This limit attained, we are brought to the next point in the history

of the insect pupa. The beautiful organization of the perfect insect

has been going on under the dry and repulsive exterior. Its delicate

limbs, exquisitely wrought wings, and the other most wonderful organs

with which the perfect insect is furnished, are now completed. Nothing

remains but to cast off the slough of its pupa case; and it will then

be set free to range whither it will in the great atmosphere into which

it will emerge. If the reader has been watching these insect changes

with the natural object before him, he will immediately confirm our

statement, when we mention that it is often possible to tell when

the pupa case is about to disclose its occupant. The general form of

the limbs is often very clearly to be seen, and the movements of the

included insect become much more sensible and conspicuous. If the

beautiful gilded pupæ, called, as we have before said, _Chrysalides_,

or _Aureliæ_, have been thus nursed with a view to observe their

change, it will be noticed that they lose entirely that golden

lustre which made them at first such attractive objects. These signs

infallibly foretoken the approaching transformation.

CHAPTER V.

THE GREAT CHANGE.

We must now spend a short time in narrating the particular

circumstances which attend this interesting event,--the extrication

of the insect from its pupa case. We shall, in the first place, speak

of such pupæ as are not aquatic, and, afterwards, of the singular

ones which are so. In the case of the butterfly, which, as we have

recommended repeatedly its being nursed and bred, it will be expedient

to mention first, the extrication of the insect is, comparatively

with some others, a very simple operation. The insect within is seen

to struggle for a time, twisting its body in various ways, until at

length a longitudinal slit appears down the middle of its thorax. The

slit extends gradually along the head, and down the parts which compose

the breast, until the insect emerges from the outer case. The inner

membranes are now to be removed, and this, after a little time, is

fairly accomplished, and the butterfly emerges, and, leaving the pupa

skin behind it, by-and-by plunges for the first time upon the soft

waves of the summer air. This is one of the simplest of these methods

of extrication.

[Illustration: _Pupa of Goat-Moth._]

A very natural difficulty will arise in the mind as to what possible

means of escape can be granted to such insects as live in the pupa

state in the interior of old trunks of trees, or even in little caves

of the earth. These cases have all been satisfactorily provided for,

puzzling as they may seem. Take, for instance, the pupa of the great

goat-moth, the _Cossus ligniperda_, of which we give a representation

here. This creature lies buried in a deep excavation, formerly made by

itself when in the larva form, inside the trunk of a willow. How is

it to get back to the hole at which it entered? Without legs, without

any other apparatus by which it might drag itself forward, one would

say it is in a hopeless case; it must lie there and perish, for there

appears no way of extricating it from its den. But not so. Helpless as

it appears, it will certainly make its way out, and taste the sweets

of liberty, and be wafted along the fields of air. But how? Let us

suppose a man in such a condition; let his feet be bandaged together,

so that they cannot move; let a strait-jacket be put upon his body, and

secure his arms and hands; after this, let a leathern bag be put over

his head, and tied down round his middle; then put him in a cellar,

and bid him work his way out and up the stairs until he reached the

front door, where he must undo his bandages, and slip himself out of

his strait-jacket and hood; after which, he may go wherever he likes.

What a feeling of despair would fill the poor prisoner's mind, promised

his release on condition that he should accomplish it in that way! To

him it would be a task altogether impossible, even though his life were

offered as the reward of his success. It is not less a question of life

and death to the insect than it might be to him; yet its extrication is

accomplished, not only in a very simple, but in a very easy manner.

If the reader will carefully examine the representation of the insect

given in the last page he will notice that the pupa case is provided

with certain sharp points, which are all directed towards the

tail of the insect; these sharp points are called by entomologists

_adminicula_. They are of infinite consequence to the insect. Who has

not himself performed, or been the subject of, the trick of causing

a grain of barley to creep up the sleeve? The manner in which it is

gradually pushed up is strikingly similar to that in which the pupa of

the _cossus_ is forced upwards and out of its wooden gallery. It will

be readily supposed that, in consequence of the peculiar direction

assumed by the tooth-like processes in question, it will be very

difficult to push the pupa backwards, as the points would catch in any

obstacle and arrest its progress in that direction; but they offer no

resistance to its moving in a forward direction. The manner in which

the insect proceeds, then, is as follows:--Being capable of slightly

shortening and lengthening the lower part of its body, which is the

part thus provided with hooks, it begins to push backwards, but the

hooks catch in the sides of the wood, and thus prevent it from moving

back, and it is, consequently, actually driven forwards; and so it

continues to thrust itself gradually forwards in this simple manner,

just as a boy with his hands tied might thrust himself forwards as he

lay on the ground, by pushing against any object with his feet. In this

way the patient creature moves, we may be sure, by very slow degrees;

but that matters little; it moves until it has at length reached the

opening of its gallery outside the tree, where it may often be seen

sticking out half way. Here, by a remarkable instinct, it ceases to

move forwards, for it would otherwise tumble down, and probably destroy

itself. At length, after violent struggles, its swathing bands are all

either torn asunder, or slidden off, and the insect wings its way in

unrestrained freedom far from the scene of its triumphs of patience

and hope. The pupa of the "father long-legs" makes its way up from the

subterranean chamber in which it has so long been sheltered, fed, and

protected, and reaches at length the surface of the ground, where it

becomes the perfect insect.

[Illustration: _Swelling of the Head of the Fly._]

But other pupæ, although not, perhaps, quite so arduously placed as in

the last instance, nevertheless present us with an extremely difficult

puzzle, as to how the included insect is to be extricated from its

swathing bands. The common flesh-fly, or blow-fly, for instance, in

the pupa state is shut up in a membranous case, out of which there

seems no escape; but there is a way, and the manner in which the insect

gets out of its prison is a remarkably curious one, well repaying the

trouble of a little close observation. At the larger end, under which

the head of the fly lies, and from which it always issues, there is

commonly a sort of lid which can be pushed off like the lid of a box,

and the insect can then walk out at pleasure. But in the case of the

pupa of the blow-fly this lid is not very easily removed, and the fly,

therefore, is furnished with a most ingenious method of thrusting it

off. On opening the larger end of such a pupa, if the fly within is

ready to come out, a most curious phenomenon will be seen. The insect

moves towards the lid, and there begins to blow out its head in the

most extraordinary manner, swelling it to twice its natural size; a

moment after it will resume its natural size; then again it will puff

it out, making its two eyes to start asunder, and its head to assume

several different shapes in succession! Two representations are annexed

of the striking figure of the insect's head when it thus causes it to

swell out. After repeating this action several times, the fly emerges

from the pupa. The cause of this remarkable dilatation is the filling

of a membrane, situated at the middle part of the head, with air, by

which it is blown out into a sort of bladder as large as the head

itself. This acts as a kind of lever, and eventually pushes up the lid

of the pupa case, allowing the insect to make its exit unmolested. This

part generally disappears afterwards, and the head becomes alike firm

and unyielding in all its parts; but it may, in at least its rudiments,

be seen even in the head of the adult fly, by slightly pressing its

head between the fingers, when it appears as at _x_ in the cut.

[Illustration: _Head of a Fly magnified. It shows opposite the letter x

the remains of the membranous bag._]

More singular still are the circumstances which mark the exit of the

insect from the pupa case in other instances; and yet more strikingly

than those narrated, do they exhibit to us the amazing exercise of the

Divine attributes of wisdom and forethought in the case of these humble

beings. The larva of a species of moth, which dwells in a wooden cell

scooped out of the poplar tree, to which there is no door by which

it can escape readily, gnaws away the wood until it leaves only an

extremely delicate layer between it and the outside of the tree, which

is as thin as writing paper. This done, it enters into the pupa state.

Its time in that condition being accomplished, it moves itself by the

same contrivance as the _cossus_, and actually pushes through the thin

layer, and appears on the outside of the tree, thus making its escape

from prison by pushing down a part of its prison wall!

An instance described by the naturalist Bonnet is yet more ingenious

in the arrangements by which the insect escapes. While in the larva

form it takes up its abode inside the leaf of an ash, curiously rolled

up into a cone; and then, after a time, it becomes a pupa, forming a

silken cocoon of a very slight texture, and, therefore, easily ruptured

by the insect, which it suspends like a hammock in the midst of its

habitation. It is the closely joined sides of its leafy dwelling that

form a barrier which, were it not for the precaution of the larva,

would be impenetrable to so small and weak an animal. But, like the

last-mentioned, this larva seems to be aware of the feebleness of its

next condition, and gnaws in the leaf a round opening, taking care

not to cut through the exterior thin layer of tissue, or _epidermis_.

