THE BULL ONTHOPHAGUS: THE CELL
Begun to-day and dropped to-morrow, taken up again later and again
abandoned, according to the chances of the day, the study of instinct
makes but halting progress. The changing seasons bring unwelcome
delays, forcing the observer to wait till the following year or even
longer for the answer to his eager questions. Moreover, the problem
often crops up unexpectedly, as the result of some casual incident of
slight interest in itself, and it comes in a form so vague that it
gives little basis for precise investigation. How can one investigate
what has not yet been suspected? We have no facts to go upon and are
consequently unable to tackle the problem frankly.
To collect these facts by fragments, to subject those fragments to
varied tests in order to try their value, to make them into a sheaf of
rays lighting up the darkness of the unknown and gradually causing it
to emerge: all this demands a long space of time, especially as the
favourable periods are brief. Years elapse; and then very often the
perfect solution has not appeared. There are always gaps in our sheaf
of light; and always behind the mysteries which the rays have
penetrated stand others, still shrouded in darkness.
I am perfectly aware that it would be preferable to avoid repetitions
and to give a complete story every time; but, in the domain of
instinct, who can claim a harvest that leaves no grain for other
gleaners? Sometimes the handful of corn left on the field is of more
importance than the reaper’s sheaves. If we had to wait until we knew
every detail of the question studied, no one would venture to write the
little that he knows. From time to time, a few truths are revealed,
tiny pieces of the vast mosaic of things. Better to divulge the
discovery, however humble it be. Others will come who, also gathering a
few fragments, will assemble the whole into a picture ever growing
larger but ever notched by the unknown.
And then the burden of years forbids me to entertain long hopes.
Distrustful of the morrow, I write from day to day, as I make my
observations. This method, one of necessity rather than choice,
sometimes results in the reopening of old subjects, when new
investigations throw light within and enable me to complete or it may
be to modify the first text.
Years ago, I obtained a few noteworthy particulars about the
Onthophagi, thanks to a very rough and ready method of rearing a few of
them jumbled up with other Beetles in whom I was more interested. One
of the earlier volumes gives a rapid sketch of them. [57] The results,
hurriedly and almost fortuitously acquired, inspired me with a wish to
observe systematically and closely the habits, industry and development
of an insect which I had already introduced to the reader in too
summary a fashion. Let us speak once more of the Onthophagi, that
nation of little horned dung-worshippers.
Lately, I have reared the following species, according as I chanced to
pick them up: Onthophagus taurus, Linn., O. vacca, Linn., O furcatus,
Fabr., O. Schreberi, Linn., O. nuchicornis, Linn., O. lemur, Fabr.
There has been no choice on my part; I accept all that present
themselves in sufficient numbers. The first especially abound. I am
delighted, for the Bull Onthophagus is the chief of the clan. There is
none to equal him, if not in dress, for this may be a richer copper in
the others, at least in the handsome horns which are the masculine
prerogative. He will be the object of special attention in my
menagerie. For the rest, as what he teaches me is repeated elsewhere
without noteworthy variations, his history will be that of the whole
tribe.
I capture him, as well as the others, in the course of May. At this
period of genetic awakening, I find them swarming very busily under the
Sheep-droppings, not those which are moulded into olives and scattered
in trails, but those which are ejected in slabs of some size. The first
are too dry and too scanty and the Onthophagus thinks nothing of them;
the second are goodly messes and he works them in preference to any
other material.
The Mule’s copious heap is also largely utilized; but it is very
stringy and, though the Beetle finds plenty in it for his own feasts,
he very seldom uses it for his offspring. Where the nests are
concerned, the Sheep is the main purveyor. Her exceptionally plastic
product at once attracts the custom of the Onthophagi, who are just as
dainty epicures as the Sacred Beetle, the Copris or the Sisyphus. If,
however, the ovine pottage be lacking, they fall back upon the coarser
lump of the Mule, with the aid of a scrupulous selection.
