THE MANTIS - THE NEST





Let us take a more pleasant aspect of the insect whose loves are so

tragic. Its nest is a marvel. In scientific language it is known as the

_ootek_, or the "egg-box." I shall not make use of this barbarous

expression. As one does not speak of the "egg-box" of the titmouse,

meaning "the nest of the titmouse," why should I invoke the box in

speaking of the Mantis? It may look more scientific; but that does not

interest me.



The nest of the Praying Mantis may be found almost everywhere in places

exposed to the sun: on stones, wood, vine stocks, the twigs of bushes,

stems of dried grass, and even on products of human industry, such as

fragments of brick, rags of heavy cloth, and pieces of old boots. Any

support will suffice, so long as it offers inequalities to which the

base of the nest may adhere, and so provide a solid foundation. The

usual dimensions of the nest are one and a half inches long by

three-quarters of an inch wide, or a trifle larger. The colour is a pale

tan, like that of a grain of wheat. Brought in contact with a flame the

nest burns readily, and emits an odour like that of burning silk. The

material of the nest is in fact a substance similar to silk, but instead

of being drawn into a thread it is allowed to harden while a mass of

spongy foam. If the nest is fixed on a branch the base creeps round it,

envelops the neighbouring twigs, and assumes a variable shape according

to the accidents of support; if it is fixed on a flat surface the under

side, which is always moulded by the support, is itself flat. The nest

then takes the form of a demi-ellipsoid, or, in other words, half an egg

cut longitudinally; more or less obtuse at one end, but pointed at the

other, and sometimes ending in a short curved tail.



In all cases the upper face is convex and regular. In it we can

distinguish three well-marked and longitudinal zones. The middle zone,

which is narrower than the others, is composed of thin plates arranged

in couples, and overlapping like the tiles of a roof. The edges of these

plates are free, leaving two parallel series of fissures by which the

young can issue when the eggs are hatched. In a nest recently abandoned

this zone is covered with fine cast-off skins which shiver at the least

breath, and soon disappear when exposed to the open air. I will call

this zone the zone of issue, as it is only along this bell that the

young can escape, being set free by those that have preceded them.



In all other directions the cradle of this numerous family presents an

unbroken wall. The two lateral zones, which occupy the greater part of

the demi-ellipsoid, have a perfect continuity of surface. The little

Mantes, which are very feeble when first hatched, could not possibly

make their way through the tenacious substance of the walls. On the

interior of these walls are a number of fine transverse furrows, signs

of the various layers in which the mass of eggs is disposed.



Let us cut the nest in half transversely. We shall then see that the

mass of eggs constitutes an elongated core, of very firm consistency,

surrounded as to the bottom and sides by a thick porous rind, like

solidified foam. Above the eggs are the curved plates, which are set

very closely and have little freedom; their edges constituting the zone

of issue, where they form a double series of small overlapping scales.



The eggs are set in a yellowish medium of horny appearance. They are

arranged in layers, in lines forming arcs of a circle, with the cephalic

extremities converging towards the zone of issue. This orientation tells

us of the method of delivery. The newly-born larvae will slip into the

interval between two adjacent flaps or leaves, which form a prolongation

of the core; they will then find a narrow passage, none too easy to

effect, but sufficient, having regard to the curious provision which we

shall deal with directly; they will then reach the zone of issue. There,

under the overlapping scales, two passages of exit open for each layer

of eggs. Half the larvae will issue by the right-hand passage, half by

that on the left hand. This process is repeated for each layer, from end

to end of the nest.



Let us sum up those structural details, which are not easily grasped

unless one has the nest before one. Lying along the axis of the nest,

and in shape like a date-stone, is the mass of eggs, grouped in layers.

A protective rind, a kind of solidified foam, envelops this core, except

at the top, along the central line, where the porous rind is replaced by

thin overlapping leaves. The free edges of these leaves form the

exterior of the zone of issue; they overlap one another, forming two

series of scales, leaving two exits, in the shape of narrow crevices,

for each layer of eggs.



To be present at the construction of the nest--to learn how the Mantis

contrives to build so complex a structure--such was the main point of my

researches. I succeeded, not without difficulty, as the eggs are laid

without warning and nearly always at night. After a great deal of futile

endeavour, chance at last favoured me. On the 5th of September one of my

guests, fecundated on the 29th of August, began to make her preparations

under my eyes, at four o'clock in the afternoon.



