CHAPTER II.

HABITS OF THE LARVA.

Generally, for a little while after the larva has emerged from the shell, it is in a very weak and languid condition. The effort of extricating itself from its little prison-house, seems to leave it almost without strength; and for a period which varies in different insects, it lies helpless and almost motionless at the mercy of any wandering adversary, and might be demolished without resistance. But this hour of weakness, except in a few cases, is not prolonged. In the course of an hour or two, or even much less in some instances, the larva revives, takes heart, and begins by eating whatever food may happen to lie in its way; and now the larva becomes a terror to the world of insects, or even, indirectly, to man and to nations. Instead of simply eating, in order to live, like most other beings, it only lives to eat; it has no other duty to perform at present but to eat as fast and as much as it possibly can in a certain time; and it must be confessed, the larva, generally speaking, leaves little to be desired on the score of a sharp appetite. Unlike other creatures who allow themselves a certain period between their meals, the larva sets to its feast and does not leave the table until it has devoured all its contents,--upon which it immediately begins again elsewhere. No _gourmand_ in the world, whether among human beings or brutes, can compare with the insect in this form for the amount of food consumed. Morning, noon, and night, is to it only a continued round of feasting; and, as may well be imagined, the larva grows very rapidly accordingly. Some larvæ consume animal, others vegetable food; or, in the language of science, some are _carnivorous_, some are _graminivorous_ or _herbivorous_, and some will eat anything almost that comes before them--these would be called, and very appropriately so, _omnivorous_.

Let us speak of carnivorous larvæ first. The larvæ which have carnivorous propensities render themselves often truly terrible to the insect world around them. The most mighty warrior that ever lived in his whole career never slew half so many of his own species as the larva of a beautiful fly does of _aphides_ in a few hours. Well does Réaumur call them the "lions of the aphides," and thus does he describe their method of proceeding:--

"There is no beast of prey in nature who hunts so entirely at his ease as does this larva. Resting upon a twig or a leaf, he is surrounded on every side by the insects on which he feeds; often, indeed, they touch his sides, and he is able to catch hundreds of them without changing his position. Not only do the poor little aphides not fly from him, but they may be often seen creeping over the body of their enemy. It is only after the larva has eaten up the greater number of his prey around him, that he has any need to remove to a spot as thickly inhabited by them as that in which he has been making his cruel ravages. In order to observe the manner in which he attacks them, the best plan is to take him, put him between two leaves, and shut him up in a box for ten or twelve hours to sharpen his appetite. After this fast he must be placed on some spot where the aphides are found in abundance. Immediately he begins exploring around for prey, which he does simply by the sense of touch, as he does not appear to be able to see. At length an unhappy insect comes within his reach. Brandishing a trident with which he is armed, he immediately transfixes the insect, just as we take up a morsel of food upon a fork!" The little creature is then sucked into a sort of cavity like the neck of a bottle, where it is retained by a couple of pins until its juices are emptied by the destroyer, when he casts it away, now nothing more of it being left but a dry, shrivelled, empty skin. The aphis-lion, however, loses no time, and presently seizes another, which he pierces and sucks dry as quickly as the last.[D] When very hungry he will devour one a minute. Réaumur says, "I have seen him eat twenty of these insects one after another in twenty minutes; nor did this satisfy him: for in the course of two hours he devoured more than a hundred insects with which I supplied him!" These larvæ do repose a little, but never for long, for they are seldom without some prey in hand. "I have seen," adds the last author, "twigs of the elder seven or eight inches in length entirely covered with these insects, (the _aphides_,) and in four days' time there remained not one alive."

This larva is a rare specimen of courage, as well as of destructive powers; for when it is quite young it often seizes upon an insect twice as big as itself. It is very amusing to see the unequal contest between the little but courageous foe, and his great, bulky, and stupid adversary. Immediately the larva thrusts its trident into the body of the enemy, who, stupid as he is, does not like the sensation of the wound in his side, and makes off as fast as he can. The lion-hearted larva follows him up and wrestles with him, and at length actually boards him, to use a sailor's term, clambering up his sides, and, in triumph, piercing him through and slaying him. What is perhaps most singular of all, the larvæ of some species of these flies not only slay their victims, but actually clothe themselves, after the manner of Hercules on his victory over the Nemæan lion, with the skins of their prey!

