil_, is shown by

this experiment to be not quite _nil_; for the attempt to meet the

exigencies of the case by first going round the box to seek another

entrance, before taking the labour to remove the earth from the known

entrance, implies a certain rudimentary degree of adaptive capacity

which belongs to the category of the rational.

Another point of considerable interest, as bearing on the general

intelligence of ants, is one that was brought out as the result of a

laborious series of hourly observations, extending without intermission

from 6.30 A.M. to 10 P.M. for a period of three months. The object of

these observations was to ascertain whether the principle of the

division of labour is practised by the ants. The result of these

observations was to show that during the winter-time, when the ants are

not active, certain individuals are told off to forage for supplies, and

that when any casualty overtakes these individuals, others are told off

to supply their places. Thus, in the words of Sir John Lubbock's

analysis of his lengthy tables,--

The feeders at the beginning of the experiment were

those known to us as Nos. 5, 6, and 7. On the 22nd of

November a friend, registered as No. 8, came to the

honey, and again on the 11th December; but with these

two exceptions the whole of the supplies were carried

in by Nos. 5 and 6, with a little help from No. 7.

Thinking now it might be alleged that possibly these

were merely unusually active or greedy individuals, I

imprisoned No. 6 when she came out to feed on the 5th.

As will be seen from the table, no other ant had been

out to the honey for some days; and it could therefore

hardly be accidental that on that very evening another

ant (then registered as No. 9) came out for food. This

ant, as will be seen from the table, then took the

place of No. 6 (No. 5 being imprisoned). On the 11th

January No. 9 took in all the supplies, again with a

little help from No. 7. So matters continued until the

17th, when I imprisoned No. 9, and then again, _i.e._

on the 19th, another ant (No. 10) came out for the

food, aided, on and after the 22nd, by another (No.

11). This seems to me very curious. From the 1st

November to the 5th January, with two or three casual

exceptions, the whole of the supplies were carried in

by three ants, one of whom, however, did comparatively

little. The other two are imprisoned, and then, but

not till then, a fresh ant appears on the scene. She

carries in the food for a week, and then she being

imprisoned, two others undertake the task. On the

other hand, in nest 1, when the first foragers were

not imprisoned, they continued during the whole time

to carry in the necessary supplies.

The facts, therefore, certainly seem to indicate that certain ants are

told off as foragers, and that during winter, when but little food is

required, two or three such foragers are sufficient to provide it.

Although Sir John Lubbock's ants showed such meagre resources of

intelligent adjustment, other species of ants, which we have already had

occasion to consider, appear to be as remarkable in this respect as they

are in respect of their instinctive adjustments. Unfortunately

observations on this subject are very sparse, but such as they are they

hold out a strong inducement for any one who has the opportunity to

experiment with the view of testing the intelligence of those species in

connection with which the following observations have been made.

Réaumur states that ants will make no attempt to enter

an inhabited beehive to get at the contained honey,

knowing that the bees will slaughter them if they do

so. But if the hive is uninhabited, or the bees all

dead, the ants will swarm into the hive as long as any

honey is to be found there.

P. Huber records that a wall which had been partly erected by ants was

observed by him--

As though it were intended to support the still

unfinished arched roof of a large room, which was

being built from the opposite side. But the workers

which had begun the arch had given it too low an

elevation for the wall on which it was to rest, and if

it had been continued on the same lines it would have

met the partition wall halfway up, and this was to be

avoided. I had just made this criticism to myself,

when a new arrival, after looking at the work, came to

the same conclusion. For it began at once to destroy

what had been done, and to heighten the wall on which

it was supported, and to make a new arch with the

materials of the old one under my very eyes. When the

ants begin an undertaking it seems exactly as if an

idea slowly ripened into execution in their minds.

Thus if one of them finds two stalks lying crosswise

on the nest, which make possible the formation of a

room, or some little rafters which suggest the walls

and the corners, it first observes the various parts

accurately, and then quickly and neatly heaps little

pellets of earth in the interspaces and alongside the

stalks. It brings from every side materials that seem

appropriate, and sometimes takes such from the

uncompleted works of its companions, so much is it

urged on by the idea which it has once conceived, and

by the desire to execute it. It goes and comes and

turns back again, until its plan is recognisable by

the others.