This door is to serve the insect for its exit in due time. But in

proportion to its bulk, its green chamber is of considerable size.

How, then, shall the insect know the exact place where its portal is

situated? How, without a clue, shall it discover in its dark abode the

precise circle which requires only a push to throw open its gate? Even

this is foreseen and provided for. Out of all other positions in which

the little hammock, of which we spoke, might have been hung, and they

are numerous, the larva has been directed so to place it, that the

silken cord which suspends the head is fastened close to the side of

the door which it has previously constructed; and the insect, when it

emerges from the pupa, guided by this thread, like Theseus, makes its

way out of an apartment which, but for this contrivance, might have

been to it a labyrinth as inextricable as that of Minos. Other insects

adopt the same precaution of gnawing a doorway for the escape of the

perfect insect, only leaving a sufficient thickness of outside tissue

to protect the helpless pupa within from the invasion of enemies from

without.

[Illustration: _Cocoon of Emperor Moth._]

Upon the pear or willow tree may sometimes be found an illustration

of escape from the pupa, altogether well deserving our notice. In

such situations the brown flask-shaped cocoon of the emperor moth may

occasionally be discovered. In structure it is composed of a solid

tissue of layers of silk, almost of the texture of parchment; but

at the narrow end, or that which may be compared to the neck of the

flask, it is composed of a series of loosely attached longitudinal

threads, converging like so many bristles to a blunt point, in the

middle of which is a circular opening, through which the moth makes

its escape, the threads readily yielding to pressure from within,

and acting somewhat on the principle of the wires of the opening to

a rat-trap, or the willow cricks of an eel-trap. The silk of its

cocoon is of so strong a texture, and so closely gummed, that had

both ends been similarly closed, the egress of the insect would have

been impracticable. But, it may be thought, such a cocoon is exposed

to the attacks of a number of insect enemies, who might easily find

entrance to it at the opening thus left at one of its ends. This

source of peril has been foreseen. Within the exterior funnel-shaped

end, at some little distance down, the insect has constructed a second

funnel composed of a similar circle of needle-pointed threads, which,

proceeding from the sides of the cocoon, converge to a point, and form

a cone through which not the smallest aperture is left. From the arched

structure of this singular dome, and from the fact just mentioned, that

no visible opening can be discerned in it from without, it is rendered

quite impenetrable to the most violent attacks of besiegers, while it

yields to the slightest pressure from within, and allows the insect to

emerge from its cocoon with the utmost facility. When it has passed

through it, the elastic threads resume their former position, and the

empty cocoon presents just the same appearance that it did before.

A celebrated naturalist (Rösel), was sorely perplexed at this, the

first time he had the gratification of watching the insect escape. He

states that he could scarcely help thinking that there was something

supernatural in the appearance of one of these fine emperor moths in

a box in which he had put a cocoon of this kind; but in which he could

not discover the slightest appearance of any insect having escaped from

it, until he slit it longitudinally, and then found it to be empty!

Mr. Rennie mentions an instance, perhaps not so ingenious, but equally

curious, with this history of the proceedings of the emperor moth, in

a little insect, also a moth, which also dwells upon the willow. It

spins an elastic shroud for its pupa, of the singular shape of a boat

with the keel uppermost. Its first step is to spin two walls of whitish

silk of the required form; and when these are completed, it draws them

forcibly together with elastic threads, so placed as to retain them

closely shut. The passage of the moth out of this cocoon might have

struck Rösel with still greater surprise than he had felt at witnessing

that of the emperor moth; for in that cocoon there was at least no

apparent difficulty to prevent the egress of the insect, as the opening

existed in it at one end, whereas in this there is no opening at all.

The insect escapes at the joining of the sides, the threads giving way

in a particular spot; and the sides, though originally requiring force

to draw them together into the requisite form, become so elastic as to

close again when the moth has passed between them, and made its escape.

The cocoon preserves precisely the same form after the insect has

quitted it as before, and it is impossible, by the naked eye, to detect

the place of its exit.

As a general rule, insects make their escape from the pupa case head

foremost; but there occurs a very singular exception in the case of

some of the gall insects. The males of these insects contrive to make

their escape out of the pupa case, formed of the dried skin, tail

foremost; and as they thus back out of their dwelling, their wings are

necessarily turned backwards over their heads; but a little exercise

soon puts the ruffled insect in proper plume again, and the wings

resume their customary position.

Some curiosity may be felt to know in what way the silk-worm moth

escapes from the double prison,--the pupa case, and the cocoon,--in

which she is concealed. How is the moth to make its way through the

dense mass of fibres all glued together, which walls her in on every

side? Her delicate wings and body would never endure anything like the

severity of the struggle necessary to enable her to force her way

through this, to her, solid and resisting mass. Though much attention

has been paid to the transformations of this particular insect, it

is somewhat curious that it is still a matter on which opinions are

divided, as to how the insect succeeds in making its egress. Some

suppose that the eyes, which are the only hard organs of the head, are

the instruments by which the threads are divided, their numerous minute

facets serving the purpose of a file. Others hold the belief that the

insect pours out a fluid which acts upon the gum and silken fibres of

one end of the cocoon, and so softens them that they easily give way

to the slightest pressure from within. "Perhaps the two opinions,"

observe Messrs. Kirby and Spence, "may be reconciled by supposing the

silk-worm first to moisten, and then to break, the threads of the

cocoon. In those that are of a slighter texture, a mere push against

the moistened end is probably sufficient; and hence we find in so many

newly-disclosed moths the hair in that part wet and closely pressed

down."

It has been supposed, in cases where the cocoon is a hard, almost

wooden cell, that the feeble insect prisoner within is provided

with a peculiar chemical fluid, of greater powers of solution than

are requisite in the last instance. The cocoon of the "pussmoth,"

in particular, is so hard and dense, as to resist even the point of

a penknife; and the insect it holds confined within it is a weak

creature, totally unprovided with any apparatus fit for penetrating

walls so hard and dense as these. What is it to do? "Here," observe the

writers last quoted, "the eyes are clearly incompetent; nor could any

ordinary fluid assist their operations, for the gum which unites the

woody particles of the cocoon is indissoluble in _aqueous_ menstrua.

What an aqueous solvent cannot effect, an _acid_ is competent to; and

with a bag of such acid our moth is furnished. The contents of this

she pours out as soon as she has forced her head through the skin of

the pupa, and upon the opposite end of the cocoon. The acid instantly

acts upon the gum, loosens the cohesion of the grains of wood, and a

very gentle effort suffices to break down what was, a minute ago, a

strong barrier. How admirable and effectual a provision! But there is

yet another marvel connected with it. Ask a chemist of what materials

a vessel ought to be to contain so potent an acid; he will reply,--Of

_glass_.[O] Yet our moth has no glass recipient; her bottle is a

membranous bag; but of so wonderful a fabric as not to be acted upon by

a menstruum, which a gum, apparently of a resinous nature, is unable to

resist! This fact can only be explained by the analogous insensibility

of the stomach to the gastric juice, which can dissolve bone; and it

is equally worthy of admiration. In both cases, the _vitality_ of the

membranous or fleshy receptacle secures it from the action of the

included fluid; but _how_, who shall explain?"

[Illustration: _Glazed Ant-hill of M. Huber._]

The naturalist, Huber, the patient historian of the ants, gives us a

very interesting account of the proceedings of these wonderful insects,

in actually _assisting_ the young out of their silken cases. These

pupæ are enclosed in a tissue of silk, of so compact a texture, and

formed of so strong a silk, as to render it impossible for the prisoner

within to rupture the fibres, and get out of prison. The worker ants,

therefore, are instructed by a heavenly Ruler and Guide to give

help to the prisoners, and to secure their egress. But how do these

indefatigable attendants ascertain precisely the moment when their aid

is required? The insect within has no power of voice to cry out for

help, nor those without, in all probability, the faculty of hearing, if

it could do so. It seems probable that they are acquainted with it from

some slight movements which take place within, which they ascertain by

means of their antennæ. Whatever it be, the attendants never interfere

at a wrong time. Their manner of proceeding is beautifully described in

the following words of this author:--"Several males and females lay in

their envelopes in one of the largest cavities of my glazed ant-hill.