It is almost to be regretted that the insect world has not had the privilege of having its combats sung by the poets. Who can forget the animated scenes, painted in such life-like colours by Homer and Virgil, of the conflicts, hand to hand, of the heroes of their verse? But the history of insects supplies us with more singular and more interesting deeds of fight than have ever yet been fabled by poets, or commemorated in song. In the instance we are about to quote, the larva of the ant-lion is the crafty Giant Grim, who lives by entrapping, as we have before said, poor wayfaring travellers. Like those giants of old, of whom we read in books a little more wonderful than true, this subtle and powerful enemy lies deeply ensconced in his subterraneous cavern, patiently abiding the time when his unsuspecting prey shall fall into his power. His trap is depicted on the opposite page.

This insect is naturally a very helpless being, it can only walk at a slow pace, and strange to add, it can only walk backwards, and not forwards! Yet its food is the juice of insect bodies. How, then, is it to seize upon them circumstanced so unfavourably as it is, having neither swiftness nor ability to direct its motions sufficiently actively to fit it for such a task? It succeeds by an artifice of the most refined character. Nothing daunted by what we might call its natural disadvantages, the insect sets bravely to work to construct a trap for its prey; and the manner in which this is performed may well strike us with wonder, and raise our admiration up to Him who has so marvellously endowed this humble being with wisdom and skill. It first takes care to choose out a proper site for the work it is about, and in this always selects a soil composed of fine, loose, and dry sand, well aware that, as we shall presently see, no other would be fit for its purpose. Generally it chooses such a soil under the shelter of an old wall, where the rain cannot easily penetrate and ruin its work. In so doing it shows its wisdom; for thither, when the heat of the sun is great, or when the rain-drops fall heavily, crowds of insects come for shelter, and fall into its cruel embrace.

The site being chosen, the next important step is to mark out the bounds of its habitation, and with this view the insect begins digging a circular ditch, walking backwards until it has completed the circle. This defines the outer limits of its trap, and is a sort of guide line to it in its future operations. Then it sets about the more proper task of excavating its trap. Would that our readers could see this insect at work! Of all the wonderful sights presented to us in the insect world there is none to equal it in interest, none so calculated to enlist our sympathies on the part of the patient, skilful, and unwearied little labourers of this kingdom of nature. Guided by the line it has marked out, the workman steps into the circle, and sets to work with a hearty good will, and with a degree of diligence and excavating skill that would put our railroad "navigators" to the blush. Shower after shower of sand is seen flying up and beyond the boundary described, with the most unintermitting diligence, until the insect has completed the circle again; arrived there, it turns round and excavates back again until it arrives at the same point. But it may perhaps be asked, where are its tools, and by what means does it succeed in casting up these loads of earth? We fear that at best any written description will hardly do justice to our ingenious labourer; its method, however, is as follows:--It uses the head as the spade, or rather shovel, and in the strangest manner it fills the shovel with one of its feet with a load of sand, and then by a quick movement of the head tosses it out of the cavity. By working in alternate directions it manages so as never to over-fatigue one leg, for on its return the leg previously in use is at rest, while the one on the opposite side is now called into duty. The insect thus works on until its trap is completely excavated, the task occupying a variable time; sometimes being finished in half an hour, sometimes even in less, but occasionally occupying several hours, the little labourer being obliged to rest a certain time. Réaumur, who has given a fascinating account of these insects, writes, "I have had at times hundreds of ant-lions in a large box, and I have often been amused with filling up their traps. Some of them would immediately begin to form another; but the greater number in the warm long days of summer deferred executing the work until the sun began to go down. They seldom worked in the heat of the day; but in cold or cloudy weather they would excavate at any hour."

