Ant wonders—Leaves cut for mushroom-growing—How ants plant
mushrooms—A nest in a mushroom-bed—“Psychic plasticity”—Two
opinions—Ant stupidity—Unfair comparisons—The ant and
the servant-maid—Mushroom-growing beetles—Choked by
ambrosia—Intelligent uselessness—Automatic phraseology—A
curious insect.
ANTS, as everybody knows, have a special faculty for doing extraordinary
things. Only a few of these have been mentioned in the last and
preceding chapters, and only a few more can be touched upon in this. To
do the subject anything like justice, a whole large book would be
required, not a few chapters merely of a quite small one. What ants do,
indeed, reminds me of the refrain, constantly repeated, of a certain old
ballad lately brought to my notice, viz.—
“Wonders, notable wonders! never the like was heard.”
For instance, they grow mushrooms (rice, or some cereals, they used to
grow and reap, but lately they have not been allowed to); they use their
own larvæ as an implement to sew or stick things together with, thus
making little shuttles of them; they make bridges of their own bodies,
by which they pass over rivers—even wide ones, it would seem, at least
for them—which otherwise would be impassable; they allow themselves to
be made into honey-pots and kept full for the good of the general
community, who take a little of them when they want it; they have
cemeteries, and would appear even to feel something like awe or respect
in the presence of their own dead; they cause certain plants to grow and
come to maturity, which would otherwise die, in order to make a house in
them, and so on and so on, many other wonders equally notable, to say
nothing of those which have already been recounted.
To take the first on the list—I hardly believe in a classification of
wonders—Belt, who was an engineer, but ought to have given up his whole
life to observations of this sort, was the first, I believe, to find out
that ants were mushroom-growers. Like others, when he came to Nicaragua
he saw the leaf-cutting ants passing in long, double columns backwards
and forwards between their nests and the trees, the homeward-bound
column laden with their little crescent-shaped bits of green leaf, the
outgoing one empty-handed. “The first acquaintance a stranger generally
makes with them,” says Belt, “is on encountering their paths on the
outskirts of the forest crowded with the ants; one lot carrying off the
pieces of leaves, each piece about the size of a sixpence, and held up
vertically between the jaws of the ant; another lot hurrying along in an
opposite direction empty-handed, but eager to get loaded with their
leafy burdens. If he follows this last division, it will lead him to
some young trees or shrubs, up which the ants mount; and where each one,
stationing itself on the edge of a leaf, commences to make a circular
cut, with its scissor-like jaws, from the edge, its hinder feet being
the centre on which it turns. When the piece is nearly cut off it is
still stationed upon it, and it looks as though it would fall to the
ground with it, but on being finally detached the ant is generally found
to have hold of the leaf with one foot, and soon righting itself, and
arranging its burden to its satisfaction, it sets off at once on its
return. Following it again, it is seen to join a throng of others, each
laden like itself, and, without a moment’s delay, it hurries along the
well-worn path. As it proceeds, other paths, each thronged with busy
workers, come in from the sides, until the main road often gets to be
seven or eight inches broad, and more thronged than the streets of the
city of London. Standing near the mounds, one sees from every point of
the compass ant-paths leading to them, all thronged with the busy
workers carrying their leafy burdens. As far as the eye can distinguish
their tiny forms, troops upon troops of leaves are moving up towards the
central point and disappearing down the numerous tunnelled passages. The
outgoing empty-handed hosts are partly concealed amongst the bulky
burdens of the incomers, and can only be distinguished by looking
closely amongst them.”[60]
It used to be supposed that these leaves themselves, in a decaying
state, were the food of the ants, whilst another theory was that they
were used to make a sort of underground roof to the nest with. Belt’s
discovery took everybody—including himself—completely by surprise. “I
believe,” he says, “the real use they make of them is as a manure, on
which grows a minute species of fungus, on which they feed: that they
are in reality mushroom growers and eaters”;[60] and he thus narrates
the circumstances which led him to this conclusion:—
“When I first began my warfare against the ants that attacked my garden,
I dug down deeply into some of their nests. In our mining operations we
also, on two occasions, carried our excavations from below up through
very large formicariums, so that all their underground workings were
exposed to observation. I found their nests below to consist of numerous
rounded chambers, about as large as a man’s head, connected together by
