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D. S. (David Samuel) Margoliouth.

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very long, they make regular depots for their provisions under large leaves,
stones, or other suitable places, and let certain workers have the duty of carry-
ing them from depot to depot.

No less, therefore, than the leaf -cutting ants already described, do
these harvesting ants appreciate the benefits arising from the division
of labor ; and, as we shall presently see, there is a kind of ant exhib-
iting widely different habits, which shows appreciation of this prin-
ciple in an even higher degree.

When the grain is taken into their nest by the harvesters, it is
>tored in regular granaries, but not until it has been denuded of its
'• husks " or " chaff." The denuding process, which corresponds to
thrashing, is carried on below-ground, and the chaff is brought up to
the surface, where it is laid in heaps to be blown away by the wind.
It is not yet understood why the seed, when thus stored in subter-
ranean chambers just far enough below the surface to favor germina-
tion, does not germinate. Moggridge proved that the vitality of the
seeds is not impaired, for he grew some plants from seeds taken from
the granaries ; and he also found that the seeds would germinate even
in the granaries, if the ants were prevented from obtaining access to
iliem for two or three days. The non-germination of the seeds must,
therefore, be due to some influence exerted by the ants. Moggridge
: nought this influence might be the exhalations from the ants, and so
aied inclosing some seeds in a bottled test-tube, containing also earth
and ants. The seeds, however, sprouted ; and even an atmosphere of
formic-acid vapor was found not to prevent germination. Probably,
therefore, the ants in their granaries do something to the seeds for the
express purpose of preventing germination ; and, if so, it would be
interesting to botanists to ascertain what this process can be.

But, be this as it may, there is no doubt that the ants are fully
aware of the importance in this connection of keeping their garnered
-ceds as dry as possible ; for when the latter prove over-moist after
collection, or have been subsequently wetted by soaking rains, the
insects bring them up to the surface and spread them out to dry, to
lie again brought into the nest after a sufficient exposure.

Lastly, Moggridge observed that tho i.mr^o^s. wb-itovr it ;<, where-



820 THE POPULAR SCIENCE MONTHLY.

by the ants prevent germination, is not invariably successful, but that
a small percentage of stored seeds sometimes do begin to germinate.
When this was the case, he also observed the highly interesting fact
that the ants then knew the most effective method of checking further
germination, for he found that in these cases they gnawed off the tip
of the sprouting radicle. This fact deserves to be considered as one
of the most remarkable among the many remarkable facts of ant
psychology.

Passing on now to the harvesting ants of the Kew "World, the in-
sects here remove all the herbage above their nest in the form of a
perfect circle, or " disk," fifteen to twenty feet in diameter. Every
grass or weed within the disk is carefully felled, and, as the nests are
situated in thickly-grown localities, the effect of the bald or shaven
disk is highly conspicuous and peculiar, exactly resembling in min-
iature the " clearings " which are made by settlers in the backwoods.
The disk, however, is not merely cleared of herbage, but also carefully
leveled — all inequalities of the surface being reduced by pellets of soil
being built into the hollows to an extent sufficient to make a uniformly
flat surface. In the center of the disk is the gateway of the nest.
From the disk in various directions there radiate out-roads or avenues,
which are cleared and smoothed like the disk. These roads course
through the thick grass, branching and narrowing as they go, till they
eventually taper away. They are usually four to seven inches wide at
their origin, and may be from sixty to three hundred feet in length.
Along these roads there is always passing during the daytime a con-
stant double stream of ants, one being laden and the other not.

In their manner of gathering and garnering grain these harvesters
resemble in general the haiwesters of Europe ; but it is alleged by Dr.
Lincecum that in one respect their habits manifest an astonishing, and
indeed wellnigh incredible, advance upon those of their European
allies. For this observer, who, it must be remembered, was the first
to call attention to these ants in the New AVorld, and whose other
observations, extending over a number of years, have since been fully
confirmed — this observer states in the most positive terms that the
ants actually sow the seeds of a certain plant called the ant-rice, for
the purpose of subsequently reaping a harvest of grain ; hence these
ants have been called the " agricultural ants." Now, there is no doubt,
from the subsequent observations of McCook and others, that the ant-
disks do very frequently support this peculiar kind of grass, and that
the ants are particularly fond of its seed. Nevertheless, McCook did
not himself witness the process of sowing, although he is not disposed
to doubt the statements of his predecessor upon the subject. These
statements, as already observed, are most emphatic and precise — Lin-
cecum saying, in italics, that he knows and is certain about the fact ;
but until corroborated it is safest to regard the fact as not yet fully
established.