Ebrard, in his 'Etudes de Moeurs' (p. 3), gives the following

remarkable instance of the display of intelligence of _F. fusca_:--

The earth was damp and the workers were in full

swing. It was a constant coming and going of ants,

coming forth from their underground dwelling, and

carrying back little pellets of earth for building. In

order to concentrate my attention I fixed my gaze on

the largest of the rooms which were being built,

wherein several ants were busy. The work had made

considerable progress; but although a projection could

be plainly seen along the upper edge of the wall,

there remained an interspace of about twelve or

fifteen millimetres to fill in. Here would have been

the place, in order to support the earth still to be

brought in, to have had recourse to those pillars,

buttresses, or fragments of dried leaves, which many

ants are wont to use in building. But the use of this

expedient is not customary with the ants I was

observing (_F. fusca_). Our ants, however, were

sufficient for the occasion. For a moment they seemed

inclined to leave their work, but soon turned instead

to a grass-plant growing near, the long narrow leaves

of which ran close together. They chose the nearest,

and weighted its distal end with damp earth, until its

apex just bent down to the space to be covered.

Unfortunately the bend was too close to the extremity,

and it threatened to break. To prevent this

misfortune, the ants gnawed at the base of the leaf

until it bent along its whole length and covered the

space required. But as this did not seem to be quite

enough, they heaped damp earth between the base of the

plant and that of the leaf, until the latter was

sufficiently bent. After they had thus attained their

object, they heaped on the buttressing leaf the

materials required for building the arched roof.

The characteristic _trait_ of the building of ants,

says Forel, is the almost complete absence of an

unchangeable model, peculiar to each species, such as

is found in wasps, bees, and others. The ants know how

to suit their indeed little perfect work to

circumstances, and to take advantage of each

situation. Besides, each works for itself and on a

given plan, and is only occasionally aided by others

when these understand its plan. Naturally many

collisions occur, and some destroy that which others

have made. This also gives the key to understanding

the labyrinth of the dwelling. For the rest, it is

always those workers which have discovered the most

advantageous method, or which have shown the most

patience, which win over to their plan the majority of

their comrades and at last the whole colony, although

not without many fights for supremacy. But if one

succeeds in obtaining a second to follow it, and this

second draws the others after it, the first is soon

lost again in the crowd.

Espinas also observed ('Thierischen Gesellschaften,' German translation,

1879, p. 371) that each single ant made its own plan and followed it

until a comrade, which had caught the idea, joined it, and then they

worked together in the execution of the same plan.

Moggridge says of the harvesters of Europe,--

I have observed on more than one occasion that when in

digging into an ants' nest I have thrown out an

_elater_ larva, the ants would cluster round it and

direct it towards some small opening in the soil,

which it would quickly enlarge and disappear down. At

other times, however, the ants would take no notice of

the _elater_, and it is my belief that the attentions

paid to it on former occasions were purely selfish,

and that they intended to avail themselves of the

tunnel thus made down into the soil, with the view of

reopening communications with the galleries and

granaries concealed below, the approaches to which had

been covered up. I have frequently watched the ants

make use of these passages mined by the _elater_ on

these occasions.

And again, as showing apparently intelligent adaptation of their usual

habits to altered circumstances, he gives an account of the behaviour of

these ants when a great crowd of them were confined by him in a glass

jar containing earth. He says:--

On the following morning the openings were ten in

number, and the greatly increased heaps of excavated

earth showed that they must probably have been at work

all night. The amount of work done in this short time

was truly surprising, for it must be remembered that,

eighteen hours before, the earth presented a perfectly

level surface, and the larvæ and ants, now housed

below, found themselves prisoners in a strange place,

bounded by glass walls, and with no exit possible.

