Chapter 4

Larva of the Tiger-Beetle.

Mention has already been made in the previous chapter of the insects called Ichneumons, which deposit their eggs in the bodies of the larvæ ofother insects. These, when hatched, are also to be reckoned among the larvæ which prey upon flesh, since they devour the bodies of the larvæ in which they have been deposited. They are thus most useful to mankind in destroying the devourers of his vegetable food.

Larva of the Dragon-fly.

The Mask partly open.The same partly closed.

We may now see an instance yet more strange of a carnivorous larva. We must wend our way to the riverside in the months of May or June. There, after a diligent search at the bottom, in some moderately shallow portion of the stream shall we find a larva, the study of which might well occupy us for many pages. Yet it is the larva of an insect well known to every angler and brook-side wanderer—the dragon-fly. This larva is provided with one of the most remarkable contrivances for seizing its prey and conveying it to its mouth, of any being in the zoological kingdom. By the assistance of the engraving, we may perhaps be able to render this apparatus, which is somewhatcomplicated, intelligible to the reader. Looking at the larva's head, we are reminded somewhat of that of a horse who has got blinders over his eyes, and a nose-bag over his nose, and partly up his cheeks. Now suppose the two blinders thrown back on each side, then conceive that the lower part of the face which we have supposed covered with a nose-bag were to be uncovered, we should then see the following curious contrivance. The lower lip of this larva is lengthened downwards into a sort ofarm, if we may so speak; at what we may call theelbow, is a joint connecting the upper and lower portions of it, and the place of the hand is occupied by two cross plates, with a claw at the end of each. Suppose an unhappy insect, or even a tadpole, swims carelessly by the larva, immediately the two sides of the mask, or blinders, as we have called them, fly open; the arm is uncovered, the forearm let down, and bymeans of the plates, which we have compared to the hand, the victim is caught, and bending the arm back, is presented to the mouth of the larva. There is much similarity in this organ with the wonderful apparatus of the elephant called its trunk; but of the two, the trunk of this insect is the most beautiful piece of animal mechanism. When the prey has been devoured, the arm folds up, covers the mouth and part of the face of the insect, and the blinders, or two side pieces of the mask, fall in, and lock together in a toothed manner, as the engraving in the last page shows.

The apparatus in the act of seizing.

Thus provided, the larva is a formidable creature to the inhabitants of the pond or brook; few, indeed, more so. It preys with incessant activity on all aquatic insects that happen to come in its way, and sometimes, as we have said, even upon tadpoles. They do not even spare one another, and woe to the unhappy relative of the family who happens to wander near the abode of another of thesame family, anxious to begin his feasting for the day! So ferocious are they, that they even attack small fish, and make little work of swallowing them up. Not only are these creatures fierce, but they also possess all the cunning of a tiger or a cat. To watch them seize their prey is an interesting occupation, and as the larvæ are common enough, and may be easily recognised by comparing them with the accompanying cut, we may venture to recommend the amusement of observing their proceedings to the reader. A little way off lies an unsuspecting insect delighting in the warm sunshine, and securely floating upon the waters on the corner of a leaf. Such an idea as danger at hand is probably the very last from its conceptions, and pluming its bright and glossy wings, it beguiles away the sunny hour unmolested by a passing enemy, or a breath of air. The larva has marked it already for its own.[E]See it rouse itself up, and noiselessly make ready to pounce upon the unsuspecting lounger. It creeps stealthily along, concealing itself from view as far as possible, and not even the tell-tale glassy surface of the water feels its movements. Measuring its distance well, thelarva prepares to seize its prey; in a moment, swifter than the eye can follow, the victim is caught by the apparatus we have described, and in another instant, is in all the agonies of a violent death in the mouth of the larva. So exceedingly cautious are these larvæ in their movements, and so expert and active in darting upon their prey, that it scarcely ever escapes their power.

Cockchafer.

Larva.

