Produced by Ron Swanson
THE GLOW-WORM AND OTHER BEETLES
BOOKS BY J. HENRI FABRE
THE LIFE OF THE SPIDER
THE LIFE OF THE FLY
THE MASON-BEES
BRAMBLE-BEES AND OTHERS
THE HUNTING WASPS
THE LIFE OF THE CATERPILLAR
THE LIFE OF THE GRASSHOPPER
THE SACRED BEETLE AND OTHERS
THE MASON-WASPS
THE GLOW-WORM AND OTHER BEETLES
THE GLOW-WORM AND OTHER BEETLES
BY
J. HENRI FABRE
TRANSLATED BY ALEXANDER TEIXEIRA DE MATTOS
FELLOW OF THE ZOOLOGICAL SOCIETY OF LONDON
NEW YORK
DODD, MEAD AND COMPANY
1924
COPYRIGHT, 1919
BY DODD, MEAD AND COMPANY, INC.
CONTENTS
PAGE
I THE GLOW-WORM . . . . . . . . . . . . . . . . . 1
II THE SITARES . . . . . . . . . . . . . . . . . . 28
III THE PRIMARY LARVA OF THE SITARES . . . . . . . 46
IV THE PRIMARY LARVA OF THE OIL-BEETLES . . . . . 84
V HYPERMETAMORPHOSIS . . . . . . . . . . . . . . 109
VI CEROCOMAE, MYLABRES AND ZONITES . . . . . . . . 144
VII THE CAPRICORN . . . . . . . . . . . . . . . . . 185
VIII THE PROBLEM OF THE SIREX . . . . . . . . . . . 207
IX THE DUNG-BEETLES OF THE PAMPAS . . . . . . . . 235
X INSECT COLOURING . . . . . . . . . . . . . . . 273
XI THE BURYING-BEETLES: THE BURIAL . . . . . . . . 294
XII THE BURYING-BEETLES: EXPERIMENTS . . . . . . . 319
XIII THE GIANT SCARITES . . . . . . . . . . . . . . 352
XIV THE SIMULATION OF DEATH . . . . . . . . . . . . 370
XV SUICIDE OR HYPNOSIS? . . . . . . . . . . . . . 390
XVI THE CRIOCERES . . . . . . . . . . . . . . . . . 411
XVII THE CRIOCERES (_continued_) . . . . . . . . . . 428
XVIII THE CLYTHRAE . . . . . . . . . . . . . . . . . 446
XIX THE CLYTHRAE: THE EGG . . . . . . . . . . . . . 463
TRANSLATOR'S NOTE
This is the second volume on Beetles in the complete English edition
of Henri Fabre's entomological works. The first is entitled _The
Sacred Beetle and Others_; the second and the third will be known as
_The Life of the Weevil_ and _More Beetles_ respectively.
_The Glow-worm_, which gives its name to the present book, did not
form part of the _Souvenirs entomologiques_ as originally published.
It is one of two essays written specially, at my request, for
translation into English, towards the close of Henri Fabre's life; in
fact, this and _The Ant-lion_, a short essay for children, were the
last works that came from the veteran author's pen. _The Glow-worm_
appeared first in the _Century Magazine_. Of the remaining chapters,
several have appeared in various periodicals, notably the _English
Review_ and in _Land and Water_, the editor and proprietors of which
admirable weekly have shown the most enlightened interest in Fabre's
work.
A part of the chapter entitled _The Dung-beetles of the Pampas_
figures in Messrs. Adam & Charles Black's volume, _The Life and Love
of the Insect_ (New York: the Macmillan Co.), translated by myself;
and the chapters on the Capricorn and Burying-beetles will be found in
Mr. T. Fisher Unwin's volume, _The Wonders of Instinct_ (New York: the
Century Co.), translated by myself and Mr. Bernard Miall, which also
contains _The Glow-worm_. These chapters are included in the present
edition by consent of and arrangement with the publishers named.
Lastly, Mr. Bernard Miall has earned my gratitude by the valuable
assistance which he has given me in preparing the translation of the
greater part of this volume.
