CURIOSITIES RESPECTING INSECTS.--(_Continued._)

_Luminous Insects._

Many insects are possessed of a luminous preparation or secretion, which has all the advantages of our lamps and candles, without their inconveniences; which gives light sufficient to direct our motion; which is incapable of burning; and whose l.u.s.tre is maintained without needing fresh supplies of oil, or the application of snuffers.

Of the insects thus singularly provided, the common GLOW-WORM (_Lampyris noctiluca_) is the most familiar instance.--This insect in shape somewhat resembles a caterpillar, only it is much more depressed; and the light proceeds from a pale-coloured patch that terminates, the under side of the abdomen.

It has been supposed by many, that the males of the different species of lampyris do not possess the property of giving out any light; but it is now ascertained that this supposition is inaccurate, though their light is much less vivid than that of the female. Ray first pointed out this fact with respect to (_L. noctiluca_.) Geoffrey also observed, that the male of this species has four small luminous points, two on each of the two last segments of the belly: and his observation has been recently confirmed by Miller. This last entomologist, indeed, saw only two shining spots; but from the insects having the power of withdrawing them out of sight, so that not the smallest trace of light remains, he thinks it is not improbable that at times two other points, still smaller, may be exhibited, as Geoffrey has described. In the males of _L. splendidula_, and of _L. hemiptera_, the light is very distinct, and may be seen in the former while flying. The females have the same faculty of extinguishing or concealing their light; a very necessary provision to guard them from the attacks of nocturnal birds. Mr. White even thinks that they regularly put it out between eleven and twelve every night, and they have also the power of rendering it for a while more vivid than ordinary.

Though many of the females of the different species of lampyris are without wings, and even elytra, (in _Coleoptera_,) this is not the case with all. The female of _L. Italica_, a species common in Italy, and which, if we may trust to the accuracy of the account given by Mr. Waller, in the Philosophical Transactions for 1684, would seem to have been taken by him in Hertfordshire, is winged; and when a number of these moving stars are seen to dart through the air in a dark night, nothing can have a more beautiful effect. Dr. Smith says, that the beaus of Italy are accustomed in an evening to adorn the heads of the ladies with these artificial diamonds, by sticking them into their hair; and a similar custom prevails amongst the ladies of India.

Besides the golden species of the genus _Lampyris_, all of which are probably more or less luminous, another insect of the beetle tribe, _Elater noctilucus_, is endowed with the same property, and that in a much higher degree. This insect, which is an inch long, and about one-third of an inch broad, gives out its princ.i.p.al light from two transparent eye-like tubercles placed upon the thorax; but there are also two luminous patches concealed under the elytra, which are not visible except when the insect is flying, at which time it appears adorned with four brilliant gems of the most beautiful golden-blue l.u.s.tre: in fact, the whole body is full of light, which shines out between the abdominal segments when stretched. The light emitted by the two thoracic tubercles alone is so considerable, that the smallest print may be read by moving one of these insects along the lines; and in the West India islands, particularly in St. Domingo, where they are very common, the natives were formerly accustomed to employ those living lamps, which they called _cucuij_, instead of candles, in performing their evening household occupations. In travelling at night, they used to tie one to each great toe; and in fishing and hunting, required no other flambeau.--_Pietro Martire's Decades of the New World_, _quoted in Madoc_, p. 543. Southey has happily introduced this insect in his "Madoc," as furnishing the lamp by which Coatel rescued the British hero from the hands of the Mexican priests.

"She beckon'd and descended, and drew out, From underneath her vest, a cage, or net It rather might be called, so fine the twigs Which knit it, where, confined, two fire-flies gave Their l.u.s.tre. By that light did Madoc first Behold the features of his lovely guide."

Pietro Martire tells us, that cucuij serve the natives of the Spanish West India islands not only instead of candles, but as extirpators of the gnats, which are a dreadful pest to the inhabitants of the low grounds.

