CHAPTER II.

THE STRUCTURE AND ORGANS OF THE IMAGO.

We must now ask the reader's attention to a very important part of the history of the insect--the knowledge of its various parts, and their uses in the insect economy. Men of science would call this the anatomy and physiology of insects; and if there is a desire felt to know and retain the proper terms employed by those versed in this science when they treat of these subjects, it will be well to bear these names in mind. We may, however, convey some notion of the nature of the studies called by these names, by the following illustration. Let us take yonder butterfly as our example, and, arresting it in its zig-zag career over flowers and fields, let us carefully bring it in-doors, and there look closely at its various parts and appendages. There we find two long, delicate, thread-like organs springing from the head; then we come to the head, with its different organs; farther back is a separate portion, distinct from the head, and distinct, also, from the remainder of the body of the insect; at the side of it are the wings; below are the legs; last of all we bring under our notice the remaining division of the insect's body, the abdomen. Now if Anatomy stood at our right hand while we took notice of each part, she would point out all the peculiarities of its structure, and would tell us of how many other parts it was made up, and how all were beautifully and wonderfully put together by the skill of the Great Creator. Further than this, she would, very probably, strongly insist upon our remembering each part by a particular name; and, as we may add, since she is particularly fond of, and learned in, Latin and Greek, we may rest quite assured each name she communicated to us would be in one or other of these classical languages; for example, instead of saying the butterfly was one of the "_scale-winged_" insects, which would be far too homely for her, she would declare that it belonged to the _Lepidoptera_, which is the same thing in Greek; and its "head" she would inform us was the "_caput_," which is the Latin for that word! This done, her strict duties would be exactly fulfilled, and she would summon her sister-science, Physiology, to give us further information about the butterfly. Physiology, who, we may remark, is a far less stern-looking personage than her austere relative, and appears with a countenance which expresses that she has much to tell us which will greatly interest us, would next take up the panting insect. She would tell us to consider attentively the head of the little creature, while we listened to her elegant account of the purposes it was intended to subserve. She would dilate with eloquence upon the exquisite machinery which was compacted into so small a compass as its mouth; and she would render us almost breathless with amazement, as with rising animation she revealed to us the astonishing optical wonders of an insect's eye, telling us, perhaps, that an insect may probably see like the fabled Argus, behind, and before, and on every side, at the same time! Then she would tell us, in order, the nature and uses of each part, and, in a word, give us a minute, but delightful account of everything that is known about the Life of an Insect.

From this it will be manifest that we have hitherto chiefly listened to the voice of Physiology in this little book, although the leading particulars of the Anatomy of the insect in its various stages have also been brought before us. We must now address ourselves for some little time to learn, from the combined sciences of Anatomy and Physiology, the structure and uses of the different organs, and their principal parts, in the insect, in the _imago_ or perfect state. In order to follow the account we shall have to give the reader, it will be convenient to take some common insect, such as a _wasp_, and fix in the memory the names of the various parts we shall have to distinguish, in thus treating of the _imago_-insect. A dragon-fly is a good example also. We shall first mention the general arrangement of the insect's structure; and subsequently take up each part separately.

It must first be mentioned, that insects possess no _internal_ bony skeleton, like that possessed by ourselves and many other animals. If we were to cut open the dead body of a fly, we should look in vain for anything like the back-bone, or the bones of the legs. But it must not, therefore, be thought that insects have no skeleton at all. Their skeleton is the thick, hard, horny substance which forms their external covering. In the wasp, for instance, it will be easily perceived, on pressing the head or the trunk of the insect between the fingers, that there is a very firm, solid coating, protecting the tender and delicate organs within. It is a very singular fact that the wisdom of the Creator has so ordered this outside coating, that where it is most necessary to be strong, as for example, when an insect has to burrow through the ground, or is in danger of being often crushed, there its thickness is greatest; and again where, as in the case of those insects which live chiefly in the air, this thickening is less necessary, because there is less risk of injury to its body, there the external covering is thinner and softer. So extraordinarily is one insect strengthened in its external coats, that it is scarcely possible to crush it by the hardest squeezing between the thumb and fingers. It has, on this account, been compared to a once famous London character, called "_Leather-coated Jack_," who used to suffer carriages to be driven over his body without receiving any harm!

