If you seek among writers for information as to the habits of Scarabæus
sacer in particular, and on the dung robbers in general, you find that
science has not got beyond some of the beliefs current in the time of
the Pharaohs. We are told that the ball which is dragged along contains
an egg, and is a cradle where the larva will find board and lodging.
The parents roll it over rough ground to make it round, and when shocks
and shakes and tumbles all along the slopes have shaped it properly,
they bury it and abandon it to mother earth.
So rough a start in life always seemed to me unlikely. How could a
beetle’s egg, so tender and fragile as it is, endure the rocking of its
rolling cradle? There exists in the germ a spark of life which the
slightest touch, the merest trifle, can extinguish, and is it likely
that the parents should take it into their heads to lug it about over
hill and dale for hours? Not they; maternal tenderness does not subject
its progeny to the martyrdom of Regulus.
However, something more than logical reasoning was required to sweep
away received opinions. I therefore opened hundreds of balls rolled by
the dung beetles and others out of holes dug under my eyes, and never,
never did I find either a central niche or an egg in the pellets. They
are invariably rough heaps of food, hastily shaped, with no particular
structure inside them, merely provender with which the beetles shut
themselves up to enjoy an orgy in peace for some days. They covet and
steal them with an energy which they certainly would not show if it
implied new family cares. It would be absurd for one Scarabæus to steal
the eggs of another, each having enough to do in securing the future of
its own. So on that point no more doubt can exist; the balls rolled by
beetles never contain eggs.
My first attempt to resolve the thorny question as to the bringing up
of the larva was by constructing an ample enclosure with an artificial
soil of sand and soil constantly renewed. Some twenty Scarabæus sacer
were introduced, together with Copris, Gymnopleurus, and Onthophagus,
and never did entomological experiment cost me so many mortifications.
The main difficulty was to renew the food. My landlord owned a stable
and a horse. I gained the confidence of his servant, who first laughed
at my plans, and then allowed himself to be gained over by a silver
coin. Every breakfast for my beetles cost twopence halfpenny; never
before did the budget of a scavenger beetle amount to such a sum, I can
still see and shall always see Joseph, as, when after grooming his
horse of a morning, he would raise his head a little above the wall
between the two gardens and call “Heigh! heigh!” on which I would hurry
to receive a pot of manure. Discretion on both sides was necessary, as
will be seen. One day his master appeared at the moment of transfer,
and made up his mind that all his manure went over the wall, and that
what he wanted for his cabbages went to grow my verbenas and narcissus.
Vainly did I try to explain; my explanations seemed to him mere jests.
Joseph got a sound scolding, was called this and that, and threatened
with dismissal if it happened again. It did not.
I still had the resource of going bashfully along the road with a twist
of paper to gather up stealthily provisions for my pupils. I did so,
and do not blush for it. Sometimes fate was kind. A donkey carrying the
produce of the market-gardens of Château-Renard and Barbentane to
Avignon would depose an offering as he passed my door. Such a gift,
instantly collected, enriched me for several days. In short, by hook or
by crook, by watching for a dropping, or turning diplomatist to get
one, I succeeded in feeding my captives. If success is earned by an
experiment conducted with a fervour that nothing can discourage, my
experiment deserved to prosper. It did not. After some time my
Scarabæi, consumed by home-sickness in a space which deprived them of
their wider movements, let themselves die miserably without revealing
their secret. Gymnopleurus and Onthophagus responded better to my
expectations. In due time I shall use the information furnished by
them.
Along with my attempts at education in an enclosed space, I carried on
direct researches, the results of which were far from what I desired. I
felt that I must have assistants. Just then a joyous band of children
were crossing the high land. It was a Thursday, and oblivious of school
and hated lessons, an apple in one hand and a piece of bread in the
other, they were coming from the neighbouring village of Les Angles and
wending their way to search on the bare hill where the bullets drop
when the garrison is shooting at a mark. A few bits of lead, worth
about a halfpenny, were the object of this early morning expedition.
