CHAPTER XIX.

WE

OF INSECTS.

E are not writing a system of natural history; therefore we have not attended to the classes into which the subjects of that science are distributed. What we had to observe concerning different species of animals, fell easily, for the most part, within the divisions which the course of our argument led us to adopt. There remain, however, some remarks upon the insect tribe, which could not properly be introduced under any of these heads; and which therefore we have collected into a chapter by themselves.

The structure, and the use of the parts, of insects, are less understood than that of quadrupeds and birds, not only by reason of their minuteness, or the minuteness of their parts (for that minuteness we can, in some measure, follow with glasses), but also by reason of the remoteness of their manners and modes of life from those of larger animals. For instance : Insects under all their varieties of form, are endowed with antenna, which is the name given to those long feelers that rise from each side of the head: but to what common use or want of the insect kind, a provision so universal is subservient, has not yet been ascertained: and it has not been ascertained, because it admits not of a clear, or very probable, comparison,

the shrubbery deposited by the gardener in the farm-yard; how carefully and how skilfully the gallant horse culls them over, how readily he picks out the sweet blades of grass, and how uniformly he rejects the poisonous leaves and branches of the flower-garden. By no chance does he ever eat the hemlock (Conium Maculatum), the deadly nightshade (Atropa Belladonna), or the bane berry (Actoa Spicata), or a hundred other unwholesome products swept from the garden; his instinct teaches him that they are noxious, yet the goat and the sheep greedily devour the first and last named with perfect impunity. The rabbit riots in parsley; but the horse rejects it entirely and this instinct is not the effect of habit and long practice; the English race-horse turned out under the palms of India, selects his food just as carefully and successfully as the Arab on the heaths of Newmarket, neither are deceived by the tempting appearance of strange plants around them. The rabbit always rejects the fenuel and the nettle; and were it not so, some of the barren drifting sands of Norfolk and Suffolk, which are only tenanted by these animals, would be shelterless, for there the luxuriant clumps of nettles afford the only shade the rabbits enjoy from the sun and wind.

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The tastes too of different animals differ as strongly ; the bitter sowthistle and the lettuce are greedily eaten by the horse; but he will not taste the poppy, which the cow will readily pasture upon: the first, when in a state of nature, seeks the sweet short grass of the upland pastures, which he is provided with teeth to bite off close to the ground, just as it is springing into life; he is careful in selecting the cleanest spots, and anxiously avoids where other animals have preceded him. The cow, on the contrary, under the same circumstances, haunts the rankest and deepest pastures; her mouth is ill adapted for close feeding; and she is by no means so particular in selecting the sweetest and most cleanly spots.

By this arrangement, the different tribes of animals which are intended to herd sociably together, are not naturally induced to seek the same pastures; they are found on different elevations, contentions and destruction of food are avoided, and universal enjoyment promoted.

Then again this marvellous instinct of animals is not confined to their food, but extends to other substances, which are neither nutritious nor naturally inviting: thus the health of all herbivorous animals is increased by their taking a certain portion of salt; and it is found that in a state of nature, all this class of animals take it regularly; that the rein-deer of Lapland seeks the sea shore in spring; the wild cattle of America haunt the salt pools, or salt licks, so constantly that the huntsman always expects to find his game in their vicinity; the horse licks the dirty saline exudations of the stable with avidity, but ceases to do so if he has a piece of rock salt placed in his manger, which he then regularly prefers; sheep do the same, if it is placed with them in their pastures; the very bee in summer seeks the sea shore, drains, &c. where salt can be obtained.

This habit does not result merely from the grateful flavour of the substances ingested; the dog has no taste for the grass which makes him vomit; there is nothing tempting to her palate in the sandy pebbles, or pieces of calcareous earth, which every hen consumes with such unvaried regularity, and yet countless generations have steadily followed the practice, guided merely by an unerring instinct.

