THE SACRED BEETLE: THE LARVA
Under the thin ceiling of the burrow, the Sacred Beetle’s egg undergoes
the varying influences of the sun, the supreme incubator. Consequently
there is not, nor can there be, any fixed date for the quickening of
the germ. In very hot, sunny weather, I have obtained a grub five or
six days after the egg was laid; with a more moderate temperature, I
have had to wait until the twelfth day. June and July are the
hatching-months.
As soon as the new-born grub has flung aside its swaddling clothes, it
forthwith bites into the walls of its chamber. If starts eating its
house, not anyhow, but with unerring wisdom. If it nibbled at the thin
side of its cell—and there is nothing to dissuade it, for here as
elsewhere the materials are of excellent quality—if its mandibles
scraped the extreme end of the nipple, the weakest point, it would make
a breach in the protecting wall before it had sufficient putty to
repair that breach. This putty is the material which we shall see the
larva using later, when accidents of that kind occur from external
causes.
If it ate into its heap of provisions at random, it would expose itself
to serious risks from the outside; at the very least it would be liable
to slip out of its cradle and tumble to the ground through the open
window. Once it falls out of its cell, there is no hope for the little
grub. It will not know how to make its way back to the larder; and, if
it does find its heap of provisions again, it will be repelled by the
hard rind with its bits of grit and sand. In its wisdom, greater than
any possessed by the young of the higher animals, which are always
watched over by a mother, the new-born larva, still sleek and shiny
with the slime of the egg, thoroughly knows the danger and avoids it by
masterly tactics.
Though all the food around it is alike and all is to its taste,
nevertheless it tackles exclusively the floor of its cell, a floor
continued by the bulky sphere in which bites will be permissible in
every direction, as the consumer pleases.
Can any one explain why this particular spot is chosen as the
starting-point, when there is nothing to distinguish it, from the point
of view of food? Could the tiny creature be warned of the proximity of
the outer air by the effect which a thin wall has on its sensitive
skin? If so, how is this effect produced? Besides, what does a grub,
that moment born, know of outside dangers? I am quite in the dark.
Or rather I begin to see daylight. I recognize once again, under
another aspect, what was taught me some years ago by the Scolia-wasps
[22] and the Sphex-wasps, [23] those scientific eaters, those skilful
anatomists, who can discriminate so well between the lawful and the
unlawful and are consequently able to devour their prey without killing
it until the end of the meal. The Sacred Beetle has his own complicated
art of eating. Though he need not trouble about the preservation of the
victuals, which are not liable to go bad, he has nevertheless to guard
against ill-timed mouthfuls, which would rob him of his shelter. Of
these dangerous mouthfuls, the earliest are the most to be feared,
because of the creature’s weakness and the thinness of the wall. As its
protection, therefore, the grub has, in its own way, the primal
inspiration without which none would be able to live; it obeys the
imperious voice of instinct, which says:
‘There shalt thou bite and no elsewhere.’
And, respecting all the rest, however tempting, it bites at the
prescribed spot; it eats into the pear at the bottom of the neck. In a
few days it has worked its way deep down into the mass, where it waxes
big and fat, transforming the filthy material into a plump larva
gleaming with health, ivory-white with slate-coloured reflections and
without a speck of dirt upon it. The matter which has disappeared, or
rather which has been remelted in life’s crucible, leaves empty a round
cell into which the grub fits itself, curving its back under the
spherical dome and bending double.
The time has come for a sight stranger than any yet displayed to me by
the industrial prowess of an insect. Anxious to observe the grub in the
intimacy of its home, I open in the belly of the pear a little
peep-hole half a centimetre [24] square. The head of the recluse at
once appears in the opening, to enquire what is happening. The breach
is perceived. The head disappears. I can just see the white back
turning about in the narrow cabin; and, then and there, the window
which I have made is closed with a soft, brown paste, which soon
hardens.
The inside of the cabin, said I to myself, is no doubt a semifluid
porridge. Turning round, as is shown by the sudden slide of its back,
the grub has collected a handful of this material and, completing the
circuit, has stuck its load, by way of mortar, in the breach which it
considered dangerous. I remove the plug. The grub acts as before, puts
its head at the window, withdraws it, spins round as easily as a nut in
its shell and forthwith produces a second plug as ample as the first.
Forewarned of what was coming, this time I saw more clearly.
What a mistake I had made! However, I am not so much startled as I
might be: in the art of defence, animals often employ means which our
imagination would not dare to contemplate. It is not the grub’s head
that is presented at the breach, after the preliminary twisting: it is
the other extremity. It does not bring a lump of its alimentary dough,
gathered by scraping the walls: it excretes upon the aperture to be
closed, which is a much more economical proceeding. Sparingly measured
out, the rations must not be wasted: there is just enough to live upon.