In looking at an insect, we perceive that it is naturally divisible into three principal parts: first, there is the head, or _caput_; next, the trunk, or _thorax_; and thirdly, the hinder portion of the body, or _abdomen_. If we turn to a Latin dictionary, and hunt out the word _insecta_, which is the Latin term for "insect," we shall find that it is derived from a verb which signifies "to be cut in," or "notched." From this we see that the very word _insect_ has arisen from perceiving what we are now alluding to, the natural notching of the body of these creatures into certain portions. We mentioned, however, at page 89, that the insect in the _larva_ form had a body which was, in almost every instance, divided into _thirteen_ segments, or parts. It may be asked, Are these all lost in the perfect insect; or are they still to be traced in it? They are still to be traced in it. The head is one, three form the trunk or thorax, and the remaining number constitute the abdomen: but, in order to save disappointment, it must be added, that it is rare to find the full number of segments or distinct parts in the abdomen; we seldom, in fact, find more than seven or eight, the remaining two or one being generally hidden. It is interesting, however, to trace in the perfect insect these indications of its previous larval condition, especially when we remember the strange appearance it underwent while a pupa.

Now the various parts in the _head_ division are, to speak generally, the _head proper_, the _mouth_, the _eyes_, and the _antennæ_. Entomologists describe a large number of other parts, which would also be mentioned here if this little treatise were intended to give a minute account of the insect's anatomy; and those features which are of most prominence and importance, will be mentioned in addition when we come to speak particularly of these several chief organs.

The middle portion of the insect, or _thorax_, is divided into three parts--a front, middle, and hinder part; or, in the language of entomology, a _pro-thorax_, a _meso-thorax_, and a _meta-thorax_. Attached to the thorax are the _wings_ and the _legs_. The remaining portion, or _abdomen_, is furnished with organs and appendages, not requiring special mention in this place.

Let us consider briefly the organs which are seated in these divisions; and, beginning with the head, let us glean a few particulars upon that most interesting topic--the eyes of insects. We might well fill a volume with this subject alone, for truly it is almost inexhaustible. In the other sections of the animal kingdom, the eyes, though organs of the highest importance, are, nevertheless, simple, and little varied in their number and arrangement. But in insects, whether we consider their number, their structure, their arrangement, or their size, we are lost in amazement at finding these organs assume an importance in the insect's economy, of which we have no parallel elsewhere. Look, for example, at the accompanying representation of the eyes of a bee, and then let us ask whether, in all the world beside, we can find a creature whose two eyes are larger than all the rest of its head put together? What should we think of a quadruped as large as a bull, whose eyes occupied great part of its head, its forehead, and the greater portion of its face? What astonishing powers of sight it would possess!

The first thing we learn about them is, that some insects possess what are called _simple eyes_, and _compound eyes_. The accompanying cut represents in part the head of a _flea_, and is annexed in order to give a specimen of a _simple_ eye. The little circle represents the position of the simple eye. All the organs connected with the head are supposed to be cut off. The head of the bee on the preceding page furnishes us with an excellent illustration of a _compound eye_. All perfect insects are provided with compound eyes, and a large number with simple eyes too; but no imago or perfect insect has simple eyes alone. We see, therefore, that the simple eyes are only additional or supplementary organs to the compound eyes, which are the chief organs of sight in these creatures. These simple eyes are minute lenses generally placed upon the crown of the head, or the forehead; in the bee this is their position; and by means of a pocket-glass, they can be readily seen in this insect, by looking at its head from above. They will be found arranged in a triangular form. Sometimes an insect is furnished with as many as sixteen of these simple eyes; the spider is, among others, thus endowed. But more commonly they are only three in number. Sometimes they are not imbedded in the substance of the head, as might be supposed; but are actually placed upon the end of a little stalk, presenting an appearance as singular, as if at the end of a bull's horn the animal were to possess an eye in addition to his two others. Swammerdam and Réaumur performed some singular experiments upon these eyes in the bee. Réaumur varnished the back of the head, where these eyes are situated, in more than twenty bees, so as, of course, entirely to blind these eyes; but leaving the large compound eye untouched. The bees were then set at liberty within a few paces from the hive, but not one of them knew where to find it again! nor, indeed, did they appear to make any search for it. They flew at random to the adjacent plants, but never to a distance; and though they seemed to have no difficulty in flying, they did not attempt to fly up into the air.