They introduce a few fire-flies, to which the gnats are a grateful food, into their houses, and by means of these "commodious hunters," are soon rid of the intruders. "How they are a remedy (says this author) for so great a mischiefe, it is a pleasant thing to hear. Hee who understandeth that he has those troublesome guestes (the gnattes) at home, diligently hunteth after the cucuij. Whoso wanteth cucuij, goeth out of the house in the first twilight of the night, carrying a burning fire-brande in his hande, and ascendeth the next hillock, that the cucuij may see it, and hee swingeth the fire-brande about, calling Cucuie aloud, and beating the ayre with often calling out, Cucuie, Cucuie." He goes on to observe, that the simple people believe the insect is attracted by their invitations; but that, for his part, he is rather inclined to think that the fire is the magnet. Having obtained a sufficient number of cucuij, the beetle-hunter returns home, and lets them fly loose in the house, where they diligently seek the gnats about the beds and the faces of those asleep, and devour them.--_Martire ubi supr. Colonies_, i. 128. These insects are also applied to purposes of decoration. On certain festival-days, in the month of June, they are collected in great numbers, and tied all over the garments of young people, who gallop through the streets on horses similarly ornamented, producing on a dark evening the effect of a large moving body of light. On such occasions, the lover displays his gallantry by decking his mistress with these living gems.--_Walton's Present State of the Spanish Colonies._ And according to P. Martire, "many wanton wilde fellowes" rub their faces with "the flesh of a killed cucuij," as boys with us use phosphorus, "with purpose to meet their neighbours with a flaming countenance," and derive amus.e.m.e.nt from their fright.

Besides _Elater noctilucus_, _E. ignitus_, and several others of the same genus, are luminous: not fewer than twelve species of this family are described by Illiger in the Berlin Naturalist Society's Magazine.

The brilliant nocturnal spectacle presented by these insects to the inhabitants of the countries where they abound, cannot be better described than in the language of the poet above referred to, who has thus related its first effect upon British visitors of the new world:

"------------------------sorrowing we beheld The night come on: but soon did night display More wonders than it veil'd; innumerable tribes From the wood-cover swarm'd, and darkness made Their beauties visible; one while they stream'd A bright blue radiance upon flowers that clos'd Their gorgeous colours from the eye of day; Now motionless and dark, eluding search, Self-shrouded; and anon starring the sky, Rose like a shower of fire."

If we are to believe Mouffet, (and the story is not incredible,) the appearance of the tropical fire-flies on one occasion led to a more important result than might have been expected from such a cause. He tells us, that when Sir Thos. Cavendish and Sir John Dudley first landed in the West Indies, and saw in the evening an infinite number of moving lights in the woods, which were merely these insects, they supposed that the Spaniards were advancing upon them, and immediately betook themselves to their ships: a result as well ent.i.tling the elatera to a commemoration feast, as a similar good office by the land-crabs of Hispaniola, which, as the Spaniards tell, (and the story is confirmed by an anniversary _Fiesta de los Cangrejos_,) by their clattering being mistaken for the sound of Spanish cavalry close upon their heels, in like manner scared away a body of English invaders from the city of St. Domingo.--_Walton's Hispaniola_, i. 39.

An anecdote less improbable, perhaps, and certainly more ludicrous, is related by Sir James Smith, of the effect of the first sight of the Italian fire-flies upon some Moorish ladies, ignorant of such appearances.

These females had been taken prisoners at sea, and, until they could be ransomed, lived in a house in the outskirts of Genoa, where they were frequently visited by the respectable inhabitants of the city; a party of whom, on going one evening, were surprised to find the house closely shut up, and their Moorish friends in the greatest grief and consternation. On inquiring into the cause, they ascertained that some of the Lampyris Italica had found their way into the dwelling, and that the ladies within had taken it into their heads that these brilliant guests were no other than the troubled spirits of their relations; and some time elapsed before they could be divested of this idea. The common people in Italy have a superst.i.tion respecting these insects somewhat similar, believing that they are of a spiritual nature, and proceed out of the graves; and hence carefully avoid them.--_Tour on the Continent_, 2d ed. iii. 85.

The insects. .h.i.therto adverted to have been beetles, or of the order _Coleoptera_. But, besides these, a genus in the order _Hemiptera_, called _Fulgora_, includes several species, which emit so powerful a light, as to have obtained in English the generic appellation of lantern-flies. Two of the most conspicuous of this tribe are the _F. lanternaria_ and _F.

candelaria_; the former a native of South America, the latter of China.