The tiny rosy flowers of wild geranium enamelled the turf which for a
brief moment beautified this Arabia Petrea; the water wagtail, half
black, half white, uttered its scornful cry as it fluttered from one
point of rock to another; on the threshold of burrows, dug at the foot
of tufts of thyme, the field-crickets filled the air with their
monotonous symphony. And the children were happy in this festival of
spring—happier still at their prospective riches—that halfpenny which
they would get in return for the bullets they would find, that
halfpenny which would enable them next Sunday to buy at the stall set
up before the church two peppermint bull’s-eyes—two great bull’s-eyes
at a farthing apiece!
I accosted the tallest, whose wide-awake air gave me hopes of him; the
little ones formed a circle, each munching his apple; I explained the
matter and showed them Scarabæus sacer rolling his ball, and told them
that in a like ball, buried somewhere, I knew not where, a hollow is
sometimes found, and in this hollow a grub. The thing to be done was to
search about and watch the beetles in order to find such a ball. Those
with no maggot would not count. To stimulate the children by a fabulous
sum which would henceforward secure to me the time hitherto devoted to
some farthing’s worth of lead, I promised a franc, a lovely new coin
worth twenty halfpennies, for each inhabited ball. At the mention of
this sum eyes opened wide with delightful naïveté. I had quite upset
their ideas on the subject of money by naming this exorbitant price as
the value of a piece of dirt. Then, to show I was in good earnest, I
distributed some halfpence to clinch the bargain. The following week at
the same day and hour I was to appear at the same place and faithfully
perform the conditions of our compact towards all who should have made
the precious discovery. Having thoroughly posted up all the party, I
dismissed the children. “He really means it!” they said as they went
away; “he really means it! If we could only get one apiece!” and with
hearts swelling with sweet hope, they clinked their pence in the hollow
of the hand. The flattened bullets were forgotten. I saw the children
scatter over the plain and hunt about.
On the appointed day the week after I returned to the tableland
confident of success. My young helpers would no doubt have mentioned
this lucrative trade in beetle-balls to their comrades and shown their
handsels to convince the incredulous. Accordingly I found a larger
party assembled than the first time. On seeing me they ran up, but
there was no eagerness, no shout of joy. I saw that things had gone
ill. Many times on coming out of school had they sought for what I had
described, but in vain. Some balls, found underground with the
Scarabæus, were brought, but they were mere heaps of food, and there
was no grub. Fresh explanations were given and a new appointment was
made for the following Thursday. Again the same want of success. The
seekers, discouraged, were now few. I made a last appeal, but nothing
came of it. Finally, I paid the most zealous, those who had been
faithful to the last, and we dissolved partnership. I could count on no
one but myself for researches, which seemed simple enough, but really
were exceedingly difficult. Even up to the present time, after many
years, excavations made in favourable spots and hopeful opportunities
have not yet given any clear, consistent result. I am reduced to
combining incomplete observations and to filling up gaps by analogy.
[4] The little which I have seen, together with observations on other
dung beetles—Gymnopleurus, Copris, and Onthophagus—in my enclosure is
summed up in the following statement.
The ball destined for the egg is not fashioned in public, in the
hurry-scurry of the general workshop. It is a work of art and much
patience, demanding minute care impossible amid a crowd. One must
retire to meditate one’s plans and set to work, so the mother makes a
hollow from four to eight inches deep in the sand. It is a rather
spacious hall, communicating with the outside by a much narrower
gallery. The insect carries down choice materials, no doubt first
rolled into pellets. She must make many journeys, for the contents of
the hole are out of all proportion with the door, and could not be
carried in at once. I recollect a Spanish Copris which, at the moment I
came upon it, was finishing a ball as large as an orange at the bottom
of a burrow only communicating with the outside world by means of a
gallery where I could but just insert my finger. It is true that the
Copris do not roll balls or make long journeys to fetch food. They dig
a hole immediately under the dung, and crawl backward with successive
loads to the bottom of their cavity. The facility for provisioning and
the security offered by working under the manure favour a taste for
luxury not to be expected in the same degree among beetles belonging to
the rude trade of ball-rollers; but should it return two or three
times, Scarabæus sacer can amass wealth of which Copris hispanica might
well be jealous.