ALEXANDER TEIXEIRA DE MATTOS.
CHELSEA, _5 September_, 1919.
CHAPTER I
THE GLOW-WORM
Few insects in our climes vie in popular fame with the Glow-worm, that
curious little animal which, to celebrate the little joys of life,
kindles a beacon at its tail-end. Who does not know it, at least by
name? Who has not seen it roam amid the grass, like a spark fallen
from the moon at its full? The Greeks of old called it [Greek:
lampouris], meaning, the bright-tailed. Science employs the same term:
it calls the lantern-bearer, _Lampyris noctiluca_, LIN. In this case,
the common name is inferior to the scientific phrase, which, when
translated, becomes both expressive and accurate.
In fact, we might easily cavil at the word "worm." The Lampyris is not
a worm at all, not even in general appearance. He has six short legs,
which he well knows how to use; he is a gad-about, a trot-about. In
the adult state, the male is correctly garbed in wing-cases, like the
true Beetle that he is. The female is an ill-favoured thing who knows
naught of the delights of flying: all her life long, she retains the
larval shape, which, for the rest, is similar to that of the male, who
himself is imperfect so long as he has not achieved the maturity that
comes with pairing-time. Even in this initial stage, the word "worm"
is out of place. We French have the expression "Naked as a worm," to
point to the lack of any defensive covering. Now the Lampyris is
clothed, that is to say, he wears an epidermis of some consistency;
moreover, he is rather richly coloured: his body is dark brown all
over, set off with pale pink on the thorax, especially on the lower
surface. Finally, each segment is decked at the hinder edge with two
spots of a fairly bright red. A costume like this was never worn by a
worm.
Let us leave this ill-chosen denomination and ask ourselves what the
Lampyris feeds upon. That master of the art of gastronomy,
Brillat-Savarin,[1] said:
"Show me what you eat and I will tell you what you are."
[Footnote 1: Anthelme Brillat-Savarin (1755-1826), author of _La
Psychologie du gout_.--_Translator's Note_.]
A similar question should be addressed, by way of a preliminary, to
every insect whose habits we propose to study, for, from the least to
the greatest in the zoological progression, the stomach sways the
world; the data supplied by food are the chief of all the documents of
life. Well, in spite of his innocent appearance, the Lampyris is an
eater of flesh, a hunter of game; and he follows his calling with rare
villainy. His regular prey is the Snail.
This detail has long been known to entomologists. What is not so
well-known, what is not known at all yet, to judge by what I have
read, is the curious method of attack, of which I have seen no other
instance anywhere.
Before he begins to feast, the Glow-worm administers an anaesthetic:
he chloroforms his victim, rivalling in the process the wonders of our
modern surgery, which renders the patient insensible before operating
on him. The usual game is a small Snail hardly the size of a cherry,
such as, for instance, _Helix variabilis_, DRAP., who, in the hot
weather, collects in clusters on the stiff stubble and on other long,
dry stalks, by the roadside, and there remains motionless, in profound
meditation, throughout the scorching summer days. It is in some such
resting-place as this that I have often been privileged to light upon
the Lampyris banqueting on the prey which he had just paralyzed on its
shaky support by his surgical artifices.
But he is familiar with other preserves. He frequents the edges of the
irrigating-ditches, with their cool soil, their varied vegetation, a
favourite haunt of the mollusc. Here, he treats the game on the
ground; and, under these conditions, it is easy for me to rear him at
home and to follow the operator's performance down to the smallest
detail.
I will try to make the reader a witness of the strange sight. I place
a little grass in a wide glass jar. In this I install a few Glow-worms
and a provision of Snails of a suitable size, neither too large nor
too small, chiefly _Helix variabilis_. We must be patient and wait.
Above all, we must keep an assiduous watch, for the desired events
come unexpectedly and do not last long.
