Proboscis of the Honey-Bee.
Proboscis of Carpenter-Bee
To the variations in the mouth of each of these insects it has been thought good to attach a distinct name. When, for example, we speak of a bee'sproboscis,[V]we speak actually of its mouth. The mouth of the butterfly is called by most entomologistsantlia; that of the aphis apromuscis; that of the flea arostrulum. But the readermust not allow himself to be confused by these terms; they all are but names for modifications of the same part—the mouth. When the butterfly plunges its long tube into the flower—when the fly intoxicates itself with a drop of syrup, using itsproboscisto pump it up—and when the flea thrusts itsrostruluminto our flesh, and quaffs our life-blood as though it were nectar,—let us not forget the mouth is the organ employed in each of these cases, varied and altered in form though it certainly be.
Diagram of the mouth.—a.TheLabrum, or upper lip;b.TheMandibles, or upper jawsc.TheMaxillæ, or lower jaws;d.TheLabium, or lower lip.
In all cases, the various parts of the mouth may be reduced to six, the names of which deserve remembering, and this will be rendered easier by the accompanying diagram, in which they are all separated and lettered, so as to distinguish each part; these six parts consist of four side-pieces, and two other organs, one above, the other below. The name of the upper organ is theupper lip, or in Latin,labrum; that of the oppositelower one, is thelower lip, orlabium. The upper pair, of side-pieces, are called themandibles, or upper jaws; the pair below are the lower jaws, ormaxillæ.
Let us now briefly mention the use of these various parts of the insect's mouth; beginning with the upper lip, (a) orlabrum. Unlike that organ in ourselves, the insect's upper lip is generally, in such insects as bite their food, a plate of horny substance, which serves the purpose of an upper covering to the rest of the mouth. Like our own upper lips, however, that is to say, like those of men, at least, it is fringed with a sort ofmoustachein most cases.
Themandibles, (b) or upper jaws, in the biting insects, are instruments for cutting the food in pieces. When we bite our food, the movement of our jaw is upwards and downwards; but in the insect it is like that of a pair of scissors, or from side to side! These jaws are sometimes frightful-looking instruments, resembling, in the stag-beetle,horns; and their power is proportionally great. Although their general use is to masticate or crush the food for the insect, this apparatus is often employed as a formidable weapon ofdefence, or offence; and very frequently in the excavation of a nest or retreat for the insect. They are sometimes so constructed, as to look as if they were furnished with several teeth.
The Stag-Beetle, representing its enlarged Mandibles, like horns.
Themaxillæ, orlower jaws, are less firm and strong than the preceding; but they are more complicated in their structure, and have attached to their sides remarkably delicate little processes like the antennæ, which are called thepalpi, or, less properly,feelers. The lower jaws are muchvaried in structure in different insects; as may well be imagined, when it is mentioned that the long and beautiful spiral tube of the butterfly, by which it drains the juices of the flower, is, in reality, composed of the maxillæ, or lower jaws. In ordinary cases, the principal use of the lower jaws appears to be to hold the food, while the upper jaws bruise and crush it; but their use, of course, varies with their structure and modifications.
The last part of the mouth is thelabium, or lower lip. This also is a very complicated organ, generally serving to close the mouth from beneath, like the upper from above. It boasts, like the same organ in higher animals, of achinbelow it, called thementum, and on each side of it are a pair of feelers, orpalpi, like those of the maxillæ. In the centre a little tongue-like projection is visible in the figure, which is sometimes called thetongue, but perhaps not correctly, if by that term is meant the apparatus fortasting. The lower lip is as much varied as the maxillæ.
It would be impossible, without going too far into minute technical details, to explain to the reader how all these various parts of the mouth are so modified, and altered, as to assume the verydifferent appearances presented to us in the insects already mentioned. This pleasure must be reserved for the time when, well acquainted with the generalities of insect history, which alone form the scope and subject of this little work, he feels anxious to study entomology as a science; and he will find a number of excellent books which will then well repay his attentive perusal, and satisfactorily answer all his inquiries on this and other difficult topics connected with this science.
It cannot fail to be noticed, that in this description of the insect's mouth no mention has been made of its organs oftaste. Its eye, and probably ears, and means of touch, have all come before us; but where, it will be asked, is its tongue? The little organ mentioned as a part of the insect's lower lip, although strikingly resembling a tongue in some instances, is in others very different from it, and appears in such cases to be quite unfitted to act as the organ of taste. We must, therefore, suppose, that other parts of the lower lip or mouth have the same faculty in addition to the so-called tongue. It is very certain that insects have the faculty of tasting, and also of discriminating between their food; as few will be disposed toquestion, who will place a plate of salt, and a plate filled with moist sugar, in a sunny window on a fine day; it will soon become evident which will be favoured with the attention of the flies.