There is no difficulty about bringing up Onthophagi. A spacious
vivarium that lends itself to frolicsome sports is not necessary here;
it would even be inconvenient and would not favour close observation,
because of the tumult prevailing in a numerous and varied crowd. I
prefer a number of separate establishments, simpler and smaller, which
I can carry into my private workroom. They will lend themselves better
to assiduous inspection, without putting me to the trouble of digging.
What receptacles shall I choose?
There are certain glass pots fitted with a tin lid which you screw over
their mouths. They are used for honey, preserved fruits, jam, jelly and
similar products dear to the heart of materfamilias when the winter
scarcity sets in. I procure a dozen of these by clearing the cupboard
in which the preserves are kept. They hold, on the average, about a
pint and three-quarters.
Half-filled with fresh sand and supplied in addition with provisions
obtained from the Sheep’s pastry-shop, each jar receives its share of
Onthophagi, of separate species and with both sexes present. When the
glass houses are used up and the population becomes too dense, I resort
to ordinary flower-pots, furnished according to rule and closed with a
pane of glass. The whole collection is arranged on my large
laboratory-table. My captives are satisfied with their installation,
which provides them with a mild temperature, a nicely-shaded light and
first-class fare.
What more is needed to complete the Dung-beetles’ happiness? Nothing
but the raptures of pairing. They indulge in these freely. Interned in
the second half of May, with not a thought to the new state of things
which puts a stop to their frolics among the thyme, eagerly they seek
one another out, make their overtures and group themselves in couples.
This is an excellent occasion to find the reply to a primary question:
do the Onthophagus father and mother work in conjunction when looking
after the brood; have they a permanent household, similar to that which
we have seen in the Geotrupes, the Sisyphus and the Minotaur; [58] or
is the mating followed by a sudden and definite rupture? The Bull
Onthophagus shall tell us.
I delicately transfer two insects in the act of coupling and establish
them in another, separate jar, provided with victuals and fresh sand.
The moving is performed safely; the entwined pair remain united. A
quarter of an hour afterwards, they separate; the great job is
finished. The food is close at hand. They refresh themselves for a
moment; and then each, without bothering in the least about the other,
digs his burrow and buries himself in solitude.
A week or so passes. The male reappears on the surface; he is restless,
he makes desperate efforts to climb out; the relations are done, quite
done; he wants to get away. By and by, the female comes up in her turn;
she tries the nearest cake, picks the best of it and takes it
underground. She is building her nest. As to her companion, he does not
even notice what is happening: these things do not concern him.
The other captives, of no matter what species, when consulted in the
same manner, give the same reply. The Onthophagus tribe knows nothing
of household ties.
In what respect are those who know them and who observe them so
faithfully any the better off? I do not quite see; or, to be more
candid, I do not see at all. If, in the case of the Geotrupes, I see in
the bulky pudding some slight excuse for the collaboration of the
father, who is a valuable assistant in the fabrication of this kind of
preserve, and if, in that of the Minotaur, the immensely deep well
might suggest to me the need for the trident-wearing helper, who shoots
out the rubbish while the mother goes on digging, I should still be
without an explanation when I came to the Sisyphus, who is very
economical both in provisions and in the labour of excavation and
requires no help with either. I will not deny that, in this last case,
the male is of some use, watching over the pill, lending occasional
help and encouraging the female with his presence; but, after all, the
part which he plays as a collaborator is a very secondary one, and the
mother, one would say, could do without any assistance, as is the rule
among the Scarabæi. Here, besides, we have the Bull Onthophagus, who is
even smaller than the Sisyphus; and this dwarf, unacquainted with a
partnership that would increase her powers twofold, fulfils a task
which is almost equivalent to that of the Beetles who roll their pills
in double harness.
Then how are talents and industries distributed? If we go on
accumulating fact upon fact, observation upon observation, shall we
ever come to know? I venture to doubt it.
