The cabbage of our modern kitchen-gardens is a semi-artificial plant,
the produce of our agricultural ingenuity quite as much as of the
niggardly gifts of nature. Spontaneous vegetation supplied us with the
long-stalked, scanty-leaved, ill-smelling wilding, as found, according
to the botanists, on the ocean cliffs. He had need of a rare
inspiration who first showed faith in this rustic clown and proposed to
improve it in his garden-patch.
Progressing by infinitesimal degrees, culture wrought miracles. It
began by persuading the wild cabbage to discard its wretched leaves,
beaten by the sea-winds, and to replace them by others, ample and
fleshy and close-fitting. The gentle cabbage submitted without protest.
It deprived itself of the joys of light by arranging its leaves in a
large compact head, white and tender. In our day, among the successors
of those first tiny hearts, are some that, by virtue of their massive
bulk, have earned the glorious name of chou quintal, as who should say
a hundredweight of cabbage. They are real monuments of green stuff.
Later, man thought of obtaining a generous dish with a thousand little
sprays of the inflorescence. The cabbage consented. Under the cover of
the central leaves, it gorged with food its sheaves of blossom, its
flower-stalks, its branches and worked the lot into a fleshy
conglomeration. This is the cauliflower, the broccoli.
Differently entreated, the plant, economizing in the centre of its
shoot, set a whole family of close-wrapped cabbages ladder-wise on a
tall stem. A multitude of dwarf leaf-buds took the place of the
colossal head. This is the Brussels sprout.
Next comes the turn of the stump, an unprofitable, almost wooden,
thing, which seemed never to have any other purpose than to act as a
support for the plant. But the tricks of gardeners are capable of
everything, so much so that the stalk yields to the grower's
suggestions and becomes fleshy and swells into an ellipse similar to
the turnip, of which it possesses all the merits of corpulence, flavour
and delicacy; only the strange product serves as a base for a few
sparse leaves, the last protests of a real stem that refuses to lose
its attributes entirely. This is the cole-rape.
If the stem allows itself to be allured, why not the root? It does, in
fact, yield to the blandishments of agriculture: it dilates its pivot
into a flat turnip, which half emerges from the ground. This is the
rutabaga, or swede, the turnip-cabbage of our northern districts.
Incomparably docile under our nursing, the cabbage has given its all
for our nourishment and that of our cattle: its leaves, its flowers,
its buds, its stalk, its root; all that it now wants is to combine the
ornamental with the useful, to smarten itself, to adorn our flowerbeds
and cut a good figure on a drawing-room table. It has done this to
perfection, not with its flowers, which, in their modesty, continue
intractable, but with its curly and variegated leaves, which have the
undulating grace of Ostrich-feathers and the rich colouring of a mixed
bouquet. None who beholds it in this magnificence will recognize the
near relation of the vulgar "greens" that form the basis of our
cabbage-soup.
The cabbage, first in order of date in our kitchen-gardens, was held in
high esteem by classic antiquity, next after the bean and, later, the
pea; but it goes much farther back, so far indeed that no memories of
its acquisition remain. History pays but little attention to these
details: it celebrates the battle-fields whereon we meet our death, but
scorns to speak of the ploughed fields whereby we thrive; it knows the
names of the kings' bastards, but cannot tell us the origin of wheat.
That is the way of human folly.
This silence respecting the precious plants that serve as food is most
regrettable. The cabbage in particular, the venerable cabbage, that
denizen of the most ancient garden-plots, would have had extremely
interesting things to teach us. It is a treasure in itself, but a
treasure twice exploited, first by man and next by the caterpillar of
the Pieris, the common Large White Butterfly whom we all know (Pieris
brassicae, Lin.). This caterpillar feeds indiscriminately on the leaves
of all varieties of cabbage, however dissimilar in appearance: he
nibbles with the same appetite red cabbage and broccoli, curly greens
and savoy, swedes and turnip-tops, in short, all that our ingenuity,
lavish of time and patience, has been able to obtain from the original
plant since the most distant ages.
But what did the caterpillar eat before our cabbages supplied him with
copious provender? Obviously the Pieris did not wait for the advent of
man and his horticultural works in order to take part in the joys of
life. She lived without us and would have continued to live without us.
A Butterfly's existence is not subject to ours, but rightfully
independent of our aid.
Before the white-heart, the cauliflower, the savoy and the others were
invented, the Pieris' caterpillar certainly did not lack food: he
browsed on the wild cabbage of the cliffs, the parent of all the
latter-day wealth; but, as this plant is not widely distributed and is,
in any case, limited to certain maritime regions, the welfare of the
Butterfly, whether on plain or hill, demanded a more luxuriant and more
common plant for pasturage. This plant was apparently one of the
Cruciferae, more or less seasoned with sulpheretted essence, like the
cabbages. Let us experiment on these lines.
I rear the Pieris' caterpillars from the egg upwards on the wall-rocket
(Diplotaxis tenuifolia, Dec.), which imbibes strong spices along the
edge of the paths and at the foot of the walls. Penned in a large
wire-gauze bell-cage, they accept this provender without demur; they
nibble it with the same appetite as if it were cabbage; and they end by
producing chrysalids and Butterflies. The change of fare causes not the
least trouble.
I am equally successful with other crucifers of a less marked flavour:
white mustard (Sinapis incana, Lin.), dyer's woad (Isatis tinctoria,
Lin.), wild radish (Raphanus raphanistrum, Lin.), whitlow pepperwort
(Lepidium draba, Lin.), hedge-mustard (Sisymbrium officinale, Scop.).
On the other hand, the leaves of the lettuce, the bean, the pea, the
corn-salad are obstinately refused. Let us be content with what we have
seen: the fare has been sufficiently varied to show us that the
cabbage-caterpillar feeds exclusively on a large number of crucifers,
perhaps even on all.