The compound eyes of insects are, perhaps, among the most wonderful works of the Creator's hands. In those gigantic creatures whose fossilized bones are all now remaining to tell us of their history, the _mastodon_, and _megatherium_, and in such vast creatures as the elephant and the whale, we behold the great power, skill, and wisdom of God; but here, in a little object which we may cover with a pin's head or with a large grain of sand, is a more wonderful instance of His infinite and amazing power than all these. The eye of a dragon-fly is a good instance of a compound eye: and of all the beautiful, radiant, gem-like objects that can be selected for inspection through the microscope, this is the most exquisite. Professor Müller, the great German physiologist, has with wonderful patience and care dissected the eye of this insect, and has given a most beautiful account of its structure. On examining the eye of this insect, even with a good pocket magnifying glass, such as those commonly sold by opticians for a few shillings, it will be found to present the appearance of a beautiful net-work, or very fine grating, as is shown in the cut. When a greater magnifying power is employed, it will be seen that each space in this net-work is a six-sided or _hexagonal_ figure. Now each of these little spaces is filled by a beautiful minute lens of the same shape set in it. On making a perpendicular cut into the eye it has been found to consist of various layers: the outer layer is a hard clear membrane composed of a multitude of six-sided facets, each forming a more or less distinct cone-shaped cylinder, which runs towards the centre of the eye, as seen in the cut. Under this is a layer of coloured matter, sometimes of a violet, or green, or even reddish hue, which is pierced with as many holes as there are facets. Beneath this there is a varnish of a black colour, within which is a second layer of coloured matter; and in the space between this last and the first coloured layer the delicate fibres of the nerve of sight, or optic nerve, run. These fibres then converge together at the back of the eye into a single large nerve, which is connected with the insect's brain, and conveys the impression of sight to that organ.

Perhaps this account may be followed with some difficulty; let us, therefore, take a single facet, and trace it to its termination. Each facet being in fact a distinct eye, we shall be able, in so doing, to get a clear comprehension of the whole organ, which is after all only made up of a large number of these distinct eyes. Separating, then, one facet from the rest, we find this single eye to consist of several portions: 1. the six-sided facet; 2. the cone-shaped cylinder, clear and transparent; 3. a delicate fibre of nerve connected with the bottom of this cone; and, 4. the large nerve itself. The diagram on the next page will make this perfectly intelligible.

But it may be asked, What of the colouring matter? It exists in three places. 1. The first layer surrounds the cones (2), and separates them from one another, and from the nerve below in part. 2. The second layer surrounds the nerve fibres (3). And, 3. the last layer is at the junction of the nerve fibre (3) with the nerve itself (4).

This apparently complicated mechanism well deserves the reader's attention; nor should the subject be quitted until it is clearly understood. We are unable to enter into further particulars upon the structure and functions of this beautiful apparatus; but it must be added, that the following is the manner in which the ray of light becomes perceived by the insect. It first passes through the facet (_a_), next enters the cone (_b_), then strikes upon the nerve (_c_) which conveys the impression, taking the large nerve (_d_) to the brain. The colouring layers are intended to prevent any rays of light from passing to other parts of the insect's eye, and so confusing the impressions made upon its senses by external objects.

The number of these facets, or, if we choose to call them so, distinct eyes, varies in different insects. In some there are comparatively few, in others an amazing multitude. The following list of their number is given by Müller, as observed by various entomologists:--

In the Ant there are 50 " Convolvulus Sphinx 1,300 " Common House-fly 4,000 " Silk-worm Moth 6,236 " Goat Moth 11,300

In the Dragon-fly 12,544 " Butterfly 17,355 " Mordella 25,088

According to the calculations of another author there cannot be fewer than 34,650 in the compound eye of a butterfly. Amazing thought! each of this immense host is considered to be a separate eye, receives separate impressions of light, and has a separate structure and organization, both perfect in their kind.