Neither has any mention been made of anose.[W]A common flesh-fly, however, will soon satisfy us, that it is not devoid of some organ or other which answers this purpose. If we cover a piece of meat under a cloth, or put it into a wire safe where it is certain that the fly cannot see it, it will scent it out as readily, or even more so, than a cat or a dog would. Sometimes this insect's nose proves a treacherous guide, for a plant has been described, called thecarrion-flower, which diffuses an odour like that of putrid meat, which attracts the fly, and induces it to deposit its eggs thereon, under the idea that its future young will thus be hatched upon a certain source of food; but in vain, for they perish almost as soon as born, finding nothing in the plant whereon to exist.[X]But as to the precise seat of theorgan of this sense, opinions are greatly at variance. Some believe it to exist in thespiracles, some in the mouth, and some in a special organ which they call the nose, but which does not seem in reality to fulfil that office, at any rate, in the generality of cases. M. Huber showed the existence of this faculty to lie somewhere about the mouth, by some interesting experiments upon bees. He presented successively to all parts of a bee's body a camel-hair pencil dipped in oil of turpentine, to which most insects are extremely averse, but the bee took no notice of it. He then took a very fine hair pencil, while the bee had extended its proboscis, and presented it to its eyes and antennæ without effect; but when he pointed it near the cavity of the mouth, above the insertion of the proboscis, the creature started back in an instant, quitted its food, clapped its wings, and walked about in great agitation, and would have taken flight if the pencil had not been removed. On this it began to eat again; but on the experiment being repeated, it showed signs of similar discomposure; oil of marjoram produced the same effect, and more promptly and entirely. He then seized several bees, forced them to unfold theirproboscises, and stopped their mouths with paste. When this was sufficiently dry to prevent their getting rid of it, he restored them to their liberty; they appeared by no means incommoded at being thus gagged, but moved about and breathed as readily as their companions. Huber then tempted them with honey, and presented to them, near the mouth, oil of turpentine and other odours that they usually have an aversion to; but all produced no sensible effect upon them, and they even walked upon pencils saturated with them!
Leaving now the head of the insect, it is necessary for us to make some mention of the parts attached to thethorax, or trunk. In the head division we have seen that the various organs of the senses are situated: we shall now find that in the thorax division are placed the organs by which the insect is either wafted in rapid evolutions to the highest air, or runs with incredible rapidity along the surface of the earth. We have already described, on a previous page, the general structure of an insect's wing. It remains, therefore, for us here to advert to a few other facts in connexion with these elegant appendages.
The House Fly. Natural size and magnified.
Scales of Insects Wings magnified.
The natural number of wings in the insect world is four, arranged in two pairs. But this number is obscured by the modifications to which in many instances one or other of the pairs becomes subject; and we should, if this were not remembered, become somewhat confused at taking up the first insect that came in our way, which would probably be the common fly, and finding that we could only recognise two large wings instead of four. In this tribe of insects the hinder pair of wings is reduced to a pair of slender knobbed filaments. Some insects are without wings at all. The ant, the bee, the dragon-fly, the house-fly, and many other insects, are furnished with wings of gauze-like transparency and structure, often crossed in a curious manner by thenervures, of which we before had occasion to speak. These wings are calledmembranaceous. In the moth and butterfly tribes the wings are covered with what appears to be a delicate, beautiful powder, but is in reality a multitudeof exquisite scales, of the singular forms represented. The engraving shows the shape of the scales on the wings of these insects; on examination with a good lens, it appears that the long and hair-like scales are planted at the margin of the wings, and contribute to give to the edges that beautiful feathery look which is so much admired, while the short scales were placed principally on the middle portion of the wings; their numbers are almost infinite. If a butterfly is allowed to flutter awhile in a box it will cover every portion of its surface with them, and yet, on being permitted to fly out, we may scarcely perceive that it has lost any of its fairy plumes. Whether Leuwenhoek actually took the trouble to count so many, or arrived at the result from calculation after counting those on a given space, we do not know, but he declares that he found more than four hundred thousand on the wings of the silk-worm moth; and in those of largermoths and butterflies the number must greatly exceed this. They are generally arranged like the tiles on a house-roof; and if they are scraped off, the minute dots where each was attached becomes distinctly visible. The term used to indicate the tribe of insects to which the moth and butterfly appertain, is, as has been before remarked,Lepidoptera, or "scale-winged," from this very fact. Some membranaceous wings are clothed with fine hairs.
Blight-Beetle. Natural size and magnified.
If we take up a beetle, and look for its wings, for the first time, we shall probably fail in detecting them, that is, of course, if the insect has not been observed in the act of flying. On examining the body we see, indeed, a pair of shining horny plates on its back; but surely these are not wings? Presently, the insect having mounted to the top of our finger, prepares for flight; its two hard cases fly up, and, behold! from beneath them appears a pair of the most beautiful gauze-like wings,which it quickly unfolds, puts into motion, and then flies away. The two thick and horny covers for these delicate organs are calledelytra, or "wing-cases." They are really the first pair of wings, much thickened; and their use is to protect the delicate membranous wings of the hinder pair, beneath them. When the insect flies, they open like a box-lid, and are carried out of the way of the other wings; when the insect rests it carefully folds up its other wings, and then these close over them, and preserve them from all injury. As the insects in which they are found frequent places of danger, burrow underground, or take up their abode under stones, it is manifest how admirable a contrivance this is for such purposes, and how efficiently the fragile wings will be covered and protected by such shields. The first pair of wings is sometimes thickened to the consistence of parchment as a cover to the other wings; and they are then calledtegmina, or "wing-covers."