Von Buch's Travels in Norway. Dr. Paris, Pharm. Lambert An. Rev., 1804, 3767. Lord Somerville on Sheep, 104. Johnson on the use of Salt in Agriculture, p. 106. Dr. Bevan on Bees, 186-197. Sir John Pringle, Phil. Trans. vol. 46, p. 557. Howard, Com. Board of Agri. 1812, p. 213. Dr. Fordyce on Digestion, p. 25.This well-known physician found by experiment that without canary birds, for instance, have access to calcareous earth at the time of their laying, they frequently die from their eggs not coming properly to maturity.

He divided a number of these littie birds, when they were breeding, into two parties; and supplied one party with a piece of old mortar which they devoured greedily, and all of them lived and laid their eggs as usual: but of the other party, not supplied with lime, many died.— Ibid. p 26.

with any organs which we possess ourselves, or with the organs of animals which resemble ourselves in their functions and faculties, or with which we are better acquainted than we are with insects. We want a ground of analogy. This difficulty stands in our way as to some particulars in the insect constitution, which we might wish to be acquainted with. Nevertheless, there are many contrivances in the bodies of insects, neither dubious in their use, nor obscure in their structure, and most properly mechanical. These form parts of our argument.

I. The elytra, or scaly wings of the genus of scarabæus or beetle, furnish an example of this kind. The true wing of the animal is a light, transparent membrane, finer than the finest gauze, and not unlike it. It is also, when expanded, in proportion to the size of the animal, very large. In order to protect this delicate structure, and, perhaps, also, to preserve it in a due state of suppleness and humidity, a strong, hard case is given to it, in the shape of the horny wing which we call the elytron. When the animal is at rest, the gauze wings lie folded up under this impenetrable shield. When the beetle prepares

for flying, he raises the integument, and spreads out his thin membrane to the air. And it cannot be observed without admiration, what a tissue of cordage, i. e. of muscular tendons, must run in various and complicated, but determinate directions, along this fine surface, in order to enable the animal, either to gather it up into a certain precise form, whenever it desires to place its wings under the shelter which nature hath given to them; or to expand again their folds when wanted for action.

In some insects, the elytra cover the whole body; in others, half; in others only a small part of it; but in all, they completely hide and cover the true wings. Also,

Many or most of the beetle species lodge in holes in the earth, environed by hard, rough substances, and have frequently to squeeze their way through narrow passages; in which situation, wings so tender, and so large, could scarcely have escaped injury, without both a firm covering to defend them, and the capacity of collecting themselves up under its protection.

II. Another contrivance, equally mechanical, and equally clear, is the awl, or borer, fixed at the tails of various species of flies; and with which they pierce, in some cases, plants; in others, wood; in others, the skin and flesh of animals: in others, the coat of the chrysalis of insects of a different species from their own; and in others, even lime, mortar, and stone. I need not add, that having pierced the substance, they deposit their eggs in the hole. The descriptions which naturalists give of this organ, are such as the following: It is a sharp-pointed instrument, which, in its inactive state, lies concealed in the extremity of the abdomen, and which the animal draws out at pleasure, for the purpose of making a puncture in the leaves, stem, or bark, of the particular plant, which is suited to the nourishment of its young. In a sheath, which divides and opens whenever the organ is used, there is enclosed a compact, solid, dentated stem, along which runs a gutter or groove, by which groove, after the penetration is effected, the egg, assisted, in some cases, by a peristaltic motion, passes to its destined lodgment. In the oestrum or gad-fly, the wimble draws out like the pieces of a spy-glass: the last piece is armed with three hooks, and is able to bore through the hide of an ox. Can any thing more be necessary to display the mechanism, than to relate the fact?

