Ant language—Stridulatory organs—How white ants
communicate—Conversation through convulsions—Nests
in tubes—Detection of a “crepitus”—Mutual
recognition—Cannibalistic propensities—Royal jealousy—Loyal
assassins—A kingly feast—Methods of feeding—Foundation of
colonies—Swarming habits.
IT used to be supposed that such communication as ants are capable of
holding with one another took place entirely, or almost entirely,
through the mutual stroking of the antennæ, and Sir John Lubbock (now
Lord Avebury) was unable to satisfy himself, after numerous experiments,
that they could either hear or utter any sound. It is now known,
however, that not only can some ants emit various sounds at their
pleasure—as, indeed, is sufficiently obvious in the case of one or two
species—but also that they possess special structures enabling them to
do so, and the existence of which is inconceivable, except on the
supposition that they both hear and attach a meaning to the notes thus
evolved. Thus at a meeting of the Entomological Society held in the year
1893, Dr. David Sharp (author of the “Insects” portion of _The Cambridge
Natural History_) declared that “examination revealed the existence in
ants of the most perfect stridulating or sound-producing organs yet
discovered in insects, these being situated on the second and third
segments of the abdomen in certain species. The sounds produced were of
the greatest delicacy, and it appeared doubtful whether the microphone
would be able to assist the human ear in their detection”—which, indeed,
it has not yet done.[7] Later, in the work above mentioned, Dr. Sharp
remarks, “In many ants these parts”—that is to say the abdominal
segments—“bear highly developed stridulating organs, and the delicacy
and perfection of the articulations allow the parts to be moved, either
with or without producing stridulation.”[8]
As these ant utterances are not sufficiently loud to be audible to our
human ears, they must, I suppose, be inferred from the existence of the
organs above-mentioned, and the way in which they work; but this is
surely sufficient data to go upon, since it is hardly possible for one
hard substance to grate upon another silently. Forel, accordingly, as
well as Janet and other observers, now believe sound to be one of the
principal means by which ants hold converse with each other, and it is
interesting to find that Grassi and Sandias have arrived at the same
conclusion in regard to white ants, or termites. Their opinion, together
with the facts upon which it has been founded, is thus expressed:—
“Several writers have mentioned the convulsive movements characteristic
of Termites. These movements, or quiverings, are easily observed in
Calotermes, and may be repeated periodically at very short intervals,
almost at the frequency of the pulse-rate. In the act of quivering, the
legs are held motionless, whilst the body is shaken forwards and
backwards. Sometimes a white ant may stop, whilst running, in order to
quiver one or more times. Occasionally these convulsive movements are
repeated a few times only, and then stop altogether; but at other times
they recur after a few seconds’ or, at most, a few minutes’ rest, and
may thus be continued, sometimes, for hours, at regular or irregular
intervals. In the intervals between successive convulsions the insect
remains still, or progresses for a short distance only. These movements
are executed by all members of the colony except the newly hatched ones.
I have satisfied myself,” continues Professor Grassi, “by careful
observation of the phenomena exhibited in tube-nests, that these
convulsions serve as a cry to summon help or give alarm, or as a lament:
in short as a mode of intercommunication.”[9]
The same observers then go on to tell us that if white ants are
disturbed in any sudden way, as by the too rough shaking of their nest,
or by a light being suddenly flung upon it, or if otherwise annoyed,
“all the members of the colony begin to quiver, except those that are
running briskly about in search of a better situation.”[9] When dying,
too, they will sometimes quiver in this way, at intervals of a few
minutes, for as much as an hour or two, or even longer. Should an
enemy—such as those we have been speaking of—be introduced of a sudden
into the nest, the less valiant members of it prefer to run away, but in
the midst of their retreat they may often be seen to stop and quiver
with unusual energy. Their object in these cases seems to be to raise a
general alarm, nor is it long before they are successful. Again, if
whilst one insect is burrowing into wood another outside should quiver
in this way, the burrower quickly comes out, as though in response to
some signal of alarm. From all this it seems evident that these curious
movements must be accompanied by some sound, or sounds, inaudible to our
human ears, and perhaps having a varied range, and with considerable
power of modulation. To produce them, however, some stridulating or
other organs would seem to be necessary, and of these, though they must,
if there, be visible under the microscope, Professor Grassi says
nothing. Possibly, however, sounds may be produced by the rubbing
together of various parts of the body without any special apparatus
having been developed, in which case the language, if we may call it so,
cannot be so rich or copious.
The above remarks apply more especially to the larger of the two white
ants of Southern Europe. In regard to the smaller one, Professor Grassi
makes the following interesting remarks: “Termes makes the same
convulsive movements as does Calotermes, but the soldier of this species
is able to produce a special creaking sound, which arises, whenever the
head is held horizontally, during the act of quivering, by friction
between the back of the head and the front part of the thorax. But
whenever the head, during this act, is held in the usual position, which
is not quite horizontal, no perceptible sound is produced, owing to the
absence of such friction. The soldiers of Termes, therefore, possess two
distinct modes of communication, whilst those of Calotermes have only
one, in which no perceptible sound is produced. This characteristic
_crepitus_,” continues the Professor, “may be heard, at frequent
intervals, by applying the ear to a tube containing a nest of Termites.
