THE OAK EGGAR, OR BANDED MONK
Yes: I was to find it. I even had it already in my possession. An urchin
of seven years, with an alert countenance, not washed every day, bare
feet, and dilapidated breeches supported by a piece of string, who
frequented the house as a dealer in turnips and tomatoes, arrived one
day with his basket of vegetables. Having received the few halfpence
expected by his mother as the price of the garden-stuff, and having
d them one by one into the hollow of his hand, he took from his
pocket an object which he had discovered the day before beneath a hedge
when gathering greenstuff for his rabbits.
"And this--will you have this?" he said, handing me the object. "Why,
certainly I will have it. Try to find me more, as many as you can, and
on Sunday you shall have lots of rides on the wooden horses. In the
meantime here is a penny for you. Don't forget it when you make up your
accounts; don't mix it with your turnip-money; put it by itself."
Beaming with satisfaction at such wealth, little touzle-head promised to
search industriously, already foreseeing a fortune.
When he had gone I examined the thing. It was worth examination. It was
a fine cocoon, thick and with blunt ends, very like a silkworm's cocoon,
firm to the touch and of a tawny colour. A brief reference to the
text-books almost convinced me that this was a cocoon of the _Bombyx
quercus_. If so, what a find! I could continue my inquiry and perhaps
confirm what my study of the Great Peacock had made me suspect.
The Bombyx of the oak-tree is, in fact, a classic moth; indeed, there is
no entomological text-book but speaks of its exploits at mating-time. It
is said that a female emerged from the pupa in captivity, in the
interior of an apartment, and even in a closed box. It was far from the
country, amidst the tumult of a large city. Nevertheless, the event was
known to those concerned in the woods and meadows. Guided by some
mysterious compass, the males arrived, hastening from the distant
fields; they went to the box, fluttered against it, and flew to and fro
in the room.
These marvels I had learned by reading; but to see such a thing with
one's own eyes, and at the same time to devise experiments, is quite
another thing. What had my penny bargain in store for me? Would the
famous Bombyx issue from it?
Let us call it by its other name, the Banded Monk. This original name of
Monk was suggested by the costume of the male; a monk's robe of a modest
rusty red. But in the case of the female the brown fustian gives place
to a beautiful velvet, with a pale transversal band and little white
eyes on the fore pair of wings.
The Monk is not a common butterfly which can be caught by any one who
takes out a net at the proper season. I have never seen it around our
village or in the solitude of my grounds during a residence of twenty
years. It is true that I am not a fervent butterfly-catcher; the dead
insect of the collector's cabinet has little interest for me; I must
have it living, in the exercise of its functions. But although I have
not the collector's zeal I have an attentive eye to all that flies or
crawls in the fields. A butterfly so remarkable for its size and
colouring would never have escaped my notice had I encountered it.
The little searcher whom I had enticed by a promise of rides upon wooden
horses never made a second find. For three years I requisitioned friends
and neighbours, and especially their children, sharp-sighted snappers-up
of trifles; I myself hunted often under heaps of withered leaves; I
inspected stone-heaps and visited hollow tree-trunks. Useless pains; the
precious cocoon was not to be found. It is enough to say that the Banded
Monk is extremely rare in my neighbourhood. The importance of this fact
will presently appear.
As I suspected, my cocoon was truly that of the celebrated Oak Eggar. On
the 20th of August a female emerged from it: corpulent, big-bellied,
coloured like the male, but lighter in hue. I placed her under the usual
wire cover in the centre of my laboratory table, littered as it was with
books, bottles, trays, boxes, test-tubes, and other apparatus. I have
explained the situation in speaking of the Great Peacock. Two windows
light the room, both opening on the garden. One was closed, the other
open day and night. The butterfly was placed in the shade, between the
lines of the two windows, at a distance of 12 or 15 feet.
The rest of that day and the next went by without any occurrence worthy
of notice. Hanging by the feet to the front of the wire cover, on the
side nearest to the light, the prisoner was motionless, inert. There was
no oscillation of the wings, no tremor of the antennae, the female of the
Great Peacock behaved in a similar fashion.
The female Bombyx gradually matured, her tender tissues gradually
becoming firmer. By some process of which our scientists have not the
least idea she elaborated a mysterious lure which would bring her lovers
from the four corners of the sky. What was happening in this big-bellied
body; what transmutations were accomplished, thus to affect the whole
On the third day the bride was ready. The festival opened brilliantly. I
was in the garden, already despairing of success, for the days were
passing and nothing had occurred, when towards three in the afternoon,
the weather being very hot and the sun radiant, I perceived a crowd of
butterflies gyrating in the embrasure of the open window.