tunnelled passages leading from one chamber to another. Notwithstanding
that many columns of the ants were continually carrying in the cut
leaves, I could never find any quantity of these in the burrows, and it
was evident that they were used up in some way immediately they were
brought in. The chambers were always about three-parts filled with a
speckled brown flocculent, spongy-looking mass of a light and loosely
connected substance. This mass, which I have called the ant-food, proved
on examination to be composed of minutely subdivided pieces of leaves,
withered to a brown colour and overgrown and lightly connected together
by a minute white fungus that ramified in every direction throughout
it.”[60] Belt assured himself in many ways, but not through actually
seeing them do so, that this fungus was what the ants fed on, and he
adds, “that they do not eat the leaves themselves I convinced myself;
for I found near the tenanted chambers deserted ones filled with the
refuse particles of leaves that had been exhausted as manure for the
fungus, and were now left, and served as food for larvæ of
_Staphylinidæ_ and other beetles.”[60]
Belt’s conclusions have been since amply verified, and the actual
process of preparing the leaves and laying down the mushroom-beds, as
well as the clipping and—if I mistake not—eating of the mushrooms, has
been observed. Herr Möller—a German observer who resided for some years
in tropical America—is usually referred to in this connection; but such
extracts from his writings as I have come across are to me less
_convincing_ than the following account of Mr. Edward Tanner, which is
contained in the _Journal of the Trinidad Field Club_.[61] The
observations were made with ants in confinement, as were Herr Möller’s
also, I believe. “Each forager,” says Mr. Tanner, “drops her portion of
leaf in the nest, which is taken up as required by the small workers,
and carried to a clear space in the nest to be cleaned. This is done
with their mandibles, and if considered too large, it is cut into
smaller pieces. It is then taken in hand by the larger workers, who lick
it with their tongues. Then comes the most important part, which is
almost always done by the larger workers, who manipulate it between
their mandibles, the ant using her palpi, tongue, three of her legs, and
her antennæ while doing so. It now becomes a small, almost black ball,
varying in size from a mustard-seed to the finest dust-shot, according
to the size of the piece of leaf that has been manipulated, which varies
from ⅛ by ⅛ to ¼ by ¼ of an inch. These balls, really pulp, are then
built on to an edge of the fungus-bed by the larger workers, and are
slightly smoothed down as the work proceeds. The new surface is then
planted by the smaller workers with slips of the fungus brought from the
older part of the nest. Each plant is planted separately, and they know
exactly how far apart the plants should be. It sometimes looks as if the
plants had been put in too scantily in places, yet in about forty hours,
if the humidity is regulated, it is all evenly covered with a mantle as
if of very fine snow. It is this fungus they eat, and with small
portions of it the workers feed the larvæ.”
The statement herein contained that the ants plant the new portion of
their mushroom-bed with slips or plants taken from the already growing
fungus is, as far as I know, new. I do not remember it in Herr Möller’s
paper,[62] who speaks of the _hyphæ_ of the fungus growing through and
round the little leaf-balls within a few hours, but without reference to
their being planted, nor is it alluded to by Professor Wheeler, who has
studied the mushroom-growing ant—whether the same or a similar species I
know not—in Texas. Forel, again, speaking of an allied form in Colombia,
says, “The largest workers triturate the leaves”; and again, “the
medium-sized workers of the minim caste are for ever clipping the
threads of the fungus, which then develops the ‘Kohlrabi’ (the little
round swellings, that is to say), on which the ants feed.”[62] Possibly
this last may allude to the planting, but if so, it is the reverse of
clearly put. Professor Wheeler also alludes to this constant clipping of
the fungus, and sees in it the probable cause of the mutilation of the
antennæ of the little blind cockroaches that live with these ants and
take toll of their mushrooms.[63] But as these constitute the sole food
of their insect cultivators, it is natural that the latter should
frequently clip in order to eat them, and the clipping would, no doubt,
stimulate their growth. All this, however, is different from the actual
deliberate planting of the fungus on newly laid-down portions of the
bed—an act which would imply a very clear intention, and make the ants
farmers in the same way that we are. This, however, need not be the case
if they only lay down the beds, for these at one time probably
constituted their actual food, the crop of fungus being merely
incidental. But if the ants deliberately plant the fungus, then, indeed,
they must know precisely, in a human way, what they are about.