This proves that the quivering motions are a constant feature in
undisturbed nests, so that they cannot be employed only as signals of
alarm or distress. I conclude, therefore, that besides such special
significations these convulsive movements must also have the value of
ordinary speech; that they constitute, in short, a means of
intercommunication. The same conclusion holds good for Calotermes (the
one we have hitherto been talking about), and I imagine that the
quivering of both species produces a sound which is perceptible to the
insects themselves, but inaudible to the human ear.”[9]
Members of the same ant community are known to recognise each other, and
this is no less the case with the white ants, or termites. Thus when a
few of the latter were removed from the termitary and returned to it
after five or six hours, the population showed no signs of alarm—not
scurrying wildly about as they would have done had strangers been
introduced—but remained quiet and orderly. It was objected, however,
though I cannot see the force of such an objection, that the exiles, on
their return, would have instantly recognised their old nest, and thus,
knowing exactly where to go and what to do, they would have created no
disorder, and consequently roused no suspicion, amongst the other
members of the colony. To meet this theory Professor Grassi provided one
of his colonies with a new nest from which he excluded a certain number
of individuals, so that when these were introduced into it, an hour or
two after their companions had settled down in their fresh abode, it
was, of course, quite unfamiliar to them. In spite of this, however,
they caused no disturbance, but were clearly recognised as friends.
When, however, a few strangers of the same species were introduced, they
created great alarm amongst the rightful proprietors, who scattered in
all directions. In a little while, however, all was again quiet, and as
no fighting was observed, it would appear that, amongst the termites,
strangers from different nests soon become friendly with one another.
This, however, applies to the commoners only, it is not the same where
royalty is concerned. Thus when a second king and queen were introduced
into a termitary already provided with a pair, they were at once
attacked by the subjects of the latter, who loyally bit off their legs.
Two days afterwards the reigning queen was herself seen to attack the
male pretender, or rather unfortunate victim of scientific curiosity.
He, however, though without legs to assist him, managed to drag himself
away, but was afterwards found dead, with the outraged queen nibbling
vindictively at his mutilated stumps. Next day the stranger queen was
also found dead, and the same thing always happened whenever the
experiment was repeated. Sometimes, indeed, the supernumerary royal
pair, or pairs, had disappeared altogether, from which it seems clear
that they must have been not only killed, but eaten.
Cannibalism, indeed, is rather an institution than a vice in the
termitary. To begin with, the cast skin of every member is eaten by the
others as a matter of course. With this view, any individual who is
ready to moult receives the skilled aid of two or more assistants, who
either eat the outer portion of their friend, bit by bit, as they shred
it off, or else carry it away whole and devour it at their leisure.
Sometimes, moreover, one, after licking another affectionately, in the
way that ants do, may be seen to give it a covert bite, as though
desirous of something more filling, whilst any sick member is eaten by
its companions before it is dead. Royalty is not exempt from this
treatment, and, on one occasion, nine individuals, including one
soldier, were observed by Professor Grassi in the act of enjoying a meal
on the body of a substitute king who was in process of moulting. The
wretched animal was still alive, and writhed all over its body, to free
itself from the torture. The nine assassins were probably annoyed at the
light, for they at once stopped eating, and jointly carried off the
victim to a darker part of the nest. Meanwhile many others crowded up to
partake in this feast of royal flesh.[9]
A soldier, too, has been observed to kill and partially eat one of its
worker companions, nor is it altogether uncommon for an individual of
any class, after licking, for some little while, the leg of another,
suddenly to snap it off. The bond of union, therefore, though
sufficiently developed to allow of an elaborate social organisation, is
not so strong between members of the same termitary as it is in the case
of ants, amongst which latter such unseemly conduct is never known to
occur. So, too, unless a particular chemical substance, which seems to
have a maddening effect, be flung amongst them, ants of one community
never attack each other. Amongst white ants, however, warfare will
occasionally break out within the nest, more especially if this be
disturbed, in which case the soldiers are apt to turn savagely on those
nearest to them, perhaps considering them as the cause of the calamity.
Still, upon the whole, order, and, if not friendship, at least
co-operation, is conspicuously displayed, and the majority often
interfere to put a stop to such individual or partial combats as may
from time to time break out.