There are two other circumstances in connexion with this part of our subject, which deserve noticing. If the reader will take into his hand a large blow-fly, and carefully examine its bodywith a lens near the spot where the wings are connected to it, he will succeed in discovering two organs of a curious kind. One of these, is a small membranous piece connected with the trunk-end of the wings, and is generally called thewinglet, oralula. The other looks like a little drumstick hanging down, and is called thebalancer, orpoiser, or in Latin, thehalter, or bridle. It is not clear of what use either of these organs is. Since the winglets are the largest in the heaviest bodies, and are altogether wanting in the lightest, it appears probable that one of their principal uses is to assist the wings during flight. If one might hazard the conjecture, perhaps they act like theparachuteof a balloon. As to the so-calledbalancers, it has been considered that they serve to poise the insect while flying. Dr. Derham considered that they kept the body steady during flight; and he states that if either a poiser or a winglet is cut off, it will fly awkwardly and unsteadily, as if it had lost some very necessary part. Another observer states, that he cut off the winglets of a fly, leaving both its wings and poisers; but it could no longer fly. He also cut off, in another fly, the poisers alone, and the same result took place. Oncutting off both the poisers of a crane-fly, he says it was unable either to fly or walk.[Y]Mr. Westwood says he has seen the poisers beat rapidly upon the winglets like drumsticks on a drum, and it has been supposed that this action is the cause of thehummade by the insect in flying. This is doubtful, because it has been found that after the winglets are cut away the humming sound is still produced; and some humming insects have no winglets.
So much importance did Linnæus, the great father of natural history, attach to the character of the wings in insects, that he arranged the various families of insects under several heads expressive of the leading character of their wings. The orders into which he thus divided insects are seven in number: 1.Coleoptera, or case-winged; 2.Hemiptera, or half-winged; 3.Lepidoptera,or scale-winged; 4.Neuroptera, or nerve-winged; 5.Hymenoptera, or membrane-winged; 6.Diptera, two-winged; and, 7.Aptera, or wingless: the Greek wordpteron, signifying "a wing," furnishes the termination to each of these titles; the prefix is also derived from the Greek, and its import may be derived from the translationattached to each. This system has been extended by modern entomologists, who have subdivided the 2d, 5th, and 7th orders into additional ones.
In the opposite cut the insects represented illustrate each of the Linnæan orders. They are—1. a Beetle; 2. an Aphis; 3. a Butterfly; 4. a Bee; 5. a Dragon-fly; 6. a House-fly; and, 7. a Spider.
As these organs exhibit to us in the most conspicuous manner the exquisite beauties wherewith it has pleased God, the Almighty Creator, to adorn the insect world, we may be allowed to make some reference to the colours of the wings, before proceeding to speak of those organs by which the insect moves on earth. Some, of the beetle tribe, are like tiny masses of burnished metal gleaming with colours of the most exquisite description. A vast number of locusts are remarkable for the splendour of their wings. Many dragon-flies are adorned with wings vying with those of the butterfly in loveliness. The wings of many flies are exquisitely painted with the most brilliant metallic hues, green and gold; and even those of a house-fly are often very beautiful by their having the property ofiridescence, or reflectingthe prismatic colours of light. But insects of every tribe, however splendid in attire, fade before the glories of the butterfly tribe. Linnæus, speaking of the splendid colours of these insects, and particularly of the gorgeous tints which appear on the upper surface of the wings of a butterfly called the Morpho Menelaus, and another, justly observes, that there is scarcely anything in nature that for brightness and splendour can be paralleled with this colour. It is a kind of rich ultramarine, that vies with the deepest and purest azure of the sky; and what must cause a striking contrast in flight, the prone surface of the wings is as dull and dark as the opposite is brilliant; so that one can conceive this insect to appear like a planet in full radiance, and under eclipse, as its wings open and shut in the blaze of a tropical sun. The scales on the wings of some species shine with such extraordinary intenseness and brilliancy, that it is impossible to look at them in a bright light, as they completely dazzle the beholder. Messrs. Kirby and Spence say, they "know no insect upon which the sight rests with such untired pleasure as upon the lovely butterfly that bears the name of the unhappy Trojan king(Papilio Priamus); the contrast of the rich green and black of the velvet of its wings with each other, and with the black of its abdomen, is, beyond expression, regal and magnificent." What adds to the beauty of the wings of this tribe of insects is the appearance of the beautiful spots like eyes, which are so familiar to us, and which are almost without a parallel, except in the animal world. This ornament gives to the wings of a butterfly an indescribable life and beauty, and constrains us as we contemplate it to acknowledge that 'Solomon, in all his glory, was not arrayed like one of these.' The astonishing variety of combination in the colours communicates an inexpressible charm to these insect glories: here is a lustrous blue, a glowing orange, a delicate lemon, an exquisite pink, a fiery copper, or a spotless white. None but a Divine hand could have produced such effects as are exhibited in these most gorgeously painted organs. No work of man will endure comparison with them. The most elaborately finished miniature upon which the artist may, in the features and dress of the person, have expended all the resources of his art in the production of harmonious and pleasing tones of colour,appears but as a muddy, lustreless patch, when placed side by side with one of the butterfly-beauties of the tropics, or even of our own green fields.