As these experiments are made in the enclosure of a bell-cage, one
might imagine that captivity impels the flock to feed, in the absence
of better things, on what it would refuse were it free to hunt for
itself. Having naught else within their reach, the starvelings consume
any and all Cruciferae, without distinction of species. Can things
sometimes be the same in the open fields, where I play none of my
tricks? Can the family of the White Butterfly be settled on other
Crucifers than the cabbage? I start a quest along the paths near the
gardens and end by finding on wild radish and white mustard colonies as
crowded and prosperous as those established on cabbage.
Now, except when the metamorphosis is at hand, the caterpillar of the
White Butterfly never travels: he does all his growing on the identical
plant whereon he saw the light. The caterpillars observed on the wild
radish, as well as other households, are not, therefore, emigrants who
have come as a matter of fancy from some cabbage-patch in the
neighbourhood: they have hatched on the very leaves where I find them.
Hence I arrive at this conclusion: the White Butterfly, who is fitful
in her flight, chooses cabbage first, to dab her eggs upon, and
different Cruciferae next, varying greatly in appearance.
How does the Pieris manage to know her way about her botanical domain?
We have seen the Larini (A species of Weevils found on
thistle-heads.--Translator's Note.), those explorers of fleshy
receptacles with an artichoke flavour, astonish us with their knowledge
of the flora of the thistle tribe; but their lore might, at a pinch, be
explained by the method followed at the moment of housing the egg. With
their rostrum, they prepare niches and dig out basins in the receptacle
exploited and consequently they taste the thing a little before
entrusting their eggs to it. On the other hand, the Butterfly, a
nectar-drinker, makes not the least enquiry into the savoury qualities
of the leafage; at most dipping her proboscis into the flowers, she
abstracts a mouthful of syrup. This means of investigation, moreover,
would be of no use to her, for the plant selected for the establishing
of her family is, for the most part, not yet in flower. The mother
flits for a moment around the plant; and that swift examination is
enough: the emission of eggs takes place if the provender be found
suitable.
The botanist, to recognize a crucifer, requires the indication provided
by the flower. Here the Pieris surpasses us. She does not consult the
seed-vessel, to see if it be long or short, nor yet the petals, four in
number and arranged in a cross, because the plant, as a rule, is not in
flower; and still she recognizes offhand what suits her caterpillars,
in spite of profound differences that would embarrass any but a
botanical expert.
Unless the Pieris has an innate power of discrimination to guide her,
it is impossible to understand the great extent of her vegetable realm.
She needs for her family Cruciferae, nothing but Cruciferae; and she
knows this group of plants to perfection. I have been an enthusiastic
botanist for half a century and more. Nevertheless, to discover if this
or that plant, new to me, is or is not one of the Cruciferae, in the
absence of flowers and fruits I should have more faith in the
Butterfly's statements than in all the learned records of the books.
Where science is apt to make mistakes instinct is infallible.
The Pieris has two families a year: one in April and May, the other in
September. The cabbage-patches are renewed in those same months. The
Butterfly's calendar tallies with the gardener's: the moment that
provisions are in sight, consumers are forthcoming for the feast.
The eggs are a bright orange-yellow and do not lack prettiness when
examined under the lens. They are blunted cones, ranged side by side on
their round base and adorned with finely-scored longitudinal ridges.
They are collected in slabs, sometimes on the upper surface, when the
leaf that serves as a support is spread wide, sometimes on the lower
surface when the leaf is pressed to the next ones. Their number varies
considerably. Slabs of a couple of hundred are pretty frequent;
isolated eggs, or eggs collected in small groups, are, on the contrary,
rare. The mother's output is affected by the degree of quietness at the
moment of laying.
The outer circumference of the group is irregularly formed, but the
inside presents a certain order. The eggs are here arranged in straight
rows backing against one another in such a way that each egg finds a
double support in the preceding row. This alternation, without being of
an irreproachable precision, gives a fairly stable equilibrium to the
whole.
To see the mother at her laying is no easy matter: when examined too
closely, the Pieris decamps at once. The structure of the work,
however, reveals the order of the operations pretty clearly. The
ovipositor swings slowly first in this direction, then in that, by
turns; and a new egg is lodged in each space between two adjoining eggs
in the previous row. The extent of the oscillation determines the
length of the row, which is longer or shorter according to the layer's
fancy.
The hatching takes place in about a week. It is almost simultaneous for
the whole mass: as soon as one caterpillar comes out of its egg, the
others come out also, as though the natal impulse were communicated
from one to the other. In the same way, in the nest of the Praying
Mantis, a warning seems to be spread abroad, arousing every one of the
population. It is a wave propagated in all directions from the point
first struck.
The egg does not open by means of a dehiscence similar to that of the
vegetable-pods whose seeds have attained maturity; it is the new-born
grub itself that contrives an exit-way by gnawing a hole in its
enclosure. In this manner, it obtains near the top of the cone a
symmetrical dormer-window, clean-edged, with no joins nor unevenness of
any kind, showing that this part of the wall has been nibbled away and
swallowed. But for this breach, which is just wide enough for the
deliverance, the egg remains intact, standing firmly on its base. It is
now that the lens is best able to take in its elegant structure. What
it sees is a bag made of ultra-fine gold-beater's skin, translucent,
stiff and white, retaining the complete form of the original egg. A
score of streaked and knotted lines run from the top to the base. It is
the wizard's pointed cap, the mitre with the grooves carved into
jewelled chaplets. All said, the Cabbage-caterpillar's birth-casket is
an exquisite work of art.