One remark before proceeding: all the nests I have obtained in the

laboratory--and I have obtained a good number--have without exception

been built upon the wire gauze of the covers. I have been careful to

provide the insects with roughened stones and tufts of thyme, both being

very commonly used as foundations in the open fields. The captives have

always preferred the network of wire gauze, which affords a perfectly

firm foundation, as the soft material of the nest becomes incrusted upon

the meshes as it hardens.



In natural conditions the nests are never in any way sheltered; they

support the inclemencies of winter, resist rain, wind, frost, and snow,

without becoming detached. It is true that the female always selects an

uneven support on which the foundations of the nest can be shaped, thus

obtaining a firm hold. The site chosen is always the best obtainable

within reach, and the wire gauze is constantly adopted as the best

foundation obtainable in the cages.



The only Mantis that I was able to observe at the moment of laying her

eggs worked upside-down, clinging to the wire near the top of the cover.

My presence, my magnifying-glass, my investigations did not disturb her

in the least, so absorbed was she in her labours. I was able to lift up

the dome of wire gauze, tilt it, reverse it, turn it over and reverse it

again, without causing the insect to delay her task for a moment. I was

able, with my tweezers, to raise the long wings in order to observe

rather more closely what was taking place beneath them; the Mantis took

absolutely no notice of me. So far all was well; the female did not

move, and lent herself impassively to all the indiscretions of the

observer. Nevertheless, matters did not proceed as I had wished, so

rapid was the operation and so difficult observation.



The end of the abdomen is constantly immersed in a blob of foam, which

does not allow one to grasp the details of the process very clearly.

This foam is of a greyish white, slightly viscous, and almost like

soapsuds. At the moment of its appearance it adheres slightly to the end

of a straw plunged into it. Two minutes later it is solidified and no

longer adheres to the straw. In a short time its consistency is that of

the substance of an old nest.



The foamy mass consists chiefly of air imprisoned in minute bubbles.

This air, which gives the nest a volume very much greater than that of

the abdomen of the Mantis, evidently does not issue from the insect

although the foam appears at the orifice of the genital organs; it is

borrowed from the atmosphere. The Mantis builds more especially with

air, which is eminently adapted to protect the nest against changes

of temperature. She emits a glutinous substance like the liquid

secretion of silk-worms, and with this composition, mixed

instantaneously with the outer air, she produces the foam of which the

nest is constructed.



She whips the secretion as we whip white of egg, in order to make it

rise and stiffen. The extremity of the abdomen opens in a long cleft,

forming two lateral ladles which open and shut with a rapid, incessant

movement, beating the viscous liquid and converting it into foam as it

is secreted. Beside the two oscillating ladles we see the internal

organs rising and falling, protruding and retreating like a piston-rod,

but it is impossible to observe the precise nature of their action,

bathed as they are in the opaque blob of foam.



The end of the abdomen, continually palpitating, rapidly closing and

opening its valves, oscillates right and left like a pendulum. From each

of these oscillations results a layer of eggs in the interior, and a

transversal crevice on the exterior. As it advances in the arc

described, suddenly, and at frequent intervals, it plunges deeper into

the foam, as though burying something at the bottom of the frothy mass.

Each time it does so an egg is doubtless deposited; but the operation is

so rapid, and takes place under conditions so unfavourable for

observation, that I have never once been enabled to see the oviduct at

work. I can only judge of the advent of the eggs by the movements of the

end of the abdomen, which is immersed more deeply with a sudden plunging

movement.



At the same time the viscous composition is emitted in intermittent

waves, and is beaten into a foam by the terminal valves. The foam thus

obtained spreads itself over the sides and at the base of the layer of

eggs, and projects through the meshes of the wire gauze as a result of

the pressure of the abdomen. Thus the spongy envelope is progressively

created as the ovaries are gradually emptied.



I imagine, although I cannot speak as the result of direct observation,

that for the central core, where the eggs are surrounded by a material

more homogeneous than that of the outer shell, the Mantis must employ

her secretion as it emerges, without beating it into a foam. The layer

of eggs once deposited, the two valves would produce the foam required

to envelop the eggs. It is extremely difficult, however, to guess what

occurs beneath the veil of foam-like secretion.