Both, as indeed is the case with the whole genus, have the material which diffuses their light included in a hollow subtransparent projection of the head. In _F. candelaria_ this projection is of a subcylindrical shape, recurved at the apex, above an inch in length, and the thickness of a small quill. We may easily conceive, as travellers a.s.sure us, that a tree studded with mult.i.tudes of these living sparks, some at rest and others in motion, must during the night have a superlatively splendid appearance.

In _F. lanternaria_, which is an insect two or three inches long, the snout is much larger and broader, and more of an oval shape, and sheds a light, the brilliancy of which transcends that of any other luminous insect. Madam Merian informs us, that the first discovery she made of this property caused her no small alarm. The servants had brought her several of these insects, which by day-light exhibited no extraordinary appearance, and she inclosed them in a box till she should have an opportunity of drawing them, placing them upon a table in her lodging-room. In the middle of the night the confined insects made such a noise as to awake her, and she opened the box, the inside of which, to her great astonishment, appeared all in a blaze; and in her fright letting it fall, she was not less surprised to see each of the insects apparently on fire. She soon, however, divined the cause of this unexpected phenomenon, and re-inclosed her brilliant guests in their place of confinement. She adds, that the light of one of these fulgora was sufficiently bright to read a newspaper by. Another species, _F. pyrrhorynchus_, is described by Donovan, in his Insects of India; of which the light, though from a smaller snout than that of _F. lanternaria_, must a.s.sume a more splendid and striking appearance, the projection being of a rich deep purple from the base to near the apex, which is of a fine transparent scarlet; and these tints will of course be imparted to the transmitted light.

With regard to the immediate source of the luminous properties of these insects, Mr. Macartney, to whom we are indebted for the most recent investigation on the subject, has ascertained, that in the common glow-worm, and in _Elater noctilucus_ and _ignitus_, the light proceeds from ma.s.ses of a substance not generally differing, except in its yellow colour, from the interst.i.tial substance _corps graisseux_, of the rest of the body, closely applied underneath those transparent parts of the insects' skin which afford the light. In the glowworm, besides the last-mentioned substance, which, when the season for giving light is pa.s.sed, is absorbed, and replaced by the common interst.i.tial substance, he observed on the inner side of the last abdominal segment two minute oval sacks, formed of an elastic spirally-wound fibre, similar to that of the trachea, containing a soft yellow substance, of a closer texture than that which lines the adjoining region, and affording a more permanent and brilliant light. This light he found to be less under the control of the insect than that from the adjoining luminous substance, which it has the power of voluntarily extinguishing, not by retracting it under a membrane, as Carradori imagined, but by some inscrutable change which depends upon its will: and when the latter substance was extracted from living glowworms, it afforded no light, while the two sacks in like circ.u.mstances shone uninterruptedly for several hours. Mr. Macartney conceives, from the radiated structure of interst.i.tial substance surrounding the oval yellow ma.s.ses immediately under the transparent spot in the thorax of _Elater noctilucus_, and the subtransparency of the adjoining crust, that the interst.i.tial substance in this situation has also the property of shining; a supposition which, if De Geer and other authors be correct in stating, that this insect has two luminous patches over its elytra, and that the incisures between the abdominal segments shine when stretched, may probably be extended to the whole of the interst.i.tial substance of its body.

With respect to the remote cause of the luminous property of insects, philosophers are considerably divided in opinion. The disciples of modern chemistry have in general, with Dr. Darwin, referred it to the slow combustion of some combination of phosphorus secreted from their fluids by an appropriate organization, and entering into combination with the oxygen supplied in respiration. This opinion is very plausibly built upon the ascertained existence of phosphoric acid as an animal secretion; the great resemblance between the light of phosphorus in slow combustion, and animal light; the remarkably large spiracula in glowworms; and upon the statement, that the glowworm is rendered more brilliant by the application of heat and oxygen gas, and is extinguished by cold and by hydrogen and carbonic acid gases. From these last facts, Spallanzani was led to regard the luminous matter as a compound of hydrogen and carburetted hydrogen gas. Carradori having found that the luminous portion of the belly of the Italian glowworm, _lampyris Italica_, shone in vacuo, in oil, in water, and when under other circ.u.mstances where the presence of oxygen gas was precluded,--with Brugnatelli, ascribed the property in question to the imbibition of light, separated from the food or air taken in the body, and afterwards secreted in a sensible form.[15] Lastly, Mr. Macartney having ascertained, by experiment, that the light of a glowworm is not diminished by immersion in water, or increased by the application of heat; that the substance affording it, though poetically employed for lighting the fairies' tapers,[16] is incapable of inflammation, if applied to the flame of a candle or red-hot iron; and when separated from the body, exhibits no sensible heat on the thermometer's being applied to it,--rejects the preceding hypothesis as unsatisfactory, but without subst.i.tuting any other explanation; suggesting, however, that the facts he observed are more favourable to the supposition of light being a quality of matter, than a substance.