It seems to me that the ants displayed extraordinary

intelligence in having thus at a moment's notice

devised a plan by which the superabundant number of

workers could be employed at one time without coming

in one another's way. The soil contained in the jar

was of course less than a tenth part of that comprised

within the limits of an ordinary nest, while the

number of workers was probably more than a third of

the total number belonging to the colony. If therefore

but one or two entrances had been pierced in the soil,

the workers would have been for ever running against

one another, and a great number could never have got

below to help in the all-important task of preparing

passages and chambers for the accommodation of the

larvæ. These numerous and funnel-shaped entrances

admitted of the simultaneous descent and ascent of

large numbers of ants, and the work progressed with

proportionate rapidity. After a few days only three

entrances, and eventually only one, remained open.

Concerning the harvesting ant of Texas, the following quotation may be

made, under the present head, from MacCook. After remarking that these

ants always select sunny places wherein to build their nests, or disks,

he goes on to say that within a few paces of his tent--

A nest was made which was partly shaded by a small

mesquite tree that stood just beyond the margin of the

clearing. The sapling had probably grown up after the

location of the community, and for some reason had

been permitted to remain until too old to kill off.

The shadow thrown upon the pavement was very slight;

nevertheless, fifteen feet distant a new formicary was

being established. The path from the ranch to the

spring ran between this new hill and the old one, and

ants were in communication between the two. An opening

had been made in the ground, and the beginnings of a

new formicary were quite apparent. This is the only

instance observed of what seemed an attempt at

colonising or removing, and I associated it with the

presence of the small but growing shadow of the young

tree.

He also gives us a still more remarkable observation, which indeed, I

must candidly say, does not appear to me credible. I am, therefore, glad

to add that it does not appear very distinctly from the account whether

the author himself made the observation, or had it narrated to him by

his guide. But here is the observation in his own words:--

While studying the habits of the cutting ant I was

tempted to make a night visit to a farm some distance

from camp, by the farmer's story of depredations made

by these insects upon certain plants and vegetables. A

long, dark tramp, a blind and vain search among the

fields, compelled us at last to call out the

countryman from his bed. He led us directly to one of

the cutting ants' nests, which was overshadowed by a

young peach tree. 'There they be, sir,' cried he

triumphantly. They were agriculturals! So also were

the other nests shown. The reason for this confounding

of the two ants on the part of the people hereabouts,

and the reason for the 'cutting' operations of our

harvesters, will be explained farther on. It is only

in point here to say that the farmer affirmed that the

ants under the peach tree had stripped off the first

tender leaves last spring, so that scarcely one had

been left upon the limbs. I am convinced that the

reason for this onslaught was the desire to be rid of

the obnoxious shade, and open the formicary to the

full light of the sun.

From this account it is not very clear whether the writer himself saw

evidence of the former denudation of the tree, and if so whether there

was any indication, other than the word of the farmer, that the

denudation had been effected by the ants. To make this conclusion

credible the best conceivable evidence would be required, and this,

unfortunately, is just what we find wanting. Somewhat the same remarks

may be made on the following quotation from the same writer, though in

this case his view is to some extent supported by an observation of

Moggridge, as well as by that of Ebrard already quoted:--

Here I observed what appeared to be a new mode of

operation. The workers, in several cases, left the

point at which they had begun a cutting, ascended the

blade, and passed as far out toward the point as

possible. The blade was thus borne downward, and as

the ant swayed up and down it really seemed that she

was taking advantage of the leverage thus gained, and

was bringing the augmented force to bear upon the

fracture. In two or three cases there appeared to be a

division of labour; that is to say, while the cutter

at the roots kept on with her work, another ant

climbed the grass blade and applied the power at the

opposite end of the lever. This position may have been

quite accidental, but it certainly had the appearance

of a voluntary co-operation. I was sorry not to be

able to establish this last inference by a series of

observations, as the facts were only observed in this

one nest.

The observation of Moggridge, to which I have alluded as in some measure

rendering support to the foregoing, is as follows. Speaking of European

harvesters which he kept in an artificial nest for the purposes of close

observation, he says:--

I was also in this way able to see for myself much

that I otherwise could not have seen. Thus I was able

to watch the operation of removing roots which had

pierced through their galleries, belonging to seedling

plants growing on the surface, and which was performed

by two ants, one pulling at the free end of the root,

and the other gnawing at its fibres where the strain

was greatest, until at length it gave way.