We well know what perplexity a chain of rocky hills causes to a railroad engineer, and what vast outlays of money, labour, and time are necessary in order to overcome the obstacle thus presented to the path of the engine and its train. But it may be safely said that we can furnish a parallel instance of difficulty and of patient, all-surmounting exertion from the history of the insect before us. M. Bonnet was curious to know what it would do if a stone or some such obstacle were met with in the process of its excavations, and one day had the gratification of observing the behaviour of the insect under these trying circumstances. Not being able to cast it out with its head, the insect determined to carry it out, if possible, on its back. With this view it contrived by various manoeuvres to place the stone upon its back and to balance it there. This was the least difficult part of the undertaking. The insect had to climb up an inclined plane upon soil, chosen with other views purposely by itself, as shifting and unsteady as possible, and not only so, but to preserve the balance of the stone with which it was encumbered. Undaunted by these difficulties it made the attempt, but the first step brought down a shower of sand, and tumbled the little rock to the bottom. Again and again did the heroic insect attempt the same feat, and with the same ill success, and we might have thought we beheld a realization of the fable of Sisyphus and the rolling-stone, in the vain endeavours of the insect to get rid of its encumbrance. Five or six times did the insect repeat its endeavours, and at last, after one or two narrow escapes, the stone was fairly lodged on the outside of the trap, and the insect returned to its subterraneous recess at the bottom of the cell in triumph.

The traps vary in size in proportion to the age of the insects which construct them. The young insects only form very small ones; but as even from the moment of their birth they are destined to toil for their food, they do not wait in idleness and hunger because they cannot make large efforts, but are content to make little traps not more than a few parts of an inch in diameter. Thus they set us the needful example of not despising to do small things because our strength is not yet equal to the performance of as much as we could desire. The diameter of the trap formed by a full-grown insect is about three inches; the depth about two.

When its labours are over, it has been well remarked, the insect now only requires patience--but it must have a good deal of it! It generally buries itself, all but its jaws, in the sand at the bottom, and here awaits its victims. If it requires much patience, surely it also needs to have much power of endurance of hunger, for it may wait for days sometimes without catching any prey. Frequently, when this is the case, it marches out of its trap, and tries its fortune in some more favourable spot. But see! an ant who has been out foraging for the young ants at home is hastening back laden with sweet treasures, when suddenly she finds her path arrested by what appears to her to be a deep but smooth precipice. To plunge down and rise on the opposite side is a shorter cut, in her estimation, than to go round; or perhaps she is led by curiosity to wish to explore this singular cavity, and she plants her feet on its treacherous edge, causing a few grains of sand to roll down and give notice to the wary giant below that a victim is at hand. A step back, and her life would be saved; but no, she leaves the bank, trusts herself to the unfaithful soil of the sides of the precipice, and instantly rolls down in a cloud of dust to the bottom. Terror has now laid hold of her, and with all speed she strives to clamber up the unsteady sides. For a moment escape appears possible, but the Argus-eyed monster below starts up into activity, and piling upon his head a huge load of sand, he shoots it after the escaping ant, and once more brings her down covered with dust into his embrace. The terrible jaws are instantly closed upon the unhappy insect, and in a few minutes her existence is at an end, the savage enemy shaking her violently, or dashing her quivering frame against the earth.

Singular to add, the ant-lion loves not dead prey, and will indignantly cast it out of its trap. Says Réaumur, "They appear so much to delight in the glory of a victory, that they disdain to touch an insect who is not, to say the least, in a condition to contend with them!" It certainly is not that the food when offered to it dead is not fresh enough that it is thus treated; for if only killed an instant before the insect still refuses to touch it. Réaumur is disposed to believe that, like our sportsmen, these interesting but cruel insects destroy prey more for the pleasure of exhibiting their superior skill, than to appease their hunger. But it is rather uncharitable even to the ant-lion, to say so much as this. When the insect has sucked all the juices out of its victim's body, it casts it out of its trap, and the earth around, strewed with dead bodies, is thus the silent witness to the destroying powers of the giant within.

