They who see no cruelty in the sports of the field, as they are called, can never, of course, consistently allege such a charge against the entomologist; the tortures of wounded birds, of fish that swallow the hook and break the line, or of the hunted hare, being, beyond comparison, greater than those of insects destroyed in the usual mode. With respect to utility, the sportsman, who, though he adds indeed to the general stock of food, makes amusement his primary object, must surely yield the palm to the Entomologist, who adds to the general stock of mental food, often supplies hints for useful improvements in the arts and sciences, and the objects of whose pursuit, unlike those of the former, are preserved and may be applied to use for many years.
But in the view even of those few who think inhumanity chargeable upon the sportsman, it will be easy to place considerations which may rescue the entomologist from such reproof. It is well known that, in proportion as we descend in the scale of being, the sensibility of the objects that constitute it diminishes. The tortoise walks about after losing its head; and the polypus, so far from being injured by the application of the knife, thereby acquires an extension of existence. Insensibility almost equally great may be found in the insect world. This, indeed, might be inferredà priori, since Providence seems to have been more prodigal of insect life than of that of any other order of creatures, animalcula perhaps alone excepted. No part of the creation is exposedto the attack of so many enemies, or subject to so many disasters; so that the few individuals of each kind which enrich the valued museum of the entomologist, many of which are dearer to him than gold or gems, are snatched from the ravenous maw of some bird or fish or rapacious insect; would have been driven by the winds into the waters and drowned; or trodden underfoot by man or beast,—for it is not easy, in some parts of the year, to set foot to the ground without crushing these minute animals; and thus also, instead of being buried in oblivion, they have a kind of immortality conferred upon them. Can it be believed that the beneficent Creator, whose tender mercies are over all his works, would expose these helpless beings to such innumerable enemies and injuries, were they endued with the same sense of pain and irritability of nerve with the higher orders of animals?
But this inference is reduced to certainty, when we attend to the facts which insects every day present to us, proving that the very converse of our great poet's conclusion, as usually interpreted,
... The poor beetle that we tread upon,In corporal sufferance finds a pang as greatAs when a giant dies,
... The poor beetle that we tread upon,In corporal sufferance finds a pang as greatAs when a giant dies,
must be regarded as nearer the truth[83]. Not to mention the peculiar organization of insects, which strongly favours the idea I am inculcating, but which will be consideredmore properly in another place, their sang-froid upon the loss of their limbs, even those that we account most necessary to life, irrefragably proves that the pain they suffer cannot be very acute. Had a giant lost an arm or a leg, or were a sword or spear run through his body, he would feel no great inclination for running about, dancing, or eating. Yet a crane-fly (Tipula) will leave half its legs in the hands of an unlucky boy who has endeavoured to catch it, and will fly here and there with as much agility and unconcern as if nothing had happened to it; and an insect impaled upon a pin will often devour its prey with as much avidity as when at liberty. Were a giant eviscerated, his body divided in the middle, or his head cut off, it would be all over with him; he would move no more; he would be dead to the calls of hunger; or the emotions of fear, anger, or love. Not so our insects. I have seen the common cock-chafer walk about with apparent indifference after some bird had nearly emptied its body of its viscera: a humble-bee will eat honey with greediness though deprived of its abdomen; and I myself lately saw an ant, which had been brought out of the nest by its comrades, walk when deprived of its head. The head of a wasp will attempt to bite after it is separated from the rest of the body; and the abdomen under similar circumstances, if the finger be moved to it, will attempt to sting. And, what is more extraordinary, the headless trunk of a male Mantis has been known to unite itself to the other sex[84]. These facts, out of hundreds that might be adduced, are surely sufficient to prove that insects do not experience the same acute sensations of pain with the higher ordersof animals, which Providence has endowed with more ample means of avoiding them; and since they were to be exposed so universally to attack and injury, this is a most merciful provision in their favour; for, were it otherwise, considering the wounds, and dismemberments, and lingering deaths that insects often suffer, what a vast increase would there be of the general sum of pain and misery! You will now, I think, allow that the most humane person need not hesitate a moment, whether he shall devote himself to the study of Entomology, on account of any cruelty attached to the pursuit.
But if some morbid sentimentalist should still exclaim, "Oh! but I cannot persuade myself even for scientific purposes to inflict the slightest degree of pain upon the most insensible of creatures—" Pray, sir or madam, I would ask, should your green-house be infested by Aphides, or your grapery by the semianimate Coccus, would this extreme of tenderness induce you to restrict your gardener from destroying them? Are you willing to deny yourself these unnecessary gratifications, and to resign your favourite flowers and fruit at the call of your fine feelings? Or will you give up the shrimps, which by their relish enable you to play a better part with your bread and butter at breakfast, and thus, instead of adding to it, contribute to diminish the quantity of food? If not, I shall only desire you to recollect that, for a mere personal indulgence, you cause the death of an infinitely greater number of animals, than all the entomologists in the world destroy for the promotion of science.
To these considerations, which I have no doubt you will think conclusive as to the unreasonableness and inconsistency of the objections made against the study ofEntomology on the score of cruelty, I shall only add that I do not intend them as any apology for other than the most speedy and least painful modes of destroying insects; and these will be pointed out to you in a subsequent letter. Every degree of unnecessary pain becomes cruelty, which I need not assure you I abhor; and from my own observations, however ruthlessly the entomologist may seem to devote the few specimens wanted for scientific purposes to destruction, no one in ordinary circumstances is less prodigal of insect life. For my own part, I question whether the drowning individuals, which I have saved from destruction, would not far outnumber all that I ever sacrificed to science.
My next letter will be devoted to themetamorphosesof insects, a subject on which some previous explanation is necessary to enable you to understand those distinctions between their different states, which will be perpetually alluded to in the course of our correspondence: and having thus cleared the way, I shall afterwards proceed to the consideration of theinjuriesandbenefitsof which insects are the cause.
I am, &c.
Were a naturalist to announce to the world the discovery of an animal which for the first five years of its life existed in the form of a serpent; which then penetrating into the earth, and weaving a shroud of pure silk of the finest texture, contracted itself within this covering into a body without external mouth or limbs, and resembling more than any thing else an Egyptian mummy; and which, lastly, after remaining in this state without food and without motion for three years longer, should at the end of that period burst its silken cerements, struggle through its earthy covering, and start into day a winged bird,—what think you would be the sensation excited by this strange piece of intelligence? After the first doubts of its truth were dispelled, what astonishment would succeed! Amongst the learned, what surmises!—what investigations! Amongst the vulgar, what eager curiosity and amazement! All would be interested in the history of such an unheard-of phenomenon; even the most torpid would flock to the sight of such a prodigy.
