Ants and white ants—Guest insects—Ants’-nest beetles—Doubtful
relations—A strange forbearance—Yellow ants and white
wood-lice—Beetles fed by ants.
FROM what has been said about the Termites in the last chapter, it is
clear that they very much resemble ants in their habits, so that it is
no wonder that they have long passed for ants in popular estimation.
Such a similarity is quite enough to justify one part of the name, as
names go; and as for the word white, which entomologists are always
complaining about, that is quite near enough too, for though their
bodies are not white, but yellow, yet the greater part of them—the soft
fat abdomen, which particularly catches the eye—is of such a light
yellow that it suggests white in contrast to the darker colouring of
most ants. Scientific men—unless their particular science is
philology—are dreadful pedants in regard to names, and always want to
substitute their own manufactured ones, which have no real life in them,
for what has sprung up naturally on the lips of the people. Thus,
instead of hedge-sparrow—a name that explains itself to anyone who has
seen the bird and knows something of its ways—ornithologists would have
us say “hedge-accentor”—a preposterous concoction—and stormy petrel
should, according to them, be “storm-petrel,” because the bird itself
cannot be stormy, whatever the sea may be. No imagination behind the
common use of language, then. No poetic transference of attributes. All
is to be as prosy as professors can make it, and “we must speak by the
card, or equivocation will undo us.” But names, which are a part of
language, come into being as language itself does—spontaneously, that is
to say, and by a natural growth. They are right because they exist; and
the very errors contained in them—telling, as they do, of popular
beliefs and superstitions—are of greater and wider interest than the
rectitudes of a few pedants. Could they play with substance as they can
with breath, these wise simpletons would first draw up a theory of
anatomy, and then annul all bodies that did not conform to it. Such and
such a word or name is wrong, in their eyes, though it exists quite as
naturally as any nerve or muscle, and is quite as tough though only made
of air. This last they will find if they live long enough, and
“hedge-sparrow” and “stormy petrel” will survive all their lifeless
substitutions, though embalmed in many dull paragraphs of many dull
books.
But let us come back from words to things. Much as the white ants
resemble real ones in many of their habits, the more remarkable ones
that distinguish the latter are not practised by them. They make no
slaves and keep no domestic animals—at least I have never heard of their
doing so, though in natural history one must always be prepared for new
discoveries. Many insects do, in fact, live with them in the termitary,
just as others live in the formicaries of ants, and it is quite possible
that, when these have been better studied, some of them will be found to
have special relations—involving mutual intelligent action—with their
landlords.
At present, however, we seem to have little or no information on this
head. With ants it is different, and perhaps one of the most interesting
chapters in their history is that which has to do with these
_myrmecophilous_, or guest insects, as they are called.[10] Take, for
instance, the ants’-nest beetles, and especially one family—the
_Paussidæ_—which numbers some 200 species, every one of which passes the
whole of its life, when not flying by night, within the nest of some
species of ant. These beetles are small, as might be expected, the
largest being not more than half an inch in length, but present an
extraordinary appearance owing to the antennæ ending in two broad
palmated surfaces, like the horns of a moose deer, which project
outwards, one on each side, at right angles with two short stalks,
forming the only serviceable joints of these strangely modified feelers.
All the other ones (in some species, at any rate) have been fused and
welded together to form these flattened club-like structures, the use of
which is not at first-sight apparent, and may not be fully understood.
If, however, a _paussus_ is laid on its back upon a flat surface, a
predicament which would be as embarrassing to many beetles as it is to a
turtle, one of their special functions is at once seen. Turning back the
two clubs till they rest on the ground, and making the joint rigid, the
insect uses the one most conveniently placed as a lever, and soon gets
on to its legs again. Could we imagine that such an expedient would
often need to be resorted to, the curious modification of the antennæ is
at once explained; but it probably rarely happens that any small beetle
finds itself on its back in a place where there are no irregularities to
aid it in righting itself. Possibly, however, the smooth galleries or
chambers of some of the larger ants might expose these _Myrmicophilæ_ to
such a catastrophe, though, for my part, I suppose that the antennæ are
used in some other special way which is of far more importance to their
owners.