The lovers had at last come to visit their lady. Some were emerging from
the room, others were entering it; others, clinging to the wall of the
house, were resting as though exhausted by a long journey. I could see
others approaching in the distance, flying over the walls, over the
screens of cypress. They came from all directions, but at last with
decreasing frequency. I had missed the opening of the convocation, and
now the gathering was almost complete.
I went indoors and upstairs. This time, in full daylight and without
losing a detail, I witnessed once more the astonishing spectacle to
which the great nocturnal butterfly had first introduced me. The study
contained a cloud of males, which I estimated, at a glance, as being
about sixty in number, so far as the movement and confusion allowed me
to count them at all. After circling a few times over the cage many of
them went to the open window, but returned immediately to recommence
their evolutions. The most eager alighted on the cover, trampling on one
another, jostling one another, trying to get the best places. On the
other side of the barrier the captive, her great body hanging against
the wire, waited immovable. She betrayed not a sign of emotion in the
face of this turbulent swarm.
Going and entering, perched on the cover or fluttering round the room,
for more than three hours they continued their frenzied saraband. But
the sun was sinking, and the temperature was slowly falling. The ardour
of the butterflies also cooled. Many went out not to return. Others took
up their positions to wait for the gaieties of the following day; they
clung to the cross-bars of the closed window as the males of the Great
Peacock had done. The rejoicings were over for the day. They would
certainly be renewed on the morrow, since the courtship was without
result on account of the barrier of the wire-gauze cover.
But, alas I to my great disappointment, they were not resumed, and the
fault was mine. Late in the day a Praying Mantis was brought to me,
which merited attention on account of its exceptionally small size.
Preoccupied with the events of the afternoon, and absent-minded, I
hastily placed the predatory insect under the same cover as the moth.
It did not occur to me for a moment that this cohabitation could lead to
any harm. The Mantis was so slender, and the other so corpulent!
Alas! I little knew the fury of carnage animating the creature that
wielded those tiny grappling-irons! Next morning I met with a
disagreeable surprise: I found the little Mantis devouring the great
moth. The head and the fore part of the thorax had already disappeared.
Horrible creature! at what an evil hour you came to me! Goodbye to my
researches, the plans which I had caressed all night in my imagination!
For three years for lack of a subject, I was unable to resume them.
Bad luck, however, was not to make me forget the little I had learned.
On one single occasion about sixty males had arrived. Considering the
rarity of the Oak Eggar, and remembering the years of fruitless search
on the part of my helpers and myself, this number was no less than
stupefying. The undiscoverable had suddenly become multitudinous at the
call of the female.
Whence did they come? From all sides, and undoubtedly from considerable
distances. During my prolonged searches every bush and thicket and heap
of stones in my neighbourhood had become familiar to me, and I can
assert that the Oak Eggar was not to be found there. For such a swarm to
collect as I found in my laboratory the moths must have come from all
directions, from the whole district, and within a radius that I dare not
Three years went by and by chance two more cocoons of the Monk or Oak
Eggar again fell into my hands. Both produced females, at an interval of
a few days towards the middle of August; so that I was able to vary and
repeat my experiments.
I rapidly repeated the experiments which had given me such positive
results in the instance of the Great Peacock moth. The pilgrims of the
day were no less skilful at finding their mates than the pilgrims of the
night. They laughed at all my tricks. Infallibly they found the
prisoners in their wire-gauze prisons, no matter in what part of the
house they were placed; they discovered them in the depths of a
wall-cupboard; they divined the secret of all manner of boxes, provided
these were not rigorously air-tight. They came no longer when the box
was hermetically sealed. So far this was only a repetition of the feats
of the Great Peacock.
A box perfectly closed, so that the air contained therein had no
communication with the external atmosphere, left the male in complete
ignorance of the recluse. Not a single one arrived, even when the box
was exposed and plain to see on the window-sill. Thus the idea of
strongly scented effluvia, which are cut off by screens of wood, metal,
card, glass, or what not, returns with double force.
I have shown that the great nocturnal moth was not thrown off the scent
by the powerful odour of naphthaline, which I thought would mask the
extra-subtle emanations of the female, which were imperceptible to human
olfactory organs. I repeated the experiment with the Oak Eggar. This
time I used all the resources of scent and stench that my knowledge of
drugs would permit.
A dozen saucers were arranged, some in the interior of the wire-gauze
cover, the prison of the female, and some around it, in an unbroken
circle. Some contained naphthaline; others the essential oil of
spike-lavender; others petroleum, and others a solution of alkaline
sulphur giving off a stench of rotten eggs. Short of asphyxiating the
prisoner I could do no more. These arrangements were made in the
morning, so that the room should be saturated when the congregation of
lovers should arrive.