But you ask, "To what do all these improbable suppositions tend?" Simply to rouse your attention to themetamorphosesof the insect world, almost as strange and surprising, to which I am now about to direct your view,—miracles, which, though scarcely surpassed in singularityby all that poets have feigned, and though actually wrought every day beneath our eyes, are, because of their commonness, and the minuteness of the objects, unheeded alike by the ignorant and the learned.
That butterfly which amuses you with its aërial excursions, one while extracting nectar from the tube of the honeysuckle, and then, the very image of fickleness, flying to a rose as if to contrast the hue of its wings with that of the flower on which it reposes—did not come into the world as you now behold it. At its first exclusion from the egg, and for some months of its existence afterwards, it was a worm-like caterpillar, crawling upon sixteen short legs, greedily devouring leaves with two jaws, and seeing by means of twelve eyes so minute as to be nearly imperceptible without the aid of a microscope. You now view it furnished with wings capable of rapid and extensive flights: of its sixteen feet ten have disappeared, and the remaining six are in most respects wholly unlike those to which they have succeeded; its jaws have vanished, and are replaced by a curled-up proboscis suited only for sipping liquid sweets; the form of its head is entirely changed,—two long horns project from its upper surface; and, instead of twelve invisible eyes, you behold two, very large, and composed of at least twenty thousand convex lenses, each supposed to be a distinct and effective eye!
Were you to push your examination further, and by dissection to compare the internal conformation of the caterpillar with that of the butterfly, you would witness changes even more extraordinary. In the former you would find some thousands of muscles, which in the latter are replaced by others of a form and structureentirely different. Nearly the whole body of the caterpillar is occupied by a capacious stomach. In the butterfly this has become converted into an almost imperceptible thread-like viscus; and the abdomen is now filled by two large packets of eggs, or other organs not visible in the first state. In the former, two spirally-convoluted tubes were filled with a silky gum; in the latter, both tubes and silk have almost totally vanished; and changes equally great have taken place in the economy and structure of the nerves and other organs.
What a surprising transformation! Nor was this all. The change from one form to the other was not direct. An intermediate state not less singular intervened. After casting its skin even to its very jaws several times, and attaining its full growth, the caterpillar attached itself to a leaf by a silken girth. Its body greatly contracted: its skin once more split asunder, and disclosed an oviform mass, without exterior mouth, eyes, or limbs, and exhibiting no other symptom of life than a slight motion when touched. In this state of death-like torpor, and without tasting food, the insect existed for several months, until at length the tomb burst, and out of a case not more than an inch long, and a quarter of an inch in diameter, proceeded the butterfly before you, which covers a surface of nearly four inches square.
Almost every insect which you see has undergone a transformation as singular and surprising, though varied in many of its circumstances. That active little fly, now an unbidden guest at your table[85], whose delicate palate selects your choicest viands, one while extending hisproboscis to the margin of a drop of wine, and then gaily flying to take a more solid repast from a pear or a peach; now gamboling with his comrades in the air, now gracefully currying his furled wings with his taper feet,—was but the other day a disgusting grub, without wings, without legs, without eyes, wallowing, well pleased, in the midst of a mass of excrement.
The "grey-coated gnat," whose humming salutation, while she makes her airy circles about your bed, gives terrific warning of the sanguinary operation in which she is ready to engage, was a few hours ago the inhabitant of a stagnant pool, more in shape like a fish than an insect. Then to have been taken out of the water would have been speedily fatal; now it could as little exist in any other element than air. Then it breathed through its tail; now through openings in its sides. Its shapeless head, in that period of its existence, is now exchanged for one adorned with elegantly tufted antennæ, and furnished, instead of jaws, with an apparatus more artfully constructed than the cupping-glasses of the phlebotomist—an apparatus which, at the same time that it strikes in the lancets, composes a tube for pumping up the flowing blood.
The "shard-born beetle," whose "sullen horn," as he directs his "droning flight" close past your ears in your evening walk, calling up in poetic association the lines in which he has been alluded to by Shakespear, Collins, and Gray, was not in his infancy an inhabitant of air; the first period of his life being spent in gloomy solitude, as a grub, under the surface of the earth.—The shapeless maggot, which you scarcely fail to meet with in some one of every handful of nuts you crack, wouldnot always have grovelled in that humble state. If your unlucky intrusion upon its vaulted dwelling had not left it to perish in the wide world, it would have continued to reside there until its full growth had been attained. Then it would have gnawed itself an opening, and having entered the earth, and passed a few months in a state of inaction, would at length have emerged an elegant beetle furnished with a slender and very long ebony beak: two wings, and two wing-cases, ornamented with yellow bands; six feet; and in every respect unlike the worm from which it proceeded.
That bee—but it is needless to multiply instances. A sufficient number has been adduced to show, that the apparently extravagant supposition with which I set out may be paralleled in the insect world; and that the metamorphoses of its inhabitants are scarcely less astonishing than would be the transformation of a serpent into an eagle.
These changes I do not purpose explaining minutely in this place: they will be adverted to more fully in subsequent letters. Here I mean merely to give you such a general view of the subject as shall impress you with its claims to attention, and such an explanation of the states through which insects pass, and of the different terms made use of to designate them in each, as shall enable you to comprehend the frequent allusions which must be made to them in our future correspondence.
The states through which insects pass are four: theegg; thelarva; thepupa; and theimago.
The first of these need not be here adverted to. In thesecond, or immediately after the exclusion from the egg, they are soft, without wings, and in shape usuallysomewhat like worms. This Linné called thelarvastate, and an insect when in it alarva, adopting a Latin word signifying amask, because he considered the real insect while under this form to be as it were masked. In the English language we have no common term that applies to the second state of all insects, though we have several for that of different tribes. Thus we call the coloured and often hairy larvæ of butterflies and mothscaterpillars; the white and more compact larvæ of flies, many beetles, &c.grubsormaggots[86]; and the depressed larvæ of many other insectsworms. The two former terms I shall sometimes use in a similar sense, rejecting the last, which ought to be confined to truevermes; but I shall more commonly adopt Linné's term, and call insects in their second state,larvæ[87].
In this period of their life, during which they eat voraciously and cast their skin several times, insects live a shorter or longer period, some only a few days or weeks, others several months or years. They then cease eating; fix themselves in a secure place; their skin separates once more and discloses an oblong body, and they have now attained thethirdstate of their existence.