The labourer-ants assembled together, and appeared to be in continual

motion around them. I noticed three or four mounted upon one of these

cocoons, endeavouring to open it with their teeth, at that extremity

answering to the head of the pupa. They began to thin it by tearing

away some threads of silk where they wished to pierce it, and at length

by dint of pinching and biting this tissue, so extremely difficult to

break, they formed in it a vast number of apertures. They afterwards

attempted to enlarge these openings, by tearing or drawing away the

silk; but these efforts proving ineffectual, they passed one of their

mandibles into the cocoon, through the apertures they had formed, and

by cutting each a thread, one after the other, with great patience, at

length effected a passage, of a line[P] in diameter, in the superior

part of the web. They now uncovered the head and feet of the prisoner,

to which they were desirous of giving liberty; but, before they could

effect its release, it was absolutely necessary to enlarge the

opening. For this purpose these guardians cut out a portion in the

longitudinal direction of the cocoon, with their teeth alone, employing

these instruments as we are in the habit of employing a pair of

scissors. To expedite the work some raised up a little slip cut out in

the length of the cocoon, whilst others drew the insect gently from its

imprisonment. When the ant was extricated from its enveloping membrane,

it was not, like other insects, capable of enjoying its freedom, and

taking flight; it could neither fly, nor walk, nor without difficulty

stand, for the body was still confined by another membrane, from which

it could not by its own exertions disengage itself.

"In this fresh embarrassment the labourer-ants did not forsake it: they

removed the satin-like pellicle which embraced every part of the body,

drew the antennæ gently from their investment; then disengaged the feet

and the wings, and lastly, the body, with the abdomen and its peduncle.

The insect was now in a condition to walk, and receive nourishment,

for which it appeared there was urgent need; the first attention,

therefore, paid it by the guardians was that of giving it the food I

had placed within their reach."

It is droll to add, and it may be some of our readers may feel somewhat

abashed at the fact, that these labourer-ants are extremely particular

in the observance of great order and regularity in their chambers;

and they therefore carefully sweep up all the cast-off coverings,

which are collected together, and deposited in one of the most distant

lodges of their habitation. Could man, with all the powers of reason,

and the faculties of an immortal being, have evinced a more striking

instance of careful, gentle, and patient assistance in the hour of need

than we see manifested in the case of these insects? Alas! how often

does man need to come to them to learn not only a lesson of wisdom

and order, but of the tenderest sympathy and affection. How often

lies a poor fellow-creature in the bondage of hopeless poverty, or in

the embarrassment of inextricable difficulties! How seldom does his

emergency meet with that resolute and thorough-minded earnestness of

brotherly love, which will patiently give him help and pity, until his

troubles are surmounted, and his steps set free!

It is time that we spoke somewhat upon the extrication of insects

from their pupa cases, even when under water. Here arises a great

difficulty;--the wings of the insects thus placed, if wet with water,

would be unfitted for flight, and would probably frequently lead to the

death of the insect by drowning. Yet it is to leave its sub-aqueous

abode, mount up through the waves overhead, and finally emerge without

a drop of water clinging to its body, and from the glassy surface of

the water it is to take its flight into the air. Some will be tempted

to exclaim,--"This is a clear impossibility!" Far from it. The little

worm so well known to anglers as the "caddis-worm," performs this feat

with the greatest ease, and in the following manner:--

[Illustration: _The Pupa-case, Larva and Fly of Caddis-worm._]

[Illustration: _Grating of the Pupa-case._]

It has been mentioned that the larva known under this name constructs

for itself a case of various materials in which it dwells at the bottom

of the waters, where the hand of the young angler knows well to find

them. This case is heavier than water, and consequently cannot float,

and so carry the insect to the surface. As the insect enters the pupa

state it weaves, at the entrance of its singular habitation, a grating

of silk, which, strange to say, is not only not softened and melted

away by the water, but hardens under it until it is as hard as gum.

This little grating is of a circular form, and fits exactly into the

opening, and is perforated with holes, so as to look something like

the gratings which cover our coal-cellar mouths in the pavement of

cities. These holes are for the purpose of letting in fresh water for

the respiration of the insect. Out of this under-water cell the insect

must make its escape. To enable it so to do the pupa is furnished

with two strong curved jaws, which are of no other use than to assist

it in making an opening in one of the silken doors of its case, as

they are cast off immediately afterwards, and there remains not a

vestige of them in the perfect insect. This opening made, the pupa

forces its way out at that end. But what then? How is it to reach the

surface, even now? Its legs, as will be seen by looking at the cut,

are furnished with a number of hair-like processes, which assist it in

swimming; it therefore, still enclosed in the waterproof coat--the pupa

skin--strikes upwards to the surface, and reaching it, its skin splits,

its impervious raiment is cast aside, and the insect springs from the

surface into the air without the minutest drop of water to impede her

flight, or injure the delicate tissue of her wings!

[Illustration: _Caddis-fly's Legs magnified to show the Hairs._]

[Illustration: _Escape of the Gnat from its Pupa-case._]

We may take another common insect for an illustration of this mode of

escape from the pupa, of an equally interesting kind. If the reader

will on some fine summer day resort to any place of standing water by

the road-side, he may probably succeed in discovering the emergence of

a number of _gnats_; and a very amusing occupation it is to stand by

and watch the insect,--this moment an occupant of the waters, and the

next darting in the air, a new and air-breathing form of existence!

About ten days after the gnat has become pupa, it prepares for leaving

that state and becoming a perfect insect by raising itself to the

surface of the water, stretching out its body there, the thorax, or,

in simpler language, the front enlarged part being raised above it.

Immediately the eye of the observer detects the fact that some change

is taking place in the insect; the enlarged portion cracks and splits,

and through this opening the head of the gnat makes its appearance;

then the trunk of the insect rises in a curious manner through the

breach, and more and more of its body rises, preserving all the time

a perpendicular position, so that it looks just as if it were rising

out of the water, and not out of the horizontal pupa case floating on

the surface. The upright body of the gnat now resembles a mast in a

boat, only that it is continually being raised higher and higher by

the gradual emergence of the insect. Its wings and legs are all folded

closely down its sides as is shown in the cut; and it has therefore no

power at all to prevent its being overset by a breeze, and drowned in

the little waves below; the lower portion of its body alone retains

it in this position, being as yet contained within the pupa case. No

ship-builder dare venture to put a mast of such proportions into any

of his vessels, for fear of their being top-heavy, and hence liable to

heel over in a gale of wind. And undoubtedly many gnats, particularly

in windy weather, are shipwrecked as soon as they emerge. This is, in

fact, a moment of peculiar danger to the little insect-mariner, and a

breath of untoward air will frequently drive it about like a ship in a

tempestuous ocean; and if it is once laid on its side, all is over with

the gnat; no patent apparatus can save it; and we have the mournful

testimony of Réaumur, that in stormy weather he has seen a vast number

of such shipwrecks in the mimic ocean of a pool of water. Generally

speaking, the peril is only momentary, and the insect emerges in

safety. Having thus raised itself to the perpendicular position, the

gnat withdraws its two forelegs from the pupa case, and stretches them

out; then it draws out its two next; and now feeling safe, it quits the

perpendicular position and bends toward the water, plants its feet on

its glistening surface, which is to it as safe as the land, since it

has the faculty of walking on the waves. It is now in perfect safety,

its wings expand and become dry, and presently the insect will for the

first time make use of them by flying to some adjoining twig.

[Illustration: _Blood-worms, natural size and magnified._]

But we need not in many cases leave our homes to see an escape from the

pupa in every respect as singular as the last, and in many, precisely

identical. Before the writer's study-window was an artificial fountain,

in which, as the water was not constantly allowed to play, aquatic

insects of various kinds had permission to establish themselves. Nor

were they long in availing themselves of this liberty. A week or two of

genial summer weather was sufficient to people the water with various

inhabitants among them was a little creature which will be recognised

by every reader when we mention its title--"the blood-worm." It is

in reality not a worm at all, although resembling worm in shape, and

in its serpent-like movements. This little creature was for a time

particularly active; and in a tumbler of water taken from the fountain

might be seen perhaps a dozen of them twisting about in a very singular

manner. By-and-by a change came over them, and it turned out that the

worm-like creatures had become pupæ of a blackish colour, thus at once

deciding their insect character. They belong, in fact, to the insect

called the _Chironomus plumosus_. These black pupæ were scarcely less

active than the red blood-worms, or larvæ of the same insect. They

flapped about their tails with great vehemence, and thus, although

their bodies naturally sink in the water, they were able to swim from

the bottom to the surface, or from side to side. Observing that they

had finished their appointed period in the pupa form, we became anxious

to watch their change into the perfect insect. Neglecting, however, to

notice them at the proper period,--the afternoon of a warm sunny day,

we were astonished the next morning to find a surprising number of pupa

skins lying empty of their tenants on the surface, as though some of

the water fairies enumerated in fable had been dancing on the waves all

night, and left their little black shoes behind them in their haste to

flee from the light of the smiling morning. We determined to be better

prepared for the observation on that day; and as the afternoon came we

had the gratification of seeing a large number of these insects rise

from the water, all in the following[Q] manner:--They rose up from

the bottom and reached the surface by the peculiar movement of their

tails just described; there the thorax was thrust above the water,

and immediately the insect burst its cerements, elevated itself by a

wave-like motion from the rest of the pupa-case, which filled with air,

and now glistened like silver; it then planted its forelegs on the

water, withdrew the rest of its body from the case, unfolded its wings,

and in a few moments was sailing in the thin air. On one stormy day the

surface of our fountain was bestrewn with the dead and dying bodies of

these insects drowned in the waves.

