THE CIGALE LEAVES ITS BURROW

The first Cigales appear about the summer solstice. Along the beaten

paths, calcined by the sun, hardened by the passage of frequent feet, we

see little circular orifices almost large enough to admit the thumb.

These are the holes by which the larvae of the Cigale have come up from

the depths to undergo metamorphosis. We see them more or less

everywhere, except in fields where the soil has been disturbed by

ploughing. heir usual position is in the driest and hottest situations,

especially by the sides of roads or the borders of footpaths. Powerfully

equipped for the purpose, able at need to pierce the turf or sun-dried

clay, the larva, upon leaving the earth, seems to prefer the hardest

spots.



A garden alley, converted into a little Arabia Petraea by reflection from

a wall facing the south, abounds in such holes. During the last days of

June I have made an examination of these recently abandoned pits. The

soil is so compact that I needed a pick to tackle it.



The orifices are round, and close upon an inch in diameter. There is

absolutely no debris round them; no earth thrown up from within. This is

always the case; the holes of the Cigales are never surrounded by

dumping-heaps, as are the burrows of the Geotrupes, another notable

excavator. The way in which the work is done is responsible for this

difference. The dung-beetle works from without inwards; she begins to

dig at the mouth of the burrow, and afterwards re-ascends and

accumulates the excavated material on the surface. The larva of the

Cigale, on the contrary, works outward from within, upward from below;

it opens the door of exit at the last moment, so that it is not free for

the discharge of excavated material until the work is done. The first

enters and raises a little rubbish-heap at the threshold of her burrow;

the second emerges, and cannot, while working, pile up its rubbish on a

threshold which as yet has no existence.



The burrow of the Cigale descends about fifteen inches. It is

cylindrical, slightly twisted, according to the exigencies of the soil,

and always approaches the vertical, or the direction of the shortest

passage. It is perfectly free along its entire length. We shall search

in vain for the rubbish which such an excavation must apparently

produce; we shall find nothing of the sort. The burrow terminates in a

cul-de-sac, in a fairly roomy chamber with unbroken walls, which shows

not the least vestige of communication with any other burrow or

prolongation of the shaft.



Taking its length and diameter into account, we find the excavation has

a total volume of about twelve cubic inches. What becomes of the earth

which is removed?



Sunk in a very dry, crumbling soil, we should expect the shaft and the

chamber at the bottom to have soft, powdery walls, subject to petty

landslips, if no work were done but that of excavation. On the contrary,

the walls are neatly daubed, plastered with a sort of clay-like mortar.

They are not precisely smooth, indeed they are distinctly rough; but

their irregularities are covered with a layer of plaster, and the

crumbling material, soaked in some glutinous liquid and dried, is held

firmly in place.



The larva can climb up and down, ascend nearly to the surface, and go

down into its chamber of refuge, without bringing down, with his claws,

the continual falls of material which would block the burrow, make

ascent a matter of difficulty, and retreat impossible. The miner shores

up his galleries with uprights and cross-timbers; the builder of

underground railways supports the sides and roofs of his tunnels with a

lining of brick or masonry or segments of iron tube; the larva of the

Cigale, no less prudent an engineer, plasters the walls of its burrow

with cement, so that the passage is always free and ready for use.



If I surprise the creature just as it is emerging from the soil in order

to gain a neighbouring bough and there undergo transformation, I see it

immediately make a prudent retreat, descending to the bottom of its

burrow without the slightest difficulty--a proof that even when about to

be abandoned for ever the refuge is not encumbered with rubbish.



The ascending shaft is not a hurried piece of work, scamped by a

creature impatient to reach the sunlight. It is a true dwelling, in

which the larva may make a long stay. The plastered walls betray as

much. Such precautions would be useless in the case of a simple exit

abandoned as soon as made. We cannot doubt that the burrow is a kind of

meteorological observatory, and that its inhabitant takes note of the

weather without. Buried underground at a depth of twelve or fifteen

inches, the larva, when ripe for escape, could hardly judge whether the

meteorological conditions were favourable. The subterranean climate

varies too little, changes too slowly, and would not afford it the

precise information required for the most important action of its

life--the escape into the sunshine at the time of metamorphosis.



Patiently, for weeks, perhaps for months, it digs, clears, and

strengthens a vertical shaft, leaving only a layer of earth a finger's

breadth in thickness to isolate it from the outer world. At the bottom

it prepares a carefully built recess. This is its refuge, its place of

waiting, where it reposes in peace if its observations decide it to

postpone its final departure. At the least sign of fine weather it

climbs to the top of its burrow, sounds the outer world through the thin

layer of earth which covers the shaft, and informs itself of the

temperature and humidity of the outer air.