And again,--

Two ants sometimes combine their efforts, when one

stations itself near the base of the peduncle, and

gnaws it at the point of greatest tension, while the

other hauls upon and twists it. . . . I have occasionally

seen ants engaged in cutting the capsules of certain

plants, drop them, and allow their companions below to

carry them away.

Lastly, the statements of these three observers taken together serve to

render credible the following quotation from Bingley,[43] who says that

in Captain Cook's expedition in New South Wales ants were seen by Sir

Joseph Banks and others--

As green as a leaf, which live upon trees and build

their nests of various sizes, between that of a man's

head and his fist. These nests are of a very curious

structure: they are formed by bending down several of

the leaves, each of which is as broad as a man's hand,

and gluing the points of them together so as to form a

purse. The viscous matter used for this purpose is an

animal juice. . . . Their method of bending down leaves

we had no opportunity to observe; but we saw thousands

uniting all their strength to hold them in this

position, while other busy multitudes were employed

within, in applying this gluten, that was to prevent

their returning back. To satisfy ourselves that the

leaves were bent and held down by the efforts of these

diminutive artificers, we disturbed them in their

work; and as soon as they were driven from their

station, the leaves on which they were employed sprang

up with a force much greater than we could have

thought them able to conquer by any combination of

their strength.

This remarkable fact also seems to be corroborated by the following

independent observation of Sir E. Tennent:--

The most formidable of all is the great red ant, or

Dimiya. It is particularly abundant in gardens and on

fruit-trees; it constructs its dwellings by gluing the

leaves of such species as are suitable from their

shape and pliancy into hollow balls, and these it

lines with a kind of transparent paper, like that

manufactured by the wasp. I have watched them at the

interesting operation of forming these dwellings;--a

line of ants standing on the edge of one leaf bring

another into contact with it, and hold both together

with their mandibles till their companions within

attach them firmly by means of their adhesive paper,

the assistants outside moving along as the work

proceeds. If it be necessary to draw closer a leaf too

distant to be laid hold of by the immediate workers,

they form a chain by depending one from the other till

the object is reached, when it is at length brought

into contact, and made fast by cement.

I shall now pass on to the remarkable observation communicated to Kirby

by Colonel Sykes, F.R.S., and which is thus narrated by Kirby in his

'History, Habits, and Instincts of Animals:'--

When resident at Poona, the dessert, consisting of

fruits, cakes, and various preserves, always remained

upon a small side table, in a verandah of the

dining-room. To guard against inroads, the legs of the

table were immersed in four basins filled with water;

it was removed an inch from the wall, and, to keep off

dust from open windows, was covered with a tablecloth.

At first the ants did not attempt to cross the water,

but as the strait was very narrow, from an inch to an

inch and a half, and the sweets very tempting, they

appear, at length, to have braved all risks, to have

committed themselves to the deep, to have scrambled

across the channel, and to have reached the objects of

their desires, for hundreds were found every morning

revelling in enjoyment: daily vengeance was executed

upon them without lessening their numbers; at last the

legs of the table were painted, just above the water,

with a circle of turpentine. This at first seemed to

prove an effectual barrier, and for some days the

sweets were unmolested, after which they were again

attacked by these resolute plunderers; but how they

got at them seemed totally unaccountable, till Colonel

Sykes, who often passed the table, was surprised to

see an ant drop from the wall, about a foot above the

table, upon the cloth that covered it; another and

another succeeded. So that though the turpentine and

the distance from the wall appeared effectual

barriers, still the resources of the animal, when

determined to carry its point, were not exhausted, and

by ascending the wall to a certain height, with a

slight effort against it, in falling it managed to

land in safety upon the table.

Colonel Sykes was a good observer, so that this statement, standing upon

his authority, ought not, perhaps, to be questioned. But in all cases of

remarkable intelligence displayed by animals, we naturally and properly

desire corroboration, however good the authority may be on which the

statement of such cases may rest. I will, therefore, add the following

instances of the ingenious and determined manner in which ants overcome

obstacles, and which so far lend confirmation to the above account.

Professor Leuckart placed round the trunk of a tree, which was visited

by ants as a pasture for aphides, a broad cloth soaked in tobacco-water.