III. The stings of insects, though for a different purpose, are, in their structure, not unlike the piercer. The sharpness to which the point in all of them is wrought; the temper and firmness of the substance of which it is composed; the strength of the muscles by which it is darted out, compared with the smallness and weakness of the insect, and with the soft or friable texture of the rest of the body; are properties of the sting to be noticed, and not a little to be admired. The sting of a bee will pierce through a goat-skin glove. It penetrates the human flesh more readily than the finest point of a needle. The action of the sting affords an example of the union of chymistry and mechanism, such as, if it be not a proof of contrivance, nothing is. First, as to the chymistry; how highly concentrated must be the venom, which, in so small a quantity, can produce such powerful effects! And in the bee we may observe, that this venom is made from honey, the only food of the insect, but the last material from which I should have expected that an exalted

poison could, by any process or digestion whatsoever, have been prepared. In the next place, with respect to the mechanism, the sting is not a simple, but a compound instrument. The visible sting, though drawn to a point exquisitely sharp, is in strictness only a sheath; for, near to the extremity, may be perceived by the microscope two minute orifices, from which orifices, in the act of stinging, and, as it should seem, after the point of the main sting has buried itself in the flesh, are launched out two subtile rays, which may be called the true or proper stings, as being those through which the poison is infused into the puncture already made by the exterior sting. I have said, that chymistry and mechanism are here united: by which observation I meant, that all this machinery would have been useless, telum imbelle, if a supply of poison, intense in quality, in proportion to the smallness of the drop, had not been furnished to it by the chymical elabo ration which was carried on in the insect's body; and that, on the other hand, the poison, the result of this process, could not have attained its effect, or reached its enemy, if, when it was collected at the extremity of the abdomen, it had not found there a machinery fitted to conduct it to the external situations in which it was to operate, viz. an awl to bore a hole, and a syringe to inject the fluid. Yet these attributes, though combined in their action, are independent in their origin. The venom does not breed the sting; nor does the sting concoct the venom.

IV. The proboscis, with which many insects are endowed, comes next in order to be considered. It is a tube attached to the head of the animal. In the bee, it is composed of two pieces, connected by a joint: for, if it were constantly extended, it would be too much exposed to accidental injuries; therefore, in its indolent state, it is doubled up by means of the joint, and in that position lies secure under a scaly penthouse. In many species of the butterfly, the proboscis when not in use, is coiled up like a watch-spring. In the same bee, the proboscis serves the office of the mouth, the insect having no other; and how much better adapted it is, than a mouth would be, for the collecting of the proper nourishment of the animal, is sufficiently evident. The food of the bee is the nectar of flowers; a drop of syrup, lodged deep in the bottom of the corollæ, in the recesses of the petals, or down the neck of a monopetalous glove. Into these cells the bee thrusts its long narrow pump, through the cavity of which it sucks up this precious fluid, inaccessible to every other approach. It is observable also, that the plant is not the worse for what the bee does to it. The harmless plunderer rifles the sweets, but leaves the flower uninjured. The ringlets of which the proboscis of the bee is composed, the muscles by which it is extended and contracted, form so many microscopical wonders. The agility also, with which it is moved, can hardly fail to excite admiration. But it is enough for our purpose to observe, in general, the suitableness of the structure to the use, of the means to the end, and especially the wisdom by which nature has departed from its most general analogy (for, animals being furnished with mouths are such), when the purpose could be better answered by the deviation.

In some insects, the proboscis, or tongue, or trunk, is shut up in a sharp-pointed sheath : which sheath, being of a much firmer texture than the proboscis itself, as well as sharpened at the point, pierces the substance which contains the food, and then opens within the wound, to allow the enclosed tube, through which the juice is extracted, to perform its office. any mechanism be plainer than this is; or surpass this?

V. The metamorphosis of insects from grubs into moths and flies, is an astonishing process. A hairy caterpillar is transformed into a butterfly. Observe the change. We have four beautiful wings, where there were none before; a tubular proboscis, in the place of a mouth with jaws and teeth; six long legs, instead of fourteen feet. In another case, we see a white, smooth, soft worm, turned into a black, hard, crustaceous beetle, with gauze wings. These, as I said, are astonishing processes, and must require, as it should seem, a proportionably artificial apparatus. The hypothesis which appears to me most probable is, that, in the grub, there exist at the same time three animals, one within another, all nourished by the same digestion, and by a communicating circulation; but in different stages of maturity. The latest discoveries made by naturalists, seem to favour this supposition. The insect, already equipped with wings, is descried under the membranes both of the worm and