Hind Leg of a Bee.
We must not, however, allow the fascination of these beautiful objects to engross our whole attention; and it is now time for us to state some particulars connected with thelegsof the imago, or perfect insect. Six is the true number of legs which belong to the insect in the imago state. They are connected to its body at the thorax, and are formed of a series of minute tubes, provided internally with muscles and nerves. They are commonly divided into four parts;athe haunch,bthe thigh,cthetibia, andd ethe foot.
The front pair of legs, or, as they are generally called, theforelegs, are considered by some authors to be really the insect'sarms, the last portion of them being thehand. Certainly they are often as useful to the insect as is this admirable organ to ourselves; not only are they serviceable in walking, but they also enable the insect to climb, to lay hold of various objects, or to catch their prey, to dig in the earth, and in many instances to clean the head and face of the creature; an operation in which many of them, and particularly flies and bees among our domestic insects, are most praiseworthily particular; having apparently an aversion to nothing so much as to adirty face and unbrushed jacket! The other pairs of legs are altered in various manners in order to fit them for the different purposes for which they are required by the insect.
The purposes for which the legs are put into requisition are, as will be easily guessed, for walking or running, for jumping, for climbing, and for swimming. Most surprising in all these respects is the degree of agility and swiftness with which it has pleased the Divine Creator to endow these insect-organs. M. Delisle once observed a fly,only as large as a grain of sand, which ran three inches in half a second, and in that space made the enormous number offive hundred and forty steps. If a man were to be able to walk as fast in proportion to his size, supposing his step to measure two feet, he would, in the course of a minute, have run upwards oftwenty miles, a task far surpassing our express railroad engines, or the famous Seven League Boots recorded in the nursery fable. In leaping, also, insects far excel man, or any other animal whatever. The flea can leap two hundred times its own length; so also can the locust. If a man were six feet long, and could leap as high and as far as one of these insects, he might stand near Bow Church in Cheapside, leap up into the air over the top of St. Paul's cross and alight at the bottom of Ludgate Hill; which would be something more wonderful than it has ever entered into the minds of the writers of fairy tales to conceive of. The insect called the frog-hopper can leap more than two hundred and fifty times its own length. Some spiders can leap a couple of feet upon their prey. The legs of insects that swim are generally peculiarly fitted for it, either by their being expanded somewhatlike an oar, or by having a dense fringe of hairs upon them. The water-beetles, after rising to the surface of the stream for a supply of fresh air, dive down to their watery home again, taking a clear silvery bubble along with them; and, in this action, they move with considerable rapidity their swimming legs, which are clothed with hairs. The water boatman swimsupon his backby means of his singularly formed legs. The little whirl-gig, of which we have before spoken, swims by means of its legs, which are paddle-shaped. By means, it may be, of some peculiar secretion, which repels the water, some insects can actually walk upon its surface, and that as readily or more so than upon land. Those who know the pleasures of shooting with polished skates over clear ice, when it almost seems as if we were moving in the air, and no more condemned to earth, can imagine something of the delight these insects must experience, who can glide as swift as thought over the glassy surface of the brook. Sometimes the shape of the hind-legs is remarkably altered, and, perhaps,the most extraordinary instance of this in the whole insect world is, the foreign insect, which has been called theKangaroobeetle. The cut represents faithfully this most wonderful creature; and we could almost fancy, as we looked at it, that by some accident the front pair of legs and the head had been twisted round, leaving the hind legs and part of the body turned in the opposite direction. It need scarcely be added, that the origin of this insect's curious title was derived from the resemblance borne by its hind legs to those of the animal whose name it bears. In some insects the legs fold upon each other, and are packed into a very small compass: this is particularly the case in a species of wood-louse, which roll themselves up into balls precisely resembling beads or pills, as may be imagined from the following anecdote. A servant maid of the great Swammerdam, while walking in the garden oneday, found a large number of round, black, shining beads, which were streaked with white bands, and presented a very pretty and attractive appearance. Gathering a number of these in her hand, she thought she would convert them into a necklace, or, for ought we know, into a rosary, when, to her great surprise, the beads became animated as soon as ever they felt the point of the needle, with which she was about to thread them, and began to struggle actively to get away; not, however, too quickly for her; for with a violent scream, imagining the beads were bewitched, she ran into the house. Some of the beetle tribe thus fold up their legs, and roll themselves up so as to resemble little globular pebbles.
Kangaroo Beetle.
The Abdomenis, then, the only remaining portion of the insect which we have now to notice. It has no legs attached to it, and contains the intestines, and other portions of the insect's internal anatomy. It is formed of a varying number of rings, which are easily distinguishable in the wasp and many other insects, and these rings are connected together by delicate folds of membrane, fitting sometimes into each other like the tubes of a telescope; in other instances fastened together,like so many hoops, by their edges. In consequence of this mode of structure it is often very movable, and may even be bent into a half curve, in various directions, at the pleasure of the insect. The common earwig is particularly gifted with this movableness of its abdomen; and so are many insects which carry weapons of offence or defence in their tails. These organs, or appendages, are deserving of a brief notice, although it is probable that the structure of some of them is already familiar to most readers.