I have friends who sometimes say to me:
‘Now that you have collected such a mass of details, you ought to
follow up analysis with synthesis and promulgate a comprehensive theory
of the origin of instincts.’
There’s a rash proposal for you! Because I have turned over a few
grains of sand on the seashore, am I qualified to talk about the ocean
depths? Life has its unfathomable secrets. Human knowledge will be
struck off the world’s records before we know all that is to be said
about a Gnat.
Equally obscure is the question of nest-building. By a nest we
understand any residence constructed purposely to receive the eggs and
to protect the development of the young. The Bees and Wasps excel in
the art. They know how to make cabins out of cotton-stuffs, wax, leaves
or resin; they build turrets of clay and domes of masonry; they mould
earthenware urns. The Spiders vie with them. Remember the
flying-machines, the rose-patterned paraboloids of certain Epeiræ; the
globular bag of the Lycosa; the Labyrinth Spider’s cloisters with their
Gothic arches; the Clotho Spider’s tent and lentiform pockets. [59]
The Locust makes pits surmounted by a frothy chimney; the Mantis whips
her glair into a frothy mass. [60] The Fly and the Butterfly, on the
other hand, know nothing of these fond attentions: they limit
themselves to laying their eggs at spots where the young can find board
and lodging for themselves. [61] The Beetle also is generally extremely
ignorant of the finer points of nest-building. By a very singular
exception, the Dung-beetles, alone among the immense host of wearers of
armoured wing-cases, have a special art of rearing, a system of
upbringing which can bear comparison with that of the most gifted
insects. How did they come by this industry?
Venturesome minds, deluded by the greatly daring theorists, tell us
that the science of the future, rich in evidence drawn from the
mysteries of fibre and cell, will draw up an affiliation-table in which
the animal kingdom will be classified so that the place occupied by a
creature shall inform us of its instincts, without any need of
preliminary observation. We shall determine the aptitudes by means of
learned formulæ, even as numbers are determined by their logarithms. It
is most impressive; but beware: we are dealing with Dung-beetles; let
us consult them before we draw up the logarithmic table of instincts.
The Onthophagus is related to the Copris, the Scarab and the Sisyphus,
all of whom are versed in the art of making shapely pellets. Let us try
to tell beforehand, according to the place which she occupies in the
insect-table, going merely by the formula, what she is able to do in
the way of nest-building.
She is small, I agree; but littleness does not diminish talent in the
least, as witness the Titmouse, with his pendulous nest, the Wren and
the Canary, who, although among the smallest of our little birds, are
incomparable artists. The near kinswomen of the Onthophagus excel in
making beautiful ovoids and pear-shaped gourds. She herself, so tiny
and so precise, ought to do even better.
Well, the table deceives us, the formula lies: the Onthophagus is a
very indifferent artist; her nest is a rudimentary piece of work,
hardly fit to be acknowledged. I obtain it in profusion from the six
species which I have brought up in my jars and flower-pots. The Bull
Onthophagus alone provides me with nearly a hundred; and I find no two
precisely alike, as pieces should be that come from the same mould and
the same workshop.
To this lack of exact similarity, we must add inaccuracy of shape, now
more now less accentuated. It is easy, however, to recognize among the
bulk the pattern upon which the clumsy nest-builder works. It is a sack
shaped like a thimble and standing erect, with the spherical
thimble-end at the bottom and the circular opening at the top.
Sometimes the insect establishes itself in the central region of my
apparatus, in the heart of the earthy mass; then, the resistance being
the same in every direction, the sack-like shape is pretty accurate.
But, generally, the Onthophagus prefers a solid basis to a dusty
support and builds on the walls of the jar, especially on the bottom.
When the support is vertical, the sack is a longitudinal section of a
short cylinder, with the smooth flat surface against the glass and a
rugged convexity every elsewhere. If the support be horizontal, as is
most frequently the case, the cabin is a sort of undecided oval
lozenge, flat at the bottom, bulging and vaulted at the top. To the
general inaccuracy of these contorted shapes, regulated by no very
definite pattern, we must add the coarseness of the surfaces, all of
which, with the exception of the parts touching the glass, are covered
with a crust of sand.