When the ants returning home down the trunk of the tree arrived at the

soaked cloth, they turned round, went up the tree again to some of the

overhanging branches, and allowed themselves to drop clear of the

obnoxious barrier. On the other hand, the ants which desired to mount

the tree first examined the nature of the barrier, then turned back and

procured from a distance little pellets of earth, which they carried in

their jaws and deposited one after another upon the tobacco-cloth till a

road of earth was made across it, over which the ants passed to and fro

with impunity.

This interesting, and indeed surprising observation of Leuckart's is, in

turn, a corroboration of an almost identical one made more than a

century ago by Cardinal Fleury, and communicated by him to Réaumur, who

published it in his 'l'Histoire des Insectes' (1734). The Cardinal

smeared the trunk of a tree with birdlime in order to prevent the ants

from ascending it; but the insects overcame the obstacle by making a

road of earth, small stones, &c., as in the case just mentioned. In

another instance the Cardinal saw a number of ants make a bridge across

a vessel of water surrounding the bottom of an orange-tree tub. They did

so by conveying a number of little pieces of _wood_, the choice of which

material instead of earth or stones, as in the previous case, seems to

betoken no small knowledge of practical engineering.

Büchner, after quoting these cases, proceeds to say (_loc. cit._, p.

120),--

The ants behaved in yet more ingenious fashion under

the following very similar circumstances. Herr G.

Theuerkauf, the painter (Wasserthorstr. 49, Berlin),

writes to the author, November 18, 1875: 'A maple tree

standing on the ground of the manufacturer, Vollbaum,

of Elbing (now of Dantzic), swarmed with aphides and

ants. In order to check the mischief, the proprietor

smeared about a foot width of the ground round the

tree with tar. The first ants who wanted to cross

naturally stuck fast. But what did the next? They

turned back to the tree and carried down aphides,

which they stuck down on the tar one after another

until they had made a bridge over which they could

cross the tarring without danger. The above-named

merchant, Vollbaum, is the guarantor of this story,

which I received from his own mouth on the very spot

whereat it occurred.'

Büchner also gives the following case on the authority of Karl Vogt

(_loc. cit._, p. 128). An apiary of a friend was invaded by ants:--

To make this impossible for the future, the four legs

of the beehive-stand were put into small, shallow

bowls filled with water, as is often done with food in

ant-infested places. The ants soon found a way out of

this, or rather a way into their beloved honey, and

that over an iron staple with which the stand was

attached to a neighbouring wall. The staple was

removed, but the ants did not allow themselves to be

defeated. They climbed into some linden trees standing

near, the branches of which hung over the stand, and

then dropped upon it from the branches, doing just the

same as their comrades do with respect to food

surrounded by water, when they drop upon it from the

ceiling of the room. In order to make this impossible,

the boughs were cut away. But once more the ants were

found in the stand, and closer investigation showed

that one of the bowls was dried up, and that a crowd

of ants had gathered in it. But they found themselves

puzzled how to go on with their robbery, for the leg

did not, by chance, rest on the bottom of the bowl,

but was about half an inch from it. The ants were seen

rapidly touching each other with their antennæ, or

carrying on a consultation, until at last a rather

larger ant came forward and put an end to the

difficulty. It rose to its full height on its hind

legs, and struggled until at last it seized a rather

projecting splinter of the wooden leg, and managed to

take hold of it. As soon as this was done other ants

ran on to it, strengthened the hold by clinging, and

so made a little living bridge, over which the others

could easily pass.