A Bee's Sting magnified.a, represents the pair of darts;d, a single dart;b, the poison-bag; andc, the sheath.
The sting of the bee is, perhaps, as formidable a weapon as any of those attached to the abdomen in insects; under the microscope the structure of this apparatus appears in all its beauty. It is found to consist of a sort of sheath, or scabbard, which is composed of two pieces, and is of extreme fineness, as will be readily made visible by placing a fine sewing needle by its side, when the latter will more resemble a bar of iron from the smith's forge, or a kitchen poker, than anything else; while the former will, under the strongest magnifying power, exhibit a smoothness, elegance, and polish, of the most beautiful description. When the bee thrusts forth its sting, it is the sheath which wegenerally see, and not the more delicate apparatus which is enclosed within it. Inside this scabbard is a pair of most fine darts, which are even more delicate than the human hair, and are therefore invisible to the eye, unassisted by a good lens. These darts are notched like very fine saws at the end, the teeth being so directed as to oppose the retraction of the instrument if it is thrust into the human skin; the sting being therefore left in the wound, and the wounded person having the comfort of knowing—if we should call it a comfort—that the insect will surely die speedily, in consequence of its attack upon him. An exquisite adaptation of fine muscles is attached to this weapon, by which it is forcibly driven home.The venom which produces the pain and inflammation is contained in a small muscular bag in connexion with the sting; and when the latter is thrust out, the poison is also forced out and flows into the wound. The sting of the scorpion is a less complicated, but more dangerous weapon, though not often fatal. The earwig, though unprovided with a sting, carries a most awful-looking forceps in its tail, which it can put in action with great force on occasion of danger; and since it can twist its abdomen about with great facility, it is a contrivance of which a tender finger may well be afraid.
Among the wingless insects of Linnæus, is one which he has called by a name which signifies that it hasgot a leg in its tail; and this is actually the fact, in so far as that these insects have an organ in their tail, which answers all the purpose of a leg. Some of these little creatures, which are black, may be often found in spring strewed in infinite numbers upon the surface of the water in ditches or pools; and may be seen jumping about on the surface of the water as if bewitched. At their tail is a fork-like organ, which is generally bent under the body; butwhen they spring up they do so by quickly unbending this fork, the resistance it meets with being sufficient to carry it to a certain distance. Another insect is provided with eight pair of springs in its abdomen; by means of which it can leap to a great distance with most astonishing agility. Here we shall conclude the external anatomy of the insect, in the imago state.
CHAPTER III.
RESPIRATION OF THE IMAGO.
Perfect insects breathe. That this is so, the following experiments[Z]will satisfactorily prove. A spider and a fly were put into a glass jar, the mouth of which was closed all but a hole by which a tube was admitted. The tube was then connected with a pipe by which a supply of common coal-gas was poured into the jar, and when it was considered to be full of gas, and that all the air had been displaced, the tube was closed, and the insects were left shut up in an atmosphere of gas. In a few seconds both became very uneasy, the fly more particularly so; and in a few seconds more the fly began to agitate itself, to buzz against the sides of the glass, and to tumble over in the most extraordinary manner; the spider ran hurriedly about, as if astonished, and not knowing what to make of his new position; but presently he became very quiet, and, turning on his back, looked as if dead. For aminute or two the fly, which was a large, active, flesh-fly, continued its noisy evolutions, dashing itself, as if intoxicated, on every side of its transparent prison. At length, as if exhausted, it lay on its back, its limbs paralyzed, but the wings still moving with extreme rapidity, and causing it to spin round in the most singular manner. Ultimately it, too, became perfectly without motion. After the lapse of about ten minutes, fresh air was gradually let into the jar, and it became most amusing to watch the return of both these insects, which had previously been as it were in the very jaws of death, back to life again; twitchings of their limbs, and slight convulsive movements, were the first indications of returning activity; and in a few minutes more both insects, now placed in a perfectly pure atmosphere, were as lively as before the experiment, and were allowed to make their escape into the open air. With other insects the same effects were produced by saturating a piece of blotting paper with ether, and dropping it into the jar, which was immediately covered over. In several other experiments the newly-discovered powerful fluidchloroform, by means of which the operations of surgery areperformed without pain, was employed; and it was remarkable to notice how quickly the insects were overpowered with the vapour of this potent liquid. In no instance was death produced by the gases or vapours employed. Wishing to destroy without pain a beautiful specimen of a goat-moth, it was first stupified with the gas, then transfixed with a pin, and again plunged in an atmosphere of gas all night long; but alas! for the unhappy insect, the morning dawned, and it was yet alive.