[Illustration: _Pupa and perfect Insect of the Chironomus Plumosus._]

De Geer,[R] speaking of the pupæ of a moth, states, that he was not

fortunate enough to witness the manner in which they quit their watery

abode. But he seems to think that they quit the pupa case, then mount

to the surface of the water, or up some aquatic plant, in order to

reach a dry spot, where they remain, their wings being developed

afterwards, and that thus the risk of their being wetted is avoided.

Their bodies being lighter than the water, he conceives, accounts for

their being able to rise to its surface. Too much weight, however, must

not be attached to this observation, as it is not accompanied with

satisfactory ocular evidence of the fact.

[Illustration: _Pupæ of Dragon-fly._]

[Illustration: _Pupa of Dragon-fly, showing the sharp points at the end

of its feet._]

The pupa of the "dragon-fly" furnishes us with a very interesting

example of escape; and it well deserves the reader's attention, if

he be so placed as to have the opportunity of observing it. Perhaps,

indeed, few insects afford us such a singular series of interesting

facts as are to be found in the escape of this one from its pupa. The

best method of observing their change is to procure as many of the

larvæ as possible, to put them in a basin of water, at the bottom of

which are a quantity of dead leaves, and to allow several sticks to be

in the water touching the bottom of the basin, and reaching above the

level of the water, as shown in the cut. Then we must watch carefully

to notice any of the larvæ which, having become pupæ, creep towards

the edge of the water. These are such as will in all probability be

the first to undergo the change, for they come to that position

in order that they may get dry before proceeding further. If these

are now closely observed, they will be seen after the lapse of a

little time to leave their position, and to begin creeping about in

search of a suitable spot where they may undergo their metamorphosis.

Most probably they will select for this purpose the sticks we have

introduced into the basin, and, after running up and down them, will

fix upon a particular spot, where they place themselves securely, the

head invariably uppermost. From what will be subsequently mentioned,

it is necessary that the insect should fasten itself so firmly to the

branch, that not even a violent effort would disturb its position. This

is secured by the insect thrusting the sharp claws with which its feet

are armed into the stem on which it rests. The points of these claws

are so fine and hard as even to penetrate wood with facility. They

are shown in the cut; and even after the dragon-fly has escaped out

of the pupa case, they may be easily made to fasten upon a piece of a

branch, by simply pressing the feet against it very lightly. In order

to watch the changes of this insect Réaumur once, whilst staying in the

country, collected a large number of the pupæ, and placed them on a

piece of cotton-print tapestry, where they soon felt at home, and fixed

themselves in preparation for their change, without moving far from

the spot where they had been placed. At few periods of the day could a

visit be paid to the room where this tapestry was hung without seeing a

spectacle at once diverting and extraordinary. Previous to its changes

the pupa becomes more transparent, and the large and beautiful eyes of

the insect it encloses grow increasingly brilliant. These signs always

indicate that the transformation is nigh at hand.

It comes to pass in the following manner:--Some movements of a

struggling kind take place inside the pupa case; and at length the

case splits at the upper part, near the head: through this rent the

body of the dragon-fly appears and tears it open, acting like a wedge,

until the slit extends along the head across to the two eyes. The

latter transverse slit is produced by a contrivance similar to that

mentioned in the case of the blow-fly, a sort of air bladder which the

insect distends at its pleasure, and thus causes the skin covering its

head and eyes to split open. The head and body of the insect rise and

make their appearance through the slit; and the head is now so much

larger than it appeared while in the pupa case, that it seems almost

impossible that it could ever have been contained within it. The insect

continues to rise perpendicularly out of the case, and the legs make

their exit, leaving the leg cases of the pupa undisturbed in their

attachment to the support on which it rests. In order to facilitate

the disengagement of the rest of its body the insect now bends itself

in a curved form backwards, being only kept from falling by the last

rings or segments of its body being still embraced by the sheath of

the pupa case. When it has extricated itself thus far, it begins to

move about its legs in different directions for several minutes, as if

to get them into use; but after this it ceases all movement whatever.

Not a quiver can be seen in its limbs, and the young observer would

be inclined to conclude,--as a great entomologist once did, the first

time he witnessed the changes of this insect,--that it was in reality

dead, and that it was a waste of time to watch it any longer. This

state of profound inaction may endure for a quarter, or even half an

hour: it appears to be intended in order to give time to the insect to

recruit its strength for a fresh and more violent series of efforts,

and to admit of its parts becoming hardened and dry. Suddenly, as we

are, perhaps, carelessly looking on the inanimate object, it performs

a feat of the most surprising, because unexpected agility. Its body,

which was previously much bent backwards, is now swung forwards and

bent into a curve; it then swings back, and then forwards again, and so

quickly that it almost seems to leap. It then rests its legs upon the

front part of the pupa case, and pulls the rest of its body out of the

case by degrees, and then creeps forward, leaving the pupa case behind,

still immovably fixed upon the plant.

[Illustration: EVENING FLIGHT OF EPHEMERÆ.

Page 269.]

"Behold," says Réaumur, "the dragon-fly new born, but very different

from those which traverse the air, or rest upon the plants around. It

is quite in disguise. The body, though longer than the pupa case out

of which it was drawn, has not got all its natural length. The wings,

which are the large and useful organs of these flies, have as yet

very little more volume than they had when enclosed in the short and

straitened pupa case. They are merely furrowed plates, or laminæ, of

some thickness, and arranged one over the other, as if packed together.

One can scarcely conceive how each of these wings can acquire its

proper dimensions,--how it is to enlarge and lengthen sufficiently.

They are folded into plaits like a fan, or like the leaf of a tree just

about to be developed; hence they naturally appear very narrow, and the

cause of their appearing so short is, that each of their longitudinal

portions is folded up like the paper lanterns, more frequently used by

nuns than by other persons."

The remaining portion of the dragon-fly's history will be found in the

next chapter.[S]

Some curious instances are given by various authors of the escape

of more than one insect from the same pupa. Thus we are told that a

male and female emperor moth were once produced from one larva, and

therefore one pupa, of extraordinary size. Messrs. Kirby and Spence

tell us of a German entomologist who says, that two specimens of the

pine-lappet moth were once produced from one pupa, which was of the

remarkable size of two inches in length and one in thickness. But these

are very rare instances, the common and almost universal rule being

that one pupa only contains one insect.

Nothing now remains for us to add to the insect's history in the pupa

state. Already,--for it is Spring far advanced,--the air is becoming

peopled with insect tribes--

"The insect youth are on the wing,

Eager to taste the honied spring,

And float amid the liquid noon."

A thousand times ten thousand, nay, thousands of thousands, are already

in the air; and the low hum of their wings may be heard if we stand

breathless and listen in the midst of some sequestered spot, far from

the roar and bustle and strife of town life. But the great life-season

of the insect world is yet to come; and though May whispers it is nigh,

June, July, and August must bring it to us, and with it a teeming

multitude of insect flutterers more numerous than the stars of heaven,

or the sand-grains of the sea-shore.

PART IV.--THE IMAGO.

CHAPTER I.

THE NEW-BORN PERFECT INSECT.

"Oh! start not! on thy closing eyes

Another day shall still unfold;

A sun of milder radiance rise;

A happier age of joys untold.

Shall the poor worm that shocks thy sight,

The humblest form in nature's train,

Thus rise in new-born lustre bright,

And yet the emblem teach in vain?"

