Social Life in the Insect World Part 23

The shank of the larva has the same structure, so that the object to be extracted is enclosed in a scabbard as awkwardly shaped as itself. Each spur is enclosed in a similar spur; each tooth engages in the hollow of a similar tooth, and the sheath is so closely moulded upon the shank that a no more intimate contact could be obtained by replacing the envelope by a layer of varnish applied with a brush.

Nevertheless the tibia, long and narrow as it is, issues from its sheath without catching or sticking anywhere. If I had not repeatedly seen the operation I could not believe it possible; for the discarded sheath is absolutely intact from end to end. Neither the terminal spurs nor the double rows of spines do the slightest damage to the delicate mould. The long-toothed saw leaves the delicate sheath unbroken, although a puff of the breath is enough to tear it; the ferocious spurs slip out of it without leaving so much as a scratch.

I was far from expecting such a result. Having the spiny weapons of the legs in mind, I imagined that those limbs would moult in scales and patches, or that the sheathing would rub off like a dead scarf-skin. How completely the reality surpa.s.sed my antic.i.p.ations!

From the spurs and spines of the sheath, which is as thin as the finest gold-beaters' skin, the spurs and spines of the leg, which make it a most formidable weapon, capable of cutting a piece of soft wood, emerge without the slightest display of violence, without a hitch of any kind; and the empty skin remains in place. Still clinging by its claws to the top of the wire cover, it is untorn, unwrinkled, uncreased. Even the magnifying-gla.s.s fails to show a trace of rough usage. Such as the skin was before the cricket left it, so it is now. The legging of dead skin remains in its smallest details the exact replica of the living limb.

If any one asked you to extract a saw from a scabbard exactly moulded upon the steel, and to conduct the operation without the slightest degree of tearing or scratching, you would laugh at the flagrant impossibility of the task. But life makes light of such absurdities; it has its methods of performing the impossible when such methods are required. The leg of the locust affords us such an instance.

Hard as it is when once free of its sheath, the serrated tibia would absolutely refuse to leave the latter, so closely does it fit, unless it were torn to pieces. Yet the difficulty must be evaded, for it is indispensable that the sheaths of the legs should remain intact, in order to afford a firm support until the insect is completely extricated.

The leg in process of liberation is not the leg with which the locust makes its leaps; it has not as yet the rigidity which it will soon acquire. It is soft, and eminently flexible. In those portions which the progress of the moult exposes to view I see the legs bend under the mere weight of the suspended insect when I tilt the supporting cover. They are as flexible as two strips of elastic indiarubber. Yet even now consolidation is progressing, for in a few minutes the proper rigidity will be acquired.

Further along the limbs, in the portions which the sheathing still conceals, the legs are certainly softer still, and in the state of exquisite plasticity--I had almost said fluidity--which allows them to pa.s.s through narrow pa.s.sages almost as a liquid flows.

The teeth of the saws are already there, but have nothing of their imminent rigidity. With the point of a pen-knife I can partially uncover a leg and extract the spines from their serrated mould. They are germs of spines; flexible buds which bend under the slightest pressure and resume their position the moment the pressure is removed.

These needles point backwards as the leg is drawn out of the sheath; but they re-erect themselves and solidify as they emerge. I am witnessing not the mere removal of leggings from limbs already clad in finished armour, but a kind of creation which amazes one by its prompt.i.tude.

Very much in the same way, but with far less delicate precision, the claws of the crayfish, at the period of the moult, withdraw the soft flesh of their double fingers from their stony sheath.

Finally the long stilt-like legs are free. They are folded gently against the furrowed thighs, thus to mature undisturbed. The abdomen begins to emerge. Its fine tunic-like covering splits, and wrinkles, but still encloses the extremity of the abdomen, which adheres to the moulted skin for some little time longer. With the exception of this one point the entire insect is now uncovered.

It hangs head downwards, like a pendulum, supported by the talons of the now empty leg-cases. During the whole of the lengthy and meticulous process the four talons have never yielded. The whole operation has been conducted with the utmost delicacy and prudence.

The insect hangs motionless, held by the tip of the abdomen. The abdomen is disproportionately distended; swollen, apparently, by the reserve of organisable humours which the expansion of the wings and wing-covers will presently employ. Meanwhile the creature rests and recovers from its exertions. Twenty minutes of waiting elapse.

Then, exerting the muscles of the back, the suspended insect raises itself and fixes the talons of the anterior limbs in the empty skin above it. Never did acrobat, hanging by the toes to the bar of a trapeze, raise himself with so stupendous a display of strength in the loins. This gymnastic feat accomplished, the rest is easy.

With the purchase thus obtained the insect rises a little and reaches the wire gauze, the equivalent of the twig which would be chosen for the site of the transformation in the open fields. It holds to this with the four anterior limbs. Then the tip of the abdomen is finally liberated, and suddenly, shaken by the final struggle, the empty skin falls to the ground.