The manner of procedure explains this uncouth exterior. As laying-time
draws nigh, the Onthophagus bores a cylindrical pit and descends
underground to a moderate depth. Here, working with her forehead, her
chin and her fore-legs, which are toothed like a rake, she forces back
and heaps around her the materials which she has moved, so as to obtain
as best she may a nest of suitable size.
The next thing is to cement the crumbling walls of the cavity. The
insect climbs back to the surface by way of its pit; it gathers on its
threshold an armful of mortar taken from the cake whereunder it has
elected to set up house; it goes down again with its burden, which it
spreads and presses upon the sandy wall. Thus it produces a concrete
casing, the gravel of which is supplied by the wall itself and the
cement by the produce of the Sheep. After a few trips and repeated
strokes of the trowel, the pit is plastered on every side; the walls,
encrusted all over with grains of sand, are no longer liable to give
way.
The cabin is ready: it now wants only a tenant and stores. First, a
large free space is made at the bottom: the hatching-chamber, where the
egg is laid on the wall. Next comes the collecting of the provisions
intended for the grub, a collecting done with scrupulous care.
Recently, when building, the insect worked upon the outside of the
doughy mass and took no notice of the earthy blemishes. Now, it
penetrates to the very centre of the lump, through a gallery that looks
as though it were made with a punch. When trying a cheese, the buyer
employs a scoop, the hollow, cylindrical taster which is driven well in
and pulled out with a sample taken from the middle of the cheese. The
Onthophagus, when collecting for her grub, goes to work as though
equipped with one of these tasters. She bores an exactly round hole
into the piece which she is exploiting; she goes straight to the
middle, where the material, not being exposed to the contact of the
air, has kept more savoury and pliable. Here and here alone are
gathered the armfuls which, gradually stowed away, kneaded and heaped
up to the requisite extent, fill the sack to the top. Lastly, a plug of
the same mortar, the sides of which are made partly of sand and partly
of stercoral cement, roughly closes the cell, in such a way that an
external inspection does not allow one to distinguish front from back.
To judge of the work and its merit, we must open it. A large empty
space, oval in shape, occupies the rear end. This is the birth-chamber,
huge in dimensions compared with its contents, the egg fixed on the
wall, sometimes at the bottom of the cell and sometimes on the side.
This egg is a tiny white cylinder, rounded at each tip and measuring a
millimetre [62] in length immediately after it is laid. With no other
support than the spot on which the oviduct has planted it, it stands on
its hinder end and projects into space.
A more or less enquiring glance is quite surprised to find so small a
germ contained in so large a box. What does the tiny egg want with all
that room? When carefully examined within, the walls of the chamber
suggest another question. They are coated with a fine greenish pap,
semifluid and shiny, the appearance of which does not agree with either
the external or the internal aspect of the lump from which the insect
has extracted its materials. A similar lime-wash is observed in the
nest which the Scarab, the Copris, the Sisyphus, the Geotrupes and
other makers of stercoraceous preserves contrive in the very heart of
the provisions, to receive the egg; but nowhere have I seen it so
plentiful, in proportion, as in the hatching-chamber of the
Onthophagus. Long puzzled by this brothy wash, of which the Sacred
Beetle provided me with the first instance, I at one time took the
thing for a layer of moisture oozing from the bulk of the victuals and
collecting on the surface of the enclosure without other effort than
capillary action. That was the interpretation of this varnish which I
accepted in various earlier passages.
I was wrong. The truth is something much more remarkable. To-day,
better informed by the Onthophagus, I reopen the question: is this
lime-wash, this semifluid cream, the result of a natural oozing, or is
it the product of maternal foresight? A simple and conclusive
experiment will give us the answer. I ought to have made it at the
outset. I did not think of it, because the simple is usually the last
thing that we call to our aid. Here is the experiment.