If things are not going well--if there are threats of a flood or the

dreaded _bise_--events of mortal gravity when the delicate insect issues

from its cerements--the prudent creature re-descends to the bottom of

its burrow for a longer wait. If, on the contrary, the state of the

atmosphere is favourable, the roof is broken through by a few strokes of

its claws, and the larva emerges from its tunnel.



Everything seems to prove that the burrow of the Cigale is a

waiting-room, a meteorological station, in which the larva makes a

prolonged stay; sometimes hoisting itself to the neighbourhood of the

surface in order to ascertain the external climate; sometimes retiring

to the depths the better to shelter itself. This explains the chamber

at the base of the shaft, and the necessity of a cement to hold the

walls together, for otherwise the creature's continual comings and

goings would result in a landslip.



A matter less easy of explanation is the complete disappearance of the

material which originally filled the excavated space. Where are the

twelve cubic inches of earth that represent the average volume of the

original contents of the shaft? There is not a trace of this material

outside, nor inside either. And how, in a soil as dry as a cinder, is

the plaster made with which the walls are covered?



Larvae which burrow in wood, such as those of Capricornis and Buprestes,

will apparently answer our first question. They make their way through

the substance of a tree-trunk, boring their galleries by the simple

method of eating the material in front of them. Detached by their

mandibles, fragment by fragment, the material is digested. It passes

from end to end through the body of the pioneer, yields during its

passage its meagre nutritive principles, and accumulates behind it,

obstructing the passage, by which the larva will never return. The work

of extreme division, effected partly by the mandibles and partly by the

stomach, makes the digested material more compact than the intact wood,

from which it follows that there is always a little free space at the

head of the gallery, in which the caterpillar works and lives; it is not

of any great length, but just suffices for the movements of the

prisoner.



Must not the larva of the Cigale bore its passage in some such fashion?

I do not mean that the results of excavation pass through its body--for

earth, even the softest mould, could form no possible part of its diet.

But is not the material detached simply thrust back behind the excavator

as the work progresses?



The Cigale passes four years under ground. This long life is not spent,

of course, at the bottom of the well I have just described; that is

merely a resting-place preparatory to its appearance on the face of the

earth. The larva comes from elsewhere; doubtless from a considerable

distance. It is a vagabond, roaming from one root to another and

implanting its rostrum. When it moves, either to flee from the upper

layers of the soil, which in winter become too cold, or to install

itself upon a more juicy root, it makes a road by rejecting behind it

the material broken up by the teeth of its picks. That this is its

method is incontestable.



As with the larvae of Capricornis and Buprestes, it is enough for the

traveller to have around it the small amount of free space necessitated

by its movements. Moist, soft, and easily compressible soil is to the

larva of the Cigale what digested wood-pulp is to the others. It is

compressed without difficulty, and so leaves a vacant space.



The difficulty is that sometimes the burrow of exit from the

waiting-place is driven through a very arid soil, which is extremely

refractory to compression so long as it retains its aridity. That the

larva, when commencing the excavation of its burrow, has already thrust

part of the detached material into a previously made gallery, now filled

up and disappeared, is probable enough, although nothing in the actual

condition of things goes to support the theory; but if we consider the

capacity of the shaft and the extreme difficulty of making room for such

a volume of debris, we feel dubious once more; for to hide such a

quantity of earth a considerable empty space would be necessary, which

could only be obtained by the disposal of more debris. Thus we are

caught in a vicious circle. The mere packing of the powdered earth

rejected behind the excavator would not account for so large a void. The

Cigale must have a special method of disposing of the waste earth. Let

us see if we can discover the secret.



Let us examine a larva at the moment of emerging from the soil. It is

almost always more or less smeared with mud, sometimes dried, sometimes

moist. The implements of excavation, the claws of the fore-feet, have

their points covered by little globules of mortar; the others bear

leggings of mud; the back is spotted with clay. One is reminded of a

scavenger who has been scooping up mud all day. This condition is the

more striking in that the insect comes from an absolutely dry soil. We

should expect to see it dusty; we find it muddy.



One more step, and the problem of the well is solved. I exhume a larva

which is working at its gallery of exit. Chance postpones this piece of

luck, which I cannot expect to achieve at once, since nothing on the

surface guides my search. But at last I am rewarded, and the larva is

just beginning its excavation. An inch of tunnel, free of all waste or

rubbish, and at the bottom the chamber, the place of rest; so far has

the work proceeded. And the worker--in what condition is it? Let us see.