Here we are at last. The Glow-worm for a moment investigates the prey,
which, according to its habit, is wholly withdrawn in the shell,
except the edge of the mantle, which projects slightly. Then the
hunter's weapon is drawn, a very simple weapon, but one that cannot be
plainly perceived without the aid of a lens. It consists of two
mandibles bent back powerfully into a hook, very sharp and as thin as
a hair. The microscope reveals the presence of a slender groove
running throughout the length. And that is all.
The insect repeatedly taps the Snail's mantle with its instrument. It
all happens with such gentleness as to suggest kisses rather than
bites. As children, teasing one another, we used to talk of
"tweaksies" to express a slight squeeze of the finger-tips, something
more like a tickling than a serious pinch. Let us use that word. In
conversing with animals, language loses nothing by remaining juvenile.
It is the right way for the simple to understand one another.
The Lampyris doles out his tweaks. He distributes them methodically,
without hurrying, and takes a brief rest after each of them, as though
he wished to ascertain the effect produced. Their number is not great:
half-a-dozen, at most, to subdue the prey and deprive it of all power
of movement. That other pinches are administered later, at the time of
eating, seems very likely, but I cannot say anything for certain,
because the sequel escapes me. The first few, however--there are never
many--are enough to impart inertia and loss of all feeling to the
mollusc, thanks to the prompt, I might almost say, lightning methods
of the Lampyris, who, beyond a doubt, instils some poison or other by
means of his grooved hooks.
Here is the proof of the sudden efficacity of those twitches, so mild
in appearance: I take the Snail from the Lampyris, who has operated on
the edge of the mantle some four or five times. I prick him with a
fine needle in the fore-part, which the animal, shrunk into its shell,
still leaves exposed. There is no quiver of the wounded tissues, no
reaction against the brutality of the needle. A corpse itself could
not give fewer signs of life.
Here is something even more conclusive: chance occasionally gives me
Snails attacked by the Lampyris while they are creeping along, the
foot slowly crawling, the tentacles swollen to their full extent. A
few disordered movements betray a brief excitement on the part of the
mollusc and then everything ceases: the foot no longer slugs; the
front-part loses its graceful swan-neck curve; the tentacles become
limp and give way under their weight, dangling feebly like a broken
stick. This conditions persists.
Is the Snail really dead? Not at all, for I am free to resuscitate the
seeming corpse. After two or three days of that singular condition
which is no longer life and yet not death, I isolate the patient and,
although this is not really necessary to success, I give him a douche
which will represent the shower so dear to the able-bodied mollusc. In
about a couple of days, my prisoner, but lately injured by the
Glow-worm's treachery, is restored to his normal state. He revives, in
a manner; he recovers movement and sensibility. He is affected by the
stimulus of a needle; he shifts his place, crawls, puts out his
tentacles, as though nothing unusual had occurred. The general torpor,
a sort of deep drunkenness, has vanished outright. The dead returns to
life. What name shall we give to that form of existence which, for a
time, abolishes the power of movement and the sense of pain? I can see
but one that is approximately suitable: anaesthesia. The exploits of a
host of Wasps whose flesh-eating grubs are provided with meat that is
motionless though not dead[2] have taught us the skilful art of the
paralyzing insect, which numbs the locomotory nerve-centres with its
venom. We have now a humble little animal that first produces complete
anaesthesia in its patient. Human science did not in reality invent
this art, which is one of the wonders of our latter-day surgery. Much
earlier, far back in the centuries, the Lampyris and, apparently,
others knew it as well. The animal's knowledge had a long start of
ours; the method alone has changed. Our operators proceed by making us
inhale the fumes of ether or chloroform; the insect proceeds by
injecting a special virus that comes from the mandibular fangs in
infinitesimal doses. Might we not one day be able to benefit by this
hint? What glorious discoveries the future would have in store for us,
if we understood the beastie's secrets better!
[Footnote 2: Cf. _The Hunting Wasps_, by J. Henri Fabre, translated by
Alexander Teixeira de Mattos: _passim_.--_Translator's Note_.]