There is more excuse for the soldier termites in their cannibalistic
propensities, since owing to the special development of their jaws,
which are long and slender, they are unable to triturate wood, which is
the basis of diet of these insects. They might die, therefore, but for
such occasional lapses, were it not the common practice for all members
of the community to feed one another, though the soldiers, for the above
reason, are much more dependent on such aid. The food thus administered
has just been swallowed by the individual who parts with it. Such
transfer is performed in two ways, the first of which is familiar
enough—that process, namely, known as regurgitation—but the second and
more staple one is too peculiar to be dealt with in a non-scientific
work. When a termite regurgitates, an exceedingly small round pellet of
reddish-brown colour may be seen, by attentive observation, to form
about the mouth, and gradually to increase in size till it becomes
plainly apparent, and is seen to consist of food—that is to say,
wood—which has previously been swallowed, in a moistened and softened
condition. Sometimes this pellet is used for building purposes, but
often another termite comes forward, receives, and swallows it.
Another article of diet which has a peculiar efficacy, and is used for a
certain purpose, has been already alluded to—viz. saliva. This, we are
told, “issues,” when required to do so, “as a colourless and distinctly
alkaline liquid. It collects on the labium (the insect equivalent of
lips) as a small drop, which may be employed either as a cement in
building or as food for others. These may either possess themselves of
the drop and then retreat a little way in order to swallow it gradually,
or they may receive it from the one which secretes it and clearly
provides it for them as an article of diet. The assimilation of a drop
requires a certain number of acts of deglutition, which may be counted,
and are usually four or five.”[9] Very young larvæ (the whole community,
it must be remembered, are either in this or the pupal state) are fed
after this fashion, until sufficiently advanced to be able to swallow
wood-meal. Under this course of diet the abdomen becomes remarkably
transparent, and this, in older individuals, is an indication that they
are being bred up by the workers to become royal substitutes. The
development, therefore, of termites from the larval to the perfect, or,
at least, the sexually perfect form, seems to be wholly dependent on
their being fed with this substance.
As is well known, the body of the queen termite, in the African and
other tropical species, swells, when about to lay, to an enormous size,
but this is not nearly so noticeably the case with her European
representatives. Neither is a cell, in this case, constructed for her
accommodation, but the royal pair, whether they are true king and queen,
or only substitutes, “remain, in close proximity, in the heart of the
nest, where the inmates are always most crowded.” They are not
imprisoned, therefore; but can go from one place to another, should
they, as sometimes happens, wish to change their situation. In this they
would seem to be happier than their more specially accommodated royal
cousins, but no doubt, with the latter, or at any rate with the queen,
the instinct of locomotion ceases with the capacity to indulge in it.
The purpose of the specially made cell is probably rather to guard than
to restrain the queen.
In regard to the swarming of white ants—another habit in which we are
reminded both of ants and bees—with the subsequent founding of a new
colony, Professor Grassi has the following remarks to make. They apply
more especially to the larger of the two European species, viz.
Calotermes. “Before swarming,” he tells us, “they collect near one of
the exit-holes of the termitary, and when the proper time comes, issue
from it in ones or twos, so that the twenty or thirty members who are
ready to take flight emerge in perhaps a quarter of an hour. Once
outside, they run upwards, if the locality admits of it, for a few
metres, and then only do they take wing. In a room they fly towards the
light, and if a wind is blowing they follow its direction. Some,
becoming tired, settle soon upon trunks of trees, and all may do this
eventually. Here they group themselves into pairs, the males and females
of which must frequently be derived from separate nests, since the sexes
swarm separately; this acts as a safeguard by which Calotermes
habitually avoids in and in breeding. Matrimonial alliances having been
thus formed, the work of excavation commences, each pair seeking for
some decayed spot in which to bury themselves and become, in time, the
parents of a fresh community. The wings, by this time, have been got rid
of. They may be shed by coming into contact with an obstacle, or by
getting damp and adhering to some spot, while the insect continues to
move. But, if not favoured by chance, the Calotermite purposely rids
itself of these now useless encumbrances. Thus four perfect insects were
captured after flying about the room, and put under a piece of rotten
wood. Hardly had they settled when they stripped off their wings by
resting the tips against some projecting corner of the wood, and then
moving backwards a little, so that the wings bent near the base, broke,
and dropped off. When rid of them they began to gnaw the wood, at first
along and then across the grain. When they encountered each other by
chance they first threatened to bite one another, and then ran off in
opposite directions. This was because they were of the same sex. Had
they been of opposite ones, an attachment, under such circumstances,
would no doubt have been formed between them.”[9]
This is all the space which I can afford to these interesting insects.
There are many other points in connection with them which I might have
touched upon, but I thought it better to say less about what may be read
by anyone in a score or so of works, and select as my text-book a series
of the closest and most interesting observations, which lie buried in
the pages of a scientific journal not at all likely to meet the public
eye. Where possible, I shall be guided by the same or a similar
principle throughout this small work.
-----
Footnote 7:
Nature, March 23rd, 1893.
Footnote 8:
The Cambridge Natural History, vol. 6, p. 134.
Footnote 9:
Quarterly Journal of Microscopic Science, vols. 39 and 40.
------------------------------------------------------------------------