nymph. In some species, the proboscis, the antennæ, the limbs, and wings of the fly, have been observed to be folded up within the body of the caterpillar; and with such nicety as to occupy a small space only under the two first wings. This being so, the outermost animal, which, besides its own proper character, serves as an integument to the other two, being the farthest advanced, dies, as we suppose, and drops off first. The second, the pupa or chrysalis, then offers itself to observation. This also, in its turn dies; its dead and brittle husk falls to pieces, and makes way for the appearance of the fly or moth. Now, if this be the case, or indeed whatever explication be adopted, we have a prospective contrivance of the most curious kind: we have organizations three deep; yet a vascular system, which supplies nutrition, growth, and life, to all of them together.

VI. Almost all insects are oviparous. Nature keeps her butterflies, moths, and caterpillars, locked up during the winter in their egg-state; and we have to admire the various devices to which, if we may so speak, the same nature hath resorted, for the security of the egg. Many insects inclose their eggs in a silken web; others cover them with a coat of hair, torn from their own bodies; some glue them together; and others, like the moth of the silkworm, glue them to the leaves upon which they are deposited, that they may not be shaken off by the wind, or washed away by rain: some again make incisions into leaves, and hide an egg in each incision; whilst some envelope their eggs with a soft substance, which forms the first aliment of the young animal: and some again make a hole in the earth, and having stored it with a quantity of proper food, deposit their eggs in it. In all of which we are to observe, that the expedient depends, not so much upon the address of the animal, as upon the physical resources of his constitution.

The art also with which the young insect is coiled up in the egg, presents, where it can be examined, a subject of great curiosity. The insect, furnished with all the members which it ought to have, is rolled up into a form which seems to contract it into the least possible space; by which contraction, notwithstanding the smallness of the egg, it has room enough in its apartment, and to spare. This folding of the limbs appears to me to indicate a special direction; for, if it were merely the effect of compression, the collocation of the parts would be more various than it is. In the same species, I believe, it is always the same. These observations belong to the whole insect tribe, or to a great part of them. Other observations are limited to fewer species; but not, perhaps, less important or satisfactory. I. The organization in the abdomen of the silkworm, or spider, whereby these insects form their thread, is as incontestibly mechanical as a wire-drawer's mill. In the body of the silkworm are two bags, remarkable for their form, position, and use. They wind round the intestine; when drawn out, they are ten inches in length, though the animal itself be only two. Within these bags, is collected a glue; and communicating with the bags, are two paps or outlets, perforated like a grater, by a number of small holes. The glue or gum, being passed through these minute apertures, forms hairs of almost imperceptible fineness; and these hairs, when joined, compose the silk which we wind off from the cone, in which the silkworm has wrapped itself up in the spider, the web is formed of this thread. In both cases, the extremity of the thread, by means of its adhesive quality, is first attached by the animal to some external hold; and the end being now fastened to a point, the insect, by turning round its body, or by receding from that point, draws out the thread through the holes above described, by an operation, as hath been observed, exactly similar to the drawing of wire. The thread, like the wire, is formed by the hole through which it passes. In one respect there is a difference. The wire is the metal unaltered, except in figure. In the animal process, the nature of the substance is somewhat changed, as well as the form; for, as it exists within the insect, it is a soft, clammy gum, or glue. The thread acquires, it is probable, its firmness and tenacity from the action of the air upon its surface, in the moment of exposure; and a thread so fine is almost all surface. This property, however, of the paste, is part of the contrivance.

The mechanism itself consists of the bags, or reservoirs, into which the glue is collected, and of the external holes communicating with these bags; and the action of the machine is seen, in the forming of a thread, as wire is formed, by forcing the material already prepared through holes of proper dimensions. The secretion is an act too subtile for our discernment,

except as we perceive it by the produce. But one thing answers to another; the secretory glands to the quality and consistence required in the secreted substance; the bag to its reception: the outlets and orifices are constructed, not merely for relieving the reservoirs of their burden, but for manufacturing the contents into a form and texture, of great external use, or rather indeed of future necessity, to the life and functions of the insect.