In a recent nest the zone of issue is surrounded by a layer of finely

porous matter, of a pure matt, almost chalky white, which contrasts

distinctly with the remainder of the nest, which is of a dirty white. It

resembles the icing composition made by confectioners with whipped white

of egg, sugar, and starch, for the ornamentation of cakes.



This snowy border is easily crumbled and easily detached. When it

disappears the zone of issue is clearly defined, with its double series

of leaves with free edges. Exposure to the weather, wind, and rain

result in its disappearance, fragment by fragment, so that old nests

preserve no trace of it.



At first sight one is tempted to regard this snowy substance as of a

different material to the rest of the nest. But does the Mantis really

employ two secretions? No. Anatomy, in the first place, assures us of

the unity of the materials of the nest. The organ which secretes the

substance of the nest consists of cylindrical tubes, having a curious

tangled appearance, which are arranged in two groups of twenty each.

They are all filled with a colourless, viscous fluid, which is precisely

similar in appearance in all parts of the organ. There is no indication

of any organ or secretion which could produce a chalky coloration.



Moreover, the method by which the snowy band is formed rejects the idea

of a different material. We see the two caudal appendices of the Mantis

sweeping the surface of the foamy mass, and skimming, so to speak, the

cream of the cream, gathering it together, and retaining it along the

hump of the nest in such a way as to form a band like a ribbon of icing.

What remains after this scouring process, or what oozes from the band

before it has set, spreads over the sides of the nest in a thin layer of

bubbles so fine that they cannot be distinguished without the aid of a

lens.



We often see a torrent of muddy water, full of clay in suspension,

covered with great streaks and masses of foam. On this fundamental foam,

so to call it, which is soiled with earthy matters, we see here and

there masses of a beautiful white foam, in which the bubbles are much

smaller. A process of selection results from variations in density, and

here and there we see foam white as snow resting on the dirty foam from

which it is produced. Something of the kind occurs when the Mantis

builds her nest. The two appendices whip the viscous secretion of the

glands into foam. The lightest portion, whose bubbles are of the

greatest tenuity, which is white on account of its finer porosity, rises

to the surface, where the caudal filaments sweep it up and gather it

into the snowy ribbon which runs along the summit of the nest.



So far, with a little patience, observation is possible and yields a

satisfactory result. It becomes impossible in the matter of the complex

central zone, where the exits for the larvae are contrived through the

double series of overlapping leaves. The little I have been able to

learn amounts to this: The end of the abdomen, deeply cleft in a

horizontal direction, forms a kind of fork, of which the upper extremity

remains almost motionless, while the lower continuously oscillates,

producing the foam and depositing the eggs. The creation of the central

zone is certainly the work of the upper extremity.



It is always to be seen in the continuation of this central zone, in the

midst of the fine white foam gathered up by the caudal filaments. The

latter delimit the zone, one working on either side, feeling the edges

of the belt, and apparently testing it and judging its progress. These

two filaments are like two long fingers of exquisite sensitiveness,

which direct the difficult operation.



But how are the two series of scales obtained, and the fissures, the

gates of exit which they shelter? I do not know; I cannot even imagine.

I leave the end of the problem to others.



What a wonderful mechanism is this, that has the power to emit and to

form, so quickly and methodically, the horny medium of the central

kernel, the foam which forms the protective walls, the white creamy foam

of the ribbon which runs along the central zone, the eggs, and the

fecundating liquid, while at the same time it constructs the overlapping

leaves, the imbricated scales, and the alternating series of open

fissures! We are lost in the face of such a wonder. Yet how easily the

work is performed! Clinging to the wire gauze, forming, so to speak, the

axis of her nest, the Mantis barely moves. She bestows not a glance on

the marvel which is growing behind her; her limbs are used only for

support; they take no part in the building of the nest. The nest is

built, if we may say so, automatically. It is not the result of industry

and the cunning of instinct; it is a purely mechanical task, which is

conditioned by the implements, by the organisation of the insect. The

nest, complex though it is in structure, results solely from the

functioning of the organs, as in our human industries a host of objects

are mechanically fashioned whose perfection puts the dexterity of the

fingers to shame.



