THE SPOTTED LARINUS
Larinus is a vague term, which cannot teach us anything. The word
sounds well. It is something not to afflict the ear with raucous
spittings; but the prentice reader wants more than this. He expects the
name to give him, in euphonious syllables, a brief description of the
insect named. This would help to guide him in the midst of the vast
multitude.
I cordially agree with him, while recognizing what an arduous task it
would be to devise a rational nomenclature that would give the beasts
the forenames and surnames which they deserve. Our ignorance condemns
us to be vague and often nonsensical. Let us consider a case in point.
What does Larinus mean? The Greek lexicon tells us: Λαρινός, fatty,
fat. Has the insect which is the subject of this chapter any right to
such a description? Not at all. It is corpulent, I agree, as are the
Weevils generally, but does not more than another deserve a certificate
of obesity.
Let us look a little deeper. Λαρός means pleasant to the taste,
pleasant to the eye, dainty, sweet. Are we there now? Not yet. To be
sure, the Larinus is not without daintiness, but how many among the
long-nosed Beetles excel him in beauty of costume! Our osier-beds
provide nourishment for some that are flecked with flowers of sulphur,
some that are laced with Chinese white, some that are powdered with
malachite-green. They leave on our fingers a scaly dust that looks as
though it were gathered from a Butterfly’s wing. Our vines and
poplar-trees have some that surpass copper pyrites in metallic lustre;
the equatorial countries furnish specimens of unparalleled
magnificence, true gems beside which the marvels of our jewel-cases
would pale. No, the modest Larinus has no right to be extolled as
superb. The title of dandy must be awarded to others, in the
beak-bearing family, rather than to him.
If his godfather, better-informed, had named him after his habits, he
would have called him an artichoke-thief. The group of the Larini, in
fact, establishes its offspring in the fleshy base of the flowers of
the Carduaceæ, the thistle, the cotton-thistle, the centaury, the
carline thistle and others, which, in structure and flavour, recall
more or less remotely the artichoke of our tables. This is its special
province. The Larinus is charged with the thinning out of the fierce,
encroaching thistle.
Glance at the pink, white or blue heads of a Carduacea. Long-beaked
insects swarm, awkwardly diving into the mass of florets. What are
they? Larini. Open the head, split its fleshy base. Surprised by the
air and by the light, plump, white, legless grubs sway to and fro, each
isolated in a small recess. What are these grubs? Larinus-larvæ.
Here accuracy calls for a reservation. A few other Weevils, related to
those whose history we are considering, are also partial, on behalf of
their family, to the fleshy receptacles with the artichoke flavour. No
matter: the species that take the lead in numbers, frequency and
handsome proportions are the authorized exterminators of the
thistle-heads. Now the reader knows as much as I can tell him.
All the summer, all the autumn, until the cold weather sets in, the
most ornamental of our southern thistles grows profusely by the
roadside. Its pretty, blue flowers, gathered into round, prickly heads,
have won it the botanical name of Echinops, in allusion to the Hedgehog
rolled into a ball. It is indeed like a Hedgehog. Better still: it is
like a Sea-urchin stuck upon a stalk and turned into an azure globe.
Beneath a screen of star-shaped flowerets the shapely tuft hides the
thousand daggers of its scales. Whosoever touches it with an incautious
finger is surprised to encounter such aggressiveness beneath an
innocent appearance. The leaves that go with it, green above, white and
fluffy underneath, do at least warn the inexperienced: they are divided
into pointed lobes, each of which bears an extremely sharp needle at
its tip.
This thistle is the patrimony of the Spotted Larinus (L. maculosus,
Sch.), whose back is powdered with cloudy yellow patches. The Weevil
browses very sparingly on the leaves. June is not yet over before she
is exploiting the heads, green at this time and the size of peas, or at
most of cherries, with a view to establishing her family. For two or
three weeks the work of colonization continues on globes which grow
bluer and larger day by day.