It is not difficult to remove the compound eye of an insect; and in so doing it will be found that each lens is as clear as crystal. The ingenious Réaumur actually succeeded in removing one and adjusting it to a lens; and he found that he could see through the insect's eye very distinctly, only he says the surrounding objects appeared to be greatly multiplied. There is a common optical toy which is ground into a number of facets which communicates this appearance to objects when seen through it, and thus furnishes us with a good illustration of the endless confusion of images which would have perplexed the insect, had not the various beautiful contrivances of which we have spoken been adjusted to prevent it.

But we must guard against a very natural mistake which might arise upon the subject of the eyes of insects from supposing them in any degree comparable to those of higher animals as regards their motions. When man, or an animal, wishes to look at any object, they do so by causing several muscles to be brought into action which move the eyes round so as to receive the rays of light from the particular point where this object is placed; and so admirably arranged is the mechanism by which these movements are effected, that they are as well provided for all the purposes of sight with two eyes as with twenty. In insects no such apparatus exists; the eyes are quite immovable; they are, in fact, set in the head like a gem in a lady's ring, and are altogether removed from the control of the insect. In order to obviate the annoyance and inconvenience which would result from this arrangement, their eyes are formed on the wonderful principles already mentioned, and, instead of insects being furnished with two eyes, they are provided with many thousands! They are thus enabled to enjoy not only the same extent and range of vision with ourselves, but even a much larger.

Insects are also furnished with a contrivance by which they can see objects at a little distance, and objects at a great distance--it may be at the same time; which is more than can be strictly said of ourselves. In men and animals there is a very exquisite apparatus arranged within the eye, by means of which it can accommodate itself to objects close at hand, or again to others at the greatest distance. We can see at one moment a pin at our feet, and at the next the summit of a hill some thirty or forty miles off. Now the laws of light are such, that, to effect this properly, we must have some apparatus in the eye to arrange its focal capacity, so as to receive and concentrate the lines of light proceeding from such different points as the distance of a few inches, and that of many miles. What this apparatus may be is not as yet very satisfactorily determined. But in insects the same result is obtained by a very curious provision.--_Some of their eyes are short-sighted, and some long-sighted._ The simple eyes are supposed, by Professor Müller, to be the short-sighted eyes, and the compound eyes the long-sighted ones.

The number of _compound_ eyes in insects does not often exceed two, these being made up, it will not be forgotten, by multitudes of single eyes. But in a few, whose habits require that they should be endowed with extraordinary means of vision, there are as many as four. If the reader would betake him to the brook-side, and creep noiselessly along its margin some summer afternoon, until he comes to a quiet glassy pool where the water seems to have forgotten itself and fallen asleep, so still, so silent, and so smooth does it lie, reflecting all the lustre of the deep-blue sky overhead, he will surprise a dancing party of insects busy waltzing at a wonderful rate, now skimming hither, now shooting across the glassy pavement on which they sport, now joining together and wheeling round and round, and again, as the king-fisher comes fluttering down the river as though on some errand of immense importance, breaking up their party and flying into a thousand holes and corners to wait until all is quiet. Let him exercise his activity and patience, and catch one of these giddy insects, which are known to entomologists by the name of the _Gyrinus Natator_, and he will have a good example of an insect provided with four compound eyes, so that it can see not only before and behind, but upward into the sky, and downward into the clear cool waters on whose surface its happy life is spent. Some insects, like Cyclops of old, are furnished only with one eye; and some, it is said, are quite blind--creatures that never feel the blessed influences of the pleasant sunlight. Like the simple eyes, the compound eyes are sometimes fixed on the end of a little footstalk, so as to give the insect somewhat the appearance of being furnished with a pair of opera glasses, or short telescopes.