The hatching of the lot is finished in a couple of hours and the
swarming family musters on the layer of swaddling-clothes, still in the
same position. For a long time, before descending to the fostering
leaf, it lingers on this kind of hot-bed, is even very busy there. Busy
with what? It is browsing a strange kind of grass, the handsome mitres
that remain standing on end. Slowly and methodically, from top to base,
the new-born grubs nibble the wallets whence they have just emerged. By
to-morrow, nothing is left of these but a pattern of round dots, the
bases of the vanished sacks.
As his first mouthfuls, therefore, the Cabbage-caterpillar eats the
membranous wrapper of his egg. This is a regulation diet, for I have
never seen one of the little grubs allow itself to be tempted by the
adjacent green stuff before finishing the ritual repast whereat skin
bottles furnish forth the feast. It is the first time that I have seen
a larva make a meal of the sack in which it was born. Of what use can
this singular fare be to the budding caterpillar? I suspect as follows:
the leaves of the cabbage are waxed and slippery surfaces and nearly
always slant considerably. To graze on them without risking a fall,
which would be fatal in earliest childhood, is hardly possible unless
with moorings that afford a steady support. What is needed is bits of
silk stretched along the road as fast as progress is made, something
for the legs to grip, something to provide a good anchorage even when
the grub is upside down. The silk-tubes, where those moorings are
manufactured, must be very scantily supplied in a tiny, new-born
animal; and it is expedient that they be filled without delay with the
aid of a special form of nourishment. Then what shall the nature of the
first food be? Vegetable matter, slow to elaborate and niggardly in its
yield, does not fulfil the desired conditions at all well, for time
presses and we must trust ourselves safely to the slippery leaf. An
animal diet would be preferable: it is easier to digest and undergoes
chemical changes in a shorter time. The wrapper of the egg is of a
horny nature, as silk itself is. It will not take long to transform the
one into the other. The grub therefore tackles the remains of its egg
and turns it into silk to carry with it on its first journeys.
If my surmise is well-founded, there is reason to believe that, with a
view to speedily filling the silk-glands to which they look to supply
them with ropes, other caterpillars beginning their existence on smooth
and steeply-slanting leaves also take as their first mouthful the
membranous sack which is all that remains of the egg.
The whole of the platform of birth-sacks which was the first
camping-ground of the White Butterfly's family is razed to the ground;
naught remains but the round marks of the individual pieces that
composed it. The structure of piles has disappeared; the prints left by
the piles remain. The little caterpillars are now on the level of the
leaf which shall henceforth feed them. They are a pale orange-yellow,
with a sprinkling of white bristles. The head is a shiny black and
remarkably powerful; it already gives signs of the coming gluttony. The
little animal measures scarcely two millimetres in length. (.078
inch.--Translator's Note.)
The troop begins its steadying-work as soon as it comes into contact
with its pasturage, the green cabbage-leaf. Here, there, in its
immediate neighbourhood, each grub emits from its spinning glands short
cables so slender that it takes an attentive lens to catch a glimpse of
them. This is enough to ensure the equilibrium of the almost
imponderable atom.
The vegetarian meal now begins. The grub's length promptly increases
from two millimetres to four. Soon, a moult takes place which alters
its costume: its skin becomes speckled, on a pale-yellow ground, with a
number of black dots intermingled with white bristles. Three or four
days of rest are necessary after the fatigue of breaking cover. When
this is over, the hunger-fit starts that will make a ruin of the
cabbage within a few weeks.
What an appetite! What a stomach, working continuously day and night!
It is a devouring laboratory, through which the foodstuffs merely pass,
transformed at once. I serve up to my caged herd a bunch of leaves
picked from among the biggest: two hours later, nothing remains but the
thick midribs; and even these are attacked when there is any delay in
renewing the victuals. At this rate a "hundredweight-cabbage," doled
out leaf by leaf, would not last my menagerie a week.
The gluttonous animal, therefore, when it swarms and multiplies, is a
scourge. How are we to protect our gardens against it? In the days of
Pliny, the great Latin naturalist, a stake was set up in the middle of
the cabbage-bed to be preserved; and on this stake was fixed a Horse's
skull bleached in the sun: a Mare's skull was considered even better.
This sort of bogey was supposed to ward off the devouring brood.
My confidence in this preservative is but an indifferent one; my reason
for mentioning it is that it reminds me of a custom still observed in
our own days, at least in my part of the country. Nothing is so
long-lived as absurdity. Tradition has retained in a simplified form,
the ancient defensive apparatus of which Pliny speaks. For the Horse's
skull our people have substituted an egg-shell on the top of a switch
stuck among the cabbages. It is easier to arrange; also it is quite as
useful, that is to say, it has no effect whatever.
Everything, even the nonsensical, is capable of explanation with a
little credulity. When I question the peasants, our neighbours, they
tell me that the effect of the egg-shell is as simple as can be: the
Butterflies, attracted by the whiteness, come and lay their eggs upon
it. Broiled by the sun and lacking all nourishment on that thankless
support, the little caterpillars die; and that makes so many fewer.
I insist; I ask them if they have ever seen slabs of eggs or masses of
young caterpillars on those white shells.
"Never," they reply, with one voice.
"Well, then?"
"It was done in the old days and so we go on doing it: that's all we
know; and that's enough for us."
I leave it at that, persuaded that the memory of the Horse's skull,
used once upon a time, is ineradicable, like all the rustic absurdities
implanted by the ages.
We have, when all is said, but one means of protection, which is to
watch and inspect the cabbage-leaves assiduously and crush the slabs of
eggs between our finger and thumb and the caterpillars with our feet.