INTELLIGENCE OF ANTS. 821

HoxEY-MAKiNG Ants. — These ants are found in Texas and New
Mexico. Their remarkable habits have been observed by Captain
Fleeson, who communicated his observations to Mr. Darwin.

The community consists of three distinct kinds of ants, which ap-
pear to belong to two distinct genera. These are :

I. Yellow workers ; nursers 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, Avhich surround the nest
as sentinels, and also forage for the food required for I. They are
much larger and stronger than either I or II, and are provided with
very formidable mandibles.

The nest is in the form of an absolutely perfect square, of which
each side measures from four to five feet, and the surface of which is
kept quite unbroken save at two points, at each of which there is a
very minute hole or entrance. One of these minute holes occurs near
the west side of the square, and the other near the southeast corner ;
for it must be remarked that the square is always built with precise
reference to the points of the compass, in such a way that one side
faces due north, and consequently the others due south, east, and west.
These boundaries are rendei'ed very conspicuous by the guard of black
workers or soldiers (III), which continuously parade round three of
the sides in a close double line of defense, moving in opposite direc-
tions. This sentry-path occupies the north, east, and west boundaries,
the south side of the square being left open ; but, if an enemy ap-
proaches 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-
legs on meeting the enemy, and moving their large mandibles in de-
fiance. After tearing the enemy to pieces the guards return to their
places in the line of defense, their object in destroying any insect or
other small intruders being defense of the encampment, and not the
obtaining of food.

The southern side of the square encampment, or rather fortress, is
left open as just described in order to admit of a free entry of supplies.
While some of the black workers are on duty as gurad, another and
larger division are engaged on duty as purveyors. These enter and
leave the quadrangle by its southwest coraer in a double line (one
laden and the other not), which follows exactly the diagonal of the
square to its central point, where all the booty, consisting of flowers
and aromatic leaves, is deposited in a heap. Passing from this central
heap to the entrance at the southeast corner of the quadrangle, and
therefore occupying the other semi-diagonal of the square, there is
another double line of workers constantly engaged in carrying the
booty from the central deposit into the storehouses below-ground.
These workers are exclusively composed of Class II, whose whole life



82 2 THE POPULAR SCIENCE MONTHLY.

is therefore spent in running backward and forward upon this semi-
diagonal of the square, carrying in food and feeding Class I. No
black ant is ever seen on the eastern diagonal, and no yellow ant is
ever seen on the western ; but each keeps to his own separate station,
and here works with a steadfastness and apparent adherence to dis-
cipline which are not less remarkable than those exhibited by the sen-
tries. The western hole before mentioned seems to be intended only
as a ventilating shaft ; it is never used as a gateway.

Section of the nest reveals, besides passages and galleries, a small
chamber, across which is spread, like a spider's web, a network of
squares spun by the insects. In each of these squares, supported by
the web, sits one of the honey-secreting ants (11). Here the honey-
makers live in perpetual confinement, and receive a constant supply of
flowers, pollen, etc., which is continually being brought them by I,
and which, by a process of digestion and secretion, they convert into
honey. It is particularly noteworthy that in this truly wonderful
exhibition of social cooperation the black and yellow workers appear
to belong to two distinct genera ; for hitherto this is the only case
known of two distinct species of animals cooperating for a common
end.

EciToxs. — "VYe have lastly to consider the most astonishing insects,
if not the most astonishing animals, in the world. These are the so-
called " foraging," or, as they might more appropriately be called, the
military ants of the Amazon. They belong to several species of the
same genus, and have been carefully watched by Bates, Belt, and other
naturalists. The folloAving facts must therefore be regarded as fully
established :

Eciton legionis moves in enormous armies, and everything that
these insects do is done with the most perfect instinct of military or-
ganization. The army marches in the form of a rather broad and
regular column, hundreds of yards in length. The object of the
march is to capture and plunder other insects, etc., for food, and, as
the well-organized 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, etc., over every log and
under every fallen leaf. If prey is found in suflSciently small quanti-
ties for them to manage alone, it is immediately seized and carried to
the main column , but, if the amount is too large for the scouts them-
selves to deal with, messengers are sent back to the main column,
whence there is immediately dispatched a detachment large enough to
cope with the requirements. Insects or other prey 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