The larva is much paler in colour than those which I have caught as they

emerged. The large eyes in particular are whitish, cloudy, blurred, and

apparently blind. What would be the use of sight underground? The eyes

of the larvae leaving their burrows are black and shining, and evidently

capable of sight. When it issues into the sunlight the future Cigale

must find, often at some distance from its burrow, a suitable twig from

which to hang during its metamorphosis, so that sight is obviously of

the greatest utility. The maturity of the eyes, attained during the time

of preparation before deliverance, proves that the larva, far from

boring its tunnel in haste, has spent a long time labouring at it.



What else do we notice? The blind, pale larva is far more voluminous

than in the mature state; it is swollen with liquid as though it had

dropsy. Taken in the fingers, a limpid serum oozes from the hinder part

of the body, which moistens the whole surface. Is this fluid, evacuated

by the intestine, a product of urinary secretion--simply the contents of

a stomach nourished entirely upon sap? I will not attempt to decide, but

for convenience will content myself with calling it urine.



Well, this fountain of urine is the key to the enigma. As it digs and

advances the larva waters the powdery debris and converts it into a

paste, which is immediately applied to the walls by the pressure of the

abdomen. Aridity is followed by plasticity. The mud thus obtained

penetrates the interstices of the rough soil; the more liquid portion

enters the substance of the soil by infiltration; the remainder becomes

tightly packed and fills up the inequalities of the walls. Thus the

insect obtains an empty tunnel, with no loose waste, as all the loosened

soil is utilised on the spot, converted into a mortar which is more

compact and homogeneous than the soil through which the shaft is

driven.



Thus the larva works in the midst of a coating of mud, which is the

cause of its dirtiness, so astonishing when we see it issue from an

excessively dry soil. The perfect insect, although henceforth liberated

from the work of a sapper and miner, does not entirely abandon the use

of urine as a weapon, employing it as a means of defence. Too closely

observed it throws a jet of liquid upon the importunate enemy and flies

away. In both its forms the Cigale, in spite of its dry temperament, is

a famous irrigator.



Dropsical as it is, the larva cannot contain sufficient liquid to

moisten and convert into easily compressible mud the long column of

earth which must be removed from the burrow. The reservoir becomes

exhausted, and the provision must be renewed. Where, and how? I think I

can answer the question.



The few burrows uncovered along their entirety, with the meticulous care

such a task demands, have revealed at the bottom, encrusted in the wall

of the terminal chamber, a living root, sometimes of the thickness of a

pencil, sometimes no bigger than a straw. The visible portion of this

root is only a fraction of an inch in length; the rest is hidden by the

surrounding earth. Is the presence of this source of sap fortuitous? Or

is it the result of deliberate choice on the part of the larva? I

incline towards the second alternative, so repeatedly was the presence

of a root verified, at least when my search was skilfully conducted.



Yes, the Cigale, digging its chamber, the nucleus of the future shaft,

seeks out the immediate neighbourhood of a small living root; it lays

bare a certain portion, which forms part of the wall, without

projecting. This living spot in the wall is the fountain where the

supply of moisture is renewed. When its reservoir is exhausted by the

conversion of dry dust into mud the miner descends to its chamber,

thrusts its proboscis into the root, and drinks deep from the vat built

into the wall. Its organs well filled, it re-ascends. It resumes work,

damping the hard soil the better to remove it with its talons, reducing

the debris to mud, in order to pack it tightly around it and obtain a

free passage. In this manner the shaft is driven upwards; logic and the

facts of the case, in the absence of direct observation, justify the

assertion.



If the root were to fail, and the reservoir of the intestine were

exhausted, what would happen? The following experiment will inform us: a

larva is caught as it leaves the earth. I place it at the bottom of a

test-tube, and cover it with a column of dry earth, which is rather

lightly packed. This column is about six inches in height. The larva has

just left an excavation three times as deep, made in soil of the same

kind, but offering a far greater resistance. Buried under this short

column of powdery earth, will it be able to gain the surface? If its

strength hold out the issue should be certain; having but lately made

its way through the hard earth, this obstacle should be easily removed.



But I am not so sure. In removing the stopper which divided it from the

outside world, the larva has expended its final store of liquid. The

cistern is dry, and in default of a living root there is no means of

replenishing it. My suspicions are well founded. For three days the

prisoner struggles desperately, but cannot ascend by so much as an inch.

It is impossible to fix the material removed in the absence of

moisture; as soon as it is thrust aside it slips back again. The labour

has no visible result; it is a labour of Sisyphus, always to be

commenced anew. On the fourth day the creature succumbs.