Beautiful as these lines are, and poetical as is the idea they develop,

they are incorrect. The perfect insect springing from the pupa is not

an emblem of man's glorious resurrection from this body of sin and

death; why, we shall immediately discuss. In the oftentimes beautiful

mythology of Greece, the name for the butterfly was [Greek: Psychê],

that the soul. Just as the insect bursts with brilliant wings from the

dull and grovelling form of the pupa, flutters in the blaze of day,

roams on untiring wings through the genial air, and enjoys the use of

faculties so new and strange to it, when contrasted with those of the

pupa state,--so was it imagined that the soul's arising from amid the

corruption of this vile body would prove a deliverance from the bondage

of mortality, and the countless infirmities to which it is heir. And

surely there was much poetry in the conception; but we, who must

not leave the path of true insect history for any poetical fancies,

have now to remind the reader that the simile is in many respects

inaccurate, and in so doing we shall merely bring to his recollection

what was said as to the contents of the pupa-case at p. 231. From this

it appears that the pupa state, far from being a state of death, is

one in which new parts are added to the insect; in which the insect is

actually not only alive, but in some instances capable of moving about,

as well as before or after; and, lastly, in which the various organs of

the perfect insect all exist previous to the disclosure of the latter.

Thus, if we were to slit open a pupa-case just before the insect bursts

from it, we should find that, although kept in bondage by the case,

the insect was in all respects the same as if we had allowed it to

break out of its prison in the ordinary manner. In a word, the perfect

insect is after all only the same being which we saw in the egg, larva,

and pupa states, now having cast off its last skin, and become an adult

being.

When a man or an animal dies, the particles of the body are separated

from each other, their union is destroyed, and they themselves are

dissipated in various ways. The flesh returns to dust, the spirit to

God who gave it. How different this change from that which the insect

undergoes! and how inappropriate in strictness, as

"Emblems of our own great resurrection,

Emblems of the bright and better land,"

as emblems of the mysterious union of the immortal soul and its

immortal, incorruptible body! The fable of the Phoenix was more

expressive of the real nature of this great change; for there the body

of the creature was reduced to death first, and the new-born being

sprang from its ashes. As we are anxious to convey only the most clear

and accurate idea to the reader's mind of the various stages of insect

life through which we are conducting him, it appeared expedient to

notice the mistake taught in these pleasing lines, only to avoid the

error of its being supposed that they give us an accurate idea of the

true nature of the change from pupa to _imago_.

The term _Imago_ is a Latin word, and, like those of _larva_ and

_pupa_, was given to insects in this condition by the naturalist

Linnæus. It signifies properly an image, copy, or representation of any

object. In applying it to insects in their last stage, Linnæus intended

that we should understand by it, that the insect had now reached its

stage of perfection, and had become in all respects exactly like, that

is, _the image_ of, its parent. And though a better term might probably

be found, yet as no person is likely to fall into any serious mistake

merely because we call an insect in its last state an _imago_, it is as

well to retain it; better indeed, than, by inventing another, to create

nothing but confusion and disorder in the minds of young entomologists.

In this chapter, therefore,--the last chapter of the Life of an Insect,

the word _imago_ may be considered as synonymous, or having the same

meaning, with that of "perfect insect;" it is an insect's last stage of

existence.

It would be a great mistake to suppose that the insect, so soon as

it leaves the pupa-case, is in that instant in every respect similar

to what is known to us as the perfect insect. When, for example, a

butterfly has just succeeded in extricating itself from its pupa-case,

if we were to take it up in the expectation of finding it all at once

decked with the glories of its wings, and elegant in its form, we

should be disappointed. Owing to the cramped position which its limbs,

and wings, and other organs, have so long been made to occupy, its

appearance when it emerges from the pupa is necessarily different from

that which it wears after all its limbs have been in free exercise, and

the flutter of its wings has been heard over hill and dale, throwing

the gentle air into an irregular line of tumult.

Now that summer has come, abundant opportunities for watching insects

in all their stages may be had; and by careful searching of the garden,

field, and woodland, a number of pupæ may be discovered on the very

eve of disclosing the imago, or perfect insect. Let us suppose that

the reader has not looked in vain; but has brought home in a tin box

several of these singular objects, about which so much has been said.

The pupa, ready to burst open and let loose the struggling captive

within, is before him; the skin splits, the body of the insect appears,

withdraws itself from the pupa-case and inner membranes, and the imago

appears before him. But O, how different from the splendidly adorned

insect which we know it is still to become! Its tender body is weak,

soft, and languid, and bedewed with moisture. Its wings, instead

of being of their usual size, and variegated with such glowing and

admirably contrasted colours as only a Divine hand could create, are

in the largest sized butterflies scarcely bigger than the nail of the

little finger; instead of being uplifted in full strength and beauty,

they hang drooping down over the sides of the trunk; and their colours

are all dull, and muddy, and without any of those distinct spots and

beautifully defined marks, streaks, and bands, which we observe with so

much admiration in the wings of these insects. Altogether we might take

it rather for a mutilated and imperfect insect, instead of what, in

spite of its unattractive appearance, it really is,--a perfect insect,

and in a short time to become a splendid one.

We have only to wait patiently for the lapse of a little time, and

our desires will be fully gratified in beholding all these symptoms

of weakness and imperfection disappear. The imago, attaching itself

either to the cast-off pupa-case, or to some other convenient support,

first stretches out one organ, and then another; its body loses the

coating of moisture which bedewed it, its various parts become firm and

hardened, and its colours come forth in all their beauty. All the parts

which had been forced into a constrained position, now relieved, assume

that which is natural to them in the perfect insect; and the wings no

longer have a questionable appearance, but become expanded into those

light and exquisite structures which form the peculiar beauty and

characteristic of many insects, displaying themselves almost magically

in the form, it may be, of the thin, transparent membrane of the fly,

or as the painted tissue of the moth or butterfly, extending frequently

to five or six times their previous dimensions.

Here let us take up, as an illustration of these beautiful and

interesting phenomena, the concluding portion of the history of the

dragon-fly, commenced at p. 302. The expansion of the wings of this

elegant creature, after it has left the pupa-case, and fixed itself,

generally on the stem of some pond plant, goes on so rapidly, that we

can actually see them becoming larger each moment as we look upon them.

If we were to attempt to trace their outline on paper, before the next

stroke could be added, their form would be different. During the whole

time that the development of the wings goes on, the insect continues

perfectly still and immovable. Its wings are not stirred in the least,

and the insect seems to avoid all risk of having these delicate organs

touched by any surrounding object. Its wings, which are by-and-by to

possess almost the stiffness of a thin layer of the mineral _talc_,

are at present softer and more flexible than wet writing paper, and if

they were to receive any injury while in this condition, that injury

could never be repaired; hence the insect requires to be in a perfectly

quiet condition. The dragon-fly seems to be fully aware of this, and

in order to prevent the wings, as they increase in size, from drooping

down towards, and coming in contact with, its body, it curves it in the

manner represented, so as to allow for the expansion and elongation of

the wings. At length, generally in a quarter of an hour's time, their

development is fully completed; but they are not yet sufficiently firm

and resisting to use in flying. If left to itself, the insect generally

waits three, or even four hours, before it puts them into inactivity.

In addition to the expansion and elongation of its wings, its body

also elongates, until it has acquired its full dimensions. In vain

should we look at first for the splendid colours in which these insects

are decked; all the tints are blotted and unpleasing. Those charming

species, which are spotted with beautiful blue and yellow tints

intersprinkled with black, are, when they are but just emerged from

the pupa, of a whitish yellow spotted with brown; the yellow marks,

however, are seen to change to a beautiful deep orange, the brown to

black, and some of the yellow marks to blue.

The following interesting description of the same changes as they take

place in the butterfly is from the valuable work of Messrs. Kirby and

Spence. "The pupa of a very interesting and beautiful butterfly, the

only one of its description that Britain has yet been ascertained to

produce, I mean _Papilio Machaon_, being brought to me by a friend

early in May, this year, on the sixteenth of that month I had the

pleasure of seeing it leave its pupa-case. With great care I placed

it upon my arm, where it kept pacing about for the space of more than

an hour, when all its parts appearing consolidated and developed, and

the animal perfect in beauty, I secured it, though not without great

reluctance, for my cabinet, it being the only living specimen of this

fine fly I had ever seen. To observe how gradual, and yet how rapid

was the development of the parts and organs, and particularly of the

wings, and the perfect coming forth of the colours and spots, as the

sun gave vigour to it, was a most interesting spectacle. At first it

was unable to elevate or even to move its wings; but in proportion as

the aërial or other fluid was forced by the motions of its trunk into

their nervures, their numerous corrugations and folds gradually yielded

to the action, till they had gained their greatest extent, and the film

between all the nervures became tense. The ocelli, and spots, and bars,

which appeared at first as but germs or rudiments of what they were

to be, grew with the growing wing, and shone forth upon its complete

expansion in full magnitude and beauty."