Nothing is so effective as this method, which makes great demands on
one's time and vigilance. What pains to obtain an unspoilt cabbage! And
what a debt do we not owe to those humble scrapers of the soil, those
ragged heroes, who provide us with the wherewithal to live!
To eat and digest, to accumulate reserves whence the Butterfly will
issue: that is the caterpillar's one and only business. The
Cabbage-caterpillar performs it with insatiable gluttony. Incessantly
it browses, incessantly digests: the supreme felicity of an animal
which is little more than an intestine. There is never a distraction,
unless it be certain see-saw movements which are particularly curious
when several caterpillars are grazing side by side, abreast. Then, at
intervals, all the heads in the row are briskly lifted and as briskly
lowered, time after time, with an automatic precision worthy of a
Prussian drill-ground. Can it be their method of intimidating an always
possible aggressor? Can it be a manifestation of gaiety, when the
wanton sun warms their full paunches? Whether sign of fear or sign of
bliss, this is the only exercise that the gluttons allow themselves
until the proper degree of plumpness is attained.
After a month's grazing, the voracious appetite of my caged herd is
assuaged. The caterpillars climb the trelliswork in every direction,
walk about anyhow, with their forepart raised and searching space. Here
and there, as they pass, the swaying herd put forth a thread. They
wander restlessly, anxiously to travel afar. The exodus now prevented
by the trellised enclosure I once saw under excellent conditions. At
the advent of the cold weather, I had placed a few cabbage-stalks,
covered with caterpillars, in a small greenhouse. Those who saw the
common kitchen vegetable sumptuously lodged under glass, in the company
of the pelargonium and the Chinese primrose, were astonished at my
curious fancy. I let them smile. I had my plans: I wanted to find out
how the family of the Large White Butterfly behaves when the cold
weather sets in. Things happened just as I wished. At the end of
November, the caterpillars, having grown to the desired extent, left
the cabbages, one by one, and began to roam about the walls. None of
them fixed himself there or made preparations for the transformation. I
suspected that they wanted the choice of a spot in the open air,
exposed to all the rigours of winter. I therefore left the door of the
hothouse open. Soon the whole crowd had disappeared.
I found them dispersed all over the neighbouring walls, some thirty
yards off. The thrust of a ledge, the eaves formed by a projecting bit
of mortar served them as a shelter where the chrysalid moult took place
and where the winter was passed. The Cabbage-caterpillar possesses a
robust constitution, unsusceptible to torrid heat or icy cold. All that
he needs for his metamorphosis is an airy lodging, free from permanent
damp.
The inmates of my fold, therefore, move about for a few days on the
trelliswork, anxious to travel afar in search of a wall. Finding none
and realizing that time presses, they resign themselves. Each one,
supporting himself on the trellis, first weaves around himself a thin
carpet of white silk, which will form the sustaining layer at the time
of the laborious and delicate work of the nymphosis. He fixes his
rear-end to this base by a silk pad and his fore-part by a strap that
passes under his shoulders and is fixed on either side to the carpet.
Thus slung from his three fastenings, he strips himself of his larval
apparel and turns into a chrysalis in the open air, with no protection
save that of the wall, which the caterpillar would certainly have found
had I not interfered.
Of a surety, he would be short-sighted indeed that pictured a world of
good things prepared exclusively for our advantage. The earth, the
great foster-mother, has a generous breast. At the very moment when
nourishing matter is created, even though it be with our own zealous
aid, she summons to the feast host upon host of consumers, who are all
the more numerous and enterprising in proportion as the table is more
amply spread. The cherry of our orchards is excellent eating: a maggot
contends with us for its possession. In vain do we weigh suns and
planets: our supremacy, which fathoms the universe, cannot prevent a
wretched worm from levying its toll on the delicious fruit. We make
ourselves at home in a cabbage bed: the sons of the Pieris make
themselves at home there too. Preferring broccoli to wild radish, they
profit where we have profited; and we have no remedy against their
competition save caterpillar-raids and egg-crushing, a thankless,
tedious, and none too efficacious work.
Every creature has its claims on life. The Cabbage-caterpillar eagerly
puts forth his own, so much so that the cultivation of the precious
plant would be endangered if others concerned did not take part in its
defence. These others are the auxiliaries (The author employs this word
to denote the insects that are helpful, while describing as "ravagers"
the insects that are hurtful to the farmer's crops.--Translator's
Note.), our helpers from necessity and not from sympathy. The words
friend and foe, auxiliaries and ravagers are here the mere conventions
of a language not always adapted to render the exact truth. He is our
foe who eats or attacks our crops; our friend is he who feeds upon our
foes. Everything is reduced to a frenzied contest of appetites.
In the name of the might that is mine, of trickery, of highway robbery,
clear out of that, you, and make room for me: give me your seat at the
banquet! That is the inexorable law in the world of animals and more or
less, alas, in our own world as well!
Now, among our entomological auxiliaries, the smallest in size are the
best at their work. One of them is charged with watching over the
cabbages. She is so small, she works so discreetly that the gardener
does not know her, has not even heard of her. Were he to see her by
accident, flitting around the plant which she protects, he would take
no notice of her, would not suspect the service rendered. I propose to
set forth the tiny midget's deserts.
Scientists call her Microgaster glomeratus. What exactly was in the
mind of the author of the name Microgaster, which means little belly?
Did he intend to allude to the insignificance of the abdomen? Not so.
However slight the belly may be, the insect nevertheless possesses one,
correctly proportioned to the rest of the body, so that the classic
denomination, far from giving us any information, might mislead us,
were we to trust it wholly. Nomenclature, which changes from day to day
and becomes more and more cacophonous, is an unsafe guide. Instead of
asking the animal what its name is, let us begin by asking:
"What can you do? What is your business?"