The same author publishes the following very remarkable observation,

quoted from a letter to him by Dr. Ellendorf:--

It is a hard matter to protect any eatables from these

creatures, let the custody be ever so close. The legs

of cupboards and tables in or on which eatables are

kept are placed in vessels of water. I myself did

this, but I none the less found thousands of ants in

the cupboard next morning. It was a puzzle to me how

they crossed the water, but the puzzle was soon

solved; for I found a straw in one of the saucers,

which lay obliquely across the edge of the pan and

touched the leg of the press: this they had used for a

bridge. Hundreds were drowned in the water, apparently

because disorder had reigned at first, those coming

down with booty meeting those going up. But now there

was perfect order; the descending stream used one side

of the straw, the ascending the other. I now pushed

the straw about an inch away from the cupboard leg; a

terrible confusion arose. In a moment the leg

immediately over the water was covered with hundreds

of ants, feeling for the bridge in every direction

with their antennæ, running back again and coming in

ever larger swarms, as though they had communicated to

their comrades within the cupboard the fearful

misfortune that had taken place. Meanwhile the

new-comers continued to run along the straw, and not

finding the leg of the cupboard the greatest

perplexity arose. They hurried round the edge of the

pan, and soon found out where the fault lay. With

united forces they quickly pulled and pushed at the

straw, until it again came into contact with the wood,

and the communication was again restored.

This observation is strikingly, though unconsciously, confirmed by a

recent writer in the _Leisure Hour_ (1880, pp. 718-19), who having been

much troubled by small red ants in the tropics swarming over his

provisions, placed the latter in a meat-safe detached from the wall and

standing on four legs, each of which was placed in a little tin vessel

containing water. Eight or ten days afterwards he found his provisions

in the safe swarming with ants as before, and on investigating their

mode of access to them found--

Proceeding along the whitewashed wall a string of ants

going and coming from the outer door to a height of

four feet on my wall, and corresponding with that of

the safe; and looking between it and the wall, I

discovered the secret--the bridge which these

persevering little insects had made. It consisted of a

broken bit of straw, which rested with one end on a

mud buttress fixed to the wall, and the other on the

overhanging or projecting top of the safe, which came

within an inch and a half of the wall. So they must

have carried the straw up from the floor, and resting

their end of it on the support they had prepared, let

it fall until its other end reached the safe, and then

crossed and completed the structure, for it was

fastened at both ends with the mortar composed of

their saliva and fine earth. Ruthlessly I destroyed

the bridge, and moving the safe farther from the wall,

managed to prevent their inroads for that season at

least. Since then I have frequently seen short

bridges, composed entirely of the concrete or mortar

which the white ants use to cover up their workings,

extending from a damp earthen wall to anything not

more than three-quarters of an inch from it.

Of the Ecitons Mr. Belt says:--

I shall relate two more instances of the use of a

reasoning faculty in these ants. I once saw a wide

column trying to pass along a crumbling, nearly

perpendicular slope. They would have got very slowly

over it, and many of them would have fallen, but a

number having secured their hold, and reaching to each

other, remained stationary, and over them the main

column passed. Another time they were crossing a

watercourse along a small branch, not thicker than a

goose-quill. They widened this natural bridge to three

times its width by a number of ants clinging to it and

to each other on each side, over which the column

passed three or four deep; whereas excepting for this

expedient they would have had to pass over in single

file, and treble the time would have been consumed.

Can it be contended that such insects are not able to

determine by reasoning powers which is the best way of

doing a thing?

Another observer, writing from the same part of the world to Büchner,

gives a still more wonderful account of the ingenuity of Ecitons in

crossing water. This observer is Herr H. Kreplin, of Heidemühl (Station

Ducherom), 'who lived for nearly twenty years in South America as an

engineer, and had often the opportunity of seeing the driver ants in the

forests there.' He writes to Büchner, under date May 10, 1876, as

follows:--

On both sides of the train, at about 10 mm. distance

from each other, stronger ants are to be seen,

distinguishable from the others by their foxy colour

and very thick heads with gigantic mandibles. These

'thickheads' play the same _rôle_ in the ant-state for

which they are cast in cultured communities. They look

after the order of the march, and allow none to turn

either to the right or left. The least confusion in

the regularity of the march makes them turn round and

put things straight again. While the procession of the

brown workers streams on unceasingly with a swarming

motion, the 'officers,' as the natives call these

thickheads, run constantly backwards and forwards,

ready to take the command on meeting any difficulty.