INTELLIGENCE OF ANTS. 823

pursued from branch to branch and twig to twig by their remorseless
enemies, till, 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
which are taken by the scouts, or by the detachments sent out in an-
swer to their demands for assistance, are immediately taken back to
the main army or column. When they arrive there, they are con-
veyed to the rear of that column by two smaller columns of carriers,
which are constantly running in two double rows (one of each being
laden and the other not) on either side of the main column. On either
side of the main column there are also constantly running up and down
a few individuals of smaller size, lighter color, and having larger heads
than the other ants. These appear to perform the duty of officers, for
they never leave their stations, and, while actively running up and
down the outsides of the column, they seem intent only on maintain-
ing order in the march — stopping every now and then to touch some
member of the rank and file with their antenna?, as if giving direc-
tions.

"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
larva^ in the nest are carried by the camer-columns to the rear of the
army, while the wasps fly around defenseless against the invading
multitudes. Or, if the nest of any other species of ant is found, a
similarly strong force is sent out, or even the whole army may be de-
flected toward it, when 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 Ecitons work with an
extraordinary display of organized cooperation ; 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 only just far enough
to insure that they shall not roll back again into the shaft, and, after
having deposited them at a safe distance, immediately hurry back for
more.

The 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 thousands and mill-
ions had previously covered the ground.

The habits of E. huniana and E. drepanophora are in general
similar to those of the species just described. The latter, however,
march in a narrower column (only four to six deep), which is there-
fore proportionally longer — sometimes extending to over half a mile.
Bates tried the effect of interfering with a column of this species by



824 T^^ POPULAR SCIENCE MONTHLY.

abstracting an individual from it. "News of the disturbance was
quickly communicated to a distance of sevei'al yards to the rear, and
the column at that point commenced retreating." It was also this
species that the same naturalist describes as enjoying periods of leisure
and recreation when they call a halt in " the sunny nooks of the for-
est." On such occasions,

the main column of the army and tlie branch columns were in their ordinary
relative positions; but, instead of pressing forward eagerly and plundering right
and left, they seemed to have been all smitten with a sudden fit of laziness.
Some were walking slowly about, others were brushing their antenna with
their forefeet ; but the drollest sight was their cleaning each other. ... It is
probable that these hours of relaxation and cleansing may be indispensable to
the effective performance of their harder burdens ; but, while looking at them,
the conclusion that they were engaged merely in play was irresistible.

E. pri^dator differs from the others of its genus in not hunting
in columns, but " in dense phalanxes consisting of myriads of indi-
viduals."

Nothing (says Bates) 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 summit of all the lower trees, searching every leaf to
its apes, 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.

A phalanx occupies from four to six square yards of ground, and the
ants composing it do not move "altogether in one straightforward
direction, but in variously spreading contiguous columns, now sepa-
rating 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 the main army."

Two species of Eciton are totally blind, and the habits of these
differ from those above described in that they march exclusively under
covered roads or tunnels. The van of the column is constantly en-
gaged in rapidly constructing the tunnels through which the army or
regiment advances as quickly as they are made. Under the protection
of these covered ways the ants travel at a surprising rate, and, when
they reach a rotten log or other promising hunting-ground, they pour
into all the crevices, etc., in search of prey. Bates says :

The blind Ecitons, working in numbers, build up simultaneously the sides of
their convex arcades, and contrive, in a wonderful manner, to approximate them
and fit in the key-stones without letting the loose, nncemented structure fall to
pieces. There was a very clear division of labor between the two classes of
neuters in these blind species. The large-headed class . . . act as soldiers.



INTELLIGENCE OF ANTS. 825

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-miners remained behind to repair the
dimiage, while the large-heads issued forth in a most menacing manner.