Having mentioned these particulars about carnivorous larvæ, let us consider some circumstances connected with those larvæ that are vegetable feeders—graminivorous or herbivorous. Of these, we could scarcely select a more destructive one than the larva of an insect well known to every school-boy from the times of Greece and Rome down to our own—the common cockchafer, (Melolontha vulgaris.) Our schoolboys, however, are less merciful than those of Greece, fortheyonly tied a string round the leg of the unhappy cockchafer,whilethesethrust a pin through its tail. Yet, its terrible ravages considered, the insect little deserves to be pitied; but, we are not therefore to be understood as by any means sanctioning the cruel and inhuman sport alluded to. These larvæ are hatched in a sort of little cavern dug by the parent insect's care under the ground in our meadows, or corn-fields. Here they begin their ravages by devouring the roots of the grasses which surround them on all sides. In this manner they very quickly destroy the plants, which wither and die in a manner quite mysterious to the agriculturist, if he does not happen to think of these insects. The turf soon becomes so completely undermined by these excavators, that it may be rolled off as smooth as if a knife had been used underneath to cut off all its connexions with the ground. In a few weeks, meadows which shone in all the fresh and luxuriant green raiment of Spring, change colour, and before Summer has yet come, and before the stalks of the grass are yet grown up, one would think Autumn had passed over the face of the field, from its dry and dead aspect. About seventy years ago, we are told these larvæ did so much injury to a poor farmer'sfields near Norwich, that the court of that city, out of compassion, presented him with twenty-five pounds. Some idea of their numbers on this farmer's property may be formed from the fact that the farmer and his servant declared, with very long faces, we may be sure, that they had gathered eighty bushels of them. Sometimes they even attack the roots of young trees, and in this manner do an incalculable amount of mischief to plantations. They were at one time so abundant in France, and did such immense mischief, that the Government, in order to get rid of them, offered a handsome reward for the best method of destroying them. A number of experiments were made, and it really seemed as if nothing would kill these larvæ, in the way of poison at least, for several poisons which are rapidly fatal to man and animals failed to produce the least effect on them. It was found, however, at last, that a solution of alkalies, such as potash and soda, were certain poisons to them, and should land be much infested with them, it would be worth the trial to water it with such solutions, especially as they tend rather to enrich the soil than otherwise. A French manufacturer, determining to turn the visitationof these insects to good account, has succeeded in distilling an excellentlamp-oilfrom their bodies, and offers tenpence a bushel for them. From seventeen bushels he extracted twenty-eight quarts of good oil! In Hungary, a kind of grease is obtained from them which is useful for carriage wheels. The ingenuity of man may thus even procure good out of a very formidable evil, although the mischief done by the cockchafer larva undoubtedly far exceeds the benefit it confers upon its captors in the amount of oil extracted from it.

An insect almost equally familiar to all persons is the long-legged gnat, of whom the famous children's rhyme runs:—

"'Old father long-legs' would not say his prayers;Take him by the left leg and throw him down stairs."

Many of our farmers would be glad, no doubt, if taking him by the left leg would keep him out of their meadows, for there this insect commits fearful ravages in the larva form. In some parts of England it has as completely destroyed the pasture-grass as if it had been consumed by fire. In the spring of 1813, hundreds of acres of pasture in the rich district ofSunk Islandin Holdernesswere entirely destroyed by it, being rendered as completely brown as if they had suffered a three months' drought, and no other vegetation but that of a few thistles was left on land, which, at more favoured periods, was more than commonly luxuriant. On a square foot of the turf being dug up from the affected spot, the enormous number oftwo hundred and tenlarvæ was counted in it. Fortunately, the next year showed a very different result, for then it was difficult on careful search to find one! In some districts of France it is also very destructive, the grass of large tracts being so completely destroyed by it, that enough food for the maintenance of the cattle is not to be obtained. These larvæ, like the last-named, appear to destroy by eating away the roots of the grass. From these and the foregoing facts, entomology teaches us to regard these two insects, upon which we commonly look with compassion, as occasionally becoming the formidable, though indirect, enemies of man. The scientific name for "Father Long-legs" isTipula oleracea. The French call them oddly enough milliners, or tailors, (couturiéres, tailleurs,) a name of which it is harder to guess the origin than the common one offather-long-legs, which is sufficiently expressive of one of the features of the insect in the perfect state: perhaps the French tailors are distinguished for being very long and thin!

The Gamma Moth and Larva.