Couples are formed, very peaceably, in the glad morning sunlight. The
nuptial preliminaries, resembling the embraces of jointed levers,
display a rustic awkwardness. With his fore-legs the male Weevil
masters his spouse; with his hinder tarsi, gently and at intervals, he
strokes her sides. Alternating with these soft caresses are sudden
jolts and impetuous jerks. Meanwhile, the object of these attentions,
in order to lose no time, works at the thistle-head with her beak and
prepares the lodging for her egg. Even in the midst of her wedding the
care of the family leaves this laborious insect no repose.
What precisely is the use of the Weevil’s rostrum, this paradoxical
nose, such as no carnival mummer would venture to wear? We shall find
out at leisure, taking our own time.
My prisoners, enclosed in a wire-gauze cover, are working in the
sunlight on my window-sill. A couple has just broken apart. Careless of
what will happen next, the male retires to browse for a while, not on
the blue thistle-heads, which are choice morsels reserved for the
young, but on the leaves, where a superficial scraping enables the beak
to remove some frugal mouthfuls. The mother remains where she is and
continues the boring already commenced.
The rostrum is driven right into the ball of florets and disappears
from sight. The insect hardly moves, taking at most a few slow strides
now in one direction, now in another. What we see is not the work of a
gimlet, which twists, but of an awl, which sinks steadily downwards.
The mandibles, the sharp shears affixed to the implement, bite and dig;
and that is all. In the end, the rostrum used as a lever, that is to
say, bending upon its base, uproots and lifts the detached florets and
pushes them a little way outwards. This must cause the slight
unevenness which we perceive at any inhabited point. The work of
excavation lasts a good quarter of an hour.
Then the mother turns about, finds the opening of the shaft with the
tip of her belly and lays the egg. But how? The pregnant insect’s
abdomen is far too large and too blunt to enter the narrow passage and
deposit the egg directly at the bottom. A special tool, a probe
carrying the egg to the point required, is therefore absolutely needed
here. But the insect does not possess one that shows; and things take
place so swiftly and discreetly that I see nothing of that kind
unsheathed.
No matter, I am positively convinced of it: to place the egg at the
bottom of the shaft which the rostrum has just bored, the mother must
possess a guide-rod, a rigid tube, kept in reserve, invisible, among
her tools. We shall return to this curious subject when more conclusive
instances arise.
One first point is gained: the Weevil’s rostrum, that nose which at
first sight was deemed grotesque, is in reality an instrument of
maternal love. The extravagant becomes the everyday, the indispensable.
Since it carries mandibles and other mouth parts at its tip, its
function is to eat, that is self-evident; but to this function is added
another of greater importance. The fantastic stylet prepares the way
for the eggs; it is the oviduct’s collaborator.
And this implement, the emblem of the guild, is so honourable that the
father does not hesitate to sport it, though himself incapable of
digging the family cells. Like his consort, he too carries an awl, but
a smaller one, as befits the modesty of his rôle.
A second point becomes clear. In order to insert the egg at convenient
points, it is the rule for the insect to possess an implement with two
functions, an implement which at the same time opens the passage and
guides the eggs along it. This is the case with the Cicada, [22] the
Grasshopper, [23] the Saw-fly, the Leucospis [24] and the
Ichneumon-fly, [25] all of whom carry a sabre, a saw or a probe at the
tip of the abdomen.
The Weevil divides the work and apportions it between two implements,
one of which, in front, is the perforating auger, and the other,
behind, hidden in the body and unsheathed at the moment of the laying,
is the guiding tube. Except in the Weevils, this curious mechanism is
unknown to me.
When the egg is placed in position—and this is quickly done, thanks to
the preliminary work of the drill—the mother returns to the point
colonized. She packs the disturbed materials a little, she lightly
pushes back the uprooted florets; then, without taking further trouble,
she goes away. She sometimes even dispenses with these precautions.