In these simple experiments, which were repeated sufficiently often to render the results certain, we have a most interesting proof that insects breathe. The first struggles and apparent intoxication can be compared to nothing more exactly than to the same phenomena when they take place in human beings breathing the vapours of ether, or chloroform. The subsequent state of insensibility was precisely similar to that induced in persons who are put under the influence of these vapours. An amusing instance of the restorative powers of fresh air occurred in the course of these experiments. A blue-bottle, which was purposely selected of as large a species as could be found, wasfirst intoxicated and rendered insensible by coal gas, and was then as quickly as possible put into a net of the geometric spider: instantly the spider flew upon his bulky captive, but the fresh air began to take effect on the fly, and it commenced struggling in the most furious manner. Although the spider cast out a cloud of web, and in the most energetic manner endeavoured to envelope its prey, the fly seemed likely to be the victor; one of its large and powerful wings got free and flapped violently until the meshes of the web gave way, or was, perhaps, broken by the weight of the insect, and fly and spider, being suspended in the air, spun round so swiftly as to be quite indistinguishable. Ultimately, the spider conquered; and, suspending the huge body of its victim by a rope in the air, returned for a short time to its den.
If insects do not breathe, then all these results are quite unintelligible; for it would be immaterial to the insect what atmosphere it might happen to be placed in. A number of illustrious authors have recorded the result of their experiments upon the effects of other gases on insects. Bees, and other insects, have been placed under the exhausted receiver of an air-pump, and death ensued in a shortspace of time. It has also been found, that when the bodies of insects are covered with oil or grease, so as to stop up their breathing pores, they soon expire. It has been proved by carefully conducted experiments performed by Mr. Ellis, M. Sorg, and other observers, that on placing flies in a measured quantity of atmospheric air, at the end of a day or two almost the whole amount of the oxygen of the air had disappeared, and the same amount of carbonic acid had appeared in the chamber in which the insects were confined. We need not, however, after all that has been said on the subject of the respiration of insects in their various stages, enter into any further proofs that insects breathe not less perfectly in their imago condition than in any of the preceding states; in fact, they perform this function far more prominently in this their last state than in any of the foregoing. It will also be unnecessary to enter into a consideration of the minute particulars connected with this subject, as several of these have been previously glanced at.[AA]
The Air-tubes magnified.
The air enters the body of the insect at the spiracles, or breathing-pores, which are arrangedalong the abdomen, and situated at the side of the wings, and is received by a large tube on each side of the body, running its whole length, or nearly so, as we before mentioned. This tube, and those which it gives off as branches, are calledtracheæ, or air-pipes. The tracheæ are formed in the most wonderful manner, so as to keep them always open, that the air can readily pass through them. Perhaps some of our readers have seen the contrivance adopted by sailors in order to blow air down into the hold and cabins of the ship; for those who have not, we may take the liberty of mentioning, that it is a large tube made of canvass, open at the side near the top, so as to catch the wind, while the bottom of it opens into the cabin. Now, the sailors always place the mouth of this tube towards the wind, which is forced down the tube into the cabin either by its own speed, or by that of the vessel, in the case of a steamer, and so fills the cabin below continually with fresh air. But, it will be asked, how do they contrive so to keep the sides of the bag from flapping together as to prevent them from closing? By imitating a contrivance which exists in the trachea or air-tube of theinsect; they place at certain distances inside this canvass tube a series of wooden hoops, which entirely prevent its collapsing, as it otherwise would do. The most minute air-tubes of an insect are furnished, not, indeed, with a series of rings, but with what serves the same purpose, a firm but delicate coil of cartilage like a spiral spring, over which the membranous lining of the tube is stretched. Thus these tubes remain constantly open; and, whatever may be the movements of the insect, they retain this position. The tracheæ branch out in a most wonderful manner inside the insect's body: as thickly as in our bodies and in those of animals the fine blood-vessels divide until they form a mesh so close that we cannot prick ourselves with a pin without piercing some little tubes, and drawing blood; so in those of the insect, the minute air-pipes run in every direction, and divide into countless thousands of branches, which only become visible under the highest powers of a good microscope. The large tubes are seen without difficulty in many insects; and a drawing, which may give some idea of the immense mass of air-tubes existing in the body of an insect, is annexed: all the rest of the body is supposed to be cut away,and the larger tubes only are shown, as it is impossible to represent the smaller ones so as to give a clear view of their arrangement; they would cover the drawing like a cloud of the finest and most delicate lace-work. In short, in insects, there being no separate lungs in a particular place, as in the animal frame, the air is necessarily carried all over the body, so as to be supplied even to the most minute parts; thus the lungs may be said to extend through the whole body.
The circulation in an Ephemera. The arrows represent the direction of the blood-current.