In order to ascertain by what means the bee found its way to the hive, whether by seeing it through its compound eyes, or otherwise, Réaumur performed an interesting experiment similar in character to the one before mentioned. He covered with a red varnish, which was quite opaque, the compound eyes of a number of bees taken from the same hive. He then shut them up in a box with several other bees from the same hive which he left untouched. The box was only a few paces distant from the hive from which the bees were taken. He then opened the lid of the box, and those which had not been blinded instantly flew out of it, and entered their habitation. Those whose eyes had been varnished appeared not to care to leave the box at all, and seemed very unwilling to make any attempt to fly; some of them, indeed, flew about from one side to another, but did not go far. Réaumur then threw several of them up into the air, and they immediately began to soar higher and higher, until at length they went out of sight altogether! Réaumur compares the poor insect's manoeuvres to those of a crow, whose head and eyes mischievous boys have covered with a paper bonnet: the bird flies upward until its strength is exhausted, when it drops again to the earth. Not only did those bees which he threw up into the air thus soar until they were lost to view, but all the most active of those which were left in the box did so likewise, and Réaumur saw them no more. Not one could find its way to the hive. From this experiment, and from the preceding one, it is evident that both the compound and the simple eyes are necessary to enable the insect to see perfectly; for when either was varnished over, the bees could not find their way to their home again. Réaumur imagines that the cause of the wheeling flight of bees, sometimes observed, now in this direction, now in the opposite, may arise from their eyes becoming perhaps in part obscured by the pollen, or yellow powder of the flowers into which they plunge, the bee thereby becoming partly blind-folded. These experiments are so interesting that they deserve repeating, and it might be tried whether the result would be different if only one eye were blinded. Other variations of the experiments will also suggest themselves.

Although not organs of sufficient size to give their colouring the requisite distinctness and amount of surface which would render it very conspicuous in our estimation, the eyes of insects are often exquisitely beautiful, and vie almost with precious stones in lustre. Their most common colour is black, or brown; but the eyes of many flies glow with fiery colours, some banded with green and purple, some variously figured black and red. Some again glitter like burnished gold shaded with the softest green; and some blaze with a play of colours, like the diamond set in jet. The eye of the dragon-fly, in particular, is a lustrous crystalline object of extreme beauty.

We have dwelt as long as our limits will permit on this wonderful apparatus of vision in insects: let us now turn our thoughts for a little space to a pair of organs which are, perhaps, of all others the most characteristic of the insect tribes: these are the _Antennæ_. We need scarcely explain what these are, or point them out to the reader, since they are so familiar to most persons, but under the erroneous, or, at any rate, the questionable expression--"the feelers." We have an excellent specimen of _antennæ_ in those of the butterflies, in which insects they are very long and elegant organs. They are attached to the head by means of a beautiful joint, called a ball and socket, the same as is often adapted to garden watering engine-pipes, so as to enable them to be moved about in all directions. They are never found absent in the perfect insect, and are manifestly organs of considerable importance in the insect economy. As to their structure,--when examined under a microscope, antennæ are found to be composed of a variable number of small round pieces, covered with a horny or leathery skin, but within being softer and hollow, so as to form a series of tubes placed end to end, all connected together in such a manner as to admit of free movement between each joint, so that the insect can bend them into any shape it may find expedient for its purposes. But it must not be supposed that all antennæ are similar in form, or there would be a risk of their being continually mistaken by the reader for some other organ. The cut on the next page will, at a glance, exhibit the astonishing variety of form assumed by these organs. The common cockchafer is possessed of antennæ as strikingly different in form from those of the butterfly, as if they were really distinct organs intended and adapted to serve different purposes. Some are long and thread-like, some resemble a necklace of pearls, some are notched like a saw, some have a resemblance to a fan, some are like a club, some resemble a fork, and some a feather; in short, their variety of form is almost endless: and they differ as much in length and in thickness; for while the antennæ of some insects are as long as, or even longer than, their bodies, those of others are very short, and little prominent; and while some are as thin and fine as the finest hair, others are nearly as thick as the true body of the insect. Let us now ask what is the use of these singular organs of the insect?