A few hours later, I examine the heads exploited, which may be
recognized by a certain number of faded and slightly projecting
patches, each of which shelters an egg. With the point of my penknife I
extract the little, faded bundle and open it. At the base, in a small
round cell, hollowed out of the substance of the central globule, the
receptacle of the thistle-head, is the egg, fairly large, yellow and
oval.
It is enveloped in a brown substance derived from the tissues injured
by the mother’s auger and from the exudations of the wound, which have
set like cement. This envelope rises into an irregular cone and ends in
the withered florets. In the centre of the tuft we generally see an
opening, which might well be a ventilating-shaft.
The number of eggs entrusted to a single head may easily be ascertained
without destroying the cells: all that we need do is to count the
yellow blurs unevenly distributed over the blue background. I have
found five, six and more, even in a head smaller than a cherry. Each
covers an egg. Do all these eggs come from the same mother? It is
possible. At the same time, they may be of diverse origin, for it is
not unusual to surprise two mothers both occupied in laying eggs on the
same globe.
Sometimes the points worked upon almost touch. The mother, it seems,
has a very restricted numerical sense and is incapable of keeping count
of the occupants. She drives her probe into the florets, unheeding that
the place beside her is already taken. As a rule there are too many,
far too many feasters at the niggardly banquet of the blue thistle.
Three at most will find enough to live on. The first-comers will
thrive; the laggards will perish for lack of room at the common table.
The grubs are hatched in a week: little white atoms with red heads to
them. Suppose them to be three in number, as frequently happens. What
have the little creatures in their larder? Next to nothing. The
echinops is an exception among the Carduaceæ. Its flowers do not rest
upon a fleshy receptacle expanded into a heart, like the artichoke’s.
Let us open one of the heads. In the centre, as a common support, is a
round firm nucleus, a globe hardly as large as a peppercorn, fixed on
the top of a little column which is a continuation of the axis of the
stem. That is all.
A scanty, a very scanty provision for three consumers. In bulk there is
not enough to furnish the first few meals of a single grub; still less
is there enough—for it is very tough and unsubstantial—to provide for
those fine layers of fat which make the grub look as sleek as butter
and are employed as reserves during the transformation.
Nevertheless, it is in this paltry globule and the small column which
supports it that the three boarders find, their whole life long, the
wherewithal to feed and grow. Not a bite is given elsewhere; and even
so the attack is delivered with extreme discretion. The food is rasped
and nibbled on the surface and not completely consumed.
To make much out of nothing, to fill three starveling bellies,
sometimes four, with a single crumb, would be out of the question. The
secret of the food-supply is not contained in the small amount of solid
matter that has disappeared. Let us look into this more closely.
I take out a few larvæ which are already fairly well-grown and install
dwellings and dwellers in glass tubes. For a long time, with my
pocket-lens, I watch the prisoners. I cannot see that they bite into
the central knob, which is already damaged, nor the axis, which also
has been cut into. From these surfaces, which have been scored since I
know not how long; from what appeared to be their daily bread, their
mandibles remove not the smallest particle. At most the mouth is
applied for a moment to the surface; then it is withdrawn, uneasy and
disdainful. It is evident that the ligneous fare, though still quite
fresh, does not suit.
The proof is completed by the final result of my experiments. In vain I
keep the thistle-heads fresh in glass tubes, plugged with a stopper of
wet cotton-wool: my attempts at rearing are not once crowned with
success. As soon as the head is removed from the plant, its inhabitants
begin to die of starvation, whether I intervene or whether I do not.
They all pine away in the heart of their native globe and at last
perish, no matter in what receptacle—test-tube, flask or tin box—I
place my collection. Later, on the other hand, when the feeding-period
is over, I shall find it very easy to keep the grubs in good condition
and to follow at will their preparations for the nymphosis.
This failure tells me that the larva of the Spotted Larinus does not
sustain itself with solid food; it prefers the clear broth of the sap.
It taps the cask of its azure cellar, that is to say, it makes a
careful gash in the axis of the head as well as in the central nucleus.