The relations existing between the ants and these curious beetles has
not yet been fully made out. It is true that the various species of
_Paussidæ_ have upon some part of their bodies a smooth downy
substance—a _pubescence_, to use the word dear to entomologists—which in
other ants’-nest beetles is known to exude a sweet honey-like dew which
the ants, not unnaturally, are very fond of, and for which they
assiduously lick them. As they have also been seen to lick their
_Paussi_, we seem, here, to have at least the root of the matter, nor
does the fact that, at other times, when perhaps these have ceased to
supply the attraction, they pay little attention to them, seem of much
importance, since we are all neglected when we have given what we have
to give. But there are other circumstances not of so straightforward a
nature. It has been lately discovered by a French observer—M.
Péringuey—that these _Paussidæ_, welcome guests as they generally are,
will yet, sometimes, eat the larvæ of the ants with whom they live, when
any small worker is engaged in carrying them from one place to another.
The ants resent this, and occasionally a large one, who feels himself
equal to the undertaking, will attack and even kill a _Paussus_ that he
sees behaving in such a manner. Yet, with all this, so valued are these
beetles by the ants that they often drag them back into their nests,
when they have approached, or emerge from, the entrance. On such
occasions, and also when the ants attack and even dismember them, the
_Paussidæ_ make no sort of resistance. Yet they are extremely well able
to do so, being armed with a weapon of tremendous efficiency, by which
in a moment they could kill or stun a whole crowd of ants round about
them. For they are bombardier beetles, having the power at any moment of
discharging a fluid of a highly acrid nature, and so volatile that, on
coming in contact with the air, it explodes with a puff of blue smoke,
exhaling at the same time a very pungent and unpleasant odour. When they
are tickled with a straw, even, this bombardment at once takes place,
and ants all round are seen to stagger or drop to the earth. Small
workers are killed, large ones retreat in confusion; yet the owner of
this deadly battery, which can only have been developed for the express
purpose of overwhelming an enemy, will not, even to save life or limb,
discharge it against an ant—not one, at least, to whom it stands in
these somewhat doubtful relations.
How have these relations—whatever in their entirety they may be—come
about? My own idea is that these beetles, like some other
creatures—amongst them the little white wood-louse that lives with our
own _Formica flava_—found ants’ nests very comfortable places of
retirement, since, by reason of their peculiar weapon of defence, they
could defy any attempt to interfere with them, on the part of the ants.
The ants, on their side, would soon have given up molesting them, so
that, never requiring to defend themselves against the creatures by whom
they were surrounded, the intruders got to associate them with quite
other ideas, and, having first lost the habit, at length lost the power
of turning their artillery in this direction. Meanwhile _Paussus_, owing
to its sweet secretion, which, after relations had once become amicable,
the ants would soon have discovered, had got to be a very welcome guest,
so much so that, even when it took to eating their larvæ, they retained
their love for it, as a species, though resenting such conduct upon the
individual. And now the once redoubtable invader could be punished with
impunity, for the habit of never discharging against an ant had become a
fixed, inherited instinct, not to be got rid of even though life were at
stake. Thus, as it appears to me, it may have come about that, though
armed with dynamite, and carrying bombs, no living _Paussus_ has ever
defended itself against an ant, and no living ant, perhaps, ever seen a
_Paussus_ discharge its artillery. Of course these are only conjectures,
and the last, especially, may be opposed to fact, since it has been
suggested that one way in which _Paussus_ may make itself useful within
the nest of its hosts, may be by bombarding certain obnoxious parasites,
or other would-be invaders. This does not, however, appear to me to be
likely, for how could these explosion take place, under such
circumstances, without doing damage to the ants themselves? In one’s own
house one would hardly wish a bomb to be thrown, even against one’s
greatest enemy—at any rate not in the drawing-room. That the ants
should, by this means, be able, or, if able, willing to rid themselves
of the mites which infest them, as has been conjectured, seems
especially unlikely—indeed, hardly possible. On the whole, it seems to
me that the relations at present existing between the two insects could
only have grown up through _Paussus_ having ceased to discharge, not
only at an ant, but even—owing, probably, to there never being any
occasion for it—in an ants’ nest. The experimental tickling with a straw
was, of course, an artificial stimulus. In spite of its sweet secretion,
I cannot see how a beetle with such a power at its command as _Paussus_
has, can have been originally selected by the ants for domestication,
but, on the other hand, an armed invader might easily, by coincidence,
possess some property which would make it, in time, of use and value to
the population on which it forced itself.