If we were expert anatomists, and were armed with a good microscope,

the study of the wing of a dragon-fly would prove one of great interest

to us. These beautiful organs, however, must be examined when they are

as yet but a little expanded, as in their completely developed state

we should certainly fail in detecting their real structure. Thin and

gauze-like as they seem, they are in reality double, consisting of

an upper and a lower surface, between which are several parts which

are necessary to preserve the shape and carry on the functions of

the wings. The two surfaces of the wing enclose what are called the

_nervures_, resembling in some respects the veins of a leaf. These

are really fine hollow tubes of some firmness, which ramify in large

numbers between the two membranes of the wing, and thus give strength

and stability of figure to them. Along these tubes, or nervures,

branches of the air-vessels, or _tracheæ_, and of the blood-vessels,

run.

From these necessary details let us turn to make the difficult, but

important inquiry--How are the wings expanded? by what means do

they, from being thick, soft, and moist, become thin, hard, and dry?

It is to be regretted that this inquiry cannot be answered with that

satisfactory certainty which it deserves. It is very difficult to

catch the insects in which the expansion of the wings is best observed

at the right moment; and even then it is extremely difficult to say

whether one cause more than another may contribute to this phenomenon.

The following explanation of it is given by Messrs. Kirby and Spence,

whose general accuracy on such subjects is well known. "As soon as the

insect is disclosed, a fluid enters the tubes or nervures, and being

impelled into their minutest ramifications, necessarily expands their

folds; for the nervures themselves are folded, and as they gradually

extend in length with them, the moist membranes attached to them are

also unfolded and extended. In proportion as this takes place, the

expanding membranes approach each other, and at last, being dried by

the action of the atmosphere, become one. To promote this motion of

the fluid seems the object of the agitations which, in many instances,

the animal from time to time gives to its unexpanded wings. That a

kind of circulation, or rather an injection of an aqueous fluid into

these organs, actually takes place, may be ascertained by a very simple

experiment. If you clip the wings of a butterfly during the process

of expansion, you will see that the nervures are not only hollow,

but that, however dry and empty they may subsequently be found, they

at that time actually contain such a fluid. Swammerdam, who appears

to have been the first physiologist that paid attention to this

subject, was of opinion, that an aëriform as well as an aquiform fluid

contributes to produce the effect we are considering. He had observed

that if a small portion be cut off from the wing of a bee, a fluid

of the latter kind exuded from its vessels in the form of pellucid

globules, becoming insensibly drops, which he concluded proved the

action of the latter; and he noticed also that the wings were furnished

with _tracheæ_, which were at that time distended by the injected air;

whence he justly surmised, that the action of the _air_ was also of

great importance to produce the expansion of the wing." But Swammerdam

appears only twice to have seen the expansion of the dragon-fly, in

which this phenomenon is best observed. Herold, an eminent naturalist,

also attributes the expansion of the wing to the flow of an aqueous

fluid into the nervures. M. Chabrier, a French entomologist, having

observed a fluid in the interior of the nervures of the wings of

insects, thinks it probable that they can introduce it into them and

withdraw it at their pleasure, so as to facilitate their unfolding.

When we call to mind the force with which the blow-fly, or flesh-fly,

and the dragon-fly, are able to expand their heads by forcing air into

them, we need scarcely ask for any other explanation than simply that

the tracheæ are distended with air, and by that means the soft and

yielding wings are made to assume their distended state.

It has been mentioned, that, in the case of the dragon-fly, the

completion of the unfolding of its wings occupies about a quarter of

an hour, but that sometimes it is even half an hour. The ordinary

period is from five to ten or fifteen minutes in most insects, but

it is sometimes prolonged to an hour, or to several hours. Again, in

others, as we have already seen in the history of the emergence of the

gnat, and other insects, from their aquatic state in the pupa, it is

completed in a few seconds, and the insect only rests for this brief

period on the surface of the water, previous to taking flight from its

apparently somewhat dangerous position.

Some observations of Mr. Rennie show, in a singular manner, the fact

before mentioned, that if the wings, while yet wet and soft, are in

any way pressed upon, or otherwise injured, they will never assume

their proper appearance. "The thread by which a chrysalis is suspended

may sometimes snap asunder; when this happens, and the chrysalis is

allowed to remain, it will not usually produce an insect complete in

all its parts; for the side upon which it lies being pressed against

an unyielding substance by its own weight, instead of hanging lightly

suspended by a silken cord, is prevented from becoming duly expanded,

and when the insect is excluded, it is found to be deformed. A colony

of the brown-tail moth, which we reared during the summer of 1829,

spun in the corner of a nurse-box, a common web of several chambers

for containing the pupæ. One of these chambers being accidentally

torn, a pupa fell upon the earth in the bottom of the box, and in due

time, a female moth was produced from it; but she never succeeded in

expanding her wings, which remained till her death, shrunk, rumpled,

and totally useless for the purpose of flying, though in every other

respect she was full grown, and deposited in the box a group of fertile

eggs, covered with down from her tail, as neatly as was done by her

sisters of the same brood. In the summer of 1825, the chrysalis of

a small tortoise-shell butterfly, (_Vanessa urticæ_,) lost its hold

of its silken suspensory, and fell upon the pasteboard bottom of a

nurse-box, resting in a sort of angular position, so that the case

of the upper wing on the left side, pressed upon the box with the

whole weight of the chrysalis above it. When the butterfly made its

appearance, it expanded its wings as usual; but the wing upon which

it had rested was not half the size of the one on the right side

which had lain uppermost. Another of the same brood had, from some

cause, not grown so large in the caterpillar state as the rest. It was

transformed, notwithstanding, into a chrysalis, which appeared healthy

and well-formed; but when the butterfly appeared, though it did not

differ from the usual appearance, its wings never expanded a single

hair's breadth, and remained always in the same state as when it issued

from the chrysalis."

After the insect has once withdrawn itself from the pupa-case, it

generally retains the same appearance and raiment as long as it lives,

not casting its skin like the larva, but having put on its permanent

clothing immediately upon its leaving the pupa-case. But in the case of

an aquatic insect, the _Ephemera_, of which we have before spoken, a

remarkable exception to this rule has been noticed. When these insects

leave the pupa-case, any one, on looking at them, would say that they

had completed their changes; they appear to be furnished with every

part necessary to them, and not to have any which is redundant; yet

they are destined to go through a change equivalent to that which has

just taken place, if, indeed, it is not more apparently difficult than

it, and that is,--they have to cast off their skin. That they should be

able to withdraw from thence their head, their legs, their body, and

their long tails, would be no great difficulty for us to comprehend,

because numbers of insects at their escape from the pupa-case do more

than this; but in their case we are presented with a more perplexing

enigma. In the transformation of other insects, as we have already

seen, and, indeed, in that of the insects before us, the wings are at

first very soft and pliable, and therefore can be easily withdrawn

from the cases in which they were contained. But in the _Ephemera_,

the wings, after it has left the pupa-case, are fully developed and

expanded, and seem to have acquired all their consistence, and to have

become hard and inflexible. Moreover, its wings are so thin, that we

can scarcely believe that they are in reality double; that is, that

they are covered by an outside sheath; and it seems incomprehensible

how, if such is the fact, the wings can be withdrawn from this case or

sheath, when the only opening that can be discovered for that purpose,

is a very minute hole near the spot where the wings take origin from

the body of the insect. Let us now see how all these difficulties are

overcome, and how the insect withdraws itself from this, as we might

almost call it, second pupa-case.

[Illustration: _Dance of the Ephemeræ._]

The Ephemeræ, when they leave the water, rise high into the air, and

wing their way perhaps far from the place of their birth. They may

often be found wheeling over green fields, or wandering among the

forest shades, far from the bubbling stream in whose waters so large

a portion of their existence was spent; but more frequently they are

to be found somewhere in the neighbourhood of the stream, enjoying an

aërial dance. The feet of the insect are armed with hooks of great

minuteness, and by their means the insect attaches itself to a suitable

object, sometimes to a wall, sometimes to a twig, or to the trunk of a

tree; it does not much matter where. Without at first making the least

movement, the insect patiently abides the time when it must withdraw

itself from its useless upper garment, and sometimes it has to wait a

whole day in this position. The time arrived, the skin splits, and the

body of the insect rises gradually out of it; but the difficulty is

about the wings. Nevertheless, as we watch the insect, we shall find

that it gradually draws them out of their delicate cases, and at length

emerges, as perfect in beauty and form as before. The manner in which

this is effected is as follows:--although the outer case of the wings

is hard and rigid, yet the wings which it covers over are preserved in

a soft and moist condition. In proportion, therefore, as the insect

disengages itself from the anterior part of the skin, the inner or real

wings become contracted, by a number of plaits, into a form nearly

cylindrical, which readily admits of their being pulled through the

openings lately mentioned; and as soon as the insect is released from

its envelope, these plaits unfold, and the wings return to their former

shape and dimensions. So exactly does this thin skin, thus cast off,

fit all the parts of the insect's body, that it may often be mistaken

for the insect itself, when it is found clinging to the place where it

has gone through its changes.