From these surface wounds, which are kept open by fresh strokes of the
plane as soon as a dry scab forms upon them, it laps the sap of the
thistle, which oozes up from the roots. As long as the blue globe is on
its stalk, very much alive, the sap ascends, the broached casks exude
their contents and the grub sips the nourishing draught. But, once
detached from the stem, cut off from its source of supply, the cellar
runs dry. Thereupon the larva promptly dies. This explains the fatal
catastrophe of my attempts to rear it.
All that the Larinus-larvæ need is to lick the exudations from a wound.
The method employed is henceforth obvious. The new-born grubs, hatched
upon the central globe, take their places around its axis,
proportioning the distance between them to the number of guests. Each
of them peels and slashes with its mandibles the part in front of it,
causing the nutritious moisture to exude. If the spring dries up
through healing, fresh bites revive it.
But the attack is made with circumspection, The central column and its
circular capital form the mainstay of the globe. If too extensively
injured, the scaffolding would bend before the wind and bring down the
dwelling. Moreover, the conduits of the aqueduct must be respected, if
a suitable supply of sap is to be provided until the end. Accordingly,
whether three or four in number, the grubs abstain from rasping the
surface too deeply.
The cuts, which amount to no more than a judicious paring of the
surface, imperil neither the solidity of the structure nor the action
of the vessels, so that the blossoms, their plunderers notwithstanding,
retain a very healthy appearance. They expand as usual, except that the
pretty, blue ground is stained with yellow patches, which grow wider
from day to day. At each of these points, a grub is established under
the cover of the dead florets. Each blemish marks one diner’s seat at
table.
The florets, as we said, have for their common support, for their
receptacle, the round knob surmounting the axis. It is on this globule
that the grubs begin. They attack a few of the florets at their base,
uprooting them without injuring them and thrusting them upwards with a
heave of the back. The spot thus cleared is slightly broken into and
hollowed out and becomes the first refreshment-bar.
What becomes of the items removed? Are they thrown to the ground as
inconvenient rubbish? The tiny creature is careful not to do anything
of the kind, which would mean exposing its plump back, a small but
enticing morsel, to the eyes of the foe.
Pushed back, the materials cleared away remain intact, still clustered
together in their natural position. Not a flake, not a chip falls to
earth. By means of a quick-setting, rain-proof glue, the whole of the
fragments detached are cemented to the base in a continuous sheaf, so
that the blossom is kept intact, save for the yellowish tint of the
parts wounded. As the grub increases in size, more florets are cut away
and take their place, beside the others, in the roof, which swells by
degrees and ends by bulging out.
Thus a quiet dwelling is obtained, sheltered from wind and weather and
the heat of the sun. Within, the hermit sips at his cask in safety; he
waxes big and fat. I suspected it, that the larva would be able to make
up by its own industry for the rough-and-ready installation of the egg!
Where maternal care is lacking, the grub possesses special talents as a
safeguard.
Nevertheless, nothing in the grub of the Spotted Larinus reveals the
skilful builder of thatched huts. It is a little sausage of a creature,
a rusty yellow in colour and bent into a hook. There is not a vestige
of legs; the whole equipment consists of the mouth and the opposite
end, an active auxiliary. What can this little roll of rancid butter be
capable of doing? To observe it at work is easy enough at the
propitious moment.
In the middle of August, when the larva, having achieved its full
growth, is busy strengthening and plastering its abode in view of the
approaching nymphosis, I half-open a few cells. The hulls opened, but
still adhering to the natal blossom, are arranged in a row in a glass
tube which will enable me to watch the work without disturbing the
worker. I have not long to wait for the result.
In a state of repose, the grub is a hook with the extremities very near
together. From time to time I see it bring the two ends into intimate
contact and close the circuit. Then—do not let us be shocked by the
grub’s procedure: this would mean misconceiving life’s sacred
simplicities—then with its mandibles it very neatly gathers from the
stercoral orifice a tiny drop the size of an ordinary pin’s head. It is
a muddy white liquid, flowing like gum, similar in appearance to the
resinous beads that ooze from the horned galls of the turpentine-tree
when you break them.