I pack a little glass jar, the size of a Hen’s egg, with Sheep-dung as
employed by the Onthophagus. With a glass rod, which leaves a perfectly
smooth impression, I make a cylindrical cavity in the heap about an
inch deep. After withdrawing the rod, I cover the orifice with a slab
of the same material; and I protect the whole against desiccation by
means of an hermetically closed lid. It is the Sacred Beetle’s pear,
with its hatching-chamber, on a larger scale; it is the Onthophagus’
thimble, enormously exaggerated. I may say that, after the withdrawal
of the glass rod, the surface of the cavity is a dull, greenish black,
with not a trace of extravasated shiny moisture. If an oozing by
capillary action really takes place, the semifluid varnish will appear;
if nothing of the kind should occur, the surface will remain dull.
I wait a couple of days to allow the capillary sweating to take effect,
if such a process there be. Then I examine the cavity. There is no
shiny wash on the walls; they look as dull and dry as at the beginning.
Three days later, I make a fresh inspection. Nothing has changed: the
pit made by the glass rod shows no sign of exudation; it is even a
little drier. So capillary action and its extravasations have nothing
to do with the matter.
What then is the lime-wash that is found in every cell? The answer is
inevitable: it is something produced by the mother, a special gruel, a
milk-food elaborated for the benefit of the new-born grub.
The young Pigeon puts his beak into that of his parents, who, with
convulsive efforts, force down his gullet first a casein mash secreted
in the crop and later a broth of grains softened by being partly
digested. He is fed upon disgorged foods, which are kind to the frailty
and inexperience of a young stomach. The grub of the Onthophagus is
brought up in much the same way, at the start. To assist its first
attempts at swallowing, the mother prepares for it, in her crop, a
light and strengthening cream.
To pass the dainty from mouth to mouth is impossible in her case: the
construction of new cells keeps her busy elsewhere. Moreover—and this
is a more serious point—the laying takes place egg by egg, at very long
intervals, and the hatching is pretty slow: time would fail, had the
family to be brought up in the manner of the Pigeons. Another method is
perforce required. The infants’ food is disgorged all over the walls of
the cabin, in such a way that the nurseling finds itself surrounded
with an abundance of bread and jam, in which the bread, the meat for
the strong, is represented by the uncooked material, as supplied by the
Sheep, while the jam, the food for the babe, is represented by the same
material daintily prepared beforehand in the mother’s stomach. We shall
see the grub presently lick first the jam all around it and then
stoutly attack the bread. One of our own children would behave no
otherwise.
I should have liked to catch the mother in the act of disgorging and
spreading her broth. I did not succeed in doing so. The proceedings
take place in a tiny niche; and the busy cook blocks out the view. Also
her fluster at being exhibited in broad daylight at once arrests the
work.
If direct observation be lacking, at least the appearance of the
material and the result of my experiment with the glass rod speak very
plainly and tell us that the Onthophagus, here rivalling the Pigeon,
but with a different method, disgorges the first mouthfuls for her
sons. And the same may be said of the other Dung-beetles skilled in the
art of building a hatching-chamber in the centre of the provisions.
No elsewhere in the insect world, except among the Bees, who prepare
disgorged food in the shape of honey, is such solicitude seen. The
dung-workers edify us with their morals. Several of them practise
association in couples and found a household; several anticipate the
process of suckling, that supreme expression of maternal tenderness, by
turning their crop into a nipple. Life has its freaks. It settles amid
ordure the creatures most highly endowed with domestic qualities. True,
from there it mounts, with a sudden flight, to the sublime virtues of
the bird.
Among the Onthophagi the egg grows considerably larger after it is
laid; it almost doubles its linear dimensions, thus increasing the bulk
eightfold. This growth is general among the Dung-beetles. If you note
the size of an egg recently laid by any species and measure it again
when the grub is about to be born, you will be quite surprised at the
singular progress which it has made. The Sacred Beetle’s egg, for
instance, which at first is lodged pretty spaciously in its
hatching-chamber, swells until it nearly fills the cavity.
