THE BROAD-NECKED SCARAB; THE GYMNOPLEURI
What we have learnt from the Sacred Beetle must not lead us into rash
generalizations and make us attribute it in every slightest detail to
the other Dung-beetles of the same family. Similarity of structure does
not entail parity of instincts. A common basis no doubt exists,
resulting from identity of equipment; but many variations of the
essential theme are possible and are dictated by inherent aptitudes of
which the insect’s organization gives us no inkling. In fact, the study
of these variations, of these peculiarities, with their hidden reasons,
forms the most attractive part of the observer’s researches as he
explores his corner of the entomological domain. Unsparing of time and
patience, sometimes of ingenuity, you have at last learnt what this one
does. See now what that one does, his near neighbour structurally. To
what extent does number two repeat the habits of number one? Has he
ways of his own, tricks of the trade, industrial specialities unknown
to the other? It is a highly interesting problem, for the impassable
line of demarcation between the two species is much more conspicuous in
these psychological differences than in the differences of the
wing-case or antenna.
The Scarab clan is represented in my district by the Sacred Beetle
(Scarabæus sacer, Lin.), the Half-spotted Scarab (S. semipunctatus,
Fab.) and the Broad-necked Scarab (S. laticollis, Lin.). The two former
are chilly creatures and hardly stir from the Mediterranean; the third
goes pretty far north. The Half-spotted Scarab does not leave the
coast; he abounds on the sandy beaches of the Golfe Juan, Cette and
Palavas. I have, in my time, admired his prowess at pill-rolling, of
which he is as fervent a devotee as his colleague the Sacred Beetle.
To-day, though we are old friends, I cannot, to my great regret, give
my attention to him: we are too far away from each other. I recommend
him to any one wishing to add a chapter to Scarab biography: he also
must have—I feel nearly sure of it—peculiarities worth noting.
And so, to complete this study, there remains in my immediate proximity
only the Broad-necked Scarab, the smallest of the three. He is very
rare around Sérignan, though widely distributed in other parts of the
Vaucluse. This scarcity deprives me of opportunities for observing the
insect in the open fields; and my only resource is to bring up a few
chance specimens in captivity.
Behind the wire-gauze of his prison, the Broad-necked Scarab does not
display the Sacred Beetle’s athletic prowess nor his bold and hasty
temper. In his case we see no scuffles between robber and robbed, no
pills manufactured purely for art’s sake, rolled for a little while
with wild enthusiasm and then consigned to the rubbish-heap without
being employed at all. The same blood does not flow in the veins of the
two pill-rollers.
Of a quieter disposition and less wasteful of his gleanings, the Beetle
with the broad corselet attacks discreetly the heap of manna provided
by the Sheep; he picks from the best part some armfuls of material
which he makes into a ball; he attends to his business without
troubling the others or being troubled by them. For the rest, his
methods are the same as those of the Sacred Beetle. The sphere, which
is always an easier object to convey, is fashioned on the spot before
being set in motion. With his wide fore-legs the Beetle pats and kneads
and moulds it, making it smooth and level by adding an armful here and
there. The perfect roundness of the ball is achieved before it leaves
the place.
When the requisite size has been obtained, the pill-roller makes his
way with his booty to the spot where the burrow is to be dug. The
journey is effected exactly as it would be by the Sacred Beetle. Head
downwards, hind-legs lifted against the rolling mechanism, the insect
pushes backwards. So far there is nothing new, save for a certain
slowness in the performance. But wait a little while: soon a striking
difference in habits will separate the two insects.
As each pill is carted away, I seize it, together with its owner, and
place both on the surface of a layer of fresh, close-packed sand in a
flower-pot. A sheet of glass serves as a lid, keeps the sand nice and
cool, prevents escape and admits the light. By interning each Beetle
separately, I am saved from the mistakes which might arise if I put
them in the common cage, where a number of my boarders are at work; and
I shall not risk ascribing to several what may be the performance of
one alone. By this solitary confinement, each individual Beetle’s work
can be studied more easily.
The interned mother makes hardly any protest against her servitude.
Soon she is digging the sand and disappears in it with her pill. Let us
give her time to establish her quarters and to get on with her domestic
labours.