The grub spreads its little drop over the edges of the breach made in
its dwelling; it distributes it here and there, very sparingly; it
pushes and coaxes it into the gaps. Then, attacking the adjacent
florets, it picks out the shreds and chips and bits of hairs.
This does not satisfy it. It rasps the axis and the central nucleus of
the blossom, detaching tiny scraps and atoms. A laborious task, for the
mandibles are short and cut badly. They tear rather than slice.
All this is distributed over the still fresh cement. This done, the
grub bestirs itself most strenuously, bending into a hook and
straightening out again; it rolls and glides about its cabin to make
the materials amalgamate and to smooth the wall with the pad of its
round rump.
When this pressing and polishing is finished, the larva once more
curves into a circle. A second white drop appears at the factory-door.
The mandibles take hold of the ignominious product as they would of an
ordinary mouthful; and the process is repeated as before: the cell is
first smeared with glue and then encrusted with ligneous particles.
After thus expending a certain number of trowelfuls of cement, the grub
remains motionless; it seems to be abandoning a job too much for its
means. Twenty-four hours later, the open hulls are still gaping. An
attempt has been made to repair the cell, but not to close it
thoroughly. The task is too heavy.
What is lacking? Not the ligneous materials, which can always be
obtained from the grub’s surroundings, but the adhesive cement, the
factory having closed down. And why has it closed down? The answer is
quite simple: because the vessels of the thistle-head detached from its
stalk are dry and can no longer furnish the food upon which everything
depends.
The curly-bearded Chaldean used to build with bricks of mud baked in
the kiln and cemented with bitumen. The Weevil of the blue thistle
possessed the secret of asphalt long before man did. Better still: to
put its method into practice with a rapidity and economy unknown to the
Babylonian contractors, it had and still has its own well of bitumen.
What can this viscous substance be? As I have explained, it appears in
opal drops at the waste-pipe of the intestine. Becoming hard and
resinous on contact with the air, it turns a tawny red, so much so that
the inside of the cell looks at first as though coated with
quince-jelly. The final hue is a dull brown, against which pale specks
of mixed ligneous refuse stand out sharply.
The first idea that occurs to one’s mind is that the Weevil’s glue must
be some special secretion, not unlike silk, but emerging from the
opposite pole. Can there be actually glands secreting a viscous fluid
in the grub’s hinder part? I open a larva which is busily building.
Things are not as I imagined: there is no glandular apparatus attached
to the lower end of the digestive canal.
Nor is there anything to be seen in the ventricle. Only the Malpighian
tubes, which are rather large and four in number, reveal, by their
opaline tint, the fact that they are fairly full; while the lower
portion of the intestine is dilated with a pulpy substance which
conspicuously attracts the eye.
It is a semi-fluid, viscous, treacly material of a muddy white. I
perceive that it contains an abundance of opaque corpuscles, like
finely powdered chalk, which effervesce when dissolved in nitric acid
and are therefore uric products.
This very soft pulp is, beyond a doubt, the cement which the grub
ejects and collects drop by drop; and the rectum is obviously the
bitumen-warehouse. The parity of aspect, colour, and treacly
consistency are to me decisive: the grub consolidates and cements and
creates a work of art with the refuse from its sewer.
Is this really an excremental residue? Doubts may be permitted. The
four Malpighian tubes which have poured the powdered urates into the
intestine might well supply it with other materials. They do not in
general seem to perform very exclusive duties. Why should they not be
entrusted with various functions in a poorly-equipped organism? They
fill with a chalky broth to enable the Capricorn’s larva to block the
doorway of its cell with a marble slab. It would not be at all
surprising if they were also gorged with the viscous fluid that becomes
the asphalt of the Larinus.