[Illustration: _Wingless Beetle._]

Before we leave the subject of the wings, it must be mentioned that

there are some insects which have none. The cut represents a beetle of

this class.

If the reader will now take a peep into one of the nurse-boxes in

which he may have been rearing butterflies from the pupæ, presuming

that several of them have ere this burst from their cases, and are

fluttering about anxious for liberty, he will generally detect upon

the bottom or sides of the box one or two marks of a somewhat reddish

colour; sometimes, indeed, they are very red. These spots are produced

by the insect, which, on its emergence from the pupa, generally

deposits a drop of fluid from its intestines. Almost all insects

perform the same action at this period; but we may well remark with

Réaumur, it could scarcely have been supposed, that the excrements of

a butterfly should ever have filled the minds of a whole population

with terror. Such has, however, been the case, and may, perhaps, yet

be in districts where ignorance and superstition close the minds of

the inhabitants against the truths of entomology. "Historians," says

Réaumur, "tell us of showers of blood, as having been the cause of

terror to nations, and considered as prophetic of fearful events,

of the destruction of cities, and revolutions of kingdoms. At the

beginning of the month of July, in the year 1608, one of these showers

of blood was said to have fallen in the suburbs of Aix, and for some

miles around. It turned out that the supposed drops of blood were

in reality drops deposited by the butterflies. It is not improbable

that other showers of blood recorded by historians, and taking place

about the same period of the year, might be accounted for in the same

natural and simple manner. Gregory of Tours relates that in the time

of Childebert a shower of blood fell in different places in Paris, and

particularly in a certain house situated in the territory of Senlis.

Another was said to have fallen toward the end of June, in the reign

of King Robert. In the year 1533, we are told by another author, a

prodigious multitude of butterflies appeared throughout a great portion

of Germany, sprinkling plants, leaves, buildings, clothes, and men,

with bloody drops, as if it had rained blood."

In the Gentleman's Magazine for the year 1764 we read that "a kind

of rain of a red colour, resembling blood, fell in many parts of the

Duchy of Cleves, and caused great consternation. Something of the like

kind fell also at Rhenen, in the province of Utrecht." A gentleman is

reported to have sent a bottle full of it to Dr. Schutte, to know if it

contained anything pernicious to health. Dr. Schutte wrote a learned

dissertation upon it, and gave it as his opinion that it was caused by

the particles which had been raised into the atmosphere by a strong

wind, and that it was in no way hurtful to mankind or beasts. Probably

butterflies were the real shedders of this blood-like shower, as in the

previous cases.[T]

Our next remark about the imago state of insects will, perhaps, create

some surprise--Insects in this state, with some apparent exceptions,

_do not grow larger_. When they leave the pupa state, and have all

their parts fully developed, they do not subsequently increase in size.

We are often told by ignorant people that the little house-flies which

we watch dancing in our chambers, or scrambling up our windows, are

only young flies of the same kind as flesh-flies, and that by-and-by

they will grow into a large "Blue-bottle!" This is a sad mistake. Let

the reader try. Let a fly be put under a glass, and fed with a little

sugar, or honey: in vain will he daily examine it, in the expectation

of beholding it increase in size--it will live and die nearly the same

little being unaltered to the last. If such persons only knew somewhat

of the life of an insect, such an absurd, and, unfortunately, very

prevalent mistake would not be committed. We might as reasonably call

a trout a young salmon! If we were to examine any number of flies of

the house-fly kind, (_Musca domestica_,) and carefully measure them, or

weigh them, we should find them all almost exactly of the same size;

which, of course would not be the case if they really grew larger as

they grew older.

But there are some insects which, after they leave their pupa, increase

within a very short time to a size which could scarcely be believed.

In particular, the new-born insects of a tribe of flies which produce

the aphis-lion larva before spoken of, are distinguished by this

peculiarity. We behold a very little insect emerge from the pupa-case,

and in a quarter of an hour we are astonished to find it has grown

to a great fly! This sudden increase appears the more marvellous,

because during this period the insect takes no nourishment. The wings

of this insect, when it is just born, are not more than _one-tenth_

the size they acquire in that short space of time. The insect is to

all appearance firm and plump, and offers a ridiculous contrast to the

tiny pupa-case out of which it has emerged. It appears probable that

this sudden enlargement is to be accounted for by the insect filling

itself with air, and thus causing the various parts so closely packed

together, and fitted into one another, in the pupa, to be expanded.

The experiment which puts this idea to the test is a very simple one;

we need only prick the body of the insect with a fine needle, and we

shall hear a slight sound produced by the escape of the air; and in a

few seconds the body of the creature shrinks to its former dimensions.

It appears, indeed, that the body of the insect is actually larger at

this time than at a subsequent period of its life, when it becomes

more flattened and shorter. Another beautiful insect, one of the

lace-winged flies, exhibits the same singular phenomenon. Its pupa-case

is not larger than a small pea, yet the body of the insect is nearly

half-an-inch long, and covers, when its wings and antennæ are expanded,

a surface of an inch square. It appears, in fact, almost incredible

that it could ever have been contained within so small a compass.

The cases just related may appear to be really exceptions to the rule

just laid down, as to the non-increase of insects when once emerged

from the pupa; but upon a little consideration it will be found that

the exceptions are more apparent than real. The increase in size is not

really a process of _growth_, but is simply owing to the expansion of

the body of the insect to its due size, only taking place in a sudden

manner by breathing a certain amount of air. The dragon-fly gives

us another instance of a similar enlargement soon after leaving the

pupa-case.

CHAPTER II.

THE STRUCTURE AND ORGANS OF THE IMAGO.

[Illustration: _White Hawthorn Butterfly._]

We must now ask the reader's attention to a very important part of the

history of the insect--the knowledge of its various parts, and their

uses in the insect economy. Men of science would call this the anatomy

and physiology of insects; and if there is a desire felt to know and

retain the proper terms employed by those versed in this science when

they treat of these subjects, it will be well to bear these names in

mind. We may, however, convey some notion of the nature of the studies

called by these names, by the following illustration. Let us take

yonder butterfly as our example, and, arresting it in its zig-zag

career over flowers and fields, let us carefully bring it in-doors,

and there look closely at its various parts and appendages. There we

find two long, delicate, thread-like organs springing from the head;

then we come to the head, with its different organs; farther back is a

separate portion, distinct from the head, and distinct, also, from the

remainder of the body of the insect; at the side of it are the wings;

below are the legs; last of all we bring under our notice the remaining

division of the insect's body, the abdomen. Now if Anatomy stood at our

right hand while we took notice of each part, she would point out all

the peculiarities of its structure, and would tell us of how many other

parts it was made up, and how all were beautifully and wonderfully put

together by the skill of the Great Creator. Further than this, she

would, very probably, strongly insist upon our remembering each part by

a particular name; and, as we may add, since she is particularly fond

of, and learned in, Latin and Greek, we may rest quite assured each

name she communicated to us would be in one or other of these classical

languages; for example, instead of saying the butterfly was one of the

"_scale-winged_" insects, which would be far too homely for her, she

would declare that it belonged to the _Lepidoptera_, which is the same

thing in Greek; and its "head" she would inform us was the "_caput_,"

which is the Latin for that word! This done, her strict duties would be

exactly fulfilled, and she would summon her sister-science, Physiology,

to give us further information about the butterfly. Physiology, who,

we may remark, is a far less stern-looking personage than her austere

relative, and appears with a countenance which expresses that she has

much to tell us which will greatly interest us, would next take up the

panting insect. She would tell us to consider attentively the head of

the little creature, while we listened to her elegant account of the

purposes it was intended to subserve. She would dilate with eloquence

upon the exquisite machinery which was compacted into so small a

compass as its mouth; and she would render us almost breathless with

amazement, as with rising animation she revealed to us the astonishing

optical wonders of an insect's eye, telling us, perhaps, that an insect

may probably see like the fabled Argus, behind, and before, and on

every side, at the same time! Then she would tell us, in order, the

nature and uses of each part, and, in a word, give us a minute, but

delightful account of everything that is known about the Life of an

Insect.