What does the Lampyris want with anaesthetical talent against a
harmless and moreover eminently peaceful adversary, who would never
begin the quarrel of his own accord? I think I see. We find in Algeria
a Beetle known as _Drilus maroccanus_, who, though non-luminous,
approaches our Glow-worm in his organization and especially in his
habits. He too feeds on land molluscs. His prey is a Cyclostome with a
graceful spiral shell, tight-closed with a stony lid which is attached
to the animal by a powerful muscle. The lid is a movable door which is
quickly shut by the inmate's mere withdrawal into his house and as
easily opened when the hermit goes forth. With this system of closing,
the abode becomes inviolable; and the Drilus knows it.
Fixed to the surface of the shell by an adhesive apparatus whereof the
Lampyris will presently show us the equivalent, he remains on the
look-out, waiting, if necessary, for whole days at a time. At last,
the need of air and food oblige the besieged noncombatant to show
himself; at least, the door is set slightly ajar. That is enough. The
Drilus is on the spot and strikes his blow. The door can no longer be
closed and the assailant is henceforth master of the fortress. Our
first impression is that the muscle moving the lid has been cut with a
quick-acting pair of shears. This idea must be dismissed. The Drilus
is not well enough equipped with jaws to gnaw through a fleshy mass so
promptly. The operation has to succeed at once, at the first touch: if
not, the animal attacked would retreat, still in full vigour, and the
siege must be recommenced, as arduous as ever, exposing the insect to
fasts indefinitely prolonged. Although I have never come across the
Drilus, who is a stranger to my district, I conjecture a method of
attack very similar to that of the Glow-worm. Like our own
Snail-eater, the Algerian insect does not cut its victim into small
pieces: it renders it inert, chloroforms it by means of a few tweaks
which are easily distributed, if the lid but half-opens for a second.
That will do. The besieger thereupon enters and, in perfect quiet,
consumes a prey incapable of the least muscular effort. That is how I
see things by the unaided light of logic.
Let us now return to the Glow-worm. When the Snail is on the ground,
creeping, or even shrunk into his shell, the attack never presents any
difficulty. The shell possesses no lid and leaves the hermit's
fore-part to a great extent exposed. Here, on the edges of the mantle
contracted by the fear of danger, the mollusc is vulnerable and
incapable of defence. But it also frequently happens that the Snail
occupies a raised position, clinging to the tip of a grass-stalk or
perhaps to the smooth surface of a stone. This support serves him as a
temporary lid; it wards off the aggression of any churl who might try
to molest the inhabitant of the cabin, always on the express condition
that no slit show itself anywhere on the protecting circumference. If,
on the other hand, in the frequent case when the shell does not fit
its support quite closely, some point, however tiny, be left
uncovered, this is enough for the subtle tools of the Lampyris, who
just nibbles at the mollusc and at once plunges him into that profound
immobility which favours the tranquil proceedings of the consumer.
These proceedings are marked by extreme prudence. The assailant has to
handle his victim gingerly, without provoking contractions which would
make the Snail let go his support and, at the very least, precipitate
him from the tall stalk whereon he is blissfully slumbering. Now any
game falling to the ground would seem to be so much sheer loss, for
the Glow-worm has no great zeal for hunting-expeditions: he profits by
the discoveries which good luck sends him, without undertaking
assiduous searches. It is essential, therefore, that the equilibrium
of a prize perched on the top of a stalk and only just held in
position by a touch of glue should be disturbed as little as possible
during the onslaught; it is necessary that the assailant should go to
work with infinite circumspection and without producing pain, lest any
muscular reaction should provoke a fall and endanger the prize. As we
see, sudden and profound anaesthesia is an excellent means of enabling
the Lampyris to attain his object, which is to consume his prey in
perfect quiet.
What is his manner of consuming it? Does he really eat, that is to
say, does he divide his food piecemeal, does he carve it into minute
particles, which are afterwards ground by a chewing-apparatus? I think
not. I never see a trace of solid nourishment on my captives' mouths.