II. BEES, under one character or other, have furnished every naturalist with a set of observations. I shall, in this place, confine myself to one; and that is the relation which obtains between the wax and the honey. No person, who has inspected a bee-hive, can forbear remarking how commodiously the honey is bestowed in the comb; and, amongst other advantages, how effectually the fermentation of the honey is prevented by distributing it into small cells. The fact is, that when the honey is separated from the comb, and put into jars, it runs into fermentation, with a much less degree of heat than what takes place in a hive. This may be reckoned a nicety; but, independently of any nicety in the matter, I would ask, what could the bee do with the honey, if it had not the wax? how, at least, could it store it up for winter? The wax, therefore, answers a purpose with respect to the Loney; and the honey constitutes that purpose with respect to the wax. This is the relation between them. But the two substances, though, together, of the greatest use, and, without each other, of little, come from a different origin. The bee finds the honey, but makes the wax. The honey is lodged in the nectaria of flowers, and probably undergoes little alteration; is merely collected: whereas the wax is a ductile, tenacious paste, made out of a dry powder, not simply by kneading it with a liquid, but by a digestive process in the body of the bee. What account can be rendered of facts so circumstanced, but that the animal, being intended to feed upon honey, was, by a peculiar external configuration, enabled to procure it? That, moreover, wanting the honey when it could not be procured at all, it was farther endued with the no less necessary faculty, of constructing repositories for its preservation? Which faculty, it is evident, must depend, primarily, upon the capacity of providing suitable materials. Two distinct functions go to make up the ability. First, the power in the bee, with respect to wax, of loading the farina of flowers upon its thighs. Microscopic observers speak of the spoon-shaped appendages with which the thighs of bees are beset for this very purpose; but, inasmuch as the art and will of the bee may be supposed to be concerned in this operation, there is, secondly, that which doth not rest in art or will,—a digestive faculty which converts the loose powder into a stiff substance. This is a just account of the honey and the honey-comb; and this account, through every part, carries a creative intelligence along with it.

The sting also of the bee has this relation to the honey, that it is necessary for the protection of a treasure which invites so many robbers *.

III. Our business is with mechanism. In the panorpa tribe of insects, there is a forceps in the tail of the male insect with which he catches and holds the female. Are a pair of pincers more mechanical than this provision in its structure, or is any structure more clear and certain in its design?

IV. St. Pierre tells us †, that in a fly with six feet (I do not remember that he describes the species,) the pair next the head and the pair next the tail, have brushes at their extremi

The relation between the honey and the wax may be considered further. Honey being the food assigned to the bee, and that food being required in the winter when little or none is produced by our flowers, it became necessary to have it stored in the seasons of more abundant supply. For the storehouses it was necessary to provide an undecaying material; now wax is the only vegetable compound that resists putrefaction for any lengthened time under circumstances tending to promote it—moisture and warmth. The bee, therefore, is not only gifted with the power of forming a substance plastic and convenient for the formation of its cells, but the most suitable of all others to the purpose for which it is required. Whence came also the sagacity, the sagacity acting in the perfection of correctness, that makes this insect construct its cells invariably of a hexagon form? Mathematicians by a

series of abstruse calculation, have shown that this of all other figures is the one that allows the greatest number of small structures to be crowded into a given space. Who taught this to the honey-bee? Who instructed it, when an intruding mouse or slug is slain within its hive; who taught it that a covering of wax would prevent the escape of pestilential and annoying exhalations from the carcase? Who taught the bee with provident and relentless slaughter to destroy the drones, at the conclusion of the season in which only they are serviceable? These queries founded on the instinct displayed by this insect, might be much extended, but sufficient has been noticed to demonstrate that here, as in all other parts of creation, not only is every thing best, but occurring in its most fitting mode and season.

+ Vol. i. p. 342.

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