This fall is interesting, and reminds me of the persistence with which the empty husk of the Cigale braves the winds of winter, without falling from its supporting twig. The transfiguration of the locust takes place very much as does that of the Cigale. How is it then that the acridian trusts to a hold so easily broken?

The talons of the skin hold firmly so long as the labour of escape continues, although one would expect it to shake the firmest grip; yet they yield at the slightest shock when the labour is terminated. There is evidently a condition of highly unstable equilibrium; showing once more with what delicate precision the insect escapes from its sheath.

For want of a better term I said "escape." But the word is ill chosen; for it implies a certain amount of violence, and no violence must be employed, on account of the instability of equilibrium already mentioned. If the insect, shaken by a sudden effort, were to lose its hold, it would be all up with it. It would slowly shrivel on the spot; or at best its wings, unable to expand, would remain as miserable sc.r.a.ps of tissue. The locust does not tear itself away from its sheath; it delicately insinuates itself out of it--I had almost said flows. It is as though it were expelled by a gentle pressure.

Let us return to the wings and elytra, which have made no apparent progress since their emergence from their sheaths. They are still mere stumps, with fine longitudinal seams; almost like little ropes'-ends.

Their expansion, which will occupy more than three hours, is reserved for the end, when the insect is completely moulted and in its normal position.

We have just seen the insect turn head uppermost. This reversal causes the wings and elytra to fall into their natural position. Extremely flexible, and yielding to their own weight, they had previously drooped backwards with their free extremities pointing towards the head of the insect as it hung reversed.

Now, still by reason of their own weight, their position is rectified and they point in the normal direction. They are no longer curved like the petals of a flower; they no longer point the wrong way; but they retain the same miserable aspect.

In its perfect state the wing is like a fan. A radiating bundle of strong nervures runs through it in the direction of its length and forms the framework of the fan, which is readily furled and unfurled. The intervals are crossed by innumerable cross-nervures of slighter substance, which make of the whole a network of rectangular meshes. The elytrum, which is heavier and much less extensive, repeats this structure.

At present nothing of this mesh-work is visible. Nothing can be seen but a few wrinkles, a few flexuous furrows, which announce that the stumps are bundles of tissue cunningly folded and reduced to the smallest possible volume.

The expansion of the wing begins near the shoulder. Where nothing precise could be distinguished at the outset we soon perceive a diaphanous surface subdivided into meshes of beautiful precision.

Little by little, with a deliberation that escapes the magnifier, this area increases its bounds, at the expense of the shapeless bundle at the end of the wing. In vain I let my eyes rest on the spot where the expanding network meets the still shapeless bundle; I can distinguish nothing. But wait a little, and the fine-meshed tissues will appear with perfect distinctness.

To judge from this first examination, one would guess that an organisable fluid is rapidly congealing into a network of nervures; one seems to be watching a process of crystallisation comparable, in its rapidity, to that of a saturated saline solution as seen through a microscope. But no; this is not what is actually happening. Life does not do its work so abruptly.

I detach a half-developed wing and bring it under the powerful eye of the microscope. This time I am satisfied. On the confines of the transparent network, where an extension of that network seems to be gradually weaving itself out of nothing, I can see that the meshes are really already in existence. I can plainly recognise the longitudinal nervures, which are already stiff; and I can also see--pale, and without relief--the transverse nervures. I find them all in the terminal stump, and am able to spread out a few of its folds under the microscope.

It is obvious that the wing is not a tissue in the process of making, through which the procreative energy of the vital juices is shooting its shuttle; it is a tissue already complete. To be perfect it lacks only expansion and rigidity, just as a piece of lace or linen needs only to be ironed.

In three hours or more the explanation is complete. The wings and elytra stand erect over the locust's back like an immense set of sails; at first colourless, then of a tender green, like the freshly expanded wings of the Cigale. I am amazed at their expanse when I think of the miserable stumps from which they have expanded. How did so much material contrive to occupy so little s.p.a.ce?

There is a story of a grain of hemp-seed that contained all the body-linen of a princess. Here we have something even more astonishing.

The hemp-seed of the story needed long years to germinate, to multiply, and at last to give the quant.i.ty of hemp required for the trousseau of a princess; but the germ of the locust's wing has expanded to a magnificent sail in a few short hours.

Slowly the superb erection composed of the four flat fan-like pinions a.s.sumes rigidity and colour. By to-morrow the colour will have attained the requisite shade. For the first time the wings close fan-wise and lie down in their places; the elytra bend over at their outer edges, forming a f.l.a.n.g.e which lies snugly over the flanks. The transformation is complete. Now the great locust has only to harden its tissues a little longer and to tan the grey of its costume in the ecstasy of the sunshine. Let us leave it to its happiness, and return to an earlier moment.