As we have seen, the leaves, from which, in their state of pulp, the
mushrooms spring, are stored up by the ants in large underground
chambers; but these mushroom-beds, or gardens, as they are often called,
are themselves a sort of nest, containing tunnels and chambers, and not
merely unformed heaps. It is in one or other of these chambers that the
queen ant of the nest resides, a majestic creature, almost an inch long,
but inflated both with pride and eggs to a disproportionate extent. Her
sons and virgin daughters, who will some day be queens themselves, keep
her company, whilst all about in the galleries and all over the broad,
flat surface of the garden, which resembles a large flattened sponge,
walk the different castes of workers, some large, some small, some
medium-sized, with a few big-headed soldiers here and there amongst
them, as though to keep the crowd in order. Whether they have really any
such duty assigned them we do not know, but they do not appear to do any
work, whilst the others are all busy at something, and the smaller
workers particularly keep threading the stalks and filaments of the
fungus in order to weed out any extraneous useless growth from amongst
it.[63]
It is a sad reflection—thus sighs Professor Wheeler—that so much ordered
energy, such apparent intelligence, should all be really due to—_what_
he does not seem to be quite certain about, not automatism entirely
perhaps, but if not, then semi- or demi-semi-automatism, tempered with
“psychic plasticity.” Against this view of the matter we have that of
Belt, who, after giving two instances, which came under his own
observation, of intelligent adaptation, on the part of ants, to meet
particular circumstances, exclaims, “Can it be contended that such
insects are not able to determine by reasoning powers which is the best
way of doing a thing, or that their actions are not guided by thought
and reflection?”[64] But then Belt was not provided with the term
“psychic plasticity,” and without it he could only infer intelligence
from any intelligent act.
Still it cannot be denied that a great many instances have been
given—noticeably in the case of “_our_ ants” by Sir John Lubbock[65]—in
which these paragons of insects have behaved very stupidly, or shall we
say—for why should a creature that cannot be intelligent be stupid
either?—with great “psychic _rigidity_”? Certainly such contradictions
are very puzzling, but I would suggest one way of trying to estimate
better the rigid type of ant intellect, which I believe to be absolutely
new, and that is to compare it not with one’s own brain—or Darwin’s—but
with that of a rigid type of person. It is wonderful what a difference
this might make in our conclusions. An ant, for instance, that is
unable, under some special circumstances, to get a thing down into its
nest, because it persists in holding or pulling it, in the way it has
always been accustomed to, or another that would rather be blown into
the water along a known road than leave it for a new one, makes a poor
figure in presence of the seven sages, or amidst a circle of senior
wranglers mentally called up for its confusion; but we should think,
rather, of some pin-headed servant-maid, setting an article of furniture
each morning in the place that, with evident intention, you have removed
it from overnight, or making up a larger and larger fire as the weather
gets warmer and warmer. One should think of the obstinacy with which
many people cling to old habits which changed times have made useless,
or even harmful, and of how numbers not only prefer inferior things they
are used to, to the most decisive improvements, but hate and revile such
improvements as though they were undeniable evils. Instances will occur
to everyone. I would rather not mention any for fear of alienating nine
out of every ten of my readers. We should think, also, of savages or
primitive, slow-moving peoples. What a great unadaptability, for
instance, did the Matabele show in their methods of encountering our
countrymen during the war, and throughout the rising; as also in that
rising itself, since it was against all those well-known blessings which
our empire confers upon savages.[66] It is to these less exalted levels
of human faculty that we should look when we seek to compare an ant’s
mind—when out of its usual set track—with our own, if we wish to do the
ant any justice. That we pursue an opposite plan is my own explanation
of many a partial verdict. To every experimenter in these directions
(who should happen to ask my advice) I would say, first, “Do you know,
or have you ever known, a really silly person?” and on his beginning, at
once, with “Yes, Mrs.” or “Miss” (as the case may be), I would strike in
peremptorily thus: “Then keep _her_—not Newton—in your mind as a
standard of comparison.”