Besides, the cement is of better quality; it soon sets. Lastly, the
urgent repairs are more quickly effected if the intestines lend their
kindly aid.
They do, in point of fact, and to an astonishing degree. Five, six
times in succession and oftener, I remove the plug; and, time after
time, the mortar ejects a copious discharge from its apparently
inexhaustible reservoir, which is ever at the mason’s service, without
an interval for rest. The grub is already beginning to resemble the
Sacred Beetle, whose stercoraceous prowess we know: it is a past master
in the art of dunging. It possesses above any other animal in the world
an intestinal docility which anatomy presently will undertake to
explain to us in part.
The plasterer and the mason have their trowels. In the same way, the
grub, that zealous repairer of breaches made in its home, has a trowel
of its own. The last segment is lopped off slantwise and carries on its
dorsal surface a sort of inclined plane, a broad disk surrounded by a
fleshy pad. In the middle of the disk is a slit, forming the
cementing-aperture. There you have your trowel, a most respectable one,
flattened out and supplied with a rim to prevent the compressed matter
from flowing away uselessly.
As soon as the mass of plastic matter has been emitted, the levelling-
and compressing-instrument sets to work to introduce the cement well
into the irregularities of the breach, to push it right through the
thickness of the ruined portion, to give it consistency and smooth it.
After this trowel-work, the grub turns round: it comes and finishes the
job with its wide forehead and improves it with the tip of its
mandibles. Wait a quarter of an hour; and the repaired portion will be
as firm as the rest of the shell, so quickly does the cement set.
Outside, the repairs are betrayed by the irregular projections where
the stuff has been forced out, the part which the trowel could not
reach; but, inside, there is no trace of the breakage: the usual polish
has been restored at the damaged spot. A plasterer stopping a hole in
one of our walls could produce no better piece of work.
Nor do the grub’s talents end here. With its cement it becomes the
mender of pots and pans. Let me explain. I have compared the outside of
the pear, which, when pressed and dried, becomes a stout shell, with a
jar containing fresh food. In the course of my excavations, sometimes
made on difficult soil, I have happened occasionally to break this jar
with an ill-directed blow of my trowel. I have collected the potsherds,
pieced them together, after restoring the grub to its place, and kept
the whole thing united by wrapping it in a scrap of newspaper.
On reaching home, I have found the pear put out of shape, no doubt, and
seamed with scars, but just as solid as ever. During the walk, the grub
had restored its ruined dwelling to condition. Cement injected into the
cracks joined the pieces; inside, a thick plastering strengthened the
inner wall, so much so that the repaired shell was quite as good as the
untouched shell, except for the irregularity of the outside. In its
artistically-mended stronghold the grub found the peace essential to
its existence.
The time has come to ask ourselves the reason for this plasterer’s
craft. Destined to live in complete darkness, does the larva stop the
cracks made in its house in order to avoid the unwelcome intrusion of
the light? But it is blind. There is no trace of an organ of sight on
its yellowish headpiece. The absence of eyes, however, does not
authorize us to deny the influence of the light, an influence which
perhaps is vaguely resented by the grub’s delicate skin. Proofs are
required. Here they are.
I manage to make my breach almost in the dark. The little light that
remains is just sufficient to guide my house-breaking-implement. When
the opening is made, I at once lower the shell into a dark box. A few
minutes later, the hole is stopped. Despite the darkness in which it
found itself, the grub has thought fit to seal up its cell.
In small jars packed full of provisions, I bring up larvæ taken from
their native pear. A pit is dug in the mass of foodstuffs, ending at
the bottom in a hemisphere. This cavity, representing about the half of
the pear, will be the artificial cell given in exchange for the natural
one. I put the grubs on which I am experimenting into separate cells.
The change of residence produces no appreciable anxiety. Finding the
food of my selecting very much to their taste, they bite into the walls
with their customary appetite. Exile in no way perturbs those stoical
stomachs; and my attempts at breeding are pursued unchecked.
A remarkable thing now happens. All my transplanted ones work little by
little to complete the round nest of which my pit represented only the
lower half. I have provided the flooring. They propose to add a
ceiling, a dome, and thus to shut themselves up in a spherical
enclosure. The materials are the putty supplied by the intestines; the
building-tool is the trowel, the inclined plane of the final segment.
Soft bricks are laid on the margin of the well. When these have set,
they serve as a support for a second row, sloping slightly inwards.
Other rows follow, marking the curve of the general structure more and
more distinctly. Also, from time to time, a wriggle of the hinder part
assists in determining the spherical conformation. In this way, without
any supporting scaffold, without the cradle indispensable to our
architects in building an arched roof, a commanding dome is obtained,
built upon space and completing the sphere which I began.