From another point of view the nest of the Mantis is even more

remarkable. It forms an excellent application of one of the most

valuable lessons of physical science in the matter of the conservation

of heat. The Mantis has outstripped humanity in her knowledge of thermic

nonconductors or insulators.



The famous physicist Rumford was responsible for a very pretty

experiment designed to demonstrate the low conductivity of air where

heat other than radiant heat is concerned. The famous scientist

surrounded a frozen cheese by a mass of foam consisting of well-beaten

eggs. The whole was exposed to the heat of an oven. In a few minutes a

light omelette was obtained, piping hot, but the cheese in the centre

was as cold as at the outset. The air imprisoned in the bubbles of the

surrounding froth accounts for the phenomenon. Extremely refractory to

heat, it had absorbed the heat of the oven and had prevented it from

reaching the frozen substance in the centre of the omelette.



Now, what does the Mantis do? Precisely what Rumford did; she whips her

albumen to obtain a soufflee, a froth composed of myriads of tiny

air-bubbles, which will protect the germs of life contained in the

central core. It is true that her aim is reversed; the coagulated foam

of the nest is a safeguard against cold, not against heat, but what will

afford protection from the one will afford protection from the other; so

that Rumford, had he wished, might equally well have maintained a hot

body at a high temperature in a refrigerator.



Rumford understood the athermic properties of a blanket of air-cells,

thanks to the accumulated knowledge of his predecessors and his own

studies and experiments. How is it that the Mantis, for who knows how

many ages, has been able to outstrip our physicists in this problem in

calorics? How did she learn to surround her eggs with this mass of

solidifying froth, so that it was able, although fixed to a bough or a

stone without other shelter, to brave with impunity the rigours of

winter?



The other Mantes found in my neighbourhood, which are the only species

of which I can speak with full knowledge, employ or omit the envelope of

solidifying froth accordingly as the eggs are or are not intended to

survive the winter. The little Grey Mantis (_Ameles decolor_), which

differs so widely from the Praying Mantis in that the wings of the

female are almost completely absent, builds a nest hardly as large as a

cherry-stone, and covers it skilfully with a porous rind. Why this

cellular envelope? Because the nest of the _Ameles_, like that of the

Praying Mantis, has to endure through the winter, fixed to a stone or a

twig, and is thus exposed to the full severity of the dangerous season.



The _Empusa pauperata_, on the other hand (one of the strangest of

European insects), builds a nest as small as that of the _Ameles_,

although the insect itself is as large as the Praying Mantis. This nest

is quite a small structure, composed of a small number of cells,

arranged side by side in three or four series, sloping together at the

neck. Here there is a complete absence of the porous envelope, although

the nest is exposed to the weather, like the previous examples, affixed

to some twig or fragment of rock. The lack of the insulating rind is a

sign of different climatic conditions. The eggs of the _Empusa_ hatch

shortly after they are laid, in warm and sunny weather. Not being

exposed to the asperities of the winter, they need no protection other

than the thin egg-cases themselves.



Are these nice and reasonable precautions, which rival the experiment of

Rumford, a fortuitous result?--one of the innumerable combinations which

fall from the urn of chance? If so, let us not recoil before the absurd:

let us allow that the blindness of chance is gifted with marvellous

foresight.



The Praying Mantis commences her nest at the blunter extremity, and

completes it at the pointed tail. The latter is often prolonged in a

sort of promontory, in which the insect expends the last drop of

glutinous liquid as she stretches herself after her task. A sitting of

two hours, more or less, without interruption, is required for the total

accomplishment of the work. Directly the period of labour is over, the

mother withdraws, indifferent henceforth to her completed task. I have

watched her, half expecting to see her return, to discover some

tenderness for the cradle of her family. But no: not a trace of maternal

pleasure. The work is done, and concerns her no longer. Crickets

approach; one of them even squats upon the nest. The Mantis takes no

notice of them. They are peaceful intruders, to be sure; but even were

they dangerous, did they threaten to rifle the nest, would she attack

them and drive them away? Her impassive demeanour convinces me that she

would not. What is the nest to her? She is no longer conscious of it.