Three or four weeks go by. The Beetle has not reappeared upon the
surface, a proof of her patient absorption in her maternal duties. At
last I remove the contents of the pot, very carefully, layer by layer,
until I uncover a spacious burrow. The rubbish from this cavity was
heaped up on the surface, forming a little mound. This is the secret
chamber, the gynæceum in which the mother now and for a long time to
come keeps watch over her budding family.
The original pill has disappeared. In its stead are two little pears,
elegantly shaped and wonderfully finished: two, not one, as I naturally
expected from the information already in my possession. They strike me
as being even more delicately and gracefully rounded than the Sacred
Beetle’s. Perhaps their tiny dimensions cause my preference: maxime
miranda in minimis. They measure 33 millimetres in length and 24
millimetres across their greatest width. [32] Let us drop figures and
admit that the dumpy modeller, with her slow and awkward ways, is the
artistic rival or even the superior of her famous kinswoman. I expected
to see some clumsy apprentice; I find a consummate artificer. We must
not judge people by appearances; it is a wise maxim, even when applied
to insects.
If we examine the pot somewhat earlier, it will tell us how the pear is
made. I find sometimes a perfectly round ball and a pear without any
traces of the original pill; sometimes a ball only, with a nearly
hemispherical remnant of the pill, a lump from which the materials
subjected to modelling have been detached in one piece. The method of
work can be deduced from these facts.
The pill which the Scarab fashions on the surface of the soil by taking
armfuls from the heap encountered is but a temporary piece of work,
which is given a round form with the sole object of facilitating its
transport. He gives his attention to it, no doubt, but is not unduly
anxious about it; all that he wants is that the journey should be
effected without any crumbling of his treasure or impediment in the
rolling. The surface of the sphere, therefore, is not thoroughly
treated; it is not compressed into a rind or made scrupulously even.
Underground, when it is a question of getting the egg’s casket ready,
the casket that is to be both larder and cradle, it becomes another
matter. An incision is made all round the pill, dividing it into two
almost equal portions, and one half is subjected to manipulation, while
the other lies just against it, destined to receive the same treatment
later. The hemisphere worked upon is rounded into a ball, which will be
the belly of the prospective pear. This time, the modelling is
performed with the nicest care: the future of the larva, which also is
exposed to the dangers of overdry bread, is at stake. The surface of
the ball is therefore patted at one spot after the other,
conscientiously hardened by compression and levelled along a regular
curve. The spherule thus obtained possesses geometrical precision, or
very nearly so. Let us not forget that this difficult work is
accomplished without rolling, as the clean condition of the surface
shows.
The rest of the business may be guessed from the proceedings of the
Sacred Beetle. The sphere is hollowed into a crater and becomes a sort
of bulging, shallow pot. The lips are drawn out into a pocket which
receives the egg. The pocket is closed, polished outside and joined
neatly to the sphere. The pear is finished. The other half of the pill
is now similarly treated.
The notable feature of this work is the elegant regularity of the forms
obtained without any rolling. Chance enables me to add another and a
most striking proof to the many that I have given of this modelling
done on the spot. Once and once only I managed to get from the
Broad-necked Scarab two pears closely soldered together by their
bellies and lying in opposite directions. The first one constructed can
teach us nothing new, but the second tells us this: when, for a reason
that is not apparent, for lack of room perhaps, the insect left this
second pear touching the other and soldered it to its neighbour while
working at it, obviously, with this appendage, any rolling or any
moving became impracticable. Nevertheless, the pretty shape was secured
to perfection.
From the point of view of instinct, the distinguishing features which
make of the two pear-modellers two entirely different species are
absolutely clear from these details and much more conclusive than the
peculiarities in the corselet and wing-case. The Sacred Beetle’s burrow
never contains more than one pear. The Broad-necked Scarab’s contains
two. I even suspect that there are sometimes three, when the haul is a
large one: we shall learn more on this subject from the Copres. The
first, when she gets her pill underground, uses it just as she obtained
it in the workyard and does not subdivide it at all. The second breaks
up hers, though it is a little smaller, into two equal parts and
fashions each half into a pear. The single ball gives place to two and
sometimes even perhaps to three. If the two Dung-beetles have a common
origin, I should like to know how this radical difference in their
domestic economy declared itself.
The story of the Gymnopleuri is the same as that of the Scarabs, on a
more modest scale. To pass it over in silence, for fear of too much
sameness, would be to deprive ourselves of evidence calculated to
confirm certain theories whose truth is established by the recurrence
of similar facts. Let us set it forth, in an abridged form.