This singular insect, whose exploits have detained us so long, remains in its larva form two years, growing daily in size until it has completed its existence as a larva, and must then enter upon another condition of life. It is to be regretted that it is not to be found in England, or at least it has not been for some time discovered in our island; but it is common in France and other parts of the continent, and would well repay the trouble of being brought over. As the insect is very patient of hunger, it might easily be conveyed in a little wooden box, half filled with fine sand, and its proceedings could be readily watched by placing it under a bell-glass, or in a little glass case, introducing a few ants or spiders for its food from time to time.

The insect exhibits to us a wonderful instance of what we may call, after the example of Dr. Paley, the principle of compensation in nature. It can neither run nor fly with the speed necessary to overtake its prey who are swifter of foot than itself. But God never created it to starve, and has endowed it with a rare combination of faculties by which it is enabled to live in the midst of plenty if not even of luxuriance. So it is in a thousand other cases in nature. So it is indeed in Providence likewise. If He sends us trials, "He also makes a way to escape that we may be able to bear them." If our day is to be dark and cloudy, and to call for the exercise of much faith and patience, there is still the same provision made; "as thy day so shall thy strength be." If our lot in life is one of hardship He can, and if it is sought of him aright He will, and He does bear us up, revive our drooping strength, and enable us to go on our way rejoicing.

Let us go on to speak now of some other carnivorous larva. If in the month of July we can find out a spot where we can detect the traces of the labours of the sand-wasp, of whom mention has been made at page 15, and cutting out a little mass of the sand-rock containing several of their burrows, then take the trouble to open gently one of the cells formed by these insects, we shall see a carnivorous larva in as happy a condition as a fox in a hen-roost, or a mouse in the midst of a cheese! The best way to obtain access to this securely imbedded and luxurious larva, is to moisten the mass of sand with a little water, and then slice it gently down with an old knife until we come to the cells. They are here represented. At the bottom of each we shall see the larvæ which have sprung from the eggs deposited in the manner before described, after the arduous and affectionate labours of the parent. Then above each is a heap of caterpillars, arranged with beautiful neatness, and larvæ and caterpillars are both fast locked in their prison house by the firm stopping with which the parent wasp has closed the mouth of the cells. These caterpillars are all alive, and are rolled into a ring-like form, but are so chained down that they cannot move in the least degree. The poor prisoners, like the sheep in the slaughter-yard, are only waiting their turn to be killed and devoured. The larva soon after it is hatched finds himself in the midst of a well-stored larder, and has nothing to do but eat, which he does not long delay doing. He devours at his ease, and revels in the dainty fresh food which the care of his parent had laid up. When he has eaten all his prisoners up, and grown to his full size, he lays down to sleep, to awake again in another and a far different form.

Sometimes the reader may have the opportunity, it may be, of finding out the nest of the wood-boring wasp, and he may in June or July, perhaps, succeed in discovering another instance of a larva in a happy state of plenty. The larva is sure to be found at the bottom, and above it will be piled a heap of insects for its food. What is remarkable about this store of food is, that the insects thus made prisoners are not dead, for they would, if so, soon become corrupted, and unfit for the diet of the larva; they are in a sort of half stupified condition, in all probability very like that induced by the late plan of breathing ether and other vapours to render persons insensible to pain, while surgically operated on. Since this plan has been introduced, we read in some of the newspapers--we may question with what truth--that the butchers in Albany (America,) give ether to the oxen before killing them, so as to make them insensible to the pain of the death-blow! But the wasps in question have for ages been in the habit of effecting the same end by stinging their captives, the poison not sufficing to kill them, nor yet permitting them to be actively alive.

The insects thus stored up for the larva cost the parent many a conflict in their capture. And here we may interest the reader by describing the exploits of a warrior wasp, abundant in the Isle of France. It is curious that in the Isle of France the common bee is not to be found as a native of the woods, while, in the Isle of Bourbon, it is very common, and furnishes an abundance of wax and honey. This is explained by supposing that the warriors of whom we are about to speak destroy the bees, and have thus prevented their multiplying in the island in question. Truly, like the banditti of whom we read in books, these wasps are splendidly attired, although not in the spoils of those they have robbed. Their head, chest, and body is of a resplendent lustre; now green, or, seen in another position, blue, and glistening with all the lustre of an exquisite varnish; their antennæ are black, their eyes of a brownish yellow, and their legs partly bronze-coloured, and partly of a beautiful violet. They are strong and swift of wing, and are possessed of a terrible lance, the thrusts of which even man cannot endure without far more pain and inflammation than attends an ordinary sting.