From a hint which has before been dropped, it is probable that the answer to this question will be readily anticipated. Various facts appear to show that they may be the insect's _ears_! "Can it be that such is their function?" some may exclaim, calling to mind that ears in other creatures are so different in appearance and structure from these organs. There have been many opinions on the subject, and some have maintained views completely opposed to this idea. But the greater number of entomologists seem to consider this as their most probable function. If they are not ears, we are not able to point to any other organs in the head which are. From a number of facts it is certain, that insects can hear; from which it is equally certain, that they must possess special organs. We may, therefore, until the contrary is shown with respect to them, fairly be allowed to consider the antennæ as these organs. The opinions of Messrs. Kirby and Spence on this point are conveyed in the following words:--"They conceive that antennæ by a peculiar structure may collect notices from the atmosphere, receive touches or vibrations, and communicate them to the sensorium (or brain), which, though not precisely to be called hearing, may answer the same purpose." The late celebrated Dr. W. F. Erichson of Berlin, by means of the microscope, has discovered in all insects, and especially in those most remarkable for their powers of smelling, that these organs are furnished with a number of fine pores, clothed with membrane, which he regards as organs of smell.[U]

Every one has heard of M. Pelisson, the prisoner at the Bastile, and his spider companions of the cell. This gentleman had, by patient training, engaged the attention of a spider, which used every day to come and listen to a solo on his violin, after which it would make its retreat again to its home. Now it is clear, that this little insect not only heard, but even enjoyed, the notes of his instrument; which would have been impossible, had it possessed no ears. Then again, every one must have noticed the start which a fly will make if some sharp noise be made near it, and how actively it will move its legs, and seem to be put all on the _qui vive_. A little every-day observation will furnish us with many similar instances. "A little moth," writes one of the last-mentioned authors, "was reposing on my window; I made a quiet, not loud, but distinct noise; the antenna nearest to me immediately moved towards me. I repeated the noise at least a dozen times, and it was followed every time by the same motion of that organ; till at length the insect, being alarmed, became more agitated and violent in its motions. In this instance it could not be _touch_; since the antenna was not applied to a surface, but directed towards the quarter from which the sound came, as if to listen." Can we question that the merry grasshopper, chirping all day in the field, is heard by its mate? or that the cricket on the hearth sings for its fellows, or only to please _our_ ears? or does the tap of the death-tick beetle, formerly commemorated, draw forth no answering tap from its companion on the other side of the post? All these instances, and countless more that might be mentioned, indicate, beyond a question, that insects have the faculty of hearing, and render it extremely probable that the antennæ are the organs by which this function is performed.

But it is probable that they serve another and not less important purpose. The country folk, who are generally very weather-wise, and whose sayings always deserve a great deal of attention, because they are very commonly founded both upon observation of facts, and experience, will always assure us that the high flight of swallows in their search after insects is a certain token of fair weather; their low flight of approaching wet. Why is this? Can insects foretell the state of the weather? and if so, by what means? That insects have a meteorometrical power of foretelling the state of the weather, appears beyond a doubt. To select a few instances. Bees, our exemplars in so many points, might be consulted with advantage, and would often give us better information as to whether an over-coat or an umbrella would be probably required, than the not always trustworthy barometer. When engaged in their daily labours, if a change of weather to rain is at hand, although the sun may yet shine and the sky remain clear and calm, they foresee it, and return suddenly to their hives. Hence in weather of an unsettled description they never undertake journeys far from home, but make short excursions to and from their hives, being never absent long at a time; and if we find a bee wandering far from its hive, it may be taken, on the other hand, as a pretty sure prognostic that top-coat and umbrella may be left at home for _that_ day at least. Ants, as we have already noticed, possess the same faculty of weather-wisdom, never allowing their larvæ to be caught in a shower. The abundance of insects in our houses in wet weather, is a familiar observation; we are assured that in hot countries their excessive numbers, during the rainy season, make these little creatures almost as terrible as a plague to all who are within--climbing up the walls, scrambling into the dishes, drowning themselves in the soup-tureens, or putting out the lights with their bodies. In hot and sultry weather, when a black cloud or two in the far horizon give token of a coming storm, insects abound in the air; but as the heavens grow black, they disappear; and before a drop of rain has actually fallen, we may look in vain for them.