We may yet linger awhile in the fields for another illustration of the devouring propensities of vegetable-feeding larvæ. The pretty moth represented in the accompanying engraving, together with its larva, was once the cause of more alarm in France than we can readily conceive. It is often to be seen in our meadows plunging its minute drinking apparatus into the depths of the wild flowers, and flitting to and fro at no great height from the ground all the day long, and even after sun-down. It is called generally the Gamma moth, orPlusia gamma, in consequence of the little mark in its wings, which resembles the Greek letter [Greek: g]. Its larva is striped with green,and when multiplied excessively, as was the case in France in the year 1735, produces scenes of desolation which, as the results of apparently an insignificant insect's doings, can scarcely be credited. In the months of June and July in that year they became so numerous, that the gardeners and peasantry in the districts plagued by them declared that they must have been created by enchantment. In some places Réaumur was assured that an old soldier had been seen to throw the spell. In other places an ugly old woman, who was as wicked as she was frightful, had caused all the mischief. Their prodigious numbers appeared to the ignorant and superstitious peasantry an indubitable proof that they were created by sorcery. And though we cannot, of course, sympathise with their thoughts on this subject, we can well imagine and feel for their astonishment and dismay as they beheld the wide desolation of every green thing produced by the innumerable millions of these larvæ, which covered forest, field and garden with their bodies. Many persons began to fear they were really poisonous creatures, and refused in consequence to partake of salads or other vegetable food of a similar kind. This wasprobably an equal error with the last; and it is very droll to find the talented Réaumur pleading with great earnestness that the caterpillars were not unwholesome as food. He even declares his opinion, that if these creatures were to become excessively numerous in France, the inhabitants might be compelled to treat them as the wretched inhabitants of Africa do the locusts, and when they have eaten up every green thing, fall upon and eatthem. With as much learning and eloquence as if he was treating one of his most favourite topics in entomology, M. Réaumur recommends these larvæ for human food, adding, that a very little time would enable us to conquer our disgust at such aliment, and that we should even welcome to our tables a dish of the larvæ in question as an agreeable luxury! It is to be hoped, if ever such a custom be originated, it will be confined to the place of its birth—the country of this great, but, in this respect, whimsical naturalist.

To account for their excessive multiplication, we have no need to have recourse to enchantment for a solution of the difficulty. Each of the gamma moths produces about four hundredeggs; now, if there were only twenty larvæ in a certain locality which lived through the winter, and became perfect insects in May following, the eggs deposited by these would, supposing all to be hatched, produce, according to a calculation made by Réaumur, in the course of a single year,eight hundred thousandlarvæ. Well may we exclaim, then, with this learned author, "Should we not rather wonder at the wisdom and forethought which has ordered matters so that these insects increase to annoy us so rarely?" The wonder is, in truth, not that they should multiply so excessively at particular periods, so much as that it should be so seldom that they are multiplied even to the extent of which they are naturally capable. Thus, if we suppose that all the eggs of the moths of this species were to be hatched, it is more than probable that a large portion of our vegetation would be consumed by them. How is this guarded against? In various ways. The eggs are not all capable of being hatched, or if so, are not allowed to escape injury by various accidents, and the larvæ themselves are a prey to countless enemies among the birds, while they also frequently perish owing to theseverity of winter. From these considerations we may readily perceive how completely the well-being of a great nation, with the lives of a large portion of its inhabitants, are dependent upon the preserving, protecting, and restraining influence of the providence of God. With the return of every year, we may say, the question is asked by this tribe of insects alone, "Shall we go forth to destroy and devour at once, or shall we refrain?" With every year the silent reply is experienced by man in the unmolested condition of his fields, gardens, and vineyards. "Oh!" we may ejaculate with the Psalmist, "Oh that men would consider these things! then should they understand the loving-kindness of the Lord."

Destructive Larva and its Nest.

Another and more remarkable instance of the destruction caused by vegetable-eating larvæ may be quoted from the fertile pages of the same illustrious naturalist, M. Réaumur, particularly because it is the narration of one who was an eye-witness to the facts of which he speaks. "In two journeys," he writes, "which I made from Paris to Poitou, at the commencement of the month of September in 1730, and also in 1731, I noticed that from Paris all the way to Toursevery oak, great and small, had been attacked by larvæ; the highest branches appeared to be principally selected by them. Great isolated oak trees, as well as those which formed dense forests, were alike attacked in this manner, their summits being absolutely withered and dry. Had we not known how greatly the larvæ may multiply, and what fearful ravages they are capable of committing, one might have conceived that some hot and blasting wind had reduced the leaves to this condition. In certain districts, the hedges along theroad-side had not a single leaf that was not withered up." The engraving represents one of these mischievous larvæ; it also shows the winter-nest into which they creep, and a leaf which a regiment of them have already attacked.