The Gymnopleurus family owes its name to a lateral notch in the
wing-cases, which leaves a part of the sides bare. It is represented in
France by two species. One, with smooth wing-cases (G. pilularius,
Fab.), is fairly common everywhere; the other (G. flagellatus, Fab.),
stippled on the top with little holes, as though the insect had been
pitted with small-pox, is rarer and prefers the south. Both species
abound in the pebbly plains of my neighbourhood, where the Sheep pass
amid the lavender and thyme. Their shape is not unlike that of the
Sacred Beetle; but they are much smaller. For the rest, they have the
same habits, the same fields of operation, the same nesting-period: May
and June, down to July.
Applying themselves to similar labours, Gymnopleuri and Scarabs are
brought into each other’s society rather by the force of things than by
the love of company. I not infrequently see them settling next door to
each other; I even oftener find them seated at the same heap. In bright
sunshine the banqueters are sometimes very numerous. The Gymnopleuri
predominate largely.
One would be inclined to think that these insects, endowed with powers
of nimble and sustained flight, explore the country in swarms and that,
when they find rich plunder, they all swoop down upon it at once.
Though the sight of so large a crowd might seem to mean something of
the kind, I am very sceptical about these expeditions in large
squadrons. I am more ready to believe that the Gymnopleuri have come,
from everywhere in the neighbourhood, one by one, guided by keenness of
scent. What I see is a gathering of individuals who have hastened from
every point of the compass, and not the halt of a swarm engaged on a
common search. No matter: the teeming colony is at times so numerous
that it would be possible to pick up the Gymnopleuri by handfuls.
But they hardly give one time. When the peril is realized, which soon
happens, most of them fly off with all speed; the others crouch low and
hide themselves under the heap. In a moment the tumult of activity is
succeeded by absolute stillness. The Sacred Beetle is not subject to
these sudden attacks of panic, which empty the busiest yard in the
twinkling of an eye. When surprised at his task and examined at close
quarters, however importunately, he impassively continues his work. He
knows no fear. Here we see a thorough difference in temperament between
insects which are identical in structure and which follow the same
trade.
The difference is equally marked in another respect: the Sacred Beetle
is a fervent pill-roller. When the ball is made, his supreme felicity,
his summa voluptas, is to cart it backwards for hours at a time, to
juggle with it, so to speak, under a blazing sun. His epithet
pilularius notwithstanding, the Gymnopleurus does not show so much
enthusiasm over a round pellet. Unless he means to feed upon it quietly
in a burrow or to use it as a ration for his larva, he never kneads a
ball only to roll it about ecstatically and then abandon it when this
violent exercise has given him his fill of pleasure.
Both in his wild state and in captivity, the Gymnopleurus makes his
meal on the spot where he finds his food; it is hardly his habit to
make a round loaf in order to consume it afterwards in some underground
retreat. The pill to which the insect owes its name is rolled, so far
as I have seen, only in the interests of its family.
The mother takes from the heap the amount of material required for
rearing a larva and kneads it into a ball at the spot where it is
gathered. Then, going backwards, with her head down, like the Scarabs,
she rolls it and finally stores it in a burrow, in order to give it the
necessary treatment for the egg to thrive.
Of course the rolling ball never contains the egg. The laying takes
place not on the public highway but in the privacy of the subsoil. A
burrow is dug, two or three inches deep at most. It is spacious in
proportion to its contents, proving that the Sacred Beetle’s
studio-work is repeated by the Gymnopleurus. I am speaking of that
modelling in which the artist must have full liberty of movement. When
the egg is laid, the cell remains empty; only the passage is filled up,
as witness the little mound outside, the surplus of the unreplaced
refuse.
A minute’s digging with my pocket-trowel and the humble cabin is laid
bare. The mother is often present, occupied in some trifling household
duties before quitting the cell for good. In the middle of the room
lies her work, the cradle of the germ and the ration of the coming
larva. Its shape and size are those of a Sparrow’s egg; and I am here
speaking of both Gymnopleuri, whose habits and labours are so much
alike that I need not distinguish between them. Unless we found the
mother beside it, we should be unable to tell whether the ovoid which
we have dug up is the work of the smooth or of the pock-marked insect.
At most, a slight advantage in size might point to the former; and even
so this characteristic is far from trustworthy.