Well, the Microgaster's business is to exploit the Cabbage-caterpillar,
a clearly-defined business, admitting of no possible confusion. Would
we behold her works? In the spring, let us inspect the neighbourhood of
the kitchen-garden. Be our eye never so unobservant, we shall notice
against the walls or on the withered grasses at the foot of the hedges
some very small yellow cocoons, heaped into masses the size of a
hazel-nut.
Beside each group lies a Cabbage-caterpillar, sometimes dying,
sometimes dead, and always presenting a most tattered appearance. These
cocoons are the work of the Microgaster's family, hatched or on the
point of hatching into the perfect stage; the caterpillar is the dish
whereon that family has fed during its larval state. The epithet
glomeratus, which accompanies the name of Microgaster, suggests this
conglomeration of cocoons. Let us collect the clusters as they are,
without seeking to separate them, an operation which would demand both
patience and dexterity, for the cocoons are closely united by the
inextricable tangle of their surface-threads. In May a swarm of pigmies
will sally forth, ready to get to business in the cabbages.
Colloquial language uses the terms Midge and Gnat to describe the tiny
insects which we often see dancing in a ray of sunlight. There is
something of everything in those aerial ballets. It is possible that
the persecutrix of the Cabbage-caterpillar is there, along with many
another; but the name of Midge cannot properly be applied to her. He
who says Midge says Fly, Dipteron, two-winged insect; and our friend
has four wings, one and all adapted for flying. By virtue of this
characteristic and others no less important, she belongs to the order
of Hymenoptera. (This order includes the Ichneumon-flies, of whom the
Microgaster is one.--Translator's Note.) No matter: as our language
possesses no more precise term outside the scientific vocabulary, let
us use the expression Midge, which pretty well conveys the general
idea. Our Midge, the Microgaster, is the size of an average Gnat. She
measures 3 or 4 millimetres. (.117 to .156 inch.--Translator's Note.)
The two sexes are equally numerous and wear the same costume, a black
uniform, all but the legs, which are pale red. In spite of this
likeness, they are easily distinguished. The male has an abdomen which
is slightly flattened and, moreover, curved at the tip; the female,
before the laying, has hers full and perceptibly distended by its
ovular contents. This rapid sketch of the insect should be enough for
our purpose.
If we wish to know the grub and especially to inform ourselves of its
manner of living, it is advisable to rear in a cage a numerous herd of
Cabbage-caterpillars. Whereas a direct search on the cabbages in our
garden would give us but a difficult and uncertain harvest, by this
means we shall daily have as many as we wish before our eyes.
In the course of June, which is the time when the caterpillars quit
their pastures and go far afield to settle on some wall or other, those
in my fold, finding nothing better, climb to the dome of the cage to
make their preparations and to spin a supporting network for the
chrysalid's needs. Among these spinners we see some weaklings working
listlessly at their carpet. Their appearance makes us deem them in the
grip of a mortal disease. I take a few of them and open their bellies,
using a needle by way of a scalpel. What comes out is a bunch of green
entrails, soaked in a bright yellow fluid, which is really the
creature's blood. These tangled intestines swarm with little lazy
grubs, varying greatly in number, from ten or twenty at least to
sometimes half a hundred. They are the offspring of the Microgaster.
What do they feed on? The lens makes conscientious enquiries; nowhere
does it manage to show me the vermin attacking solid nourishment, fatty
tissues, muscles or other parts; nowhere do I see them bite, gnaw, or
dissect. The following experiment will tell us more fully: I pour into
a watch-glass the crowds extracted from the hospitable paunches. I
flood them with caterpillar's blood obtained by simple pricks; I place
the preparation under a glass bell-jar, in a moist atmosphere, to
prevent evaporation; I repeat the nourishing bath by means of fresh
bleedings and give them the stimulant which they would have gained from
the living caterpillar. Thanks to these precautions, my charges have
all the appearance of excellent health; they drink and thrive. But this
state of things cannot last long. Soon ripe for the transformation, my
grubs leave the dining-room of the watch-glass as they would have left
the caterpillar's belly; they come to the ground to try and weave their
tiny cocoons. They fail in the attempt and perish. They have missed a
suitable support, that is to say, the silky carpet provided by the
dying caterpillar. No matter: I have seen enough to convince me. The
larvae of the Microgaster do not eat in the strict sense of the word;
they live on soup; and that soup is the caterpillar's blood.
Examine the parasites closely and you shall see that their diet is
bound to be a liquid one. They are little white grubs, neatly
segmented, with a pointed forepart splashed with tiny black marks, as
though the atom had been slaking its thirst in a drop of ink. It moves
its hind-quarters slowly, without shifting its position. I place it
under the microscope. The mouth is a pore, devoid of any apparatus for
disintegration-work: it has no fangs, no horny nippers, no mandibles;
its attack is just a kiss. It does not chew, it sucks, it takes
discreet sips at the moisture all around it.
The fact that it refrains entirely from biting is confirmed by my
autopsy of the stricken caterpillars. In the patient's belly,
notwithstanding the number of nurselings who hardly leave room for the
nurse's entrails, everything is in perfect order; nowhere do we see a
trace of mutilation. Nor does aught on the outside betray any havoc
within. The exploited caterpillars graze and move about peacefully,
giving no sign of pain. It is impossible for me to distinguish them
from the unscathed ones in respect of appetite and untroubled
digestion.