The crossing of streams by these creatures is the most

interesting point. If the watercourse be narrow, the

thickheads soon find trees, the branches of which meet

on the bank on either side, and after a short halt the

column set themselves in motion over these bridges,

rearranging themselves in the narrow train with

marvellous quickness on reaching the further side. But

if no natural bridge be available for the passage,

they travel along the bank of the river until they

arrive at a flat sandy shore. Each ant now seizes a

bit of dry wood, pulls it into the water, and mounts

thereupon. The hinder rows push the front ones even

further out, holding on to the wood with their feet

and to their comrades with their jaws. In a short time

the water is covered with ants, and when the raft has

grown too large to be held together by the small

creatures' strength, a part breaks itself off and

begins the journey across, while the ants left on the

bank busily pull their bits of wood into the water,

and work at enlarging the ferry-boat until it again

breaks. This is repeated as long as an ant remains on

shore. I had often heard described this method of

crossing rivers, but in the year 1859 I had the

opportunity of seeing it for myself.

It is remarkable that the military or driving ants of Africa exhibit

precisely similar devices for the bridging of streams, namely, by

forming a chain of individuals over which the others pass. By means of

similar chains they also let themselves down from trees. It must be

observed, however, that these and all the above observations, being

independently made and separately recorded, serve to corroborate one

another so strongly that we can entertain no reasonable doubt concerning

the wonderful facts which they convey.

I shall now bring these numerous instances to a close with a quotation

from Mr. Belt, which reveals in the most unequivocal manner surprising

powers of observation and rational action on the part of the

leaf-cutting ants of South America, whose general habits we have already

considered:--

A nest was made near one of our tramways, and to get

to the trees the ants had to cross the rails, over

which the waggons were continually passing and

repassing. Every time they came along a number of ants

were crushed to death. They persevered in crossing for

some time, but at last set to work and tunnelled

underneath each rail. One day, when the waggons were

not running, I stopped up the tunnels with stones; but

although great numbers carrying leaves were thus cut

off from the nest, they would not cross the rails, but

set to work making fresh tunnels underneath them.

_Anatomy and Physiology of Nerve-centres and Sense-organs._

The foregoing facts concerning the intelligence of ants fully justifies

Mr. Darwin's observation that 'the brain of an ant is one of the most

marvellous atoms of matter in the world, perhaps more so than the brain

of a man.' It may therefore be interesting in this particular case to

depart from the lines otherwise laid down throughout the present work,

and to devote a short section to the anatomy and physiology of this

nerve-centre with its appended organs of sense.

The brain of an ant, then, is proportionally larger than that of any

other insect. (See Titus Graber, 'Insects,' vol. i. p. 255.) In

structure, also, the brain of an ant is in advance of that of other

insects, its nearest analogue being the brain of a bee. The superiority

of development is particularly remarkable with reference to the 'stalked

bodies' of Dujardin; and these are largest in neuter workers, which are

the most intelligent members of the community.

Injury of the brain causes, as in higher animals, tetanic spasms and

involuntary reflex movements, followed by stupefaction.

An ant, whose brain has been perforated by the pointed

mandibles of an amazon, remains as though nailed to

its place; a shudder runs from time to time through

its body, and one of its legs is lifted at regular

intervals. It occasionally makes a short and quick

step, as though driven by an unseen spring, but, like

that of an automaton, aimless and objectless. If it is

pulled, it makes a movement of avoidance, but falls

back into its stupefied condition as soon as it is

released. It is no longer capable of action

consciously directed to a given object; it neither

tries to escape, nor to attack, nor to go back to its

home, nor to rejoin its companions, nor to walk away;

it feels neither heat nor cold, it knows neither fear

nor desire for food. It is merely an automatic and

reflex machine, and is exactly similar to one of those

pigeons from which Flourens removed the hemispheres of

the cerebrum. Just in the same way behaves the body of

an ant from which the head has been taken away. In the

numerous fights between amazons and other ants,

countless cases have been observed of slight injury to

the brain, which have caused the most remarkable

phenomena. Many of the wounded were seized with a mad

rage, and flung themselves at every one that came in

their way, whether friend or foe. Others assumed an

appearance of indifference, and walked serenely about

in the midst of the fighting. Others exhibited a

sudden failure of strength; but they still recognised

their enemies, approached them, and tried to bite them

in cold blood, in a way quite foreign to the behaviour

of healthy ants. They were also often observed to run

round and round in a circle, the motion resembling the

_manège_, or riding-school action of mammals, when one

of the crura cerebri has been removed.