From the swathed appearance of most insects in this state, in which they do not badly resemble in miniaturea child trussed up like a mummy in swaddling clothes, according to the barbarous fashion once prevalent here, and still retained in many parts of the continent; Linné has called it thepupastate, and an insect when under this form apupa;—terms which will be here adopted in the same sense. In this state, most insects eat no food; are incapable of locomotion; and if opened seem filled with a watery fluid, in which no distinct organs can be traced. Externally, however, the shape of the pupæ of different tribes varies considerably, and different names have been applied to them.
Those of the beetle and bee tribes are covered with a membranous skin, inclosing in separate and distinct sheaths the external organs, as the antennæ, legs, and wings, which are consequently not closely applied to the body, but have their form for the most part clearly distinguishable. To these Aristotle originally gave the name ofnymphæ[88], which was continued by Swammerdam and other authors prior to Linné, who calls themincompletepupæ, and has been adopted by many English writers on insects[89].
Butterflies, moths, and some of the two-winged tribe, are in their pupa state also inclosed in a similar membranous envelope; but their legs, antennæ, and wings, are closely folded over the breast and sides; and the whole body inclosed in a common case or covering of a more horny consistence, which admits a much less distinct view of the organs beneath it. As these pupæ are often tinged of a golden colour, they were called from this circumstancechrysalidesby the Greeks, andaureliæby the Romans, both which terms are in some measurebecome anglicized; and though not strictly applicable to ungilded pupæ, are now often given to those of all lepidopterous insects[90]. These by Linné are denominatedobtectedpupæ[91].
I have said thatmostinsects eat no food in the pupa state. This qualification is necessary, because in the metamorphoses of insects, as in all her other operations, nature proceeds by measured steps, and a very considerable number (the tribe of locusts, cockroaches, bugs, spiders, &c.) not only greatly resemble the perfect insect in form, but are equally capable with it of eating and moving. As these insects, however, cast their skinsat stated periods, and undergo changes, though slight, in their external and internal conformation, they are regarded also as being subject to metamorphoses. These pupæ may be subdivided into two classes: first, those comprised, with some exceptions, under the LinneanAptera, which in almost every respect resemble the perfect insect, and were called by Linnécompletepupæ; and secondly, those of the Linnean orderHemiptera, which resemble the perfect insect, except in having only the rudiments of wings, and to which the name ofsemi-completepupæ was applied by Linné, and that of semi-nymphs by some other authors[92]. There is still a fifth kind of pupæ, which are not, as in other instances, excluded from the skin of the larva, but remain concealed under it, and were hence called by Linnécoarctatepupæ. These, which are peculiar to flies and some other dipterous genera, may be termedcased-nymphs[93].
When, therefore, we employ the termpupa, we may refer indifferently to the third state of any insect, the particular order being indicated by the context, or an explanatory epithet. The termschrysalis, (droppingaurelia, which is superfluous,)nymph,semi-nymph, andcased-nymph, on the other hand definitely pointing out the particular sort of pupa meant: just as in Botany, the common termpericarpapplies to all seed-vessels, the several kinds being designated by the names of capsule, silicle, &c.
The envelope ofcased-nymphs, which is formed of the skin of the larva, considerably altered in form and texture, may be conveniently called thepuparium[94]: but tothe artificial coverings of different kinds, whether of silk, wood, or earth, &c. which many insects of the other orders fabricate for themselves previously to assuming the pupa state, and which have been called by different writers,pods,cods,husks, andbeans, I shall continue the more definite French termcocon, anglicized intococoon[95].
After remaining a shorter or longer period, some species only a few hours, others months, others one or more years, in the pupa state, the inclosed insect, now become mature in all its parts, bursts the case which inclosed it, quits the pupa, and enters upon the fourth and last state.
We now see it (unless it be an apterous species) furnished with wings, capable of propagation, and often under a form altogether different from those which it has previously borne—a perfect beetle, butterfly, or other insect. This Linné termed theimagostate, and the animal that had attained to it theimago; because, having laid aside itsmask, and cast off itsswaddling bands, being no longer disguised or confined, or in any respect imperfect, it is now become a true representative orimageof its species. This state is in general referred to when an insect is spoken of without the restricting terms larva or pupa.
Such being the singularity of the transformations of insects, you will not think the ancients were so wholly unprovided with a show of argument as we are accustomed to consider them, for their belief in the possibility of many of the marvellous metamorphoses which their poets recount. Utterly ignorant as they were of modern physiological discoveries, the conversion of a caterpillarinto a butterfly, must have been a fact sufficient to put to a nonplus all the sceptical oppugners of such transformations. And however we may smile in this enlightened age at the inference drawn not two centuries ago by Sir Theodore Mayerne, the editor of Mouffet's work on insects, "that if animals are transmuted so may metals[96]," it was not, in fact, with his limited knowledge on these subjects, so very preposterous. It is even possible that some of the wonderful tales of the ancients were grafted on the changes which they observed to take place in insects. The death and revivification of the phœnix, from the ashes of which, before attaining its perfect state, arose first aworm(σκωληξ), in many of its particulars resembles what occurs in the metamorphoses of insects. Nor is it very unlikely that the doctrine of the metempsychosis took its rise from the same source. What argument would be thought by those who maintained this doctrine more plausible in favour of the transmigration of souls, than the seeming revivification of the deadchrysalis? What more probable, than that its apparent reassumption of life should be owing to its receiving for tenant the soul of some criminal doomed to animate an insect of similar habits with those which had defiled his human tenement[97]?