In the afternoon the laboratory was filled with the most abominable
stench, in which the penetrating aroma of spike-lavender and the stink
of sulphuretted hydrogen were predominant. I must add that tobacco was
habitually smoked in this room, and in abundance. The concerted odours
of a gas-works, a smoking-room, a perfumery, a petroleum well, and a
chemical factory--would they succeed in confusing the male moths?
By no means. About three o'clock the moths arrived in as great numbers
as usual. They went straight to the cage, which I had covered with a
thick cloth in order to add to their difficulties. Seeing nothing when
once they had entered, and immersed in an extraordinary atmosphere in
which any subtle fragrance should have been annihilated, they
nevertheless made straight for the prisoner, and attempted to reach her
by burrowing under the linen cloth. My artifice had no result.
After this set-back, so obvious in its consequences, which only repeated
the lesson of the experiments made with naphthaline when my subject was
the Great Peacock, I ought logically to have abandoned the theory that
the moths are guided to their wedding festivities by means of strongly
scented effluvia. That I did not do so was due to a fortuitous
observation. Chance often has a surprise in store which sets us on the
right road when we have been seeking it in vain.
One afternoon, while trying to determine whether sight plays any part in
the search for the female once the males had entered the room, I placed
the female in a bell-glass and gave her a slender twig of oak with
withered leaves as a support. The glass was set upon a table facing the
open window. Upon entering the room the moths could not fail to see the
prisoner, as she stood directly in the way. The tray, containing a layer
of sand, on which the female had passed the preceding day and night,
covered with a wire-gauze dish-cover, was in my way. Without
premeditation I placed it at the other end of the room on the floor, in
a corner where there was but little light. It was a dozen yards away
from the window.
The result of these preparations entirely upset my preconceived ideas.
None of the arrivals stopped at the bell-glass, where the female was
plainly to be seen, the light falling full upon her prison. Not a
glance, not an inquiry. They all flew to the further end of the room,
into the dark corner where I had placed the tray and the empty
They alighted on the wire dome, explored it persistently, beating their
wings and jostling one another. All the afternoon, until sunset, the
moths danced about the empty cage the same saraband that the actual
presence of the female had previously evoked. Finally they departed: not
all, for there were some that would not go, held by some magical
Truly a strange result! The moths collected where there was apparently
nothing to attract them, and remained there, unpersuaded by the sense of
sight; they passed the bell-glass actually containing the female without
halting for a moment, although she must have been seen by many of the
moths both going and coming. Maddened by a lure, they paid no attention
to the reality.
What was the lure that so deceived them? All the preceding night and all
the morning the female had remained under the wire-gauze cover;
sometimes clinging to the wire-work, sometimes resting on the sand in
the tray. Whatever she touched--above all, apparently, with her
distended abdomen--was impregnated, as a result of long contact, with a
certain emanation. This was her lure, her love-philtre; this it was that
revolutionised the Oak Eggar world. The sand retained it for some time
and diffused the effluvium in turn.
They passed by the glass prison in which the female was then confined
and hastened to the meshes of wire and the sand on which the magic
philtre had been poured; they crowded round the deserted chamber where
nothing of the magician remained but the odorous testimony of her
The irresistible philtre requires time for its elaboration. I conceive
of it as an exhalation which is given off during courtship and gradually
saturates whatever is in contact with the motionless body of the female.
If the bell-glass was placed directly on the table, or, still better, on
a square of glass, the communication between the inside and the outside
was insufficient, and the males, perceiving no odour, did not arrive so
long as that condition of things obtained. It was plain that this
failure of transmission was not due to the action of the glass as a
screen simply, for if I established a free communication between the
interior of the bell-glass and the open air by supporting it on three
small blocks, the moths did not collect round it at once, although there
were plenty in the room; but in the course of half an hour or so the
feminine alembic began to operate, and the visitors crowded round the
bell-glass as usual.
In possession of these data and this unexpected enlightenment I varied
the experiments, but all pointed to the same conclusion. In the morning
I established the female under the usual wire-gauze cover. For support I
gave her a little twig of oak as before. There, motionless as if dead,
she crouched for hours, half buried in the dry leaves, which would thus
become impregnated with her emanations.
When the hour of the daily visits drew near I removed the twig, which
was by then thoroughly saturated with the emanations, and laid it on a
chair not far from the open window. On the other hand I left the female
under the cover, plainly exposed on the table in the middle of the room.
The moths arrived as usual: first one, then two, then three, and
presently five and six. They entered, flew out again, re-entered,
mounted, descended, came and went, always in the neighbourhood of the
window, not far from which was the chair on which the twig lay. None
made for the large table, on which, a few steps further from the window,
the female awaited them in the wire-gauze cover. They hesitated, that
was plain; they were still seeking.