In this embarrassing instance the following explanation may possibly
suffice. The Larinus’ larva observes, as we know, a very light diet,
consisting of sap instead of solid food. Therefore there is no coarse
residue. I have never seen any dirt in the cell; its cleanliness is
perfect.
This does not mean that all the nourishment is absorbed. There is
certainly refuse of no nutritive value, but it is thin and almost
fluid. Can this be the pitch that cements and stops up the chinks? Why
not? If so, the grub would be building with its excrement; with its
ordure it would be making a pretty home.
Here we must silence our repugnance. Where would you have the recluse
obtain the material for its casket? Its cell is its world. It knows
nothing beyond that cell; nothing comes to its assistance. It must
perish if it cannot find its store of cement within itself. Various
caterpillars, not rich enough to afford the luxury of a perfect cocoon,
have the knack of felting their hairs with a little silk. The Larinus
grub, that poverty-stricken creature, having no spinning-mill, must
have recourse to its intestine, its only stand-by.
This stercoral method proves once more that necessity is the mother of
invention. To build a luxurious palace with one’s ordure is a most
meritorious device. Only an insect would be capable of it. For that
matter, the Larinus has no monopoly of this architectural style, which
is not described in Vitruvius, [26] Many other larvæ, better-furnished
with building-materials—those of the Onites, the Onthophagi, [27] the
Cetoniæ, [28] for example—greatly excel it in the beauty of their
excremental edifices.
When completed, on the approach of the nymphosis, the abode of the
Larinus is an oval cell measuring fifteen millimetres in length by ten
in width. [29] Its compact structure almost enables it to resist the
pressure of the fingers. Its main diameter runs parallel with the axis
of the thistle-head. When, as is not unusual, three cells are grouped
on the same support, the whole is not unlike the fruit of the
castor-oil-plant, with its three shaggy husks.
The outer wall of the cell is a rustic bristle of chips and hairy
débris and above all of whole florets, faded and yellow, torn from
their base and pushed out of place while retaining their natural
arrangement. In the thickness of the wall the cement predominates. The
inner wall is polished, washed with a red-brown lacquer and sprinkled
with an incrustation of ligneous fragments. Lastly, the pitch is of
excellent quality. It makes a solid wall of the work; and, moreover, it
is impervious to moisture: when immersed in water, the cell does not
permit any to pass through to the interior.
In short, the Larinus’ cell is a comfortable dwelling, endowed, in the
beginning, with the pliancy of soft leather, which allows free scope
for the growing-process; then, thanks to the cement, it hardens into a
shell permitting the peaceful somnolence of the transformation. The
flexible tent of the early days becomes a stout manor-house.
Here, I told myself, the adult would pass the winter, protected against
the damp, which is more to be dreaded than the cold. I was wrong. By
the end of September most of the cells are empty, though their support,
the blue thistle, eager to open its last blooms, is still in fairly
good condition. The Weevils have gone, in all the freshness of their
flowered costume; they have broken out through the top of their cells,
which now gape like broken pitchers. A few loiterers still lag behind
at home, but are quite ready to make off, judging by their agility when
my curiosity chances to set them free.
When the inclement months of December and January have arrived, I no
longer find a single cell inhabited. The whole population has migrated.
Where has it taken refuge?
I am not quite sure. Perhaps in the heaps of broken stones, under cover
of the dead leaves, in the shelter of the tufts of grass that grow
beneath the hawthorn in the hedges. For a Weevil the country-side is
full of winter-resorts. We need not be anxious about the emigrants;
they are well able to look after themselves.
None the less, in the face of this exodus, my first impression is one
of surprise. To leave such an excellent lodging for a casual shelter,
of doubtful safety, seems to me a rash and ill-advised expedient. Can
the insect be lacking in prudence? No; it has serious motives for
decamping as quickly as possible when the autumn draws to an end. Let
me explain matters.
In the winter the echinops is a brown ruin which the north-wind tears
from its hold, flings on the ground and reduces to tatters by rolling
it in the mud of the roads. A few days of bad weather turn the handsome
blue thistle into a mass of lamentable decay.