Securely protected from the severity of the winter of 1731, in their warm nests, these larvæ quitted them again early in April of 1732, to set forth upon another mission of destruction. They had now multiplied to a degree calculated to excite the most serious public alarm. It began to be feared that the leaves of the trees would not be sufficient for the support of the devouring millions; and that if, during that year, the larvæ multiplied in the same proportion as in the preceding year, a famine more terrible than any recorded in history as produced by insect destroyers would be the result. These fears were in some measure groundless, as, in all probability, so soon as the larvæ had devoured all the leaves, they would rather have perished of hunger than have attacked the grass and other plants. But the matter was sufficiently serious as it was. The French parliament took the alarm, and determined to resist the threatened invasion of these small but formidable enemies. Anedict was therefore issued, calling upon all persons to assist in removing the larvæ from the trees, while they were as yet not reinforced by the addition of countless millions more. In orchards, gardens, and pleasure-grounds this became a far from difficult duty, because it was easy to ascend the trees and to remove the larvæ and their nests. But in dense forests, where the tall trees waved high in the air, and where every branch and every twig was loaded with larvæ, it was plainly impossible. Although, as we know, acts of parliament are able to effect a great deal, these insects set their powers at defiance, and little good was really accomplished. Having thus, as it were, manifested to the nation how powerless were their efforts to remove the plague, it pleased God to interfere by his providence, and a succession of cold rains for three days in May effectually stopped the progress of the destroyers, by utterly annihilating them.

Réaumur's remarks well deserve extracting; he says:—"I had been hoping much from the effect of these showers, and attentively watched what would be the result. I saw day by day that among the little bands of larvæ which were aggregated together in order to cover the twigs of thetrees with silk, or to despoil them of their leaves, there were many whose bodies became flabby, elongated, and devoid of roundness. These quickly perished. Every day the mortality became more serious among them. In a short time the larvæ, which had previously swarmed upon the trees, became so few, that before ten or twelve days had passed by I could not find a single one, although I looked carefully for them." It is remarkable enough, and sets forth strikingly the short-sightedness and ingratitude of man, that these very showers, which produced what no combined efforts of human power could or did effect, were bitterly complained of as inappropriate to the season, at the time when they were falling! These larvæ were hatched from eggs deposited by a common species of moth.

Although England has been often mercifully spared while continental countries have largely suffered by such visitations as we have last described, we have not always come off unscathed. The larvæ of a moth nearly allied to, if not the same as the last-mentioned, produced an alarm in 1782 in our country, perhaps even more extensive than the previous one in France. All sorts ofstrange and silly rumours were spread abroad; some believing that the larvæ were the harbingers of coming disease and death. Poor people were hired to cut off the webs of these larvæ at the rate of one shilling a bushel, and they were then burned under the inspection of the churchwardens and overseers. In the parish of Clapham, we are told by an author who wrote upon the history of this insect,eighty bushelswere collected in one day! Prayers were offered up in some churches to deliver the country from the apprehended approaching calamity.

We need not, however, dwell longer upon the vegetable-consuming larvæ out of doors. Unfortunately we are acquainted with instances equally formidable within our barns, store-houses, and larders. In vain does man lay up the increase of his fields with care in granaries of the best construction, and using all possible precautions against the introduction of insect enemies. The weevil, called scientifically theCalandra granaria, finds entrance, and in a short time makes its presence felt in the vast destruction it produces. So soon as they are discovered, they are collected with all expedition by the owners of the stores and consignedto the flames for their misdeeds. Sometimes they are collected thus by bushels, from which it may readily be conceived what has been the amount of damage they have done.

There is a little moth whose larva is equally mischievous in appropriating to its own use the food and property of man; its name is theTinea hordei. This fly, we are told, deposits perhaps twenty or thirty eggs in a single grain; but as one grain only is to be the portion of one larva, so soon as they are hatched they disperse by mutual consent in a very amicable manner, and each selects its future home, so that in a short time the whole family is comfortably lodged in twenty or thirty distinct grains of corn. There, surrounded by food, they live and thrive, eating up all the precious parts of the grain, until nothing remains but the husk. They then fall asleep and enter upon the further stages of insect development. No one could possibly tell by the external appearance of the corn, that the least mischief had taken place within, the fulness and general aspect of the grain being the same; but on carefully examining it, a very minute hole may be found in some spot or other;—it was here the enemy gotin. We need scarcely add, that for any purpose grain which has been thus attacked is rendered perfectly useless.