Finally they found. And what did they find? Simply the twig, which that
morning had served the ample matron as bed. Their wings rapidly
fluttering, they alighted on the foliage; they explored it over and
under, probed it, raised it, and displaced it so that the twig finally
fell to the floor. None the less they continued to probe between the
leaves. Under the buffets and the draught of their wings and the
clutches of their eager feet the little bundle of leaves ran along the
floor like a scrap of paper patted by the paws of a cat.
While the twig was sliding away with its band of investigators two new
arrivals appeared. The chair lay in their path. They stopped at it and
searched eagerly at the very spot on which the twig had been lying. But
with these, as with the others, the real object of their desires was
there, close by, under a wire cover which was not even veiled. None took
any note of it. On the floor, a handful of butterflies were still
hustling the bunch of leaves on which the female had reposed that
morning; others, on the chair, were still examining the spot where the
twig had lain. The sun sank, and the hour of departure struck. Moreover,
the emanations were growing feebler, were evaporating. Without more ado
the visitors left. We bade them goodbye till the morrow.
The following tests showed me that the leaf-covered twig which
accidentally enlightened me might be replaced by any other substance.
Some time before the visitors were expected I placed the female on a bed
of cloth or flannel, card or paper. I even subjected her to the rigours
of a camp-bed of wood, glass, marble, and metal. All these objects,
after a contact of sufficient duration, had the same attraction for the
males as the female moth herself. They retained this property for a
longer or shorter time, according to their nature. Cardboard, flannel,
dust, sand, and porous objects retained it longest. Metals, marble, and
glass, on the contrary, quickly lost their efficacy. Finally, anything
on which the female had rested communicated its virtues by contact;
witness the butterflies crowding on the straw-bottomed chair after the
twig fell to the ground.
Using one of the most favourable materials--flannel, for example--I
witnessed a curious sight. I placed a morsel of flannel on which the
mother moth had been lying all the morning at the bottom of a long
test-tube or narrow-necked bottle, just permitting of the passage of a
male moth. The visitors entered the vessels, struggled, and did not know
how to extricate themselves. I had devised a trap by means of which I
could exterminate the tribe. Delivering the prisoners, and removing the
flannel, which I placed in a perfectly closed box, I found that they
re-entered the trap; attracted by the effluvia that the flannel had
communicated to the glass.
I was now convinced. To call the moths of the countryside to the
wedding-feast, to warn them at a distance and to guide them the nubile
female emits an odour of extreme subtlety, imperceptible to our own
olfactory sense-organs. Even with their noses touching the moth, none of
my household has been able to perceive the faintest odour; not even the
youngest, whose sensibility is as yet unvitiated.
This scent readily impregnates any object on which the female rests for
any length of time, when this object becomes a centre of attraction as
active as the moth herself until the effluvium is evaporated.
Nothing visible betrays the lure. On a sheet of paper, a recent
resting-place, around which the visitors had crowded, there was no
visible trace, no moisture; the surface was as clean as before the
The product is elaborated slowly, and must accumulate a little before it
reveals its full power. Taken from her couch and placed elsewhere the
female loses her attractiveness for the moment and is an object of
indifference; it is to the resting-place, saturated by long contact,
that the arrivals fly. But the female soon regains her power.
The emission of the warning effluvium is more or less delayed according
to the species. The recently metamorphosed female must mature a little
and her organs must settle to their work. Born in the morning, the
female of the Great Peacock moth sometimes has visitors the night of the
same day; but more often on the second day, after a preparation of forty
hours or so. The Oak Eggar does not publish her banns of marriage before
the third or fourth day.
Let us return for a moment to the problematical function of the antennae.
The male Oak Eggar has a sumptuous pair, as has the Great Peacock or
Emperor Moth. Are we to regard these silky "feelers" as a kind of
directing compass?--I resumed, but without attaching much importance to
the matter, my previous experiment of amputation. None of those operated
on returned. Do not let us draw conclusions from that fact alone. We saw
in the case of the Great Peacock that more serious reasons than the
truncation of the antennae made return as a rule impossible.
Moreover, a second Bombyx or Eggar, the Clover Moth, very like the Oak
Eggar, and like it superbly plumed, poses us a very difficult problem.
It is fairly abundant around my home; even in the orchard I find its
cocoon, which is easily confounded with that of the Oak Eggar. I was at
first deceived by the resemblance. From six cocoons, which I expected to
yield Oak Eggars, I obtained, about the end of August, six females of
the other species. Well: about these six females, born in my house,
never a male appeared, although they were undoubtedly present in the
If the ample and feathery antennae are truly sense-organs, which receive
information of distant objects, why were not my richly plumed neighbours
aware of what was passing in my study? Why did their feathery "feelers"
leave them in ignorance of events which would have brought flocks of the
other Eggar? Once more, the organ does not determine the aptitude. One
individual or species is gifted, but another is not, despite an organic