What would become of the Weevil on this support, now the plaything of
the winds? Would her tarred cask resist the assaults of the storm?
Would she survive rolling over the rough soil and prolonged steeping in
the puddles of melted snow?
The Weevils foreknow the dangers of a crazy support; warned by the
almanac of instinct, they foresee the winter and its miseries. So they
move house while there is yet time; they leave their cells for a stable
shelter where they will no longer have to fear the vicissitudes of a
dwelling blown along the ground at random.
The desertion of the casket is not a sign of rash haste on the part of
the Larinus: it shows a clear perception of coming events. In fact, a
second Larinus will teach us presently that, when the support is safe
and solidly rooted in the ground, the natal cell is not deserted until
the return of the fine weather.
In conclusion, I ought perhaps to mention an apparently insignificant,
but very exceptional fact, which I have only once observed in my
dealings with the Spotted Larinus. Considering the scarcity of
authentic data as to what becomes of instinct when the conditions of
life are altered, we should do wrong to neglect these trifling
discoveries.
Making ample allowance for anatomy, a precious aid, what do we know of
animals? Next to nothing. Instead of inflating cabbalistic bladders
with this nothing, let us collect well-observed facts, however humble.
From a sheaf of such facts a clear, calm light may shine forth one day,
a light far preferable to the fireworks of theories which dazzle us for
a moment only to leave us in blacker darkness.
Here is this little detail. By some accident an egg has fallen from the
blue globe, its regular lodging, into the axilla of a leaf half-way up
the stem. We can even admit, if we choose, that the mother, either by
inadvertence or by intention, laid it at this point herself. What will
become of the egg under such conditions, so far removed from the rules?
What I have before my eyes tell us.
The grub, faithful to custom, has not failed to broach the stem of the
thistle, which allows the nourishing moisture to ooze from the wound.
As a defence it has built itself a pitcher similar in shape and size to
that which it would have obtained in the thistle-head. This novel
edifice lacks only one thing: the roof of dead florets bristling on the
customary hut.
The builder has contrived to do very well without its floral pantiles.
It has made use of the base of the leaf, one lobe of which is involved,
as a support, in the wall of the cell; and from both leaf and stalk it
has taken the ligneous particles which it had to imbed in the cement.
In short, except that it is bare instead of surrounded with a palisade,
the fabric adhering to the stalk does not differ from that hidden
beneath the withered florets of the thistle-head.
People set great store by environment as a modifying agent. Well, here
we see this famous environment at work. An insect is placed as much out
of its element as it can be, but without leaving the food-plant, which
would inevitably be the end of it. Instead of a ball of close-packed
flowers it has for its workshop the open axilla of a leaf; instead of
hairs—a soft fleece easily shorn off—it has for its materials the
fierce teeth of the thistle. And these profound changes leave the
builder’s talents unperturbed; the house is built according to the
usual plans.
I agree that I have not allowed for the influence of the centuries. But
what would this influence bring about? It is not very clear. The Weevil
born in an unusual place retains no trace of the accident that has
happened. I extract the adult from his exceptional cell. He does not
differ, even in size, a not very important characteristic, from the
Larini born in the regular cell. He has thriven on the axilla of the
leaf as he would have done on the thistle-head.
Let us admit that the accident is repeated, that it even becomes a
normal condition; let us suppose that the mother decides to abandon her
blue balls and to confide her eggs to the axillæ of the leaves
indefinitely. What will this change bring about? The answer is obvious.
Since the grub has once developed without hindrance on a site alien to
its habits, it will continue to thrive there from generation to
generation; with its intestinal cement it will continue to shape a
protective pitcher of the same pattern as the old, but, for want of
materials, lacking the thatch of withered florets; in short, its
talents will remain what they were in the beginning.
This example tells us that the insect, as long as it can accommodate
itself to the novel conditions imposed upon it, works in its accustomed
fashion; if it cannot do so, it dies rather than change its methods.