When the time approaches to weave the carpet for the support of the
chrysalis, an appearance of emaciation at last points to the evil that
is at their vitals. They spin nevertheless. They are stoics who do not
forget their duty in the hour of death. At last they expire, quite
softly, not of any wounds, but of anaemia, even as a lamp goes out when
the oil comes to an end. And it has to be. The living caterpillar,
capable of feeding himself and forming blood, is a necessity for the
welfare of the grubs; he has to last about a month, until the
Microgaster's offspring have achieved their full growth. The two
calendars synchronize in a remarkable way. When the caterpillar leaves
off eating and makes his preparations for the metamorphosis, the
parasites are ripe for the exodus. The bottle dries up when the
drinkers cease to need it; but until that moment it must remain more or
less well-filled, although becoming limper daily. It is important,
therefore, that the caterpillar's existence be not endangered by wounds
which, even though very tiny, would stop the working of the
blood-fountains. With this intent, the drainers of the bottle are, in a
manner of speaking, muzzled; they have by way of a mouth a pore that
sucks without bruising.
The dying caterpillar continues to lay the silk of his carpet with a
slow oscillation of the head. The moment now comes for the parasites to
emerge. This happens in June and generally at nightfall. A breach is
made on the ventral surface or else in the sides, never on the back:
one breach only, contrived at a point of minor resistance, at the
junction of two segments; for it is bound to be a toilsome business, in
the absence of a set of filing-tools. Perhaps the grubs take one
another's places at the point attacked and come by turns to work at it
with a kiss.
In one short spell, the whole tribe issues through this single opening
and is soon wriggling about, perched on the surface of the caterpillar.
The lens cannot perceive the hole, which closes on the instant. There
is not even a haemorrhage: the bottle has been drained too thoroughly.
You must press it between your fingers to squeeze out a few drops of
moisture and thus discover the place of exit.
Around the caterpillar, who is not always quite dead and who sometimes
even goes on weaving his carpet a moment longer, the vermin at once
begin to work at their cocoons. The straw-coloured thread, drawn from
the silk-glands by a backward jerk of the head, is first fixed to the
white network of the caterpillar and then produces adjacent warp-beams,
so that, by mutual entanglements, the individual works are welded
together and form an agglomeration in which each of the grubs has its
own cabin. For the moment, what is woven is not the real cocoon, but a
general scaffolding which will facilitate the construction of the
separate shells. All these frames rest upon those adjoining and, mixing
up their threads, become a common edifice wherein each grub contrives a
shelter for itself. Here at last the real cocoon is spun, a pretty
little piece of closely-woven work.
In my rearing-jars I obtain as many groups of these tiny shells as my
future experiments can wish for. Three-fourths of the caterpillars have
supplied me with them, so ruthless has been the toll of the spring
births. I lodge these groups, one by one, in separate glass tubes, thus
forming a collection on which I can draw at will, while, in view of my
experiments, I keep under observation the whole swarm produced by one
caterpillar.
The adult Microgaster appears a fortnight later, in the middle of June.
There are fifty in the first tube examined. The riotous multitude is in
the full enjoyment of the pairing-season, for the two sexes always
figure among the guests of any one caterpillar. What animation! What an
orgy of love! The carnival of these pigmies bewilders the observer and
makes his head swim.
Most of the females, wishful of liberty, plunge down to the waist
between the glass of the tube and the plug of cotton-wool that closes
the end turned to the light; but the lower halves remain free and form
a circular gallery in front of which the males hustle one another, take
one another's places and hastily operate. Each bides his turn, each
attends to his little matters for a few moments and then makes way for
his rivals and goes off to start again elsewhere. The turbulent wedding
lasts all the morning and begins afresh next day, a mighty throng of
couples embracing, separating and embracing once more.
There is every reason to believe that, in gardens, the mated ones,
finding themselves in isolated couples, would keep quieter. Here, in
the tube, things degenerate into a riot because the assembly is too
numerous for the narrow space.
What is lacking to complete its happiness? Apparently a little food, a
few sugary mouthfuls extracted from the flowers. I serve up some
provisions in the tubes: not drops of honey, in which the puny
creatures would get stuck, but little strips of paper spread with that
dainty. They come to them, take their stand on them and refresh
themselves. The fare appears to agree with them. With this diet,
renewed as the strips dry up, I can keep them in very good condition
until the end of my inquisition.
There is another arrangement to be made. The colonists in my spare
tubes are restless and quick of flight; they will have to be
transferred presently to sundry vessels without my risking the loss of
a good number, or even the whole lot, a loss which my hands, my forceps
and other means of coercion would be unable to prevent by checking the
nimble movements of the tiny prisoners. The irresistible attraction of
the sunlight comes to my aid. If I lay one of my tubes horizontally on
the table, turning one end towards the full light of a sunny window,
the captives at once make for the brighter end and play about there for
a long while, without seeking to retreat. If I turn the tube in the
opposite direction, the crowd immediately shifts its quarters and
collects at the other end. The brilliant sunlight is its great joy.
With this bait, I can send it whithersoever I please.
We will therefore place the new receptacle, jar or test-tube, on the
table, pointing the closed end towards the window. At its mouth, we
open one of the full tubes. No other precaution is needed: even though
the mouth leaves a large interval free, the swarm hastens into the
lighted chamber. All that remains to be done is to close the apparatus
before moving it. The observer is now in control of the multitude,
without appreciable losses, and is able to question it at will.
We will begin by asking:
"How do you manage to lodge your germs inside the caterpillar?"
This question and others of the same category, which ought to take
precedence of everything else, are generally neglected by the impaler
of insects, who cares more for the niceties of nomenclature than for
glorious realities. He classifies his subjects, dividing them into
regiments with barbarous labels, a work which seems to him the highest
expression of entomological science. Names, nothing but names: the rest
hardly counts. The persecutor of the Pieris used to be called
Microgaster, that is to say, little belly: to-day she is called
Apanteles, that is to say, the incomplete. What a fine step forward! We
now know all about it!