That ants should intentionally cultivate mushrooms will appear wonderful
to everybody, and some will see in it the high-water mark of their
mental development, by whatever path it has been arrived at. It seems
natural to connect such doings with the fact that “in ants the cerebral
ganglia are of extraordinary dimensions, and in all the Hymenoptera
these ganglia are many times larger than in the less intelligent orders,
such as beetles.”[67] Yet the brain of an ant—“one of the most
marvellous atoms of matter in the world, perhaps more so than the brain
of a man”—is “not so large as the quarter of a small pin’s head.”[67] Of
what size, then, can a beetle’s be?—especially that family of beetles
which grow and cultivate mushrooms, just in the same way that ants do.
It would be suggestive—though I hardly know of what—should it be found
that, comparatively speaking, _they_ have no brain at all.
The beetles alluded to have been named, with reference to the particular
kind of mushrooms they grow, ambrosia beetles, though in what the great
superiority of these over those raised by the ants lies I do not know,
for no one appears to have tasted them. It has been agreed, however, to
call them ambrosia. “One of the most remarkable facts,” says Mr.
Froggatt, “is that each group of these beetles is associated with a
certain kind of ambrosia or fungus, notwithstanding that they are found
in different timbers. This substance is actually cultivated by the
mother beetle upon a carefully prepared layer or bed of wood-débris,
generally at the end of the gallery; but in others the ambrosia is grown
only in certain brood chambers of peculiar construction, whilst in
others again it is propagated in beds near the cradles of the
larvæ!”[68] When the latter hatch, they find a supply of celestial food
awaiting them, and can walk about the various galleries, feeding upon it
to their hearts’ content.
In other cases, however—that is to say, with other species—social
development has gone further, and, besides boring galleries, the
mother-beetle excavates a number of cells in their walls, like rows of
bedrooms opening out of either side of a passage. She does not, however,
quite finish her bedrooms, but, whilst they are still incomplete, lays
an egg in each, and when this hatches, the young beetle, then in its
larval state, takes up the task where she left off, and in time
completes it. All the while they are growing up the mother feeds the
young ones, and, between the intervals of doing so, stops up the
entrance to the cell with a “plug”—such is the word employed; “to what
base uses we may return, Horatio!”—of ambrosia. In time, when they have
acquired the full imago form, each female beetle flies away to make a
burrow and rear a family of her own, and in some species she is
accompanied in this marriage flight, as it may be called, by the male.
In others, however, the males are wingless, and remain in the burrow,
till, when their appointed time comes, they die. Whether the male, when
winged, assists the female in her mining operations I am not quite sure,
inasmuch as that point seems to be avoided in the accounts which I have
been able to consult, but the wingless male would not be able to do so,
as he would be left behind in the burrow when the female flew away to
found another colony.
The fungus, when it has once commenced to grow, increases very rapidly,
so that if the number of beetles in the nest is much diminished, as,
say, by some accident, the rest cannot eat enough to keep it down, and
so, it would appear, are suffocated. It is asserted, however, that when
the wingless males are deserted by the females, and would otherwise
perish in this way, they all collect together in a few of the galleries
and feast on the ambrosia there growing. By this means, we are told,
they “prolong for a time their useless existence”—an ungrateful way of
putting it, so it seems to me, as the poor things have already been
useful in a very indispensable manner, so that their existence as a
whole is anything but useless, and to separate a part of it from the
rest and carp at that is silly as well as ill-natured. But it is the
fashion to speak in this harsh way of the male insect, beginning with
the drone bee; whereas when the female has done all that _she_ can
do—which is often just to lay her eggs—nobody talks of _her_ useless
existence. Fashion is a curious thing, and ants, even if they be
automatons, are not the only creatures that do things automatically.
It is certainly very curious, if it be true, that the wingless male
beetles should, by thus congregating together in this way, and so saving
their lives, show more intelligence than the winged females, who, under
similar circumstances, are choked with their ambrosia, as the Duke of
Clarence was with his nectar in a malmsey-butt. It is true that with the
males the thing happens every year, whereas with the females it is only
accidental; but, in the particular circumstances, it is difficult to see
how inheritance can have had anything to do with it. Here, then, are a
particular family of beetles who live the same sort of social life that
ants and bees do, which discovery appears to have been made by a Mr.