From this it will be manifest that we have hitherto chiefly listened

to the voice of Physiology in this little book, although the leading

particulars of the Anatomy of the insect in its various stages have

also been brought before us. We must now address ourselves for some

little time to learn, from the combined sciences of Anatomy and

Physiology, the structure and uses of the different organs, and their

principal parts, in the insect, in the _imago_ or perfect state. In

order to follow the account we shall have to give the reader, it will

be convenient to take some common insect, such as a _wasp_, and fix in

the memory the names of the various parts we shall have to distinguish,

in thus treating of the _imago_-insect. A dragon-fly is a good example

also. We shall first mention the general arrangement of the insect's

structure; and subsequently take up each part separately.

It must first be mentioned, that insects possess no _internal_ bony

skeleton, like that possessed by ourselves and many other animals.

If we were to cut open the dead body of a fly, we should look in

vain for anything like the back-bone, or the bones of the legs. But

it must not, therefore, be thought that insects have no skeleton at

all. Their skeleton is the thick, hard, horny substance which forms

their external covering. In the wasp, for instance, it will be easily

perceived, on pressing the head or the trunk of the insect between

the fingers, that there is a very firm, solid coating, protecting the

tender and delicate organs within. It is a very singular fact that the

wisdom of the Creator has so ordered this outside coating, that where

it is most necessary to be strong, as for example, when an insect has

to burrow through the ground, or is in danger of being often crushed,

there its thickness is greatest; and again where, as in the case of

those insects which live chiefly in the air, this thickening is less

necessary, because there is less risk of injury to its body, there the

external covering is thinner and softer. So extraordinarily is one

insect strengthened in its external coats, that it is scarcely possible

to crush it by the hardest squeezing between the thumb and fingers. It

has, on this account, been compared to a once famous London character,

called "_Leather-coated Jack_," who used to suffer carriages to be

driven over his body without receiving any harm!

In looking at an insect, we perceive that it is naturally divisible

into three principal parts: first, there is the head, or _caput_; next,

the trunk, or _thorax_; and thirdly, the hinder portion of the body,

or _abdomen_. If we turn to a Latin dictionary, and hunt out the word

_insecta_, which is the Latin term for "insect," we shall find that it

is derived from a verb which signifies "to be cut in," or "notched."

From this we see that the very word _insect_ has arisen from perceiving

what we are now alluding to, the natural notching of the body of these

creatures into certain portions. We mentioned, however, at page 89,

that the insect in the _larva_ form had a body which was, in almost

every instance, divided into _thirteen_ segments, or parts. It may be

asked, Are these all lost in the perfect insect; or are they still to

be traced in it? They are still to be traced in it. The head is one,

three form the trunk or thorax, and the remaining number constitute

the abdomen: but, in order to save disappointment, it must be added,

that it is rare to find the full number of segments or distinct parts

in the abdomen; we seldom, in fact, find more than seven or eight,

the remaining two or one being generally hidden. It is interesting,

however, to trace in the perfect insect these indications of its

previous larval condition, especially when we remember the strange

appearance it underwent while a pupa.

Now the various parts in the _head_ division are, to speak generally,

the _head proper_, the _mouth_, the _eyes_, and the _antennæ_.

Entomologists describe a large number of other parts, which would also

be mentioned here if this little treatise were intended to give a

minute account of the insect's anatomy; and those features which are of

most prominence and importance, will be mentioned in addition when we

come to speak particularly of these several chief organs.

The middle portion of the insect, or _thorax_, is divided into three

parts--a front, middle, and hinder part; or, in the language of

entomology, a _pro-thorax_, a _meso-thorax_, and a _meta-thorax_.

Attached to the thorax are the _wings_ and the _legs_. The remaining

portion, or _abdomen_, is furnished with organs and appendages, not

requiring special mention in this place.

[Illustration: _Eyes of a Bee._]

Let us consider briefly the organs which are seated in these divisions;

and, beginning with the head, let us glean a few particulars upon that

most interesting topic--the eyes of insects. We might well fill a

volume with this subject alone, for truly it is almost inexhaustible.

In the other sections of the animal kingdom, the eyes, though organs of

the highest importance, are, nevertheless, simple, and little varied

in their number and arrangement. But in insects, whether we consider

their number, their structure, their arrangement, or their size, we

are lost in amazement at finding these organs assume an importance in

the insect's economy, of which we have no parallel elsewhere. Look,

for example, at the accompanying representation of the eyes of a bee,

and then let us ask whether, in all the world beside, we can find a

creature whose two eyes are larger than all the rest of its head put

together? What should we think of a quadruped as large as a bull, whose

eyes occupied great part of its head, its forehead, and the greater

portion of its face? What astonishing powers of sight it would possess!

[Illustration]

The first thing we learn about them is, that some insects possess what

are called _simple eyes_, and _compound eyes_. The accompanying cut

represents in part the head of a _flea_, and is annexed in order to

give a specimen of a _simple_ eye. The little circle represents the

position of the simple eye. All the organs connected with the head

are supposed to be cut off. The head of the bee on the preceding page

furnishes us with an excellent illustration of a _compound eye_. All

perfect insects are provided with compound eyes, and a large number

with simple eyes too; but no imago or perfect insect has simple eyes

alone. We see, therefore, that the simple eyes are only additional or

supplementary organs to the compound eyes, which are the chief organs

of sight in these creatures. These simple eyes are minute lenses

generally placed upon the crown of the head, or the forehead; in the

bee this is their position; and by means of a pocket-glass, they can

be readily seen in this insect, by looking at its head from above.

They will be found arranged in a triangular form. Sometimes an insect

is furnished with as many as sixteen of these simple eyes; the spider

is, among others, thus endowed. But more commonly they are only three

in number. Sometimes they are not imbedded in the substance of the

head, as might be supposed; but are actually placed upon the end of a

little stalk, presenting an appearance as singular, as if at the end

of a bull's horn the animal were to possess an eye in addition to his

two others. Swammerdam and Réaumur performed some singular experiments

upon these eyes in the bee. Réaumur varnished the back of the head,

where these eyes are situated, in more than twenty bees, so as, of

course, entirely to blind these eyes; but leaving the large compound

eye untouched. The bees were then set at liberty within a few paces

from the hive, but not one of them knew where to find it again! nor,

indeed, did they appear to make any search for it. They flew at random

to the adjacent plants, but never to a distance; and though they seemed

to have no difficulty in flying, they did not attempt to fly up into

the air.

[Illustration: _Eye on a stalk._]

[Illustration: _Eye of the Dragon-Fly._]

The compound eyes of insects are, perhaps, among the most wonderful

works of the Creator's hands. In those gigantic creatures whose

fossilized bones are all now remaining to tell us of their history,

the _mastodon_, and _megatherium_, and in such vast creatures as the

elephant and the whale, we behold the great power, skill, and wisdom

of God; but here, in a little object which we may cover with a pin's

head or with a large grain of sand, is a more wonderful instance of His

infinite and amazing power than all these. The eye of a dragon-fly is

a good instance of a compound eye: and of all the beautiful, radiant,

gem-like objects that can be selected for inspection through the

microscope, this is the most exquisite. Professor Müller, the great

German physiologist, has with wonderful patience and care dissected

the eye of this insect, and has given a most beautiful account of its

structure. On examining the eye of this insect, even with a good pocket

magnifying glass, such as those commonly sold by opticians for a few

shillings, it will be found to present the appearance of a beautiful

net-work, or very fine grating, as is shown in the cut. When a greater

magnifying power is employed, it will be seen that each space in this

net-work is a six-sided or _hexagonal_ figure. Now each of these

little spaces is filled by a beautiful minute lens of the same shape

set in it. On making a perpendicular cut into the eye it has been found

to consist of various layers: the outer layer is a hard clear membrane

composed of a multitude of six-sided facets, each forming a more or

less distinct cone-shaped cylinder, which runs towards the centre of

the eye, as seen in the cut. Under this is a layer of coloured matter,

sometimes of a violet, or green, or even reddish hue, which is pierced

with as many holes as there are facets. Beneath this there is a varnish

of a black colour, within which is a second layer of coloured matter;

and in the space between this last and the first coloured layer the

delicate fibres of the nerve of sight, or optic nerve, run. These

fibres then converge together at the back of the eye into a single

large nerve, which is connected with the insect's brain, and conveys

the impression of sight to that organ.

[Illustration: _Magnified section of the Eye and its nerve._]

[Illustration: _Magnified section of part of the Eye._]