The egg-shape, with its two unequal ends, one large and round, the
other more pointed, shaped like an elliptical nipple, or even drawn out
into the neck of a pear, confirms the conclusions with which we are
already acquainted. An outline of this kind is not obtained by rolling,
which is only reconcilable with a sphere. To get it, the mother must
knead her lump of stuff. This may be already more or less round, as the
result of the work done in the yard whence it came and of the
subsequent carting, or it may still be shapeless, if the heap was near
enough to allow of immediate storing. In short, once at home, she acts
like the Sacred Beetle, and does modelling-work.
The material lends itself well to this. Taken from the most plastic
stuff supplied by the Sheep, it is shaped as easily as clay. In this
way the graceful, firm, polished ovoid is obtained, a work of art like
the pear and as exquisite in its soft curve as a bird’s egg.
Where, inside it, is the insect’s germ? If we argued rightly when
discussing the Sacred Beetle, if really the questions of ventilation
and warmth demand that the egg be as near as possible to the
surrounding atmosphere, while remaining protected by a rampart, it is
evident that the egg must be installed at the small end of the ovoid,
behind a thin defensive wall.
And this in fact is where it lies, lodged in a tiny hatching-chamber
and wrapped on every side in a blanket of air, which is easily renewed
through a slender partition and a matted plug. This position did not
surprise me; from what the Sacred Beetle had already taught me I
expected it. The point of my knife, this time no novice, went straight
to the ovoid’s pointed teat and scratched. The egg appeared,
magnificently confirming the argument which had at first been merely
suspected, then dimly seen and finally changed into certainty by the
recurrence of the fundamental facts under varying conditions.
Scarabs and Gymnopleuri are modellers who were not educated in the same
school; they differ in the outline of their masterpiece. With the same
materials, the first manufacture pears, the second for the most part
ovoids; and yet, despite this divergence, they both conform to the
essential conditions demanded by the egg and by the grub. The grub
wants provisions that are not liable to become prematurely dry. This
condition is fulfilled, so far as may be, by giving the mass a round
shape, which evaporates less quickly because of its smaller surface.
The egg requires unrestricted air and the heat of the sun’s rays,
conditions which are fulfilled in the one case by the pear with its
neck and in the other by the ovoid with its pointed end.
Laid in June, the egg of either species of Gymnopleuri hatches in less
than a week. The average is five or six days. Any one who has seen the
larva of the Sacred Beetle knows, so far as essentials go, the larva of
the two small pill-rollers. In each case it is a big-bellied grub,
curved into a hook and carrying a hump or knapsack which contains a
portion of the mighty digestive apparatus. The body is cut off
slantwise at the back and forms a stercoral trowel, denoting habits
similar to those of the Sacred Beetle’s larva.
We see repeated, in fact, the peculiarities described in the story of
the big pill-roller. In the larval state, the Gymnopleuri also are
great excreters, ever ready with mortar to make good the imperilled
dwelling. They instantly repair the breaches which I make, either to
observe them in the privacy of their home or to provoke their
plastering-industry. They fill up the chinks with putty, solder the
parts that become disjointed, mend the broken cell. When the nymphosis
approaches, the mortar that remains is expended in a layer of stucco,
which reinforces and polishes the inner walls.
The same dangers give rise to the same defensive methods. Like the
Sacred Beetles’, the shell of the Gymnopleuri is liable to crack. The
free admission of air to the interior would have disastrous
consequences, by drying the food, which must keep soft until the grub
has attained its full growth. An intestine which is never empty and
which displays unparalleled docility gets the threatened grub out of
its trouble. There is no need to enlarge upon this point; the Sacred
Beetle has told us all about it.
The insects reared in captivity tell me that, in the Gymnopleuri, the
larva lasts seventeen to twenty-five days and the nymph fifteen to
twenty. These figures are bound to vary, but within narrow limits. I
shall therefore fix each period at approximately three weeks.
Nothing remarkable happens during the nymphal stage. The only thing to
be noted is the curious costume worn by the perfect insect on its first
appearance. It is the costume which the Sacred Beetle showed us: head,
corselet, legs and chest a rusty red; wing-cases and abdomen white. We
may add that, being powerless to burst his shell, which has been turned
into a strong-box by the heat of August, the prisoner, in order to
release himself, waits until the first September rains come to his help
and soften the wall.