Any one who has ever been on a long sea-voyage will find it easy to supply us with another example of a vegetable-food devouring larva. The hard substances commonly called captain's biscuits are the objects of attack, together with flour, peas, and similar articles of food, and the attacking insect is the larva of the meal-worm, the entomological title of which isTenebrio molitor. In vain does the ship's cook, with all his art, prepare a soup composed of the richest ingredients, and calculated, as one would think, to gratify the taste of the greatest epicure. The larvæ have been beforehand with him; they have attacked and become mixed with the flour or the peas; and when the soup which has cost him so much pains is brought to table, not even the keen appetite of seafaring people can reconcile them to it, for it is full of the dead bodies of these larvæ. So likewise is the biscuit, and in disgust the guests are compelled to confine their attention principally to such articles of food as are unpalatable to their insect enemies.

We have but little experience, in our favoured land, of the more extensive domestic destructions wrought by larvæ. But in hot countries they become formidable, by reason of their numbers. In India,[F]particularly during the rainy season, the interior of the houses swarms with them; some climb the walls, some ascend the table, some feast on the viands, and altogether, by their numbers and appearance, they produce a degree of disgust and loathing at food, which cannot be overcome for a long time by fresh residents. We may mention, before concluding this part of our subject, that of those that do annoy us domestically, some have appetites for very strange kinds of food, some love wine, some vinegar, some butter and cheese; some revel in a pot of preserves, some attack our meat, and one is mentioned by Réaumur as delighting inchocolate!

If surprise be expressed that we have dwelt so long upon the eating propensities of larvæ, let it be remembered that it was formerly said at p. 94,that the principal duty of the larva, so long as it lived, wasto eat. It is born often only to eat as much as possible, and to grow as large as possible within a given time; and in obedience to this principle, we find larvæ with the sharpest of sharp appetites embark in their career of existence, eating from their birth, all the way along to their final change. It is therefore, obviously, a very important part of the larva's history of which we have been speaking for some pages past. Considering the fact to have been now brought into sufficient prominence, we shall proceed to notice the rate at which larvæ grow, and the actual quantities of food some of them devour. Let us speak of the last first.

Silk-worm Moth and her Eggs.

Silk, as the youngest of our readers knows, is the production of a little larva commonly called the silk-worm. Now, some years ago, the calculation was made that in the United Kingdom alone wasconsumed, every year, not less than five million pounds of raw silk. By means of very accurate experiments, it has been ascertained that, in order to procure one pound of raw silk, we must have twelve pounds of the cocoons spun by these larvæ. In order to produce twelve pounds of cocoons, one hundred and ninety-two pounds of mulberry-leaves must be eaten up; or, which is the same thing, for every pound of raw silk, we have to supply to the worms one hundred and ninety-two pounds of leaves. We can now leave the calculation in the reader's hands; but we may mention the sum total: it is, that for every year's consumption of raw silk by our country, there is a certain consumption ofninety-six millions of poundsof mulberry-leaves; and as one hundred pounds of leaves are calculated as the produce of one tree, it follows that nine millions six hundred thousand mulberry trees must grow, in order to supply food to the silk-worms necessary to furnish Great Britain with silk for one year. Let us add, that this five million pounds of raw silk is the production of the inconceivably great number ofeighteen thousand million silk-worms. The Count Dandolo, who has written an excellent treatise on this subject, inItalian, made a number of experiments upon the actual quantity of leaves devoured by the larvæ hatched from an ounce weight of eggs; and he found that the quantity of leaves consumed by them up to the completion of their development as larvæ, amounted to upwards of sixteen hundred and nine pounds! In a month from being first hatched, each larva consumes above an ounce of leaves. As at first each larva only weighs the hundredth part of a grain, it follows that it devours, in thirty days, about sixty thousand times its original weight of leaves. If we suppose a puppy dog, just born, to weigh a quarter of a pound, and to eat in the same proportion for one month, it would have consumed, at the month's end, fifteen thousand pounds of food. Could the puppy eat meat from the first, which, as all are aware, he cannot, he would, at this rate, devour in one month, from the time of his birth, one hundred and fifty sheep, supposing each to weigh one hundred pounds; or aboutfive sheepfor his daily food! These calculations will show how voracious the larvæ of the silk-worm are; and they are, probably, far from being among the most voracious of the larvæ, only we are better acquainted withtheir rate of devouring than with that of other insects in this state.

Growth of Silk-worm Larvæ.