With the intestines full the result is very different.



I make the same experiment with an insect which is only beginning its

work of liberation. It is swollen with fluid, which oozes from it and

moistens the whole body. Its task is easy; the overlying earth offers

little resistance. A small quantity of liquid from the intestines

converts it into mud; forms a sticky paste which can be thrust aside

with the assurance that it will remain where it is placed. The shaft is

gradually opened; very unevenly, to be sure, and it is almost choked up

behind the insect as it climbs upwards. It seems as though the creature

recognises the impossibility of renewing its store of liquid, and so

economises the little it possesses, using only just so much as is

necessary in order to escape as quickly as possible from surroundings

which are strange to its inherited instincts. This parsimony is so well

judged that the insect gains the surface at the end of twelve days.



The gate of issue is opened and left gaping, like a hole made with an

augur. For some little time the larva wanders about the neighbourhood of

its burrow, seeking an eyrie on some low-growing bush or tuft of thyme,

on a stem of grass or grain, or the twig of a shrub. Once found, it

climbs and firmly clasps its support, the head upwards, while the talons

of the fore feet close with an unyielding grip. The other claws, if the

direction of the twig is convenient, assist in supporting it; otherwise

the claws of the two fore legs will suffice. There follows a moment of

repose, while the supporting limbs stiffen in an unbreakable hold. Then

the thorax splits along the back, and through the fissure the insect

slowly emerges. The whole process lasts perhaps half an hour.



There is the adult insect, freed of its mask, and how different from

what it was but how! The wings are heavy, moist, transparent, with

nervures of a tender green. The thorax is barely clouded with brown. All

the rest of the body is a pale green, whitish in places. Heat and a

prolonged air-bath are necessary to harden and colour the fragile

creature. Some two hours pass without any perceptible change. Hanging to

its deserted shell by the two fore limbs, the Cigale sways to the least

breath of air, still feeble and still green. Finally, the brown colour

appears and rapidly covers the whole body; the change of colour is

completed in half an hour. Fastening upon its chosen twig at nine

o'clock in the morning, the Cigale flies away under my eyes at half-past

twelve.



The empty shell remains, intact except for the fissure in the back;

clasping the twig so firmly that the winds of autumn do not always

succeed in detaching it. For some months yet and even during the winter

you will often find these forsaken skins hanging from the twigs in the

precise attitude assumed by the larva at the moment of metamorphosis.

They are of a horny texture, not unlike dry parchment, and do not

readily decay.



I could gather some wonderful information regarding the Cigale were I to

listen to all that my neighbours, the peasants, tell me. I will give one

instance of rustic natural history.






Are you afflicted with any kidney trouble, or are you swollen with

dropsy, or have you need of some powerful diuretic? The village

pharmacopoeia is unanimous in recommending the Cigale as a sovereign

remedy. The insects in the adult form are collected in summer. They are

strung into necklaces which are dried in the sun and carefully preserved

in some cupboard or drawer. A good housewife would consider it imprudent

to allow July to pass without threading a few of these insects.



Do you suffer from any nephritic irritation or from stricture? Drink an

infusion of Cigales. Nothing, they say, is more effectual. I must take

this opportunity of thanking the good soul who once upon a time, so I

was afterwards informed, made me drink such a concoction unawares for

the cure of some such trouble; but I still remain incredulous. I have

been greatly struck by the fact that the ancient physician of Anazarbus

used to recommend the same remedy. Dioscorides tells us: _Cicadae, quae

inassatae manduntur, vesicae doloribus prosunt_. Since the distant days

of this patriarch of _materia medica_ the Provencal peasant has retained

his faith in the remedy revealed to him by the Greeks, who came from

Phocaea with the olive, the fig, and the vine. Only one thing is changed:

Dioscorides advises us to eat the Cigales roasted, but now they are

boiled, and the decoction is administered as medicine. The explanation

which is given of the diuretic properties of the insect is a marvel of

ingenuousness. The Cigale, as every one knows who has tried to catch it,

throws a jet of liquid excrement in one's face as it flies away. It

therefore endows us with its faculties of evacuation. Thus Dioscorides

and his contemporaries must have reasoned; so reasons the peasant of

Provence to-day.



What would you say, worthy neighbours, if you knew of the virtues of the

larva, which is able to mix sufficient mortar with its urine to build a

meteorological station and a shaft connecting with the outer world? Your

powers should equal those of Rabelais' Gargantua, who, seated upon the

towers of Notre Dame, drowned so many thousands of the inquisitive

Parisians.