An example of an invader having no such merit, but harmless, and that
has become tolerated through necessity, is, in my opinion, the little
white wood-louse before mentioned. It apparently has now lost the power
of rolling itself into a ball, but when it first began to penetrate into
the galleries of _Formica flava_—our little yellow ant—it may very well
have had it, and this would have rendered it impervious to attack,
whilst its weight and round scaly surface would have made the task of
removing it almost an impossible one. Thus, perforce, it stayed where it
wished to stay, penetrating, perhaps, deeper and deeper into the
labyrinth of galleries, as successive generations of cave animals have
retreated farther and farther from the light of day, until at length,
finding the wherewithal to live, it became wholly subterranean in its
habits, lost the power of doing what it never required to do—namely, of
rolling itself into a ball—and, through the absence of all sunlight,
lost, too, its colouring matter, and became of its present dead,
bleached white. Whether its eyesight, if it ever had any, is also gone,
I do not know; but it can hardly, under present conditions, have any use
for it, whereas its antennæ are constantly moving, and seem to be of
extreme delicacy. I could never observe—for I have kept nests of
_Formica flava_—the smallest sign of any kind of relations between these
wood-lice and their hosts; and if any scavenger work is done by the
former, from which the latter derive benefit, I believe that this is
merely incidental, and that the ants know nothing about it. But they
have got accustomed to the wood-lice being there, and put up with them
because they cannot help it.
It must be remembered, in regard to _Paussidæ_, that the family is
represented by some two hundred species, all of which pass the greater
part of their lives with ants. In regard to this Mr. Kirby remarks: “The
observations made upon the family are so contradictory that the
discrepancies can only be accounted for by supposing that different
species have very different habits. Possibly some species may perform
various useful services to the ants, while others are hostile; or they
may be so useful that the ants are willing to pay toll of a certain
number of their offspring, in return.”[11]
This last, however, does not seem very well to accord with recorded
observations as to ants attacking any individual _Paussus_ whom they may
chance to see devouring their larvæ, nor with the latter refusing to
bombard, under these circumstances, even when in danger of their lives.
It is impossible to imagine a hostile _Paussus_ not bombarding, in such
a case, unless, indeed, we suppose it to have first lost its hostility,
and then again to have become hostile, without, however, regaining the
power of using its natural weapon. But this is a state of affairs hardly
to be conceived.
We probably do not know the whole round of occupations which make up the
life by day, of the _Paussidæ_; of their life by night, we know nothing
at all. The nefarious raids upon the larvæ or eggs (for both are
appreciated) of the ants can hardly be of frequent occurrence, or the
partnership, one would think, must come to an end. Other ant-guests,
however, including sometimes smaller members of their own family, are
likewise preyed upon by these curious beetles, but very frequently, when
observed, they seem to be asleep, nor do they appear then to be taken
much notice of by the ants. Where or under what conditions their eggs
are hatched, or what is the larval and pupal history of each species, we
do not know, but only the perfect insect has as yet been found in any
ants’ nest.
Other beetles that live with ants are either indifferent or hostile to
them, but others, again, are kept and tended in the same manner as are
the aphides, and for a similar purpose. All or most of these secrete
some sweet substance, which their hosts lick up, and, in return, offer
them an asylum from all enemies, and are ready to give them their
personal protection, should this be necessary. They go even further than
this, and actually feed them as they do their own larvæ, with honey, or
something of a similar nature, which they regurgitate from their crops.
One little beetle—_Atemeles_ by name—is extremely fond of such a meal,
and solicits it from the ants by stopping in front of them and assuming
a certain attitude, accompanied with insinuating motions of the antennæ.
Whether _Atemeles_ is able to feed itself, or must live wholly upon
these ministrations, I am not quite sure; but another beetle—poor
_Clavigertestaceus_—is, according to Janet, so entirely dependent upon
the ants for subsistence that, if separated from them, he has nothing to
do but to die.
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Footnote 10:
Others call them _inquilines_.
Footnote 11:
Kirby, Marvels of Ant Life, p. 100.
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