The four stumps which emerge from their coverings shortly after the rupture of the corselet along its median line contain, as we have seen, the wings and elytra with their innumerable nervures. If not perfect, at least the general plan is complete, with all its innumerable details.

To expand these miserable bundles and convert them into an ample set of sails it is enough that the organism, acting like a force-pump, should force into the channels already prepared a stream of humours kept in reserve for this moment and this purpose, the most laborious of the whole process. As the capillary channels are prepared in advance a slight injection of fluid is sufficient to cause expansion.

But what were these four bundles of tissue while still enclosed in their sheaths? Are the wing-sheaths and the triangular winglets of the larva the moulds whose folds, wrinkles, and sinuosities form their contents in their own image, and so weave the network of the future wings and wing-covers?

Were they really moulds we might for a moment be satisfied. We might tell ourselves: It is quite a simple matter that the thing moulded should conform to the cavity of the mould. But the simplicity is only apparent, for the mould in its turn must somewhere derive the requisite and inextricable complexity. We need not go so far back; we should only be in darkness. Let us keep to the observable facts.

I examine with a magnifying-gla.s.s one of the triangular coat-tails of a larva on the point of transformation. I see a bundle of moderately strong nervures radiating fan-wise. I see other nervures in the intervals, pale and very fine. Finally, still more delicate, and running transversely, a number of very short nervures complete the pattern.

Certainly this resembles a rough sketch of the future wing-case; but how different from the mature structure! The disposition of the radiating nervures, the skeleton of the structure, is not at all the same; the network formed by the cross-nervures gives no idea whatever of the complex final arrangement. The rudimentary is succeeded by the infinitely complex; the clumsy by the infinitely perfect, and the same is true of the sheath of the wing and the final condition of its contents, the perfect wing.

It is perfectly evident, when we have the preparatory as well as the final condition of the wing before our eyes, that the wing-sheath of the larva is not a simple mould which elaborates the tissue enclosed in its own image and fashions the wing after the complexities of its own cavity.

The future wing is not contained in the sheath as a bundle, which will astonish us, when expanded, by the extent and extreme complication of its surface. Or, to speak more exactly, it is there, but in a potential state. Before becoming an actual thing it is a virtual thing which is not yet, but is capable of becoming. It is there as the oak is inside the acorn.

A fine transparent cushion limits the free edge of the embryo wing and the embryo wing-case. Under a powerful microscope we can perceive therein a few doubtful lineaments of the future lace-work. This might well be the factory in which life will shortly set its materials in movement. Nothing more is visible; nothing that will make us foresee the prodigious network in which each mesh must have its form and place predetermined with geometrical exact.i.tude.

In order that the organisable material can shape itself as a sheet of gauze and describe the inextricable labyrinth of the nervuration, there must be something better and more wonderful than a mould. There is a prototypical plan, an ideal pattern, which imposes a precise position upon each atom of the tissue. Before the material commences to circulate the configuration is already virtually traced, the courses of the plastic currents are already mapped out. The stones of our buildings co-ordinate according to the considered plan of the architect; they form an ideal a.s.semblage before they exist as a concrete a.s.semblage.

Similarly, the wing of a cricket, that wonderful piece of lace-work emerging from a tiny sheath, speaks to us of another Architect, the author of the plans according to which life labours.

The genesis of living creatures offers to our contemplation an infinity of wonders far greater than this matter of a locust's wing; but in general they pa.s.s unperceived, obscured as they are by the veil of time.

Time, in the deliberation of mysteries, deprives us of the most astonishing of spectacles except our spirits be endowed with a tenacious patience. Here by exception the fact is accomplished with a swiftness that forces the attention.

Whosoever would gain, without wearisome delays, a glimpse of the inconceivable dexterity with which the forces of life can labour, has only to consider the great locust of the vineyard. The insect will show him that which is hidden from our curiosity by extreme deliberation in the germinating seed, the opening leaf, and the budding flower. We cannot see the gra.s.s grow; but we can watch the growth of the locust's wings.

Amazement seizes upon us before this sublime phantasmagoria of the grain of hemp which in a few hours has been trans.m.u.ted into the finest cloth.

What a mighty artist is Life, shooting her shuttle to weave the wings of the locust--one of those insignificant insects of whom long ago Pliny said: _In his tam parcis, fere nullis, quae vis, quae sapientia, quam inextricabilis perfectio!_

How truly was the old naturalist inspired! Let us repeat with him: "What power, what wisdom, what inconceivable perfection in this least of secrets that the vineyard locust has shown us!"

I have heard that a learned inquirer, for whom life is only a conflict of physical and chemical forces, does not despair of one day obtaining artificially organisable matter--_protoplasm_, as the official jargon has it. If it were in my power I should hasten to satisfy this ambitious gentleman.