I have spoken of the many embraces to which the Praying Mantis submits,

and of the tragic end of the male, who is almost invariably devoured as

though a lawful prey. In the space of a fortnight I have known the same

female to adventure upon matrimony no less than seven times. Each time

the readily consoled widow devoured her mate. Such habits point to

frequent laying; and we find the appearance confirmed, though not as a

general rule. Some of my females gave me one nest only; others two, the

second as capacious as the first. The most fruitful of all produced

three; of these the two first were of normal dimensions, while the third

was about half the usual size.



From this we can reckon the productivity of the insect's ovaries. From

the transverse fissures of the median zone of the nest it is easy to

estimate the layers of eggs; but these layers contain more or fewer eggs

according to their position in the middle of the nest or near the ends.

The numbers contained by the widest and narrowest layers will give us

an approximate average. I find that a nest of fair size contains about

four hundred eggs. Thus the maker of the three nests, of which the last

was half as large as the others, produced no less than a thousand eggs;

eight hundred were deposited in the larger nests and two or three

hundred in the smaller. Truly a fine family, but a thought ungainly,

were it not that only a few of its members can survive.



Of a fair size, of curious structure, and well in evidence on its twig

or stone, the nest of the Praying Mantis could hardly escape the

attention of the Provencal peasant. It is well known in the country

districts, where it goes by the name of _tigno_; it even enjoys a

certain celebrity. But no one seems to be aware of its origin. It is

always a surprise to my rustic neighbours when they learn that the

well-known _tigno_ is the nest of the common Mantis, the _Prego-Dieu_.

This ignorance may well proceed from the nocturnal habits of the Mantis.

No one has caught the insect at work upon her nest in the silence of the

night. The link between the artificer and the work is missing, although

both are well known to the villager.



No matter: the singular object exists; it catches the eye, it attracts

attention. It must therefore be good for something; it must possess

virtue of some kind. So in all ages have the simple reasoned, in the

childlike hope of finding in the unfamiliar an alleviation of their

sorrows.



By general agreement the rural pharmacopoeia of Provence pronounces

the _tigno_ to be the best of remedies against chilblains. The method of

employment is of the simplest. The nest is cut in two, squeezed and the

affected part is rubbed with the cut surface as the juices flow from

it. This specific, I am told, is sovereign. All sufferers from blue and

swollen fingers should without fail, according to traditional usage,

have recourse to the _tigno_.



Is it really efficacious? Despite the general belief, I venture to doubt

it, after fruitless experiments on my own fingers and those of other

members of my household during the winter of 1895, when the severe and

persistent cold produced an abundant crop of chilblains. None of us,

treated with the celebrated unguent, observed the swelling to diminish;

none of us found that the pain and discomfort was in the least assuaged

by the sticky varnish formed by the juices of the crushed _tigno_. It is

not easy to believe that others are more successful, but the popular

renown of the specific survives in spite of all, probably thanks to a

simple accident of identity between the name of the remedy and that of

the infirmity: the Provencal for "chilblain" is _tigno_. From the moment

when the chilblain and the nest of the Mantis were known by the same

name were not the virtues of the latter obvious? So are reputations

created.



In my own village, and doubtless to some extent throughout the Midi, the

_tigno_--the nest of the Mantis, not the chilblain--is also reputed as a

marvellous cure for toothache. It is enough to carry it upon the person

to be free of that lamentable affection. Women wise in such matters

gather them beneath a propitious moon, and preserve them piously in some

corner of the clothes-press or wardrobe. They sew them in the lining of

the pocket, lest they should be pulled out with the handkerchief and

lost; they will grant the loan of them to a neighbour tormented by some

refractory molar. "Lend me thy _tigno_: I am suffering martyrdom!" begs

the owner of a swollen face.--"Don't on any account lose it!" says the

lender: "I haven't another, and we aren't at the right time of moon!"



We will not laugh at the credulous victim; many a remedy triumphantly

puffed on the latter pages of the newspapers and magazines is no more

effectual. Moreover, this rural simplicity is surpassed by certain old

books which form the tomb of the science of a past age. An English

naturalist of the sixteenth century, the well-known physician, Thomas

Moffat, informs us that children lost in the country would inquire their

way of the Mantis. The insect consulted would extend a limb, indicating

the direction to be taken, and, says the author, scarcely ever was the

insect mistaken. This pretty story is told in Latin, with an adorable

simplicity.





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