At the present day, however, the transformations of insects have lost that excess of the marvellous, which might once have furnished arguments for the fictions ofthe ancients, and the dreams of Paracelsus. We call them metamorphoses and transformations, because these terms are in common use, and are more expressive of the sudden changes that ensue than any new ones. But, strictly, they ought rather to be termed a series of developments. A caterpillar is not, in fact, a simple but a compound animal, containing within it the germ of the future butterfly, inclosed in what will be the case of the pupa, which is itself included in the three or more skins, one over the other, that will successively cover the larva. As this increases in size these parts expand, present themselves, and are in turn thrown off, until at length the perfect insect, which had been concealed in this succession of masks, is displayed in its genuine form. That this is the proper explanation of the phenomenon has been satisfactorily proved by Swammerdam, Malpighi, and other anatomists. The first-mentioned illustrious naturalist discovered, by accurate dissections, not only the skins of the larva and of the pupa incased in each other, but within them the very butterfly itself, with its organs indeed in an almost fluid state, but still perfect in all its parts[98]. Of this fact you may convince yourself without Swammerdam's skill, by plunging into vinegar or spirit of wine a caterpillar about to assume the pupa state, and letting it remain there a few days for the purpose of giving consistency to its parts; or by boiling it in water for a few minutes. A very rough dissection will then enable you to detect the future butterfly; and you will find that the wings, rolled up into a sort of cord, are lodged between the first and second segment of the caterpillar;that the antennæ and trunk are coiled up in front of the head; and that the legs, however different their form, are actually sheathed in its legs. Malpighi discovered the eggs of the future moth, in the chrysalis of a silkworm only a few days old[99], and Reaumur those of another moth (Hypogymna dispar) even in the caterpillar, and that seven or eight days before its change into the pupa[100]. A caterpillar, then, may be regarded as a locomotive egg, having for its embryo the included butterfly, which after a certain period assimilates to itself the animal substances by which it is surrounded; has its organs gradually developed; and at length breaks through the shell which incloses it.
This explanation strips the subject of every thing miraculous, yet by no means reduces it to a simple or uninteresting operation. Our reason is confounded at the reflection that a larva, at first not thicker than a thread, includes its own triple, or sometimes octuple, teguments; the case of a chrysalis, and a butterfly, all curiously folded in each other; with an apparatus of vessels for breathing and digesting, of nerves for sensation, and of muscles for moving; and that these various forms of existence will undergo their successive evolutions, by aid of a few leaves received into its stomach. And still less able are we to comprehend how this organ should at one time be capable of digesting leaves, at another only honey; how one while a silky fluid should be secreted, at another none; or how organs at one period essential to the existence of the insect, should at another be cast off, and the whole system which supported them vanish.
Nor does this explanation, though it precludes theidea of that resemblance, in every particular, which, at one time, was thought to obtain between the metamorphosis of insects, especially of theLepidopteraorder, and the resurrection of the body, do away that general analogy which cannot fail to strike every one who at all considers the subject. Even Swammerdam, whose observations have proved that the analogy is not so complete as had been imagined, speaking of the metamorphosis of insects, uses these strong words: "This process is formed in so remarkable a manner in butterflies, that we see therein the resurrection painted before our eyes, and exemplified so as to be examined by our hands[101]." To see, indeed, a caterpillar crawling upon the earth, sustained by the most ordinary kinds of food, which, when it has existed a few weeks or months under this humble form, its appointed work being finished, passes into an intermediate state of seeming death, when it is wound up in a kind of shroud and encased in a coffin, and is most commonly buried under the earth, (though sometimes its sepulchre is in the water, and at others in various substances in the air,) and after this creature and others of its tribe have remained their destined time in this death-like state, to behold earth, air, and water, give up their several prisoners: to survey them, when, called by the warmth of the solar beam, they burst from their sepulchres, cast off their cerements, from this state of torpid inactivity, come forth, as a bride out of her chamber,—to survey them, I say, arrayed in their nuptial glory, prepared to enjoy a new and more exalted condition of life, in which all their powers are developed, and they are arrived at the perfection of theirnature; when no longer confined to the earth they can traverse the fields of air, their food is the nectar of flowers, and love begins his blissful reign;—who that witnesses this interesting scene can help seeing in it a lively representation of man in his threefold state of existence, and more especially of that happy day, when at the call of the great Sun of Righteousness, all that are in the graves shall come forth, the sea shall give up her dead, and death being swallowed up of life, the nations of the blessed shall live and love to the ages of eternity?
But although the analogy between the different states of insects and those of the body of man is only general, yet it is much more complete with respect to his soul. He first appears in this frail body—a child of the earth, a crawling worm, his soul being in a course of training and preparation for a more perfect and glorious existence. Its course being finished, it casts off the earthy body, and goes into a hidden state of being in Hades, where it rests from its works, and is prepared for its final consummation. The time for this being arrived, it comes forth clothed with a glorious body, not like its former, though germinating from it, for though "it was sown an animal body, it shall be raised a spiritual body," endowed with augmented powers, faculties and privileges commensurate to its new and happy state. And here the parallel holds perfectly between the insect and the man. The butterfly, the representative of the soul, is prepared in thelarvafor its future state of glory; and if it be not destroyed by the ichneumons and other enemies to which it is exposed, symbolical of the vices that destroy the spiritual life of the soul, it will come to itsstate of repose in thepupa, which is its Hades; and at length, when it assumes theimago, break forth with new powers and beauty to its final glory and the reign of love. So that in this view of the subject well might the Italian poet exclaim:
Non v' accorgete voi, che noi siam' vermiNati a formar l' angelica farfalla[102]?
Non v' accorgete voi, che noi siam' vermiNati a formar l' angelica farfalla[102]?
The Egyptian fable, as it is supposed to be, of Cupid and Psyche, seems built upon this foundation. "Psyche," says an ingenious and learned writer, "means in Greek the human soul; and it means also a butterfly[103], of which apparently strange double sense the undoubted reason is, that a butterfly was a very ancient symbol of the soul—from the prevalence of this symbol, and the consequent coincidence of the names, it happened that the Greek sculptors frequently represented Psyche as subject to Cupid in the shape of a butterfly; and that even when she appears in their works under the human form, we find her decorated with the light and filmy wings of that gay insect[104]."
The following beautiful little poem falls in so exactly with the subject I have been discussing, that I cannot resist the temptation I feel to copy it for you, especiallyas I am not aware that it has appeared any where but in a newspaper.
THE BUTTERFLY'S BIRTH-DAY.
BY THE AUTHOR OF "THE BUTTERFLY'S BALL."