The Glow-worm does not eat in the strict sense of the word: he drinks
his fill; he feeds on a thin gruel into which he transforms his prey
by a method recalling that of the maggot. Like the flesh-eating grub
of the Fly, he too is able to digest before consuming; he liquefies
his prey before feeding on it.
This is how things happen: a Snail has been rendered insensible by the
Glow-worm. The operator is nearly always alone, even when the prize is
a large one, like the Common Snail, _Helix aspersa_. Soon a number of
guests hasten up--two, three or more--and, without any quarrel with
real proprietor, all alike fall to. Let us leave them to themselves
for a couple of days and then turn the shell, with the opening
downwards. The contents flow out as easily as would soup from an
overturned saucepan. When the sated diners retire from this gruel,
only insignificant leavings remain.
The matter is obvious: by repeated tiny bites, similar to the tweaks
which we saw distributed at the outset, the flesh of the mollusc is
converted into a gruel on which the various banqueters nourish
themselves without distinction, each working at the broth by means of
some special pepsine and each taking his own mouthfuls of it. In
consequence of this method, which first converts the food into a
liquid, the Glow-worm's mouth must be very feebly armed apart from the
two fangs which sting the patient and inject the anaesthetic poison
and, at the same time, no doubt, the serum capable of turning the
solid flesh into fluid. These two tiny implements, which can just be
examined through the lens, must, it seems, have some other object.
They are hollow and in this resemble those of the Ant-lion, which
sucks and drains its capture without having to divide it; but there is
this great difference, that the Ant-lion leaves copious remnants,
which are afterwards flung outside the funnel-shaped trap dug in the
sand, whereas the Glow-worm, that expert liquefier, leaves nothing, or
next to nothing. With similar tools, the one simply sucks the blood of
its prey and the other turns every morsel of his to account, thanks to
a preliminary liquefaction.
And this is done with exquisite precision, though the equilibrium is
sometimes anything but steady. My rearing-glasses supply me with
magnificent examples. Crawling up the sides, the Snails imprisoned in
my apparatus sometimes reach the top, which is closed with a glass
pane, and fix themselves to it by means of a speck of glair. This is a
mere temporary halt, in which the mollusc is miserly with its adhesive
product, and the merest shake is enough to loosen the shell and send
it to the bottom of the jar.
Now it is not unusual for the Glow-worm to hoist himself to the top,
with the help of a certain climbing-organ that makes up for his weak
legs. He selects his quarry, makes a minute inspection of it to find
an entrance-slit, nibbles it a little, renders it insensible and,
without delay, proceeds to prepare the gruel which he will consume for
days on end.
When he leaves the table, the shell is found to be absolutely empty;
and yet this shell, which was fixed to the glass by a very faint
stickiness, has not come loose, has not even shifted its position in
the smallest degree: without any protest from the hermit gradually
converted into broth, it has been drained on the very spot at which
the first attack was delivered. These small details tell us how
promptly the anaesthetic bite takes effect; they teach us how
dexterously the Glow-worm treats his Snail without causing him to fall
from a very slippery vertical support and without even shaking him on
his slight line of adhesion.
Under these conditions of equilibrium, the operator's short, clumsy
legs are obviously not enough; a special accessory apparatus is needed
to defy the danger of slipping and to seize the unseizable. And this
apparatus the Lampyris possesses. At the hinder end of the animal we
see a white spot which the lens separates into some dozen short,
fleshy appendages, sometimes gathered into a cluster, sometimes spread
into a rosette. There is your organ of adhesion and locomotion. If he
would fix himself somewhere, even on a very smooth surface, such as a
grass-stalk, the Glow-worm opens his rosette and spreads it wide on
the support, to which it adheres by its own stickiness. The same
organ, rising and falling, opening and closing, does much to assist
the act of progression. In short, the Glow-worm is a new sort of
self-propelled cripple, who decks his hind-quarters with a dainty
white rose, a kind of hand with twelve fingers, not jointed, but
moving in every direction: tubular fingers which do not seize, but
stick.