All this eating cannot, of course, be unattended with a great increase in the size of the larva. In some insects growth is prodigiously rapid. A naturalist, who closely investigated this subject in the common blow-fly, which is so apt to deposit its eggs upon meat in hot weather, found that in the space of four-and-twenty hours, the larvæ hatched from these eggs had increased to from one hundred and forty to two hundred times their original weight. The larva of the great goat moth, we are told by another, grows, altogether, to about seventy-two thousand times its weight; but it takes three years so to do. In thus growing,the larva becomes very fat and plump; and should it unhappily cross the path of any bird, it would probably be nipped up as a dainty morsel for the little ones in the distant nest. In birds, beasts, and fishes, the rate of growth is much slower, and the amount of increase much less. Fortunate is it for us that it is so; for what would become of mankind if animals of the size of dogs could grow in a month to the size ofelephants, or young elephants to the size oflittle hills? yet these comparisons are not exaggerated, remembering the increase and growth of the silk-worm and of larvæ generally.

CHAPTER III.

MOULTING OF THE LARVA.

We are now to enter upon a very interesting part of the history of a larva: this is calledmoulting, and consists in the larva casting off its old skin, and appearing clothed in a new garment, often more brilliant than before. The change is well and clearly described in the following passage from the Introduction to Entomology, of Messrs. Kirby and Spence:—"A day or two previously to each change of skin, the larva ceases eating altogether; it becomes languid and feeble; its beautiful colours fade; and it seeks a retreat in which it can undergo this important and sometimes dangerous and even fatal operation in security. Here, either fixing itself by its legs to the surface on which it rests, or, as is the case with many caterpillars, by its pro-legs, to a slight webspun for this purpose, it turns and twists its body in various directions, and alternately swells and contracts its different segments. The object of these motions and contortions seems to be, to separate the exterior skin, now become dry and rigid, from the new one just below it. After continuing these operations for some hours, resting at intervals, without motion, as if exhausted by their violence, the critical moment arrives: the skin splits in the back, in consequence of the still more violent swelling of the second and third segments. The opening thus made is speedily increased by a succession of swellings and contractions of the remaining segments; even the head itself often divides into three triangular pieces, and the enclosed larva by degrees withdraws itself wholly from its old skin." The engraving is intended to show the larva just escaping out of its old skin.

Sometimes the larva comes out of its skin at the side; sometimes it has been seen to bite off portions of the skin. The most common way is that above described. The skin, when cast in this manner, resembles a sort of universal coat, whichhas fitted into every crack and joint of the insect's body; and just as a lady's glove, if we could suppose it tinted of a flesh-colour, and marked for the various markings on the hand, might be mistaken, if cast down after inflating it with air, for a hand cut off, so, only far more closely, does the cast skin represent, in the minutest particular, the larva which has emerged from it. It is a perfect mould of all its parts, even to the very antennæ, eyes, jaws, &c. "Thus," say the authors last quoted, "if you saved the skins cast by the larva of the insect calledCallimorpha, orArctia Caja, you would appear to have ten different specimens of caterpillars, furnished with every external necessary part, and differing only in size and in the colour, perhaps, of the hairs, and all representing the same individual."

In order to show how completely this is the case, some singular experiments have been made by various observers, in the following manner:—Just before the larva was about to cast off its skin, they have, by means of a sharp instrument, cut off one or two of its feet. The larva was then allowed to moult, and was carefully examined, and it was invariably found that the feet cut off whenin its old skin were also wanting when it appeared in its new robes; thus plainly proving that the feet were really sheathed in the old skin completely. It was just as if we had gloves on our hands and were to put one finger or more between a pair of sharp and powerful shears, we should, of course, find that when we took off the glove we should be short of one or two fingers!

But the hairs are not thus sheathed. The old skin, if the larva was a hairy one, such as many of those with which we are familiar under the more popular title "caterpillars," is cast off with the hairs attached to it—a circumstance which makes the cast skin look still more like the real larva. How, then, it may be asked, does the larva acquire new hairs to take the place of the old ones? Were we to take a larva just before its moulting, and by a sharp and delicate instrument, to slit open and raise its old skin, we should soon perceive how this has been contrived. We should there perceive sundry little tufts of very delicate hairs, lying down smoothly on the surface of the larva's body, and arranged in certain directions, with great regularity. When the old skin is cast, in the course of a little time these hairs standupright, and assume precisely the same appearance as those on the former skin.