The shades of night were scarcely fled;The air was mild, the winds were still;And slow the slanting sun-beams spreadO'er wood and lawn, o'er heath and hill:From fleecy clouds of pearly hueHad dropt a short but balmy shower,That hung like gems of morning dewOn every tree and every flower:And from the Blackbird's mellow throatWas pour'd so loud and long a swell,As echoed with responsive noteFrom mountain side and shadowy dell:When bursting forth to life and light,The offspring of enraptured May,TheButterfly, on pinions bright,Launch'd in full splendour on the day.Unconscious of a mother's care,No infant wretchedness she knew;But as she felt the vernal air,At once to full perfection grew.Her slender form, ethereal light,Her velvet-textured wings infold;With all the rainbow's colours bright,And dropt with spots of burnish'd gold.Trembling with joy awhile she stood,And felt the sun's enlivening ray;Drank from the skies the vital flood,And wonder'd at her plumage gay!And balanced oft her broider'd wings,Through fields of air prepared to sail:Then on her vent'rous journey springs,And floats along the rising gale.Go, child of pleasure, range the fields,Taste all the joys that spring can give,Partake what bounteous summer yields,And live whilst yet 'tis thine to live.Go sip the rose's fragrant dew,The lily's honeyed cup explore,From flower to flower the search renew,And rifle all the woodbine's store:And let me trace thy vagrant flight,Thy moments too of short repose,And mark thee then with fresh delightThy golden pinions ope and close.But hark! whilst thus I musing stand,Pours on the gale an airy note,And breathing from a viewless band,Soft silvery tones around me float!—They cease—but still a voice I hear,A whisper'd voice of hope and joy,"Thy hour of rest approaches near,"Prepare thee, mortal!—thou must die!"Yet start not!—on thy closing eyes"Another day shall still unfold,"A sun of milder radiance rise,"A happier age of joys untold."Shall the poor worm that shocks thy sight,"The humblest form in nature's train,"Thus rise in new-born lustre bright,"And yet the emblem teach in vain?"Ah! where were once her golden eyes,"Her glittering wings of purple pride?"Conceal'd beneath a rude disguise,"A shapeless mass to earth allied."Like thee the hapless reptile lived,"Like thee he toil'd, like thee he spun,"Like thine his closing hour arrived,"His labour ceased, his web was done."And shalt thou, number'd with the dead,"No happier state of being know?"And shall no future morrow shed"On thee a beam of brighter glow?"Is this the bound of power divine,"To animate an insect frame?"Or shall not He who moulded thine"Wake at his will the vital flame?"Go, mortal! in thy reptile state,"Enough to know to thee is given;"Go, and the joyful truth relate;"Frail child of earth! high heir of heaven!"
The shades of night were scarcely fled;The air was mild, the winds were still;And slow the slanting sun-beams spreadO'er wood and lawn, o'er heath and hill:
From fleecy clouds of pearly hueHad dropt a short but balmy shower,That hung like gems of morning dewOn every tree and every flower:
And from the Blackbird's mellow throatWas pour'd so loud and long a swell,As echoed with responsive noteFrom mountain side and shadowy dell:
When bursting forth to life and light,The offspring of enraptured May,TheButterfly, on pinions bright,Launch'd in full splendour on the day.
Unconscious of a mother's care,No infant wretchedness she knew;But as she felt the vernal air,At once to full perfection grew.
Her slender form, ethereal light,Her velvet-textured wings infold;With all the rainbow's colours bright,And dropt with spots of burnish'd gold.
Trembling with joy awhile she stood,And felt the sun's enlivening ray;Drank from the skies the vital flood,And wonder'd at her plumage gay!
And balanced oft her broider'd wings,Through fields of air prepared to sail:Then on her vent'rous journey springs,And floats along the rising gale.
Go, child of pleasure, range the fields,Taste all the joys that spring can give,Partake what bounteous summer yields,And live whilst yet 'tis thine to live.
Go sip the rose's fragrant dew,The lily's honeyed cup explore,From flower to flower the search renew,And rifle all the woodbine's store:
And let me trace thy vagrant flight,Thy moments too of short repose,And mark thee then with fresh delightThy golden pinions ope and close.
But hark! whilst thus I musing stand,Pours on the gale an airy note,And breathing from a viewless band,Soft silvery tones around me float!
—They cease—but still a voice I hear,A whisper'd voice of hope and joy,"Thy hour of rest approaches near,"Prepare thee, mortal!—thou must die!
"Yet start not!—on thy closing eyes"Another day shall still unfold,"A sun of milder radiance rise,"A happier age of joys untold.
"Shall the poor worm that shocks thy sight,"The humblest form in nature's train,"Thus rise in new-born lustre bright,"And yet the emblem teach in vain?
"Ah! where were once her golden eyes,"Her glittering wings of purple pride?"Conceal'd beneath a rude disguise,"A shapeless mass to earth allied.
"Like thee the hapless reptile lived,"Like thee he toil'd, like thee he spun,"Like thine his closing hour arrived,"His labour ceased, his web was done.
"And shalt thou, number'd with the dead,"No happier state of being know?"And shall no future morrow shed"On thee a beam of brighter glow?
"Is this the bound of power divine,"To animate an insect frame?"Or shall not He who moulded thine"Wake at his will the vital flame?
"Go, mortal! in thy reptile state,"Enough to know to thee is given;"Go, and the joyful truth relate;"Frail child of earth! high heir of heaven!"
A question here naturally presents itself—Why are insects subject to these changes? For what end is it that, instead of preserving like other animals[105]the same general form from infancy to old age, they appear at one period under a shape so different from that which they finally assume; and why should they pass through an intermediate state of torpidity so extraordinary? I can only answer that such is the will of the Creator, whodoubtless had the wisest ends in view, although we are incompetent satisfactorily to discover them. Yet one reason for this conformation may be hazarded. A very important part assigned to insects in the economy of nature, as I shall hereafter show, is that of speedily removing superabundant and decaying animal and vegetable matter. For such agents an insatiable voracity is an indispensable qualification, and not less so unusual powers of multiplication. But these faculties are in a great degree incompatible. An insect occupied in the work of reproduction could not continue its voracious feeding. Its life, therefore, after leaving the egg, is divided into three stages. In the first, aslarva, it is in a state of sterility; its sole object is the satisfying its insatiable hunger; and, for digesting the masses of food which it consumes, its intestines are almost all stomach. This is usually by much the longest period of its existence. Having now laid up a store of materials for the development of the future perfect insect, it becomes apupa; and during this inactive period the important process slowly proceeds, uninterrupted by the calls of appetite. At length the perfect insect is disclosed. It now often requires no food at all; and scarcely ever more than a very small quantity; for the reception of which its stomach has been contracted, in some instances, to a tenth of its former bulk. Its almost sole object is now the multiplication of its kind, from which it is diverted by no other propensity; and this important duty being performed, the end of its existence has been answered, and it expires.