The same organ serves another purpose: that of a toilet-sponge and
brush. At a moment of rest, after a meal, the Glow-worm passes and
repasses the said brush over his head, back, sides and hinder-parts, a
performance made possible by the flexibility of his spine. This is
done point by point, from one end of the body to the other, with a
scrupulous persistency that proves the great interest which he takes
in the operation. What is his object in thus sponging himself, in
dusting and polishing himself so carefully? It is a question,
apparently, of removing a few atoms of dust or else some traces of
viscidity that remain from the evil contact with the snail. A wash and
brush-up is not superfluous when one leaves the tub in which the
mollusc has been treated.
If the Glow-worm possessed no other talent than that of chloroforming
his prey by means of a few tweaks resembling kisses, he would be
unknown to the vulgar herd; but he also knows how to light himself
like a beacon; he shines, which is an excellent manner of achieving
fame. Let us consider more particularly the female, who, while
retaining her larval shape, becomes marriageable and glows at her best
during the hottest part of summer. The lighting-apparatus occupies the
last three segments of the abdomen. On each of the first two, it takes
the form, on the ventral surface, of a wide belt covering almost the
whole of the arch; on the third, the luminous part is much less and
consists simply of two small crescent-shaped markings, or rather two
spots which shine through to the back and are visible both above and
below the animal. Belts and spots emit a glorious white light,
delicately tinged with blue. The general lighting of the Glow-worm
thus comprises two groups: first, the wide belts of the two segments
preceding the last; secondly, the two spots of the final segments. The
two belts, the exclusive attribute of the marriageable female, are the
part richest in light: to glorify her wedding, the future mother dons
her brightest gauds; she lights her two resplendent scarves. But,
before that, from the time of the hatching, she had only the modest
rush-light of the stern. This efflorescence of light is the equivalent
of the final metamorphosis, which is usually represented by the gift
of wings and flight. Its brilliance heralds the pairing-time. Wings
and flight there will be none: the female retains her humble larval
form, but she kindles her blazing beacon.
The male, on his side, is fully transformed, changes his shape,
acquires wings and wing-cases; nevertheless, like the female, he
possesses, from the time when he is hatched, the pale lamp of the end
segment. This luminous aspect of the stern is characteristic of the
entire Glow-worm tribe, independently of sex and season. It appears
upon the budding grub and continues throughout life unchanged. And we
must not forget to add that it is visible on the dorsal as well as on
the ventral surface, whereas the two large belts peculiar to the
female shine only under the abdomen.
My hand is not so steady nor my sight so good as once they were, but,
as far as they allow me, I consult anatomy for the structure of the
luminous organs. I take a scrap of the epidermis and manage to
separate pretty neatly half of one of the shining belts. I place my
preparation under the microscope. On the skin, a sort of white-wash
lies spread, formed of a very fine, granular substance. This is
certainly the light-producing matter. To examine this white layer more
closely is beyond the power of my weary eyes. Just beside it is a
curious air-tube, whose short and remarkably wide stem branches
suddenly into a sort of bushy tuft of very delicate ramifications.
These creep over the luminous sheet, or even dip into it. That is all.
The luminescence, therefore, is controlled by the respiratory organs
and the work produced is an oxidization. The white sheet supplies the
oxidizable matter and the thick air-tube spreading into a tufty bush
distributes the flow of air over it. There remains the question of the
substance whereof this sheet is formed. The first suggestion was
phosphorus, in the chemist's sense of the word. The Glow-worm has been
calcined and treated with the violent reagents that bring the simple
substances to light; but no one, so far as I know, has obtained a
satisfactory answer along these lines. Phosphorus seems to play no
part here, in spite of the name of phosphorescence which is sometimes
bestowed upon the Glow-worm's gleam. The answer lies elsewhere, no one
knows where.
We are better informed as regards another question. Has the Glow-worm
a free control of the light which he emits? Can he turn it on or down
or put it out as he pleases? Has he an opaque screen which is drawn
over the flame at will, or is that flame always left exposed? There is
no need for any such mechanism: the insect has something better for
its revolving light.