Hubbard not so many years ago, and from whose paper on the subject all
the above particulars have been taken, though only through the medium of
various magazines, since even at the British Museum I was unable to get
the paper itself. So long ago, however, as 1844 a certain Herr Theo
Hartig “published an article on the ambrosia of _Xyleborno (Bostrichus)
dispar_, in which he showed that it was a fungus growth (_pilzrasen_),
and he named the fungus _Monilia candida_.” This statement is made by
Mr. Hubbard in his much more recent account. Not feeling perfectly
certain from it whether the origin, as well as the nature, of the
strange-named substance was not also divined by the German investigator,
I quote the reference in order not to do him a possible injustice, for
to me it seems that there have been few more interesting discoveries
than this of these ant-like, ambrosia-growing beetles. But why the ants
only grow mushrooms, thus allowing themselves to be enormously outdone
by an inferior insect, is more than I can understand.
And now a word of justice to these beetles. It might be supposed that,
by burrowing into trees, they caused the death of the latter, but this
is not really the case. Writing in _The Agricultural Gazette_ of New
South Wales for August, 1900, Mr. Froggatt, the Government Entomologist,
makes the following statement absolving _Xleborus_: “This curious little
beetle (_X. solidus_) is rather plentiful about Sydney, and is
frequently sent to us taken out of the trunks of fruit trees, which it
is supposed to have killed; but in all cases that have come under my
notice it has had nothing to do with the tree dying, but is attracted to
the tree as soon as it becomes sick, the bark begins to wither, and the
first symptoms of decay set in.” Mr. Froggatt adds: “The instinct that
leads these and other wood-boring beetles to a tree as soon as it is
sick is something marvellous; in the tropics I have collected many fine,
rare species upon the freshly cut tent-poles in our camp, attracted to
the wood, but otherwise seldom found in the bush.” This instinct would
seem to be a remarkably developed scent, though why a severed branch
should smell differently from the tree of which it but a moment before
made a part it is not easy to imagine. However, we cannot, without
evidence, attribute clairvoyance to beetles, and perhaps it is the cut
from which the scent emanates.
Another example of an insect which is neither an ant, bee, wasp, nor
white ant, but which yet may be said to live a true social life, is the
little creature which, under the name of _Psocus venosus_ and as
belonging to the order _Carrodentia_, will be familiar to everyone. It
is nearly related to the so-called book-lice, but lives in the open air,
“being seen,” says Mr. Leland Howard, “upon the trunks of trees, in
flocks numbering from twelve to forty or fifty individuals.”[69] These
browse together like a herd of miniature cattle on the various lichens
that embrace the bark, and these they nibble so closely that wherever
they move they leave a bare track behind them. Sometimes one family and
sometimes several are included in the herd, all ages and stages being
represented, from the wingless but free-moving larvæ to the winged imago
form. The latter, however, though they be thus provided, will not
readily forsake their young, but the whole of them, when alarmed, first
run all together, and then, if the cause of disquietude continue,
suddenly scatter as though in panic, and run hither and thither, in all
and every direction. When the danger seems over, they close up their
ranks again, and go on browsing as before.
The female _Psocus_ lays her eggs in little clusters of from fifteen to
twenty, and protects each cluster under a sort of dome or shield of
gnawed wood which she presses upon them so that they stick to it. She is
said to brood over the eggs, but this does not appear to mean that she
actually incubates them. Rather, she remains about, keeping watchful
guard till they are hatched, and then takes the young to find pasture,
walking at their head like a hen in front of her chickens. From such
beginnings as these it seems possible that the social life of ants has
been, in the course of ages, evolved and developed.
-----
Footnote 60:
Belt, The Naturalist in Nicaragua, pp. 72, 73, 79-81.
Footnote 61:
Journal of the Trinidad Field Club, No. 3.
Footnote 62:
As quoted in The American Naturalist for November, 1900.
Footnote 63:
The American Naturalist, November, 1900.
Footnote 64:
Belt, The Naturalist in Nicaragua, pp. 27, 28.
Footnote 65:
Lubbock, Ants, Bees, and Wasps.
Footnote 66:
The greatest being speedy extinction.
Footnote 67:
Darwin, The Descent of Man, p. 54.
Footnote 68:
The Agricultural Gazette of New South Wales, March, 1900.
Footnote 69:
Leland O. Howard, The Insect Book.
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