The keeper of silk-worms can tell us well, and perhaps with many a sigh, that the period of moulting is one of great peril to his tender charge. The larvæ are sick and feeble for some time after each period of moulting; and large numbers die at this time, apparently unable to bear the exhaustion attending the loss of their old skin. Larvæ generally are much debilitated by each moult that takes place; for a variable period, sometimes for some hours, sometimes for a whole day, they will refuse food, and lie without motion. All their parts are very soft and tender, and require hardening by exposure to the air. After a certain period, however, these effects pass off; the larva recovers its original strength, its body becomes firm, its colour brightens, and appears more brilliant than ever; and, above all, like convalescents among ourselves, its appetite is twice as keen as before, which, when we call to mind what has been already said about the voracity of larvæ, it will be confessed, appears scarcely possible.

These changes of skin take place a definite number of times in the larvæ of each species. Thebreeders of silk-worms tell us that that precious, if not priceless, little larva, sheds its skin four times; other larvæ moult oftener than these: some five times, some seven times, some eight times, and some nine, or even ten times; others, again, only moult thrice. The ordinary number of moults appears to be about three or four. Some, however, never moult at all in the larva state. The larva of the common bee, and that of the flesh-fly, and some others, are among this number.

Whatever may be the general opinion upon the want of beauty and comeliness in insects, and particularly during the larva stage of their history, it is very certain that it is quite erroneous. We may possibly fail, unaided by the pencil and colours of the artist, in conveying even an approach to an adequate conception of the rich and glowing raiment with which it has pleased God to clothe these minute and humble beings. But a very little actual observation of a few even of the commoner larvæ or caterpillars of the butterfly and moth species, will convince the reader that few other created things have been so exquisitely adorned with magnificence of colour and apparelas the larvæ of these insects. Here will be found hues so rich and deep as to—

"Make the rose's blush of beauty pale,And dim the rich geranium's scarlet blaze."

Here is a larva of a moth before us whose head is a delicate orange colour, whose belly and feet a pale pure green, whose sides are of primrose tint, variegated with slashes of green, and along the back there runs a beautiful band of white, the intensity of which is most agreeably relieved by a vein of lovely pink, which divides it in the middle. There is another clothed in purple, green, and white; another, the larva of the butterfly called the "Camberwell Beauty," is of a brilliant black, dotted with spots glowing like carbuncles along its back; another has a coat which seems as if set with precious stones, blazing with an intensity of colour which cannot be conveyed by description. In a word, larvæ, on the whole, can boast as varied a display of beautiful hues as can almost the whole array of flowers in our gardens. In consequence of the, unfortunately, too general feeling of loathing, to which allusion has already been made, but few persons are in reality acquainted withtheir beauties. Their diminutive size also renders them less attractive than they might otherwise prove, since we are generally most pleased with the beauty of an object when its size makes it so manifest to our eyes, as to render it impossible it should escape our attention.

It is a very remarkable fact, and corresponds, to a certain extent, with the influence of the same agent upon plants[G]—that light seems to be in some measure necessary in order to develop the colours of the larva. Thus it has been noticed, that those larvæ which are, by their habits, much in darkness, dwelling, perhaps, in caves of the earth, or immured in the heart of a piece of timber, or inhabiting a cell scooped out of the solid rock, are, most frequently, of a uniform whitish colour. Some experiments have shown that when these whitish larvæ have been brought out of darkness and exposed to the sunlight, their colour has turned to brown. Very probably this effect is due to precisely the same kind of change as takes place when a fair-skinned European travels into a southern clime, his face and hands becoming so brown, tanned, and dark, as to form a ludicrous contrastto the whiteness of his chest or arms, which are not exposed to the influence of the solar ray.

Larvæ resembling Twigs.

There is still something more to be said about the coats of the larva. To look at some of them, it would be difficult for a person unacquainted with entomology, to guess at the real nature of the object before him. Some look like dry twigs. Some look far more like littleCactusesthan insects. Some are clothed withhairs, arranged in the most curious and eccentric manner. Some have hairs so long as to give them all the appearance of very minute shock-dogs. In some, the hairs are arranged like stars; in others, like the quills of the "fretful porcupine." The backs of other larva look just as if they were studded over with little camel-hairpencils. Madame Merian has described the larva of an insect found in Surinam as having the various divisions of its body ornamented with three blue tubercles, like turquoise beads, from each of which proceeds a long, delicate, feathery plume of a black colour. Another, described by the same lady, is splendidly adorned on each side with fifty red tubercles, shining like coral, from each of which proceed five or six long hairs. Some, again, are covered as thickly as possible with sharp processes, like thorns, sufficiently strong and sharp to pierce the skin of any one who incautiously ventures to take them up. The body of a small caterpillar brought from Brazil, is described by Kirby and Spence as possessing a body so thickly planted with spines, like the branches of a tree, as absolutely to wear the appearance of a forest or thicket in miniature! It has been stated, indeed, by some travellers, that the larva of some insects has the power of darting out, when alarmed by the approach of anything, such as the human hand, from as many knobs or protuberances in its back, eight bunches of little stings, with which it inflicts a very painful and venomous wound.