As the reader has laid his finger on his pulse, or felt his heart beating within him, or seen a drop of blood ooze from his wounded hand, have the questions never occurred to him,—Have insects blood-vessels, and a beating heart? And if so, have they blood like ours? Many a wise man ofold, even the great Baron Cuvier himself, has supposed that there was no circulation of the blood in insects. But, with a magnifying glass and a caterpillar before us, we shall soon be satisfied that this is a great mistake, for by carefully looking along the insect's back we shall perceive in that part a very evident pulsation, as though a fluid were pushed at regular intervals towards the head. The cut represents the circulation in the vessels of the larva of an Ephemera. But insects have no heart, like that of man and animals. What, then, can this beating organ be which we behold? Although it is not like our heart, it is nevertheless an organ which serves all the purpose of ours, and pumps on the blood with great regularity. Instead of being a muscular organ of small size, but great thickness, like our heart, it is in reality a long tube, called thedorsal-vessel, running along the abdomen and thorax of the insect, into which the blood is poured by the veins, and out of which it is forced on towards thehead by the regular contractions of its side. This causes the beating movement which we saw in the caterpillar. Perhaps there may be some curiosity to know whether aninsect's pulsebeats faster or slower than ours. John Hunter counted thirty-four beats in a minute in a silk-worm. Another observer counted thirty a minute in a caterpillar of the pine-moth. But in the imago state the pulse appears to move much quicker: and it is easy to make an insect's beat extremely fast, by exciting or provoking it. Mr. Newport having done so to a bee, counted as many as 142 beats a minute. In a middle-aged man the pulse beats about seventy times in a minute; in a child seven years old about eighty-five times; and at the age of fourteen about eighty times. Hence it follows that our pulse beats about twice as fast as that of an insect in the larva state: in the imago state it is probably, as a general rule, at least in winged, active insects, higher than ours.
CHAPTER IV.
FOOD AND DEATH OF THE IMAGO.
But we have something to say about the food of insects. Although it has been already laid down as a general rule, that insects in their perfect state, do not eat in any degree with the voracity they exhibit in the larva form, it is nevertheless true that they do both require and devour food in considerable quantities, and of various kinds. Some, for example, are exclusivelyvegetablefeeders. They attack all the parts of plants, not excepting even the root and the bark. Some, with an elegant taste, select the yellow pollen of flowers for their dainty and delicate food. And others, more refined still in their appetites, will have nothing but the fresh distilled honey that lies hid at the bottom of the flowers, pumping it up by the beautiful spirally-coiled tubewhich forms a part of their mouth. Need we say these are the butterflies? The fly loves a grain of sugar, or a savoury joint of meat: and to other insects, to use a quotation of Mr. Spence's, which prefer the paper of our Atlases, or maps,—
----"a river and a seaAre a dish of tea,And a kingdom bread and butter."
----"a river and a seaAre a dish of tea,And a kingdom bread and butter."
A large number also arecarnivorouscreatures: need we mention the spider-tribe? a name of terror to myriads of our summer insect-friends. The beautifulcicindelæ, called by Linnæus the "tigers to insects," prey upon the whole insect race, and are endowed with powers of offence and destruction, to a degree sufficient fully to justify this title. In France, we are told, the butchers are very glad to have wasps attend their stalls; since they drive away, and undoubtedly prey upon, the numerous flies which frequent these places. The larger species of ants are equally ferocious, attacking any small soft-bodied insect they may meet with, and when killed dragging it to their nest. The beautiful lady-birds, which we look upon with so much tenderness, remembering the ditty,
"Lady-bird, lady-bird, fly away home,Your house is on fire, your children will burn;"
"Lady-bird, lady-bird, fly away home,Your house is on fire, your children will burn;"
are in the larva state furious destroyers of other insects, and will gobble up aphides by the score in a very short time. The dragon-fly too stands conspicuous among the insect devourers, not only in its larva but in its perfect condition, and falls upon multitudes of insects, plucking off their wings, and with savage relish devouring their bodies. We are not, however, to suppose that the appetites of carnivorous insects are confined to insect-food. The blow fly lives upon and defiles by depositing its eggs in our butcher's meat. The cockroach will polish a bone as clean as, or cleaner than, any dog will, and, indeed, will consume almost anything that happens to come in its way. Lastly, we may not omit to mention, that some insects have to plunge their armed mouths into our flesh and that of other animals, and to slake their raging thirst in a draught of our life-blood: among which we will only enumerate the musquito, the gnat, and the flea. We need scarcely say, that insects are provided with proper organs of digestion.
Singular to add, some insects in the perfectstate do not eat at all. The silk-worm moth, and theEphemeræ, are amongst this number; they live so short a time, as not to require food. Some insects also possess a most extraordinary power of abstaining from food. There have been at different times wonderful tales related of human beings, who, in a supposed trance, have endured the privation of food for an extremely long time,—weeks, and even months. And more recently we have an account of an Indian who suffered himself to be buried alive, built over with bricks and mortar, and a great seal set upon the only opening to his tomb, a guard being also set; and, after the expiration of a certain time, before agreed upon, the sepulchre was opened, and he was taken out—alive! All this is extremely wonderful, if we could only feel certain that there was no deception in the case. But it is nothing to what can be adduced from the insect world. The ant-lion has been known to endure a fast ofsix entire months, and to be as lively as possible at their termination. An author quoted by Messrs. Kirby and Spence kept a spider in a sealed glass forten months, at the end of which time, though shrunk in size, it was as vigorous asever. And Mr. Baker relates that he once kept a beetle alive for three years without food of any kind whatever!