It must be confessed that some objections might be thrown out against this hypothesis, yet I think none thatwould not admit of a plausible answer. To these it is foreign to my purpose now to attend, and I shall conclude this letter by pointing out to you the variety of new relations which this arrangement introduces into nature. One individual unites in itself, in fact, three species, whose modes of existence are often as different as those of the most distantly related animals of other tribes. The same insect often lives successively in three or four worlds. It is an inhabitant of the water during one period; of the earth during another; and of the air during a third; and fitted for its various abodes by new organs and instruments, and a new form in each. Think (to use an illustration of Bonnet) but of the cocoon of the silkworm! How many hands, how many machines does not this little ball put into motion! Of what riches should we not have been deprived, if the moth of the silkworm had been born a moth, without having been previously a caterpillar! The domestic economy of a large portion of mankind would have been formed on a plan altogether different from that which now prevails.
I am, &c.
In the letter which I devoted to the defence of Entomology, I gave you reason to expect, more effectually to obviate the objection drawn from the supposed insignificance of insects, that I should enter largely into the question of their importance to us both as instruments of good and evil. This I shall now attempt; and, as I wish to leave upon your mind a pleasant impression with respect to my favourites, I shall begin with the last of these subjects—theinjurywhich they do to us.
The Almighty ordains various instruments for the punishment of offending nations: sometimes he breaks them to pieces with the iron rod of war; at others the elements are let loose against them; earthquakes and floods of fire, at his word, bring sudden destruction upon them; seasons unfriendly to vegetation threaten them with famine; the blight and mildew realize these threats; and often, the more to manifest and glorify his power, he employs means, at first sight, apparently the most insignificant and inadequate to effect their ruin; the numerous tribes ofinsectsare his armies[106], marshalled by him, and by his irresistible command impelled to the work of destruction: where he directs them they laywaste the earth, and famine and the pestilence often follow in their train.
The generality of mankind overlook or disregard these powerful, because minute, dispensers of punishment; seldom considering in how many ways their welfare is affected by them: but the fact is certain, that should it please God to give them a general commission against us, and should he excite them to attack, at the same time, our bodies, our clothing, our houses, our cattle, and the produce of our fields and gardens, we should soon be reduced, in every possible respect, to a state of extreme wretchedness; the prey of the most filthy and disgusting diseases, divested of a covering, unsheltered, except by caves and dungeons, from the inclemency of the seasons, exposed to all the extremities of want and famine; and in the end, as Sir Joseph Banks, speaking on this subject, has well observed[107], driven with all the larger animals from the face of the earth. You may smile, perhaps, and think this a high-coloured picture, but you will recollect—I am not stating the mischiefs that insects commonly do, but what they would do according to all probability, if certain counter-checks restraining them within due limits had not been put in action; and which they actually do, as you will see, in particular cases, when those counter-checks are diminished or removed.
Insects may be said, without hyperbole, to have established a kind of universal empire over the earth and its inhabitants. This is principally conspicuous in the injuries which they occasion, for nothing in nature that possesses or has possessed animal or vegetable life, is safe from their inroads. Neither the cunning of the fox, northe swiftness of the horse or deer, nor the strength of the buffalo, nor the ferocity of the lion or tiger, nor the armour of the rhinoceros, nor the giant bulk or sagacity of the elephant, nor even the authority of imperial man, who boasts himself to be the lord of all, can secure them from becoming a prey to these despised beings. The air affords no protection to the birds, nor the water to the fish; insects pursue them all to their most secret conclaves and strongest citadels, and compel them to submit to their sway. Flora's empire is still more exposed to their cruel domination and ravages; and there is scarcely one of her innumerable subjects, from the oak, the glory of the forest, to the most minute lichen that grows upon its trunk, that is not destined to be the food of these next to nonentities in our estimation. And when life departs from man, the inferior animals, or vegetables, they become universally, sooner or later, the inheritance of insects.
I shall principally bespeak your attention to the injuries in question as they affect ourselves. These may be divided into direct and indirect. Bydirectinjuries I mean every species of attack upon our own persons, and byindirect, such as are made upon our property. To the former of these I shall confine myself in the present letter.
Insects, as to theirdirectattacks upon us, may be arranged in three principal classes. Those, namely, which seek to make us their food; those whose object is to prevent or revenge an injury which they either fear, or have received from us; and those which indeed offer us no violence, but yet incommode us extremely in other ways.
I hope I shall not too much offend your delicacy if I begin the first class of our insect assailants with a very disgusting genus, which Providence seems to have created to punish inattention to personal cleanliness. But though this pest of man must not be wholly passed over, yet, since it is unfortunately too well known, it will not be at all necessary for me to enlarge upon its history. I shall only mention one fact which shows the astonishingly rapid increase of these animals, where they have once gotten possession. It is a vulgar notion, that a louse in twenty-four hours may see two generations; but this is rather overshooting the mark. Leeuwenhoek, whose love for science overcame the nausea that such creatures are apt to excite, proves that their nits or eggs are not hatched till the eighth day after they are laid, and that they do not themselves commence laying before they are a month old. He ascertained, however, that a single female louse may, in eight weeks, witness the birth of five thousand descendants[108]. You remember how wolves were extirpated from this country, but perhaps never suspected any monarch of imposing a tribute ofliceupon his subjects. Yet we are gravely told that in Mexico and Peru such apoll-tax was exacted, and that bags full of these treasures were found in the palace of Montezuma[109]!!! Were our own taxes paid in such coin, what little grumbling would there be!
Two other species of this genus, besides the common louse, are, in this country, parasites upon the human body——But already I seem to hear you exclaim, "Whydwell so long on creatures so odious and nauseating, whose injuries are confined to theprofanum vulgus? Leave them therefore to the canaille—they are nothing to us." Not so fast, my friend—recollect what historians and other writers have recorded concerning thePhthiriasisor pedicular disease, and you must own that, for the quelling of human pride, and to pull down the high conceits of mortal man, this most loathsome of all maladies, or one equally disgusting, has been the inheritance of the rich, the wise, the noble, and the mighty; and in the list of those that have fallen victims to it, you will find poets, philosophers, prelates, princes, kings, and emperors. It seems more particularly to have been a judgement of God upon oppression and tyranny, whether civil or religious. Thus the inhuman Pheretima mentioned by Herodotus, Antiochus Epiphanes, the Dictator Sylla, the two Herods, the Emperor Maximin, and, not to mention more, the great persecutor of the Protestants, Philip the Second, were carried off by it.