Some of them shorten the work. The glass wall of the little jar
occasionally comes within range. Its smooth surface suits the taste of
these fastidious polishers; its curve, to a certain extent, coincides
with that of their plan. They make use of it, doubtless not from
economy of labour and time, but because, to their mind, the smooth
round wall is a thing of their own making. In this way there is
reserved, on the sides of the cupola, a large glazed window which
answers my purpose admirably.
Well, the grubs which, all day long and for weeks on end, receive the
bright light of my study through this window of mine keep as quiet as
the others, eating and digesting, and never trouble to shut out any
unwelcome rays with a blind made of their putty. We may take it
therefore that, when the larva so eagerly closes the breach which I
have made in its chamber, its object is not to protect itself from the
light.
Does it fear draughts then, when it scrupulously fills up the least
cranny through which the air might enter? This again is not the
solution. The temperature is the same in my room and in the grub’s;
besides, when I perpetrate my burglaries, the atmosphere in my study is
absolutely still. I do not examine the prisoner in a gale, but in the
calm of my workroom, in the even profounder calm of a glass jar.
There can be no question of a cold breeze, which would be painful to a
very sensitive skin; and nevertheless the air is the enemy to be
avoided at all costs. If it flowed in at all plentifully through a
breach, with the dryness which the July heat imparts to it, the
provisions would be dried up. Faced with an uneatable biscuit, the grub
would become languid and anæmic and would soon perish of hunger. The
mother, to the best of her abilities, has guarded her offspring against
death from starvation by making her pear round and giving it a stout
rind; but, for all that, her children are not released from every
obligation to watch their rations. If they want bread that keeps soft
and fresh to the last, they must in their turn see to it that the
provision-jar is properly closed. Crevices may appear, fraught with
grave danger. It is important to stop them up without delay. This, if I
be not utterly at fault, is the reason why the grub is a plasterer
armed with a trowel and provided with a workshop that can always
furnish plenty of putty. The pot-mender repairs his cracked jar in
order to keep his bread nice and soft.
A serious objection suggests itself. The slits, the breaches, the
vent-holes which I see so zealously cemented are the work of my
instruments: tweezers, penknife, dissecting-needles. It cannot be
maintained that the grub is endowed with its strange talent to protect
itself against the troubles brought upon it by human curiosity. What
has it to fear from man, in its life underground? Nothing, or next to
nothing. Since the Sacred Beetle started rolling his ball under the
broad canopy of the sky, I am probably the first to worry his family in
order to make them talk to me and instruct me. Others will come after
me perhaps; but they will be very few! No, man’s destructive
interference is not worth the pains of providing one’s self with a
trowel and cement. Then why this art of stopping crevices?
Wait. In its apparently peaceful home, in its round shell which seems
to give it such perfect security, the grub nevertheless has its
troubles. Which of us has not, from the greatest to the smallest? They
begin at birth. Though I have only touched the fringe of the matter, I
am already aware of three or four sorts of grievous accidents to which
the Sacred Beetle’s larva is liable. Plants, animals, blind physical
forces, all work its ruin by destroying its larder.
Competition is rife around the cake served up by the Sheep. When the
mother Scarab arrives to take her share and manufacture her pill, the
bit is often at the mercy of fellow-banqueters of whom the smallest are
the most to be dreaded. There are especially little Onthophagi, earnest
workers crouching under the shelter of the cake. Some prefer to plunge
into the richest part and bury themselves ecstatically in its luscious
depths. One of these is Schreber’s Onthophagus, who is a shiny
ebon-black, with four red spots on his wing-cases. Another is the
smallest of our Aphodii (Aphodius pusillus, Herbst), who confides her
eggs, here and there, to the thick part of the cake. In her hurry, the
mother Scarab does not examine her harvest very carefully. While some
of the Onthophagi are removed, others, buried in the centre of the
mass, escape notice. Besides, the Aphodius’ eggs are so small that they
elude her vigilance. In this way a contaminated lump of paste is taken
into the burrow and moulded.
The pears in our gardens suffer from vermin which disfigure them with
scars. The Sacred Beetle’s pears suffer even worse ravages. The
Onthophagus shut in by accident ferrets about and pulls them to pieces.
When, filled to repletion, the glutton wishes to make his exit, he
pierces them with circular holes large enough to admit a lead-pencil.
The evil is worse still with the Aphodius, whose family hatch, develop
and undergo their transformation in the very heart of the provisions.
My notes contain descriptions of pears perforated in every direction,
riddled with a multitude of holes that serve for the escape of the tiny
dung-worker, a parasite in spite of himself.