The foe with whom these magnificently-dressed warriors have to contend, is a kind of insect allied to the cockroach, which, in our kitchens, has acquired the incorrect title of "black beetle." This insect is detested by the inhabitants of the island, for its ravages upon almost everything of value or delicacy, and is not less hated by the sailor for its destructiveness on ship-board. It is called _Kakerlac_, and is much larger than the cockroaches, which are the plague and terror of our cooks. Imagine that one of these great and odious insects is marching along the highway. The warrior wasp has also been making his expeditions for prey abroad, when suddenly his eager eye catches sight of the kakerlac hastening to some new scene of depredation. The warrior instantly alights, and the kakerlac stops, thinking perhaps to intimidate its adversary by its size and ferocious aspect. Both insects glare at one another;--

----"each other from afar They view, and rushing on, begin the war. They launch their spears; then hand to hand they meet, The trembling soil resounds beneath their feet; Their bucklers clash, thick blows descend from high, And flashes of fire from their hard helmets fly. Courage conspires with chance, and both engage With equal fortune yet, and mutual rage."

Virgil's description, though scarcely accurate in all points, gives us a lively image of this insect combat. The kakerlac, however, is the Turnus, and the warrior wasp the Æneas of the fight. The wasp is the first to attack, and darts upon the other, seizing it by the muzzle with its strong jaws, then bending its body so as to bring its tail under the abdomen of the kakerlac, the lance with its charge of poison is deep-plunged into the body of the unhappy foe, imbuing a deadly venom into its system. Having made this thrust, the warrior looses the foe, and soars in triumph a little way into the air, satisfied of a successful issue.

The wretched kakerlac, after a few brief convulsions, lies paralysed on the ground unable to stir a step from the spot where it encountered its terrible adversary. Fully aware of this, the victorious wasp, after taking a few turns, as if to proclaim the downfall of the Giant Kakerlac to the surrounding neighbourhood, returns to the scene where the conflict was fought. The kakerlac, unable to resist the victor, and being naturally, though a great devourer, a very faint-hearted creature, lies immovable while the wasp seizes the prostrate foe by the head, and in a sort of triumphal march drags it along the road to its nest. But though the kakerlac was not a difficult enemy to overcome, the weight and size of its body are a sore burden to the victor wasp. The way to the nest is long, tedious, and rugged. After a hard pull over all sorts of obstacles the wasp becomes completely breathless, and is obliged to let go, and for a rest it generally rises into the air, probably with a view of reconnoitring future difficulties, and of ascertaining the best route to pursue. Thus, after alternately dragging along the body of its victim and rising up to spy out the path, at length the conqueror succeeds in bringing the carcase home.

Here, however, arises another difficulty. To attempt to get the body of the huge kakerlac in, is just as if one were to attempt to get an elephant through a small street-door. What is to be done? The wasp enters the hole backwards, and, seizing the head of the kakerlac, endeavours with all its might to drag it in, but all in vain. Many times it repeats these efforts with the same want of success; and now it appears that its labours in bringing hither the corpse, and its dangers in the battle, were all for nought, for the great body cannot be put in the place the wasp had designed for it. As if exasperated with the difficulties, out comes the wasp in fury, and falling upon the body of the kakerlac, hews off the large wing-cases, together with several of the limbs, and goes back into the hole again to repeat the attempt to get it in. Success at length crowns its efforts; by little and little the body becomes lost to sight, and finally disappears altogether from view, being carried down to the very bottom of the nest. Here the larva, as soon as hatched, feeds upon it, thrives, and grows, and falls asleep, awaiting the time when itself shall awake to follow in the steps of the glittering and formidable warrior who, with the boldness of an amazon and affection of the tenderest of mothers, supplied it with nourishment during its hours of infancy.