I say by this malady,or one equally disgusting, because it is not by any means certain, though some learned men have so supposed, that all these instances, and others of a similar nature, standing also upon record, are to be referred to the same specific cause; since there is very sufficient reason for thinking that at leastthreedifferent descriptions of insects are concerned in the various cases that have been handed down to us under the common name ofPhthiriasis. As the subject of maladies connected with insects, or produced by them, is both curious and interesting, although no writer, that I am aware of, has given it full consideration, and at the same time falls in with my general design, I hope you will notregard me as guilty of presumption, and of intruding into the province of medical men, if I enter rather largely into it, and state to you the reasons that have induced me to embrace the above hypothesis, leaving you full liberty to reject it if you do not find it consonant to reason and fact. The three kinds of insects to which I allude, as concerned in cases that have been deemed Phthiriasis, are lice (Pediculi, L.) mites (Acari, L.), andLarvæin general.
As far as the habits of the genusPediculus, whether inhabiting man or the inferior animals, are at present known, it does not appear, from any well ascertained fact, that the species belonging to it are eversubcutaneous. For this observation, as far as it relates to man, I can produce the highest medical authority. "The louse feeds on the surface of the skin," says the learned Dr. Mead in hisMedica Sacra; and Dr. Willan, in his palmary work onCutaneous Diseases, remarks with respect to the body-louse, "that the nits, or eggs, are deposited on the small hairs of the skin," and that "the animals are found on the skin, or on the linen, and not under the cuticle, as some authors have represented." And he further observes, that "many marvellous stories are related by Forestus, Schenkius and others respecting lice bred under the skin, and discharged in swarms from abscesses, strumous ulcers, and vesications. The mode in which Pediculi are generated being now so well ascertained, no credit can be given to these accounts." Thus far this great man, who however supposes (in which opinion Dr. Bateman concurs with him) that the authors to whom he alludes had mistaken for lice some other species of insects, which are not unfrequently found in putrefactive sores.
If these observations be allowed their due weight, it will follow, that a disease produced by animals residing under the cuticle cannot be a true Phthiriasis, and therefore the death of the poet Alcman, and of Pherecydes Syrius the philosopher, mentioned by Aristotle, must have been occasioned by some other kind of insect. For, speaking of the lice to which he attributes these catastrophes, he says that "they are produced in the flesh in small pustule-like tumours, which have no pus, and from which when punctured, they issue[110]." For the same reason, the disorder which Dr. Heberden has described in hisCommentaries, from the communications of Sir E. Wilmot, under the name ofMorbus pedicularis, must also be a different disease, since, with Aristotle, he likewise represents the insects as inhabiting tumours, from which they may be extracted when opened by a needle. He says, indeed, that in every respect they resemble the common lice, except in being whiter; but medical men, who were not at the same time entomologists, might easily mistake an Acarus for a Pediculus[111].
Dr. Willan, in one case ofPrurigo senilis, observed a number of small insects on the patient's skin and linen. They were quick in their motion, and so minute that it required some attention to discover them. He took them at first for small Pediculi; but under a lens they appeared to him rather to be a nondescript species of Pulex[112]; yet the figure he gives has not the slightest likeness to the latter genus, while it bears a striking resemblance to theformer. It is not clear whether his draughtsman meant to represent the insect with six or with eight legs: if it had only six, it was probably a Pediculus; but if it had eight, it would form a new genus between theAcarinaand the hexapodAptera. Dr. Bateman, in reply to some queries put to him, at my request, by our common and lamented friend Dr. Reeve, relates that he understood from Dr. Willan, in conversation, that the insect in question jumped in its motion. This circumstance he regards as conclusive against its being a Pediculus; but such a consequence does not necessarily follow, since it not seldom happens that insects of the same tribe or genus either have or have not this faculty; for instance, compareScirteswithCyphon, small beetles, andAcarus Scabieiwith otherAcari[113].
Dr. Willan has quoted with approbation two cases from Amatus Lusitanus, which he seems to think correctly described as Phthiriasis. In one of them, however, which terminated fatally, the circumstances seem rather hyperbolically stated—I mean, where it is said that two black servants had no other employment than carrying baskets full of these insects to the sea!! Perhaps you will think I draw largely upon your credulity if I call upon you to believe this; I shall therefore leave you to act as you please.—Thus much for pure Phthiriasis, which term ought to be confined to maladies produced bylice. I shall only further observe, that as many species as exist of these, which are the causes of disease, so many kinds of Phthiriasis will there be.
Acari, or mites, are the next insect sources of disease in the human species, and that not of one, but probably of many kinds both local and general. They are distinguished from Pediculi not only by their form, but also often by their situation, since they frequently establish themselves under the cuticle. With respect to local disorders, Dr. Adams conjectures that Acari may be the cause of certain cases ofOphthalmia. Sir J. Banks, in a letter to that gentleman, relates that some seamen belonging to the Endeavour brig, being tormented with a severe itching round the extremities of the eyelids, one of them was cured by an Otaheitan woman, who with two small splinters of bamboo extracted from between theciliaabundance of very minute lice, which were scarcely visible without a lens, though their motion, when laid on the thumb, was distinctly perceived. These insects were probably synonymous with theCiron des paupièresof Sauvages[114].—Le Jeune, a French physician quoted in Mouffet, describes a case, in which what seems a different species, since he calls them rather large, infested the white of the eye, exciting an intolerable itching[115].—Dr. Mead, from theGerman Ephemerides, gives an account of a woman suckling her child, from whose breast proceeded very minute vermicles[116]. These were probably mites, and perhaps that species, which, from its feeding upon milk, Linné denominatesAcarus Lactis. The great author last mentioned describes an insect, a native of America, under the name ofPediculus Ricinoides, which, upon the authority of Rolander, he informs us, gets into the feet of people as they walk, sucks their blood,oviposits[117]in them, and so occasions very dangerous ulcers. It would be an Acarus, he observes, but it has only six legs. Now Hermann affirms, that some species ofTrombidium(a genus separated by Fabricius fromAcarus) have in no state more than six legs[118]. Others of the tribe ofAcarina, and the insect in question amongst the rest, may be similarly circumstanced; or those that Rolander examined might have been larvæ, which in this tribe are usually hexapods.
Linné appears to have been of opinion that many contagious diseases are caused by mites[119]. How far he was justified in this opinion I shall not here inquire; facts alone can decide the question, and observations made by men acquainted with Entomology as well as the science of diseases. Considerable deference and attention, however, are certainly due to the sentiments of so great a naturalist, in whom these necessary qualifications were united in no common degree. With respect to the dysentery and the itch, he affirms that this had been manifested to his eyes. You will wish probably to know the arguments that may be adduced in confirmation of this opinion; I will therefore endeavour to satisfy you as well as I am able. The following history given by Linné seems to prove the dysentery connected with these animals.