Can our friend at least tell us how "the Little Belly" or "the
Incomplete" gets into the caterpillar? Not a bit of it! A book which,
judging by its recent date, should be the faithful echo of our actual
knowledge, informs us that the Microgaster inserts her eggs direct into
the caterpillar's body. It goes on to say that the parasitic vermin
inhabit the chrysalis, whence they make their way out by perforating
the stout horny wrapper. Hundreds of times have I witnessed the exodus
of the grubs ripe for weaving their cocoons; and the exit has always
been made through the skin of the caterpillar and never through the
armour of the chrysalis. The fact that its mouth is a mere clinging
pore, deprived of any offensive weapon, would even lead me to believe
that the grub is incapable of perforating the chrysalid's covering.
This proved error makes me doubt the other proposition, though logical,
after all, and agreeing with the methods followed by a host of
parasites. No matter: my faith in what I read in print is of the
slightest; I prefer to go straight to facts. Before making a statement
of any kind, I want to see, what I call seeing. It is a slower and more
laborious process; but it is certainly much safer.
I will not undertake to lie in wait for what takes place on the
cabbages in the garden: that method is too uncertain and besides does
not lend itself to precise observation. As I have in hand the necessary
materials, to wit, my collection of tubes swarming with the parasites
newly hatched into the adult form, I will operate on the little table
in my animals' laboratory. A jar with a capacity of about a litre
(About 1 3/4 pints, or .22 gallon.--Translator's Note.) is placed on
the table, with the bottom turned towards the window in the sun. I put
into it a cabbage-leaf covered with caterpillars, sometimes fully
developed, sometimes half-way, sometimes just out of the egg. A strip
of honeyed paper will serve the Microgaster as a dining room, if the
experiment is destined to take some time. Lastly, by the method of
transfer which I described above, I send the inmates of one of my tubes
into the apparatus. Once the jar is closed, there is nothing left to do
but to let things take their course and to keep an assiduous watch, for
days and weeks, if need be. Nothing worth remarking can escape me.
The caterpillars graze placidly, heedless of their terrible attendants.
If some giddy-pates in the turbulent swarm pass over the caterpillars'
spines, these draw up their fore-part with a jerk and as suddenly lower
it again; and that is all: the intruders forthwith decamp. Nor do the
latter seem to contemplate any harm: they refresh themselves on the
honey-smeared strip, they come and go tumultuously. Their short flights
may land them, now in one place, now in another, on the browsing herd,
but they pay no attention to it. What we see is casual meetings, not
deliberate encounters.
In vain I change the flock of caterpillars and vary their age; in vain
I change the squad of parasites; in vain I follow events in the jar for
long hours, morning and evening, both in a dim light and in the full
glare of the sun: I succeed in seeing nothing, absolutely nothing, on
the parasite's side, that resembles an attack. No matter what the
ill-informed authors say--ill-informed because they had not the
patience to see for themselves--the conclusion at which I arrive is
positive: to inject the germs, the Microgaster never attacks the
caterpillars.
The invasion, therefore, is necessarily effected through the
Butterfly's eggs themselves, as experiment will prove. My broad jar
would tell against the inspection of the troop, kept at too great a
distance by the glass enclosure, and I therefore select a tube an inch
wide. I place in this a shred of cabbage-leaf, bearing a slab of eggs,
as laid by the Butterfly. I next introduce the inmates of one of my
spare vessels. A strip of paper smeared with honey accompanies the new
arrivals.
This happens early in July. Soon, the females are there, fussing about,
sometimes to the extent of blackening the whole slab of yellow eggs.
They inspect the treasure, flutter their wings and brush their
hind-legs against each other, a sign of keen satisfaction. They sound
the heap, probe the interstices with their antennae and tap the
individual eggs with their palpi; then, this one here, that one there,
they quickly apply the tip of their abdomen to the egg selected. Each
time, we see a slender, horny prickle darting from the ventral surface,
close to the end. This is the instrument that deposits the germ under
the film of the egg; it is the inoculation-needle. The operation is
performed calmly and methodically, even when several mothers are
working at one and the same time. Where one has been, a second goes,
followed by a third, a fourth and others yet, nor am I able definitely
to see the end of the visits paid to the same egg. Each time, the
needle enters and inserts a germ.
It is impossible, in such a crowd, for the eye to follow the successive
mothers who hasten to lay in each; but there is one quite practicable
method by which we can estimate the number of germs introduced into a
single egg, which is, later, to open the ravaged caterpillars and count
the grubs which they contain. A less repugnant means is to number the
little cocoons heaped up around each dead caterpillar. The total will
tell us how many germs were injected, some by the same mother returning
several times to the egg already treated, others by different mothers.
Well, the number of these cocoons varies greatly. Generally, it
fluctuates in the neighbourhood of twenty, but I have come across as
many as sixty-five; and nothing tells me that this is the extreme
limit. What hideous industry for the extermination of a Butterfly's
progeny!
I am fortunate at this moment in having a highly-cultured visitor,
versed in the profundities of philosophic thought. I make way for him
before the apparatus wherein the Microgaster is at work. For an hour
and more, standing lens in hand, he, in his turn, looks and sees what I
have just seen; he watches the layers who go from one egg to the other,
make their choice, draw their slender lancet and prick what the stream
of passers-by, one after the other, have already pricked. Thoughtful
and a little uneasy, he puts down his lens at last. Never had he been
vouchsafed so clear a glimpse as here, in my finger-wide tube, of the
masterly brigandage that runs through all life down to that of the very
smallest.
INDEX.
Ammophila.
Andrena.
Anoxia.
Ant-lion.
Anthidium.
Anthophora personata.
Anthrax.
Apanteles, see Microgaster glomeratus.