With table-fellows such as these, who bore ventilating-shafts in the
provisions, the Sacred Beetle’s grub dies if the miners be numerous.
Its trowel and mortar cannot cope with so great a task. They can cope
with it if the damage be slight and the intruders few. At once stopping
up every passage that opens around it, the grub holds its own against
the invader; it disgruntles him and drives him away. The pear is saved
and preserved from internal desiccation.
Various Cryptogamia have a finger in the pie. They invade the fertile
soil of the pill, make it rise in scales, split it with fissures by
implanting their pustules. In its shell cracked by this vegetation, the
grub would die were it not for the safeguard of its mortar, which puts
an end to these desiccating vent-holes.
It puts an end to them in a third case, the most frequent of all.
Without the intervention of any ravager, whether animal or plant, the
pear pretty often peels of its own accord, swells and tears. Is this
due to a reaction in the outer layer, which was too tightly pressed by
the mother when modelling? Is it due to an attempt at fermentation? Or
is it not rather the result of a contraction similar to that of clay,
which splits in drying? All three causes might very well play their
part.
But, without saying anything positive on this point, I will draw
attention to certain deep fissures which seem to threaten the soft
bread with desiccation, inadequately protected as it is by the cracked
jar. Have no fear that these spontaneous breaches will do any harm: the
larva will soon put them right. In the distribution of gifts, it was
not for nothing that the trowel and putty were awarded to the Sacred
Beetle’s grub.
We will now give a brief description of the larva, without stopping to
enumerate the articulations of the palpi and antennæ, which are
wearisome details of no immediate interest. It is a fat grub and has a
fine, white skin, with pale slate-coloured reflections proceeding from
the digestive organs, which are visible when you hold the creature to
the light. Bent into a broken arch or hook, it is not unlike the grub
of the Cockchafer, but has a much more ungainly figure, for, on its
back, at the sudden bend of the hook, the third, fourth and fifth
segments of the abdomen swell into an enormous hump, a tumour, a bag so
prominent that the skin seems on the point of bursting under the
pressure of the contents. This is the animal’s most striking feature:
the fact that it carries a knapsack.
The head is small, in proportion to the grub’s size, is slightly
convex, bright-red and studded with a few pale bristles. The legs are
fairly long and sturdy, ending in a pointed tarsus. The grub does not
use them as a means of progression. When taken from its shell and
placed upon the table, it struggles in clumsy contortions without
succeeding in shifting its position; and the helpless creature betrays
its anxiety by repeated discharges of its mortar.
Let us also mention the terminal trowel, that last segment lopped into
a slanting disk and rimmed with a fleshy pad. In the centre of this
inclined plane is the open stercoraceous slit, which thus, by a very
unusual inversion, occupies the upper surface. A huge hump and a
trowel: that gives you the insect in two words.
In his Histoire naturelle des coléoptères de France, Mulsant describes
the larva of the Sacred Beetle. He tells us with meticulous detail the
number and shape of the joints of the palpi and antennæ; he sees the
hypopygium [25] and its pointed bristles; he sees a multitude of things
in the domain of the microscope; and he does not see the monstrous
knapsack that takes up almost half the insect, nor does he see the
strange configuration of the last segment. There is not a doubt in my
mind that the writer of this minute description has made a mistake: the
larva of which he speaks is nothing like that of the Sacred Beetle.
We must not finish the history of the grub without saying a few words
about its internal structure. Anatomy will show us the works wherein
the cement employed in so eccentric a manner is manufactured. The
stomach or chylific ventricle is a long, thick cylinder, starting from
the creature’s neck after a very short œsophagus. It measures about
three times the insect’s length. In its last quarter, it carries a
voluminous lateral pocket distended by the food. This is a subsidiary
stomach in which the supplies are stored so as to yield their nutritive
principles more thoroughly. The chylific ventricle is much too long to
lie straight and twists round in front of its appendix, in the form of
a large loop occupying the dorsal surface. It is to contain this loop
and the side-pocket that the back swells into a hump. The grub’s
knapsack is, therefore, a second paunch, an annexe, as it were, of the
stomach, which is by itself incapable of holding the voluminous
digestive apparatus. Four very fine, very long tubular glands, very
much entangled, four Malpighian vessels mark the limits of the chylific
ventricle.
Next comes the intestine, which is narrow and cylindrical and rises in
front. The intestine is followed by the rectum, which pushes backwards.
This last, which is exceptionally large and furnished with stout walls,
is wrinkled across, bloated and distended with its contents. There you
have the roomy warehouse in which the digestive refuse accumulates;
there you have the mighty ejaculator, ever ready to provide cement.