Instinct, which under normal conditions amazes us with its unerring
prescience, astonishes us no less with its dense ignorance when
unaccustomed conditions supervene. Each insect has its trade, in which
it excels, its series of actions logically arranged. Here it is really
a master. Its foresight, though unwitting, here surpasses our
deliberate science; its unconscious inspiration is here the superior of
our conscious reason. But divert it from its natural course; and
forthwith darkness succeeds the splendours of light. Nothing will
rekindle the extinguished rays, not even the greatest stimulus that
exists, the stimulus of maternity.
I have given many instances of this strange antithesis, [33] which is
the death-blow to certain theories; I find another and an exceedingly
striking one in the Dung-beetles whose story I have now nearly finished
telling. We are surprised at this clear vision of the future possessed
by our manufacturers of spheres, pears and ovoids; but we are no less
surprised by something totally different, namely, the mother’s profound
indifference to the nursery which but now was the object of her
tenderest cares.
My remarks apply equally to the Sacred Beetle and the two Gymnopleuri,
all of whom display the same admirable zeal when the grub’s comfort has
to be assured, and later, with no less unanimity, the same
indifference. I surprise the mother in her burrow before she has laid
her eggs, or, if the laying be over, before she has added those
meticulous after-touches dictated by her exaggerated conscientiousness.
I install her in a pot packed full of earth, placing her on the surface
of the artificial soil, together with her work, in its more or less
advanced state. In this place of banishment, provided that it be quiet,
there is not much hesitation. The mother, who until now has held her
precious materials tight-clutched, decides to dig a burrow. As the work
of excavation progresses, she drags her pellet down with her, for it is
a sacred thing with which she must not part at any time, even amid the
difficulties of her digging. Soon the cell in which the pear or the
ovoid is to be made is in existence at the bottom of the pot.
I now intervene and turn the pot upside down. Everything is
topsy-turvy; the entrance-gallery and the terminal hall disappear. I
extract the mother and the pellet from the ruins. Once more the pot is
filled with earth; and the same test begins all over again. A few hours
are enough to restore the courage shaken by all this upheaval. For the
second time, the mother buries herself with the heap of provisions
destined for the grub. For the second time also, when the establishment
is finished, the overturning of the pot unsettles everything. The
experiment is renewed. Persisting in its maternal solicitude, if
necessary until its strength gives way, the insect again buries itself,
together with its sphere.
Four times over, in two days, I have thus seen the mother Beetle bear
up under the devastation which I have wrought and start afresh, with
touching patience, on the ruined dwelling. I did not think fit to
pursue the test. You feel some scruples in submitting maternal
affection to such tribulations as these. However, it seems probable
that, sooner or later, the exhausted and bewildered insect would have
refused to go on digging.
My experiments of this kind are numerous; and they all prove that, when
taken from her burrow with her work unfinished, the mother shows
indefatigable perseverance in burying and depositing in a place of
safety the cradle which has begun to take shape though as yet
untenanted. For the sake of a pellet of stuff which the presence of the
egg has not yet turned into a sacred thing, she displays exaggerated
prudence and caution, as well as amazing foresight. No tricks of the
experimenter, no all-upsetting accidents, nothing, unless her strength
be worn out, can divert her from her object. She is filled with a sort
of indomitable obsession. The future of her race requires that the lump
of stuff should descend into the earth; and descend it will, whatever
happens.
Now for the other side of the medal. The egg is laid; everything is in
order underground. The mother comes out. I take hold of her as she does
so; I dig up the pear or ovoid; I place the work and the worker side by
side on the surface of the soil, in the conditions that prevailed just
now. This assuredly is the right moment for burying the pill. It
contains the egg, a delicate thing which a touch of the sun will wither
in its thin wrapper. Expose it for fifteen minutes to the heat of the
sun’s rays; and all will be lost. What will the mother do in this grave
emergency?
She does nothing at all. She does not even seem to perceive the
presence of the object which was so precious to her yesterday, when the
egg was not yet laid. Zealous to excess before the laying is over, she
is indifferent afterwards. The finished work no longer concerns her.
Imagine a pebble in the place of the ovoid or pear: the mother would
treat it no better and no worse. One sole preoccupation urges her: to
get away. I can see that by the manner in which she paces the enclosure
that keeps her prisoner.
That is instinct’s way: it buries perseveringly the lifeless lump and
leaves the quickened lump to perish on the surface. The work to be done
is everything; the work done no longer counts. Instinct sees the future
and knows nothing of the past.