So far the insect has only raw material, put together anyhow. The first
thing to do is to select very carefully, taking what is most delicate
for the inner layers, upon which the larva will feed, and the coarser
for the outer ones which merely serve as a protecting shell. Then
around a central hollow which receives the egg the materials must be
arranged layer after layer, according to their decreasing fineness and
nutritive value; the strata must be made consistent and adhere one to
another; and finally, the bits of fibre in the outside crust, which has
to protect the whole thing, must be felted together. How can the
Scarabæus, clumsy and stiff as it seems, accomplish such a work in
complete darkness, at the bottom of a hole so full of provisions that
there is barely room to move? When I think how delicate is the work
done and how rude the tools of the workman,—of the angular feet fitted
to hollow the ground, and, if need be, even tufa,—I am reminded of an
elephant trying to make lace. Explain who can this miracle of maternal
industry; I give it up, especially as it has not been my good fortune
to see the artist at work. Let us restrict ourselves to describing this
masterpiece.
The ball which contains the egg is generally as large as a middle-sized
apple. In the midst is an oval cavity about a centimetre in diameter.
At the bottom is the egg, fixed vertically; it is cylindrical, rounded
at each end, yellowish-white, about as large as a grain of wheat, but
shorter. The wall of the hollow is washed over with a greenish-brown,
semi-fluid matter, manure cream, destined as the first food of the
larva. Does the mother collect the quintessence of the dung to make
this delicate food? The look of it tells me that it is a pap prepared
in the maternal stomach. The pigeon softens grain in its crop, and
turns it into a kind of milk food which it disgorges for its nestlings.
It would seem that the beetle shows the same tender care. It half
digests the choice food, and disgorges it in the shape of a delicate
film to line the walls of the cavity where the egg is laid. Thus, when
first hatched, the larva finds food easy of digestion, which rapidly
strengthens its stomach and allows it to attack the under layers which
lack the same refinement of preparation. Under the semi-fluid paste is
a choice pulp, compact and homogeneous, whence every particle of fibre
is banished. Beyond are the coarser strata where vegetable fibres
abound, and finally the outside of the ball is composed of the coarsest
materials felted together into a resistant shell. Manifestly there is a
progressive change of diet. On issuing from the egg the feeble grub
licks the fine paste on the walls of its dwelling. There is but little
of it, still it is strengthening and of high nutritious value. To the
bottle of early infancy succeeds the pap of the weanling, intermediate
between the dainty fare of the start and the coarse nourishment at the
end. This layer is thick enough and abundant enough to make the maggot
into a robust grub. Then, strong food for the strong, barley bread with
its husks, raw dung full of sharp bits of hay. The larva is
superabundantly provisioned with it, and, having attained its growth,
comes to the imprisoning outer layer. The capacity of the dwelling has
increased with that of its inhabitant. The small original cavity with
its excessively thick walls is now a large cell with sides only a few
lines thick. The inner layers have turned into larva, nymph, or
Scarabæus, as the case may be. In short, the ball is now a shell,
hiding within its spacious interior the mysteries of metamorphosis.
My observations go no further; my certificates of the birth and
condition of the Scarabæus do not go beyond the egg; I have not
actually seen the larva which, however, is known and described by
various authors. Neither have I seen the perfect insect while yet
enclosed in the cell, previous to exercising its functions as
ball-roller and excavator, and that is exactly what I should most have
desired to see. I should have liked to find the creature in its
birthplace, recently transformed, new to all labour, so that I might
have examined the worker’s hand before it set to its tasks, and for the
following reason.
Insects have each foot terminated by a kind of finger or tarsus,
composed of a series of delicate portions which may be compared to the
joints of our fingers. They end in a crooked nail. One claw to each
foot is the rule, and this claw, at least in the case of the superior
Coleoptera, especially the scavenger beetles, contains five joints. Now
by a strange exception, the Scarabæus has no tarsi on its forefeet,
while possessing well-shaped ones with five joints on the two other
pairs. They are imperfect, maimed, wanting in their front limbs in that
which represents, roughly indeed, our hand in an insect. A like anomaly
is found in the Onitis and Bubas, also of the scavenger family.