These two blind species of Eciton are particularly interesting from
the fact that in a part of the world so remote from them as Western
Africa there is another genus of military ant, also blind, which in all
its habits closely resembles the blind Ecitons of Brazil. For, like the
latter, Amiornia arcens march in long, close columns through tunnels,
have no fixed nest, but make temporary halts in shaded places, and
are no less organized, remorseless, and irresistible than their American
congeners. In one curious particular, however, they differ : the rela-
tive position of the marchers and the carriers is reversed, for here the
carrier-columns occupy the middle place, while the marching columns
with their officers occupy the flanks. When overtaken by a sudden
African rain-storm, these ants congregate in a close mass, with the
younger ants in the center ; 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.

Special Instances op the Display of High Intelligence. — I
shall conclude this brief r^ume of the more important facts at present
known concerning the psychology of ants with a few selected observa-
tions of the display of high intelligence. It is always difficult to draw
the line between instinct and reason, between adjustive action due to
hereditary or purposeless habit and adjustive action due to individual
and purposive adaptation. But we may be least diffident in accepting
as evidence of the latter cases where animals exhibit a power of adapt-
ing their actions to meet the requirements of novel circumstances — or
circumstances which can not be supposed to have been of sufficiently
frequent occun-ence in the life-history of the species to have developed
instincts of mechanical response in the individual. It is in view of
this consideration that the following instances are selected.

Ebrard records in his " Etudes de Moeurs " an observation of his
own on F.fusca. The ants were engaged in building walls, and when
the work was nearly completed there still remained an interspace of
twelve or fifteen millimetres to be covered in. For a moment the
ants were thrown out, and

seemed inclined to leave their work, but soon turned instead to a grass-jdant
growing near, the long, narrow leaves of wliich ran close together. Tliey cliose
the nearest, and weiglited its distal end with damp eartli, 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 tliis 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 bo quite enough, they heaped



826 THE POPULAR SCIENCE MONTHLY.

damp earth between the base of the plant and that of the leaf, until the latter
was sufhciently bent. After they had attained their object, they heaped on the
buttressing-leaf the materials required for building the arched roof.

This observation naturally leads to two others by two different ob-
servers. Thus, Moggridge says : " I was able to watch the operation
of removing roots which had pierced through tlicir 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 fibers where the strain was greatest, until at length it
gave way." Again, as previously quoted in another connection, he
says that two ants sometimes combine their efforts, one stationing
itself near the base of a footstalk and gnawing at the point of greatest
tension, while the other hauls upon and twists it.

The other observer to whom I have referred is McCook, who says
of the harvesting ants of America that he has seen " the workers, in
several cases, leave the point at which they had begun a cutting,
ascend the blade, and pass as far 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 fract-
ure. In two or three cases there appeared to be a division of labor ;
that is to say, while the cutter at the roots kept on with his work,
another ant climbed the grass-blade and applied the power at the oppo-
site end of the lever. This position may have been quite accidental,
but it certainly had the appearance of voluntary cooperation."

These observations serve to render less improbable the following
quotation taken from Bingley's account of Captain Cook's expedition
in New South Wales, and vouched for by Sir J. Banks. Green ants
were seen forming their nests in trees by " bending down several of
the leaves, each of w^hich is as broad as a man's hand, and gluing the
points of them together so as to form a pui'se. . . . We saw thousands
uniting all their strength to hold them in this position, while other
busy multitudes within were employed in applying the gluten that was
to prevent their returning back,"

Moggridge says that he has seen the harvesting ants of Europe
clustering round the larva of a certain beetle, and directing it toward
some small opening in the soil, " which it would quickly enlarge and
disappear down " ; and he believes that " these attentions were purely
selfish," the ants availing " themselves of the tunnel thus made down
into the soil."

McCook says of the harvesters of America that they dislike shade,
so that if a tree grows up in their vicinity and casts a shadow over
their nest they forthwith migrate. He gives in this connection a state-
ment which I regard as bordering on the incredible, and therefore I
desire it to be specially observed that it is not very evident from



INTELLIGENCE OF ANTS. 827

McCook's account whether he himself witnessed the facts. The facts,
however, which he narrates, are that a peach-tree having grown up so
as to overshadow a nest of harvesting ants, the latter climbed the tree
to strip off the leaves. " I am convinced," says McCook, " that the
reason for this onslaught was the desire to be rid of the obnoxious
shade." If this statement had been met with in any ordinary book on
animal intelligence, of course I should not have quoted it ; but as



Online LibraryD. S. (David Samuel) MargoliouthThe Popular science monthly (Volume 19) → online text (page 103 of 110)