This may be thought a scene of sad carnage, but the following will, perhaps, appear even more so. What should we say, if deep in the forests of some wild uncultivated country was found a den, the bottom of which was strewed with skulls, with bones, and mangled limbs? What fearful scenes should we not suspect to have taken place in this dark and horrid place; and as we shuddered in looking round upon its walls, as the once witnesses of terrible deeds, we might even fancy we heard the cry of the poor traveller, whose last agonies were seen by no eye but that of the monster who had waylaid and murdered him? Such a den may be found in the forest, made horrible by the cut-off heads, limbs, and wings of insects--it is the habitation of the carnivorous larva of a wasp. Nay more, as is seen in the engraving, the insect monster actually works up the cut-off wings and limbs into a sort of covering for itself, and finally buries itself in a shroud partly made of the spoils of former victims.

Perhaps the carnivorous larva of the tiger-beetle, or _cicindela_, is as ferocious a being as any in this state. In this respect, indeed, it resembles the perfect insect, whose title sufficiently indicates its swiftness, cunning, and blood-thirsty nature. "These larvæ," writes Mr. Westwood, "burrow cylindric retreats in the earth, to the depth of a foot or more, employing their legs and jaws in loosening the particles of sand and earth, which they carry to the surface upon their broad, saucer-like head, ascending by the assistance of the two hooks upon the back, somewhat after the fashion of a sweep going up a chimney! Having completed this burrow, they station themselves, by means of their legs and back hooks, at its mouth, their large flattened head and great segment filling the hole." Here they remain all day long, and many an insect might pass close by, little dreaming of the terrible foe who lay under that trap-door. Presently comes a spider scrambling over the ground in haste to mount up a branch on which to hang one of its web lines; the treacherous trap-door is in its direct path. Its feet rest on it; instantly the trap drops, and the poor insect falls into the dark den, and is caught in the powerful jaws of the artful larva. Truly, there is something even to man a little intimidating in the sight of such a monster as is represented here; how much more to the unfortunate insect who happens to be caught in its embrace, and having only time to just catch a glimpse of its fearful captor, is dragged down in a cloud of dust to be devoured in darkness at the bottom of the den. Yet this also, like other cruel creatures, is in reality a very timid larva, and instantly on the approach of danger, drops to the bottom of the cell, where, if we have courage to pursue it, we shall find it much in the attitude in which it is here represented. The singular pair of hooks on its back are used as the flukes of an anchor to sustain the insect in the position it assumes at the mouth of the cell.

Mention has already been made in the previous chapter of the insects called Ichneumons, which deposit their eggs in the bodies of the larvæ of other 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.

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 somewhat complicated, 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 of _arm_, if we may so speak; at what we may call the _elbow_, 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 by means 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.

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 the same 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, the larva 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.

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, for _they_ only tied a string round the leg of the unhappy cockchafer, while _these_ thrust 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's fields 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 visitation of these insects to good account, has succeeded in distilling an excellent _lamp-oil_ from 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 of _Sunk Island_ in Holderness were 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 of _two hundred and ten_ larvæ 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" is _Tipula 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 of father-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!

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, or _Plusia 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 was probably 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 eat _them_. 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 hundred eggs; 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 thousand_ larvæ. 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 the severity 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."

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 Tours every 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 the road-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. An edict 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 the trees 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 of strange 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 bushels_ were 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 the _Calandra 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 consigned to 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 the _Tinea 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 got in. 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 is _Tenebrio 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 in _chocolate_!

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, was _to 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, 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 was consumed, 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 of _ninety-six millions of pounds_ of 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 of _eighteen thousand million silk-worms_. The Count Dandolo, who has written an excellent treatise on this subject, in Italian, 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 about _five sheep_ for 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 with their rate of devouring than with that of other insects in this state.

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 of _elephants_, or young elephants to the size of _little hills_? yet these comparisons are not exaggerated, remembering the increase and growth of the silk-worm and of larvæ generally.