If an ant is cut in half through the thorax, so that

the great nerve ganglia of the pro-thorax remain

untouched, the behaviour of the head shows that

intelligence also remains untouched. Ants mutilated in

this way try to go forwards with their two remaining

legs, and beg with their antennæ for their companions'

aid. If one of these latter lets itself be stopped,

then we observe a lively interchange of thanks and

sympathy expressed by the actively moving antennæ.

Forel placed near to each other two such mutilated

bodies of the _F. rufibarbis_. They conversed with

each other in the above-described way, and appeared

each to beg for help. But when he put in some

similarly mutilated ants of a hostile species, _F.

sanguinea_, the picture was changed; war broke out

between these cripples just in the same way and with

the same fury as between perfect ants.[44]

The antennæ appear to be the most important of the sense-organs, as

their removal produces an extraordinary disturbance in the intelligence

of the animal. An ant so mutilated can no longer find its way or

recognise companions, and therefore is unable to distinguish between

friends and foes. It is also unable to find food, ceases to engage in

any labour, and loses all its regard for larvæ, remaining permanently

quiet and almost motionless. A somewhat similar disturbance, or rather

destruction, of the mental faculties is observable as a result of the

same mutilation in the case of bees.[45]

FOOTNOTES:

[19] While this MS. is passing through the press Sir John Lubbock has

read another paper before the Linnæan Society, which contains some

important additional matter concerning the sense of direction in ants.

It seems that in the experiment above described, the hat-box was not

provided with a cover or lid, i.e. was not a 'closed chamber,' and that

Sir John now finds the ants to take their bearings from the direction in

which they observe the light to fall upon them. For in the experiment

with the uncovered hat-box, if the source of light (candle) is moved

round together with the rotating table which supports the box, the ants

continue their way without making compensating changes in their

direction of advance. The same thing happens if the hat-box is covered,

so as to make of it a dark chamber. Direction of light being the source

of their information that their ground is being moved, we can understand

why they do not know that it is being moved when it is moved in the

direction of their advance, as in the experiment with the paper slip.

[20] It is to be noted that although ants will attack stranger ants

introduced from other nests, they will carefully tend stranger larvæ

similarly introduced.

[21] _The Naturalist in Nicaragua_, 1874, p. 26.

[22] See _Leisure Hour_, 1880, p. 390.

[23] _Introduction to Entomology_, vol. ii. p. 524.

[24] Vol. vii. pp. 443-4.

[25] Büchner, _Geistesleben der Thiere_, pp. 66-7.

[26] _Origin of Species_, 6th ed. pp. 207-8.

[27] _Loc. cit._ p. 121.

[28] _Loc. cit._ p. 123.

[29] _Origin of Species_, 6th ed. p. 218.

[30] _Geistesleben der Thiere_, pp. 145-9.

[31] _Loc. cit._

[32] _Loc. cit._ p. 337.

[33] _Loc. cit._ p. 97.

[34] _Harvesting Ants and Trap-door Spiders_, London, 1873 and

Supplement, 1874.

[35] _Journal Linn. Soc._, vol. vi. p. 29, 1862.

[36] _Agricultural Ant of Texas_, Philadelphia, 1880.

[37] _Trans. Ent. Soc. Lond._, i. 103, 1836.

[38] _Madras Journ. Lit. Sc._, 1851.

[39] For this see Moggridge, _loc. cit._ pp. 6-10, where, besides Prov.

iv. 6-8, and xxx. 25, quotations are given from Horace, Virgil, Plautus,

and others.

[40] Proc. Phil. Acad. Nat. Sci., xii. p. 445.

[41] Agricultural Ant of Texas (Lippincott & Co., Philadelphia, 1880).

[42] _Missionary Travels_, p. 328.

[43] _Animal Biography_, 'Ants.'

[44] Büchner, _Geistesleben der Thiere_, English translation, p. 49.

[45] While this work is passing through the press, an interesting Essay

has been published by Mr. MacCook on the Honey-making Ant. I am not here

able to refer to this Essay at greater length, but have done so in a

review in _Nature_ (March 2, 1882.)--G. J. R.