That the antennæ are the organs by which this knowledge of coming events with regard to the weather is obtained by the insects, appears probable. They may, perhaps, perceive by their delicate surfaces, changes in the _electrical_ condition of the air, which are quite insensible to ourselves: and as all change of weather is preceded and accompanied by changes of electrical balance of one kind or another in the air, they may be thus forewarned of the coming danger. The following is the manoeuvre of a large number of insects of the beetle tribe. When they are about to move from any station where they have been at rest, the first thing they usually do before they move a step, is to bring forward and expand their antennæ, which have previously been folded up out of the way. They open them as widely as possible, so as to expose them to all the influences of the air, and then, if they be satisfied, they unfold their wings and take their flight. We might compare this proceeding with that of one of ourselves looking up at the direction of the wind, or tapping the weather-glass in the hall, previous to setting out for the day! Too much stress, however, it must be added, is not to be laid upon this point; for while it is unquestionable that insects have knowledge of the weather, it is of course very difficult to ascertain with certainty whether it is by means of their antennæ, or by the general feeling of their bodies; analogous, perhaps, to what rheumatic persons feel when the wind goes round to the _north-east_.

There is a still more singular use of the antennæ, which deserves to be mentioned. These organs appear to be the principal instruments of _speech_, if we may use such a term, or, at any rate, of the communication of intelligence. When the soldier ants go out upon their expeditions, and have left the nest, previously to setting off, they touch each other with their antennæ and forehead on the trunk; and this is their signal for marching, for as soon as ever a soldier feels this tap, he immediately puts himself in motion. When, also, they have any discovery to communicate, they strike with them those that they meet, in a particularly impressive manner; and if a hungry ant wants to be fed, it touches with its two antennæ, moving them very rapidly, those of the individual from which it expects its meal. They appear to salute one another by gently tapping each other's antennæ, as we should shake hands on meeting an old friend!

M. Huber has related an account of some interesting experiments of his on a hive of bees, which strikingly proves that the antennæ are really organs for the transmission of intelligence. He wished to ascertain whether, when they had lost a queen, they discovered the sad event by their smell, their touch, or any unknown cause; for such a loss, in the course of a single hour, is made known in some way or other to the whole hive. In order to ascertain this, he first divided a hive by a grate which kept the two portions a few parts of an inch separated from each other, so that the bees could not come at each other, although any scent could easily have passed. In that part in which there was no queen, the bees were soon in great agitation; and as they did not discover where she was confined, in a short time they began to construct royal cells, after which they grew more calm. Mr. Huber next separated them by a partition through which they could pass their antennæ, but not their heads. In this case, the bees all remained tranquil, neither intermitting the care of the brood, nor abandoning their other employments; nor did they begin any royal cell. The means they adopted to assure themselves that their queen was safe, and to communicate with her, was to pass their antennæ through the openings of the grate, A most curious spectacle thus presented itself; an infinite number of those organs might be seen at once, as it were inquiring in all directions; and the queen was observed answering these anxious inquiries of her dutiful subjects in the most marked manner; for she was always fastened by her feet to the grate, crossing her antennæ with those of the inquirers.

While we have been anxious to show that the function of feeling is not the important and principal office of these singular organs, it would be far from correct to state that the antennæ are not occasionally employed, to use the popular term, as "feelers." All who have paid any attention to the motions of insects must have seen the antennæ actually employed as it were in exploring the number or nature of objects immediately around. From these and the preceding remarks, it becomes manifest, that, next to the organs of sight, the antennæ are most important and useful appendages to the body of the insect. When we consider the various purposes they serve, we become much perplexed to understand how it is possible for one organ to fulfil such varied duties; nor can it be explained. We are unable to conceive of the senses of insects except by comparing them with our own; and in our case there are no organs which can receive, and, at the same time, communicate, intelligence. Our ears, eyes, nose, and the other organs of the senses, have only one function severally assigned to them; and had they more, there would probably be no little confusion in our perceptions of external things. Such confusion does not probably exist in the insect; but it is very possible that its perceptions are somewhat different from ours.