Singularly coated Larva.

The larvæ of some insects again seem as if they were clothed from head to foot in the most delicate and snowy white cotton wool. These may sometimes be seen on our apple-trees; but one of the most singular is figured in the cut, from an engraving given in Baron de Geer's work. The larva is covered completely with a coat of cottony flakes of the most dazzling white, and these are arranged, as will be perceived, with great regularity. The larva has, in this white and warm raiment, somewhat of the aspect of a coachman buried in the old-fashioned great coats with the many capes.

Having dwelt so long upon the food and clothing of the insect in the larva form, it is right we should now devote a little space to consider how theybreathe. Some one perhaps will say,Breathe?—do larvæ breathe? Most certainly; and respiration, or the function of breathing, is not more necessary to us than it is to these creatures. For this purpose, however, we must begin a fresh chapter.

CHAPTER IV.

RESPIRATION OF THE LARVA.

We well know, from the various melancholy accidents which have taken place, that unless human beings have a constant supply of pure fresh air they must perish. Many years ago, a number of unfortunate persons were shut up in a narrow cell, called the Black Hole, at Calcutta, where they could scarcely find room to stand, much less obtain air to breathe. In one night the greater part of them died. More recently, as some poor Irish were being conveyed in a steamer in stormy weather, the captain, out of prudence and mistaken kindness, ordered the hatches to be all battened down, so that fresh air was prevented from getting in. A shocking spectacle was beheld soon afterwards:—in the close, suffocating cabin lay a number of dead bodies, of men, women, and children, all destroyed by the want of air. Now, precisely the same fatal resultstake place if we treat larvæ in the same manner; from which we learn that undoubtedly breathing is not only one of their functions, but a most necessary and important one.

This may be easily proved. If the reader will procure about a dozen caterpillars of any common kind, and put them into a dry phial, corking them closely up, and if he leaves them in their prison of glass a sufficient time, all will die, even though he may have supplied them, on putting them in, with an abundance of food. Clearly, therefore, they do not die of starvation, and we should be naturally disposed to say they must have died of suffocation; that is, they died because the function of breathing could not take place, as there was not the necessary change of the air contained in the phial. But suppose that other caterpillars were procured and put into another phial, with a sufficiency of green food, the mouth being covered over with a piece of muslin, or fine lace, what would then be the result? Simply that they would live and thrive for as long a period as they received their proper quantity and quality of food, and would pass through all their stages of existence as comfortably as if in the open air. The reason would be because the open fibresof the muslin, or lace, do not interfere in the least with the requisite change of air for respiration.

Again, if after corking up the bottle for a short time, we were to shake out all the caterpillars from it, and then put into it a little water, in which quick-lime has been slaked—sold by chemists under the name of lime-water,—we should find it become quite white and milk-like. This would be, because, as the physiological chemist well knows, the function of breathing causes carbonic acid gas to be poured out of the body, no matter whether it is the body of an insect or an elephant; and this gas has the property of turning lime-water of the colour mentioned. Hence we have a second and convincing proof that larvæ breathe—we need scarcely remind the reader that caterpillars are larvæ—and more than this, that the function of breathing in them resembles, so far as the discharge of this peculiar gas is concerned, the same function, whether carried on in the human body or in that of the most mighty and majestic of the beasts of the field.

The great chemist, Scheele, has experimented, somewhat in the manner we have recommended, upon the breathing of larvæ. He found that whencaterpillars and maggots, to use the customary terms for these varieties of larvæ, were confined in vessels containing only about eleven cubic inches of atmospheric air, and so stopped as to preclude the ingress of any fresh air whatever, although furnished with an abundant supply of food, they soon died. When he put them into a still smaller vessel, they died the sooner. In fact, precisely in proportion to the purity, or to the amount of the air contained in the space in which he confined them, were their lives prolonged or shortened. He found on examining the air that it contained, as above stated, carbonic acid gas.

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