Rolander, a student in Entomology, while he resided in the house of the illustrious Swede, was attacked by thedisease in question, which quickly gave way to the usual remedies. Eight days after, it returned again, and was as before soon removed. A third time, at the end of the same period, he was seized with it. All the while he had been living like the rest of the family, who had nevertheless escaped. This, of course, occasioned no little inquiry into the cause of what had happened. Linné, aware that Bartholinus had attributed the dysentery toinsects, which he professed to have seen, recommended it to his pupil to examine his feces. Rolander, following this advice, discovered in them innumerable animalcules, which upon a close examination proved to be mites. It was next a question how he alone came to be singled out by them; and thus he accounts for it. It was his habit not to drink at his meals; but in the night, growing thirsty, he often sipped some liquid out of a vessel made of juniper wood. Inspecting this very narrowly, he observed, in the chinks between the ribs, a white line, which, when viewed under a lens, he found to consist of innumerable mites, precisely the same with those that he had voided. Various experiments were tried with them, and a preparation of rhubarb was found to destroy them most effectually. He afterwards discovered them in vessels containing acids, and often under the bung of casks[120]. In the instance here recorded, the dysentery, or diarrhœa, was evidently produced by a species of mite, which Linné hence calledAcarus Dysenteriæ; but it would be going too far, I apprehend, to assert that they are invariably the cause of that disease.
ThatScabies, or the itch, is occasioned by a mite, is not a doctrine peculiar to the moderns. Mouffet mentionsAbinzoar, called also Avenzoar, a celebrated Hispano-Arabian physician of Seville, who flourished in the twelfth century, as the most ancient author that notices it. He calls these mites little lice that creep under the skin of the hands, legs, and feet, exciting pustules full of fluid[121]. Joubert, quoted by the same author, describes them under the name ofSirones, as always being concealed beneath the epidermis, under which they creep like moles, gnawing it, and causing a most troublesome itching. It appears that Mouffet, or whoever was the author of that part of theTheatrum Insectorum, was himself also well acquainted with these animals, since he remarks that their habitation is not in the pustule but near it: a remark afterwards confirmed by Linné[122], and more recently by Dr. Adams[123]. In common with the former of these authors, Mouffet further notices the effect of warmth upon them in exciting motion[124]. Our intelligent countryman also observes that they cannot be Pediculi, since they live under the cuticle, which lice never do[125]. In the epistle dedicatory, the editor speaks also of them as living in burrows which they have excavated in the skin near a lake of water; from which if they be extracted with a needle and put upon the nail, they show in the sun their red head and the feet with which theywalk[126]. And to close myveteranauthorities, Junius thus explains the word Acarus, as I find him quoted in Gouldman's useful dictionary, "A small worm, which eats under the skin, and makes burrows in itching hands[127]."
In more modern times, microscopical figures have been added to descriptions of the insect. Bonomo first furnished this valuable species of elucidation. His figures, however, which are copied by Baker in his work on the microscope, are far from accurate[128]. Those of De Geer and Dr. Adams are much more satisfactory, and mutually confirm each other[129]. From them it is evident that the same insect inhabits the scabies of Sweden and Madeira. Dr. Bateman, in the letter before alluded to, informs his correspondent, that he had seen that from Madeira, and gives it as his opinion, that there cannot be a doubt of the existence of anAcarus Scabiei; an opinion which he repeats in his late work onCutaneous Diseases; and which, according to Hermann[130], has been also rendered unquestionable by Wichmann in hisEtiologie de la Gale(Hanovre 1786), a work I have not had an opportunity of consulting. From all this we may regard the point as so far settled, that an animal of this kind exists at least as an occasional concomitant of scabies.
This fact being ascertained, a more complex inquiryremains, which branches out into two distinct questions. Is scabies always produced by these insects? Or, if this be not the case, Is theanimatescabies a distinct disease from theinanimate?
It is very remarkable that Linné, a physician as well as a naturalist; and De Geer, one of the most accurate observers that ever existed; should both assign the insect in question as the undoubted cause of thecommonscabies of their country; the one applying to the disease he was speaking of the epithet ofcommunissima, and observing the fact to be notorious, (cuique liquet,) and the other designating it by its well known French name "La Gale[131]." And is it not equally remarkable that such men as John Hunter, Dr. Heberden, Dr. Bateman, Dr. Adams, and Mr. Baker, should never, in this country, have been able to meet with it? Did it indeed exist in our common scabies, it seems impossible that it could have escaped the observation of the two last of these gentlemen; Dr. Adams being so well qualified to detect it from his observations in Madeira, and Mr. Baker from his expertness in microscopical researches. Dr. Bateman, in the letter above quoted, says, "I have hunted it with a good magnifier, in many cases of itch, both in and near the pustules, and in the red streaks or furrows, but always without success." In his work onCutaneous Diseaseshe tells us, however, that he has seen it, in one instance, when it had been taken from the diseased surface by another practitioner. And though Dr. Willan in his book speaks of the Acarus as the concomitant of this disease, yet his learned friendjust mentioned observes, that he admitted that it was not to be found in ordinary cases, and indeed never seemed to have made up his mind upon the subject. When I was at Norwich in 1812, Dr. Reeve very kindly accompanied me to the House of Industry there, to examine a patient whose body was very full of the pustules of this disorder; but though we used a good magnifier, we could discover nothing like an insect. I must observe, however, that our examination was made in December, in severe weather, when the cold might, perhaps, render the animal torpid, and less easy to be discovered.
From the above facts it seems fair to infer that this animal is not invariably the cause of scabies, but that there are cases with which it has no connexion. Now, from this inference, would not another also follow, that the disease produced by the insect is specifically distinct from that in which it cannot be found? Sauvages and Dr. Adams are both of this opinion[132], the former assigning to it the trivial name ofvermicularis; and the latter proving, by very satisfactory arguments, that it is different from the other. If they were bothanimatediseases, but derived from two distinct species of animals, (for it seems not impossible that even our common itch may be caused by a mite more minute than the other, and so more difficult to find,) they would properly be considered as distinct species; much more, therefore, if one beanimateand the otherinanimate. Nay this, I should think, would lead to a doubt whether even theirgenuswere the same. I shall dismiss this part of my subject with the mention of a discovery of Dr. Adams, which seems to haveescaped both Linné and De Geer—that theAcarus Scabieiis endowed with the faculty of leaping; (in this respect resembling the insect found by Willan inPrurigo senilismentioned above;) for which purpose its four posterior thighs are incrassated[133].