When we call to memory the intense voracity of the insect while a larva,—how insatiable its appetite, how extensive its ravages,—and contrast it with the perfect insect, we are struck with astonishment. Why is this, we ask, that in all cases insects eat less when they are fully developed, than when in their infancy and youth? It is as if a full-grown healthy man were to eat less than his little child a year or two old. The reason appears to be, that in the imago state no further changes (which consume a great deal of material, as may be imagined when we remember the loss of substance in every cast of the skin) are necessary; the insect only requires food sufficient to preserve its life and activity in the state to which it has come, and needs no laying up of stores of fat for future consumption. Fluttering awhile in glorious apparel, through a world of flowers and sunshine, the period of its life runs out, and its only further change is—to die, and return to its kindred dust.
But, before this takes place, one last duty devolvesupon the insect, which, unfulfilled, would leave the world at its death with one link in the chain of creation broken off,—this is, to make provision for the continuance of its species. We have already said, that insects, as a general rule, have been, no doubt in wisdom, destined to deposit their eggs not knowing what is to come forth of them, and never enjoying that happiness which is granted to many other beings,—the happiness of parental love. Some most interesting exceptions to this rule will have also been mentioned, in which a mother's love for her young has been exemplified in a remarkable manner.
Yet, though denied this pleasure and privilege, the mother-insect exercises, as we have before seen, all the care and forethought of the most affectionate parent, in depositing its eggs, and in making such arrangements as will be most conducive to the happiness and well-being of its future progeny. We can scarcely say that in this it shows that it possesses anything like such a feeling as that of a parent towards its child. It takes the wonderful precautions, and performs the singular actions, which have been already in part recorded in our first chapter, in allprobability without being aware of the reasons why it should do so. How can it tell that its future progeny will eat this food, or that food? How can the poor blow-fly, when it leaves its eggs on our food, be certain that it is appointing a suitable place for the birth-spot of its progeny? Why does it not select the green surface of the leaf, or the warm corner of the window, or the bare earth, for this purpose? We might say, perhaps, in this instance, that the insect is only choosing the place where it obtains its own food. But what shall we say when we find insects, such as the butterfly, depositing their eggs upon plants which they never frequent at any other time, and from which they never obtained a particle of food themselves? Some, for instance, deposit them on the nettle, although never tasting anything from this plant themselves, while the young which are to proceed forth from the eggs feed voraciously upon it.
We cannot, in any way but one, account for this forethought. The poor insect, left to itself, would undoubtedly deposit its eggs indifferently anywhere; and the result would be, that its young family, if hatched at all, would awakeonly to find themselves in a desert, without food, or hope of reaching any, and would soon perish. Need we say how it can be easily accounted for? Surely, only, because it is God who has instructed these humble creatures, enduing them, if not actually with the powers of foresight, at any rate with the instinct which impels them to proceed in such a manner as if they were thus endowed. By a most wonderful exercise of wisdom He has taught them to distinguish even between the different species of plants; and rarely, indeed, do we find that the insect commits a mistake, or selects a wrong or fatal birthplace for its young.
Insect history is full of such instances of the great Creators wisdom and love. Although they are not rendered conspicuous to every eye, they are not the less real, nor the less amazing. In our Life of an Insect, many have been the occasions when we have stopped to wonder afresh at continually new and more striking indications of His adorable goodness and power, as the different phenomena of insect-life have been paraded before us. Yet this is but a very minute portion of what really exists of the admirable and beautiful in theinsect world. Not one volume, not a hundred volumes, would suffice to relate the interesting facts which connect themselves in various ways with the insect's life. The main features only have been developed, and these imperfectly. Such being the case, what a world of wonders is the great creation, were we to consider it only as peopled with insects! What pen could write their history; what tongue narrate the many marvels of their existence! Ten thousand times ten thousand, and thousand of thousands, surround us on every side, accompany us on our excursions, and visit us in our homes, fill the air with life, and the waters with creeping things.
The history of an insect's life impresses upon us one of the most consoling truths contained in the word of God. We may learn from the tale of God's wonders in the vegetable creation, we may find also in the history of birds, beasts, and fishes, innumerable proofs of His love, and care, and goodness to all. But these are creatures whose size in the main renders them conspicuous; too much so, as we might say, to be overlooked. "Ah! then,"—were there no insects, one might doubtingly exclaim, "God may take thought forthese large creatures, while more minute beings would be beneath His notice. And so with me: God may order and arrange the great events in my life; but are not the little ones too small for Him to regard?" The life of an insect answers these doubts. It tells us, that though a being be only of the size of a grain of sand, or not larger than the full stop at the end of this sentence, God has supplied it with the most beautiful organs; has endowed it with life, and with the most wonderful instincts, thus manifesting that, in the words of Scripture, "His care is over all His works." If God, then,
"To whom an atom is an ample field,"
"To whom an atom is an ample field,"
has not thought it beneath Him to take care for such diminutive, short-lived creatures as these, how much more will He care for His own people, reconciled to Him through the blood of Jesus, and sanctified by the Holy Spirit of promise! We are not left, however, to learn this blessed truth from the page of creation alone. Our Lord has himself declared to us, that the very hairs of our head are all numbered, and has left on record thepromise, that if we "seek first the kingdom of God and His righteousness, all these things," that is, all temporal things, "shall be added unto us."
R. E.
THE END.
R. CLAY, PRINTER, BREAD STREET HILL.
Footnotes