Entomology has long noted this curious fact without being able to give
a satisfactory explanation. Is it a birth imperfection? Does the beetle
come into the world without fingers on its front limbs, or does it lose
them as soon as it enters on its toilsome labours?
One might easily suppose such mutilation a consequence of the insect’s
hard work. To grope, to excavate, to rake, to divide now among the
gravel in the soil, now in the fibrous mass of manure, is not a work in
which organs so delicate as the tarsi can be used without danger. Yet
graver is it that when the insect is rolling its ball backward, head
downward, it is with the end of the forefeet that it grips the ground.
What becomes of the weak feet, no thicker than a thread, in this
perpetual contact with all the inequalities of the soil? They are
useless—merely in the way, and sooner or later they are bound to
disappear, crushed, torn off, worn out. Our workmen, alas! are too
often maimed by handling heavy tools, and lifting great weights, and
the same may be the case with the Scarabæus which rolls a ball that to
it is a huge load. In that case the maimed arms would be a noble
certificate of a life of toil.
But serious doubts at once suggest themselves. If these mutilations be
accidental, and the result of laborious work, they should be the
exception, not the rule. Because a workman or several workmen have had
a hand crushed in machinery, it does not follow that all others should
be maimed. If the Scarabæus often, or even very often, loses the
fore-claws in its trade of ball-roller, there must be some which,
cleverer or more fortunate, have preserved their tarsi. Let us then
consult facts. I have observed a very large number of the species of
Scarabæus which inhabit France, the S. sacer, common in Provence; S.
semipunctatus, which is seldom found far from the sea, and frequents
the sandy shores of Cette, Palavas, and of the Gulf of Juan; also S.
longicollis, which is much more widely spread than the two others, and
found at least as far up the Rhône Valley as Lyons. Finally, I have
observed an African kind, S. cicatricosus, found in the environs of
Constantine, and the want of tarsi on the forefeet has proved
invariable in all four species, at all events as far as my observations
go. Therefore the Scarabæus is maimed from birth, and it must be no
accident but a natural peculiarity.
Moreover, we have further proof in another reason. Were the absence of
fore-claws accidental, and the consequence of rough labour, there are
other insects, especially among the scavenger beetles, which undertake
excavations yet more difficult than those of the Scarabæus, and which
ought therefore to be still more liable to lose their front claws, as
these are useless and in the way when the foot has to serve as a strong
tool for excavation. For instance, the Geotrupes, who deserve their
name of Earth-piercer so well, make hollows in the hard and beaten soil
of paths among pebbles cemented by clay—vertical pits so deep that to
reach the lowest cell one has to use powerful digging tools, and even
then one does not always succeed. Now these miners par excellence, who
easily open long galleries in surroundings whose surface the Scarabæus
sacer could hardly disturb, have their front tarsi intact, as if to
perforate tufa were a work calling for delicacy rather than strength.
Everything then points to the belief that, if observed in its natal
cell, the baby Scarabæus would be found mutilated like the veteran who
has travelled the world and grown worn with labour.
On this absence of fingers might be based an argument in favour of the
theories now in fashion—the struggle for life and the evolution of the
species. One might say that the Scarabæus had originally tarsi on all
its feet in conformity with the general laws of insect organisation.
One way or another, some have lost these embarrassing appendages on
their forefeet, they being hurtful rather than useful. Finding
themselves the better for this mutilation, which proved favourable to
their work, little by little they gained a superiority over the less
favoured ones, founded a race by transmitting their fingerless stumps
to their descendants, and finally, the primitively fingered insect
became the fingerless Scarabæus of our time. I am willing to agree to
this reasoning if it could first be demonstrated why, with like
labours,—labours even far harder,—the Geotrupes has preserved his
tarsi. Meantime let us continue to believe that the first Scarabæus who
rolled a ball, perhaps on the shores of some lake where bathed the
Palæotherium, was as much without tarsi as him of our own day.