Arundo donax, the great reed.
Audubon, on trapping Turkeys.
Bats.
Bell-ringing Toad.
Bembex.
Bird-catchers.
Blackbirds, Corsican.
Bluebottle.
the laying of the eggs.
hatching.
a test.
paper a protection against.
the grubs.
sand a protection against.
Bower-bird.
Brussels Sprouts, ancestry of.
Buprestis.
Burying-beetles: method of burial.
appearance of the insect.
manipulation of the corpse.
cooperation of individuals.
larvae of.
attacked by vermin.
the dismal end of.
experiments.
test conditions imposed.
conditions of burial.
nets of cordage cut through.
ligatures severed.
limitations of instinct.
Cabbage, ancestry of.
offspring.
Cabbage Butterfly, her selection of suitable Cruciferae.
eggs of.
hatching of the eggs.
Cabbage-caterpillar.
eats egg-cases on emergence.
employment of silk by.
growth and moults.
its voracity.
an old charm against.
the only true charm.
movements of the caterpillar.
its chrysalis.
its deadly enemy.
Calliphora vomitaria, see Bluebottle.
Capricorn Beetle.
the grub.
its cell.
the barricade.
the pupa.
metamorphosis and emergence.
Cauliflower.
Centauries.
Cerambyx miles.
Cerceris.
Cetonia, or Rose-chafer.
Chalicodoma.
Chat, Black-eared.
Cicada.
the grasshopper's victim.
Cicadella.
Clairville on the Burying-beetle.
Clothes-moth.
Cockchafers.
Cole-rape.
Cordillac, philosophy of.
Couch-grass.
Cricket, Italian.
Common Black.
Cruciferae, the diet of Pieris brassicae.
Dasypoda.
Dermestes.
Digger-wasps.
Dragon-fly.
Drilus maroccanus.
Dung-beetles.
Empusa.
larva of.
fore-limbs.
strange head-dress.
food of.
how killed.
metamorphosis of.
curious position assumed in captivity.
pacific nature of.
Epeira, Angular, telegraph wire of.
Epeira fasciator.
appearance of.
its web.
nature of the thread.
her station on the web.
fatty unguent of.
nature of the adhesive glue.
hunting methods.
treatment of prey.
bite of.
the alarm.
the telegraph wire.
Epeira, Silky.
Ephippigera.
Eucera.
Eumenes.
cells of different species.
nest of E. pomiformis.
prey found in nest of E. Amedei.
sex of eggs known to insect.
prey in nest of E. pomiformis.
experiments on larvae.
position of the egg.
suspension of the larvae.
the protective sheath.
Flesh-fly, Grey.
viviparous.
maggots of.
a test.
her attacks on meat-safes.
baffled by sand.
Fly.
Frog, burial of a.
Froghopper.
Geotrupes.
Gledditsch on Burying-beetles.
Glow-worm.
diet of Snails.
anaesthetises its prey.
digestive juice secreted by.
adhesive climbing appendage of.
luminous apparatus of.
regulation of light.
light displayed by females.
eyes of the male.
pairing.
eggs.
luminosity of eggs.
of larvae.
Grasshopper, Green.
the note of the.
stridulating apparatus.
habitat.
food.
mating habits.
eggs.
seminal capsule.
Greenfinch.
Halictus.
Harmas.
description of.
Harmonica.
Horn-beetle.
Hornet.
Hunting-wasp.
Laboratory, the outdoor.
Lacordaire on the Burying-beetle.
Lamellicornis.
Larini.
Linnet, dead, preserved from flies by paper.
Lizard, Eyed.
Locust.
the prey of the Epeira.
Lycosa, Narbonne.
its eyes.
its burrow.
the rampart.
use of same.
methods of catching prey.
method of laying eggs.
the egg-sac.
experiments with.
the hatching process.
the young.
experiments with.
a problem of energy.
Macrocera.
Mantis, Praying.
Mason-bees.
cells used by Osmiae.
Mason-wasps.
Massagetae, customs of the.
Megachiles.
Melolontho fullo.
Michelet.
Microgaster glomeratus.
the exterminator of the Cabbage Caterpillar.
method of feeding.
emergence from the host.
cocoons.
the adult.
pairing.
food.
the eggs laid in the Butterfly's egg.
Mole, burial of a.
a supply of corpses obtained.
Mouse, burial of a.
National festival, the.
Natterjack.
Necrophorus, see Burying-beetles.
Oryctes.
Osmia.
cells of different species.
glass nests of Three-horned Osmia.
distribution of sexes.
optional determination of sex.
Owl.
Horned Owl.
Common Owl.
Oyster-plant.
Pelopaeus.
Pérez, Professor.
Philanthus apivorus.
Phylloxera.
Pieris brassicae.
Pine Processionary.
silken road of.
nest.
use of road.
senses.
nest.
the processionary march.
experiments.
on a circular track.
Pliny, on the Cabbage Caterpillar.
Pompilus.
Rose-chafer.
Sacred Beetle.
Saprini.
Sarcophaga carnaria, see Flesh-fly.
Scarabaeus.
Scolia.
Scops.
Serin-finch.
Sex, distribution, determination and permutations of, in the Osmia.
Silpha.
Sitaris.
Snail-shell, Osmia's use of.
Snail, the prey of the Glow-worm.
Sphex.
Sphex, White-banded.
Spiders.
apprised of prey by vibration.
Staphylinus.
Stizus.
Swede.
Tadpoles.
Tarantula, Black-bellied, see Lycosa.
Thistles.
Thomisus.
Toad, Bell-ringing.
Tree-frogs.
Tree Wasps.
Turkeys, how trapped.
Ventoux, Mount.
Wasp, Common.
Woodpecker.