Before we leave the region of the head, we have the important task to fulfil, of describing the mouth of the insect: this part is more complicated than the organs we have as yet seen, and requires, therefore, a considerable degree of our careful attention to enable us to do justice to it, and to carry in the mind a clear view of this interesting portion of an insect's structure. "If," writes Mr. Westwood, "a beetle, and a butterfly, a house-fly, or an aphis, be examined whilst feeding, a totally different apparatus will be found in each, although perfectly adapted for the mode of feeding. The beetle is employed in gnawing and tearing in pieces hard or fleshy substances: its instruments of manducation are, therefore, horny and robust. The butterfly, on the contrary, has to seek its food at the bottom of the tubes of flowers; and here in the glowing beams of the sun it revels in its existence, and sips the most delicious nectar. It is necessary for this purpose that it should be provided with a long and slender instrument; but, from the very structure of this apparatus, it is essential for its defence, that, so soon as the insect has ceased feeding, the instrument should be lodged in a place of safety. It is, therefore, rolled up in a beautiful spiral direction, and laid to rest between a pair of hairy appendages, which will defend it from injury. If we observe a common fly sipping up a drop of spilt wine, or revelling upon a morsel of sugar, it will be found that its mouth is totally unlike either of the former: it is short, thick, and fleshy, and acts as a sucker, the nutriment ascending through the canal which runs upward into the throat. The aphides and all their brethren have a mouth differently constructed, being a long and slender pointed canal, of a fleshy, or leathery substance, but furnished internally with several slender bristles, which the insect employs as lancets to wound its prey. In the flea, again, the structure is quite different."

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's _proboscis_,[V] we speak actually of its mouth. The mouth of the butterfly is called by most entomologists _antlia_; that of the aphis a _promuscis_; that of the flea a _rostrulum_. But the reader must 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 its _proboscis_ to pump it up--and when the flea thrusts its _rostrulum_ into 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.

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 the _upper lip_, or in Latin, _labrum_; that of the opposite lower one, is the _lower lip_, or _labium_. The upper pair, of side-pieces, are called the _mandibles_, or upper jaws; the pair below are the lower jaws, or _maxillæ_.

Let us now briefly mention the use of these various parts of the insect's mouth; beginning with the upper lip, (_a_) or _labrum_. 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 of _moustache_ in most cases.

The _mandibles_, (_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 of defence, 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 _maxillæ_, or _lower 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 the _palpi_, or, less properly, _feelers_. The lower jaws are much varied 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 the _labium_, 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 a _chin_ below it, called the _mentum_, and on each side of it are a pair of feelers, or _palpi_, like those of the maxillæ. In the centre a little tongue-like projection is visible in the figure, which is sometimes called the _tongue_, but perhaps not correctly, if by that term is meant the apparatus for _tasting_. 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 very different 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 of _taste_. 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 to question, 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 a _nose_.[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 the _carrion-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 the organ of this sense, opinions are greatly at variance. Some believe it to exist in the _spiracles_, 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 their proboscises, 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 the _thorax_, 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 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 the _nervures_, of which we before had occasion to speak. These wings are called _membranaceous_. In the moth and butterfly tribes the wings are covered with what appears to be a delicate, beautiful powder, but is in reality a multitude of 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 larger moths 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.

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 called _elytra_, 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 called _tegmina_, 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 body with 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 the _winglet_, or _alula_. The other looks like a little drumstick hanging down, and is called the _balancer_, or _poiser_, or in Latin, the _halter_, 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 the _parachute_ of a balloon. As to the so-called _balancers_, 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. On cutting 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 the _hum_ made 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 word _pteron_, 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 translation attached 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 of _iridescence_, or reflecting the 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.

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 the _legs_ of 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; _a_ the haunch, _b_ the thigh, _c_ the _tibia_, and _d e_ the foot.

The front pair of legs, or, as they are generally called, the _forelegs_, are considered by some authors to be really the insect's _arms_, the last portion of them being the _hand_. 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 a _dirty 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 of _five 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 of _twenty 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 somewhat like 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 swims _upon his back_ by 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 the _Kangaroo_ beetle. 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 one day, 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.

_The Abdomen_ is, 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.

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 we generally 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 has _got 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; but when 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.