The thick tube supplying the light-producing sheet increases the flow
of air and the light is intensified; the same air-tube, swayed by the
animal's will, slackens or even suspends the passage of air and the
light grows fainter or even goes out. It is, in short, the mechanism
of a lamp which is regulated by the access of air to the wick.
Excitement can set the attendant air-duct in motion. We must here
distinguish between two cases: that of the gorgeous scarves, the
exclusive ornament of the female ripe for matrimony, and that of the
modest fairy-lamp on the last segment, which both sexes kindle at any
age. In the second case, the extinction caused by a flurry is sudden
and complete, or nearly so. In my nocturnal hunts for young
Glow-worms, measuring about 5 millimetres long,[3] I can plainly see
the glimmer on the blades of grass; but, should the least false step
disturb a neighbouring twig, the light goes out at once and the
coveted insect becomes invisible. Upon the full-grown females, lit up
with their nuptial scarves, even a violent start has but a slight
effect and often none at all.
[Footnote 3: .195 inch.--_Translator's Note_.]
I fire a gun beside a wire-gauze cage in which I am rearing my
menagerie of females in the open air. The explosion produces no
result. The illumination continues, as bright and placid as before. I
take a spray and rain down a slight shower of cold water upon the
flock. Not one of my animals puts out its light; at the very most,
there is a brief pause in the radiance; and then only in some cases. I
send a puff of smoke from my pipe into the cage. This time, the pause
is more marked. There are even some extinctions, but these do not last
long. Calm soon returns and the light is renewed as brightly as ever.
I take some of the captives in my fingers, turn and return them, tease
them a little. The illumination continues and is not much diminished,
if I do not press too hard with my thumb. At this period, with the
pairing close at hand, the insect is in all the fervour of its
passionate splendour; and nothing short of very serious reasons would
make it put out its signals altogether.
All things considered, there is not a doubt but that the Glow-worm
himself manages his lighting-apparatus, extinguishing and rekindling
it at will; but there is one point at which the voluntary agency of
the insect is without effect. I detach a strip of the epidermis
showing one of the luminescent sheets and place it in a glass tube,
which I close with a plug of damp wadding, to avoid too rapid an
evaporation. Well, this scrap of carcass shines away merrily, although
not quite as brilliantly as on the living body.
Life's aid is now superfluous. The oxidizable substance, the
luminescent sheet, is in direct communication with the surrounding
atmosphere; the flow of oxygen through an air-tube is not necessary;
and the luminous emission continues to take place, in the same way as
when it is produced by the contact of the air with the real phosphorus
of the chemists. Let us add that, in aerated water, the luminousness
continues as brilliant as in the free air, but that it is extinguished
in water deprived of its air by boiling. No better proof could be
found of what I have already propounded, namely, that the Glow-worm's
light is the effect of a slow oxidization.
The light is white, calm and soft to the eyes and suggests a spark
dropped by the full moon. Despite its splendour, it is a very feeble
illuminant. If we move a Glow-worm along a line of print, in perfect
darkness, we can easily make out the letters, one by one, and even
words, when these are not too long; but nothing more is visible beyond
a narrow zone. A lantern of this kind soon tires the reader's
patience.
Suppose a group of Glow-worms placed almost touching one another. Each
of them sheds its glimmer, which ought, one would think, to light up
its neighbours by reflexion and give us a clear view of each
individual specimen. But not at all: the luminous party is a chaos in
which our eyes are unable to distinguish any definite form at a medium
distance. The collective lights confuse the link-bearers into one
vague whole.
Photography gives us a striking proof of this. I have a score of
females, all at the height of their splendour, in a wire-gauze cage in
the open air. A tuft of thyme forms a grove in the centre of their
establishment. When night comes, my captives clamber to this pinnacle
and strive to show off their luminous charms to the best advantage at
every point of the horizon, thus forming along the twigs marvellous
clusters from which I expected magnificent effects on the
photographer's plates and paper. My hopes are disappointed. All that I
obtain is white, shapeless patches, denser here and less dense there
according to the numbers forming the group. There is no picture of the
Glow-worms themselves; not a trace either of the tuft of thyme. For
want of satisfactory light, the glorious firework is represented by a
blurred splash of white on a black ground.