The first idea that occurs to the mind is a very simple and tempting
one, namely, that the egg feeds. Surrounded by strongly-flavoured
effluvia, it becomes impregnated with emanations which distend its
flexible tunic; it grows by a sort of alimentary respiration, just as a
seed swells in fertile soil. That is how I pictured things at the
beginning, when the delicate problem presented itself for the first
time. But is this really what happens? Ah, if it were enough, when we
were in need of food, to stand outside a cook-shop and inhale the smell
of the good things that were being prepared inside, what a different
world it would seem, to many of us! It would be too lovely!
The Onthophagus, the Copris and the other Beetles with cream-washed
hatching-chambers are a delusion and a snare to us, with their eggs
which are so ready to swell. The Minotaurus tells me so, somewhat late
in the day; she compels me to reconsider my earlier interpretations
entirely. Her egg is not enclosed in a hollow inside the victuals whose
emanations might explain its growth; it is outside the sausage, a good
way underneath, surrounded by sand on every side; and nevertheless it
increases in size just as well as those lodged in a succulent cabin.
Moreover, the new-born grub surprises me by its chubbiness; it is seven
or eight times as big as the egg whence it comes; the contents vastly
exceed the capacity of the container. Besides, before touching the food
from which it is separated by a ceiling of sand, the grub for a certain
time continues its strange growing, as though new materials were being
added to those which came out of the egg.
Here, in the dry sand, it is impossible to talk of effluvia capable of
providing the wherewithal for the grub to wax big and fat. Then to what
do both the egg and the new-born grub owe their growth? The
Languedocian Scorpion [63] gives us an excellent clue. When passing
from a sort of larval stage to the final form, which is the same as
that of the adult, we have seen him suddenly double his length and
consequently increase eightfold in bulk before taking the least scrap
of nourishment. A highly complex process of co-ordination and
adjustment takes place in the interior of the organism; and the
dimensions increase without the addition of new material.
An animal is a structure capable of becoming more spacious with the
same amount of materials. Everything depends upon the molecular
architecture, which becomes more and more refined by the tremors of
life. The contents of the egg, a compact mass, expand into a creature
which is all the bulkier for its richness in organs for diverse
functions. Even so, the locomotive engine, the creature of industry,
occupies more space than the iron, its raw material, melted down into a
single ingot.
When the shell is able to stretch, the egg swells under the thrust of
its contents, which form into an organic whole and dilate. This is the
case with the various Dung-beetles. When the shell is hard and rigid, a
void is made by evaporation at the thick end; and this excess of space
supplies the room necessary for the increase in volume of the contents.
This is the case with the birds, which develop within a chalky
enclosure that does not alter in size. Both of them dilate, with this
difference that the soft shell allows the inside work to be perceived
outside, whereas the stiff shell reveals nothing.
Lastly, the hatching does not always stop the growth that is not
preceded by feeding. For a little while longer the larva continues to
increase in size; it completes the work of acquiring stability in its
new equilibrium, the equilibrium of a living creature; it improves its
physique by supplementary stretching. The Scorpion has already told us
this; the grub of the Minotaurus and many others assure us of the same
thing. It is, on a smaller scale, what we saw before in the Locust’s
wing, [64] which, issuing from a very small sheath, soon unfurls into a
sail of generous breadth.
Twice, therefore, am I changing my opinions in this history of the
Dung-beetles: first, on the subject of the paste spread on the walls of
the natal chamber; secondly, on the subject of the egg that increases
in size after it is laid. I have corrected my statements without being
greatly ashamed of my mistakes, for it is difficult indeed to reach the
vein of truth at the first tentative boring. There is only one means of
never blundering, which is never to do anything and, above all, to let
ideas alone.