The beacons of the female Glow-worms are evidently nuptial signals,
invitations to the pairing; but observe that they are lighted on the
lower surface of the abdomen and face the ground, whereas the summoned
males, whose flights are sudden and uncertain, travel overhead, in the
air, sometimes a great way up. In its normal position, therefore, the
glittering lure is concealed from the eyes of those concerned; it is
covered by the thick bulk of the bride. The lantern ought really to
gleam on the back and not under the belly; otherwise the light is
hidden under a bushel.
The anomaly is corrected in a very ingenious fashion, for every female
has her little wiles of coquetry. At nightfall, every evening, my
caged captives make for the tuft of thyme with which I have
thoughtfully furnished the prison and climb to the top of the upper
branches, those most in sight. Here, instead of keeping quiet, as they
did at the foot of the bush just now, they indulge in violent
exercises, twist the tip of their very flexible abdomen, turn it to
one side, turn it to the other, jerk it in every direction. In this
way, the search-light cannot fail to gleam, at one moment or another,
before the eyes of every male who goes a-wooing in the neighbourhood,
whether on the ground or in the air.
It is very like the working of the revolving mirror used in catching
Larks. If stationary, the little contrivance would leave the bird
indifferent; turning and breaking up its light in rapid flashes, it
excites it.
While the female Glow-worm has her tricks for summoning her swains,
the male, on his side, is provided with an optical apparatus suited to
catch from afar the least reflection of the calling-signal. His
corselet expands into a shield and overlaps his head considerably in
the form of a peaked cap or eye-shade, the object of which appears to
be to limit the field of vision and concentrate the view upon the
luminous speck to be discerned. Under this arch are the two eyes,
which are relatively enormous, exceedingly convex, shaped like a
skull-cap and contiguous to the extent of leaving only a narrow groove
for the insertion of the antennae. This double eye, occupying almost
the whole face of the insect and contained in the cavern formed by the
spreading peak of the corselet, is a regular Cyclop's eye.
At the moment of the pairing, the illumination becomes much fainter,
is almost extinguished; all that remains alight is the humble
fairy-lamp of the last segment. This discreet night-light is enough
for the wedding, while, all around, the host of nocturnal insects,
lingering over their respective affairs, murmur the universal
marriage-hymn. The laying follows very soon. The round, white eggs are
laid, or rather strewn at random, without the least care on the
mother's part, either on the more or less cool earth or on a blade of
grass. These brilliant ones know nothing at all of family-affection.
Here is a very singular thing: the Glow-worm's eggs are luminous even
when still contained in the mother's womb. If I happen by accident to
crush a female big with germs that have reached maturity, a shiny
streak runs along my fingers, as though I had broken some vessel
filled with a phosphorescent fluid. The lens shows me that I am wrong.
The luminosity comes from the cluster of eggs forced out of the ovary.
Besides, as laying-time approaches, the phosphorescence of the eggs is
already made manifest without this clumsy midwifery. A soft opalescent
light shines through the skin of the belly.
The hatching follows soon after the laying. The young of either sex
have two little rush-lights on the last segment. At the approach of
the severe weather, they go down into the ground, but not very far. In
my rearing-jars, which are supplied with fine and very loose earth,
they descend to a depth of three or four inches at most. I dig up a
few in mid-winter. I always find them carrying their faint
stern-light. About the month of April, they come up again to the
surface, there to continue and complete their evolution.
From start to finish, the Glow-worm's life is one great orgy of light.
The eggs are luminous; the grubs likewise. The full-grown females are
magnificent light-houses, the adult males retain the glimmer which the
grubs already possessed. We can understand the object of the feminine
beacon; but of what use is all the rest of the pyrotechnic display? To
my great regret, I cannot tell. It is and will be, for many a day to
come, perhaps for all time, the secret of animal physics, which is
deeper than the physics of the books.