Which of these opinions is the more correct, is left for future philosophers to decide.

The general use of this singular provision is not much more satisfactorily ascertained than its nature. It is conjectured that it may be a means of defence against its enemies. In different kinds of insects, however, it may probably have a different object. Thus in the lantern-flies, (_Fulgora_,) whose light precedes them, it may act the part that their name imports, enable them to discover their prey, and to steer themselves safely in the night. In the fire-flies, (_Elater_,) if we consider the infinite numbers, that in certain climates and situations present themselves every where in the night, it may distract the attention of their enemies, or alarm them. And in the glowworm, since their light is usually more brilliant in the female, it is most probably intended to conduct the s.e.xes to each other.

Thine is an un.o.btrusive blaze, Content in lowly shades to shine; And much I wish, while yet I gaze, To make thy modest merit mine!

_Mrs. Opie._

CHAP. XXVIII.

CURIOSITIES RESPECTING INSECTS.--(_Continued._)

_The Flea--On the Duration of the Life of a Flea--The Louse._

THE FLEA,--has two eyes and six feet, fitted for leaping; the feelers are like threads; the rostrum is inflected, setaceous, and armed with a sting; and the belly is compressed. Fleas bring forth eggs, which they deposit on animals that afford them a proper food. Of these eggs are hatched white worms of a shining pearl colour, which feed on the scurfy substance of the cuticle, the downy matter gathered in the piles or folds of clothes, or other similar substances. In a fortnight they come to a tolerable size, and are very lively and active; and, if at any time disturbed, they suddenly roll themselves into a kind of ball. Soon after this, they come to creep, after the manner of silk-worms, with a very swift motion. When arrived at their size, they hide themselves as much as possible, and spin a silken thread out of their mouth, wherewith they form themselves a small round bag, or case, white within as paper, but without always dirty, and fouled with dust. Here, after a fortnight's rest, the animalcule bursts out, transformed into a perfect flea, leaving its exuviae in the bag.

While it remains in the bag, it is milk-white till the second day before its eruption, when it becomes coloured, grows hard, and gets strength; so that, upon its first delivery, it springs nimbly away. The flea is covered all over with black, hard, and sh.e.l.ly scales or plates, which are curiously jointed, and folded over each other in such a manner as to comply with all the nimble motions of the creature. These scales are finely polished, and beset about the edges with short spikes, in a very beautiful and regular order. Its neck is finely arched, and resembles the tail of a lobster: the head is also very extraordinary; for from the snout-part of it proceed the two fore-legs, and between these is placed the piercer, or sucker, with which it penetrates the skin to get its food.

Its eyes are very large and beautiful, and it has two short horns, or feelers. It has four other legs, joined all at the breast. These, when it leaps, fold short, one within another; and then, exerting their spring all at the same instant, they carry the creature to a surprising distance. The legs have several joints, are very hairy, and terminate in two long and hooked sharp claws. The piercer, or sucker, of the flea, is lodged between its fore-legs, and includes a couple of darts or lancets, which, after the piercer has made an entrance, are thrust farther into the flesh, to make the blood flow from the adjacent parts, and occasion that round red spot, with a hole in the centre of it, vulgarly called a flea-bite.

This piercer, its sheath opening sidewise, and the two lancets within it, are very difficult to be seen, unless the two fore-legs, between which they are hid, be cut off close to the head; for the flea rarely puts out its piercer, except at the time of feeding, but keeps it folded inwards; and the best way of seeing it, is by cutting off first the head, and then the fore-legs, and then it is usually seen thrust out in convulsions. By keeping fleas in a gla.s.s tube corked up at both ends, but so as to admit fresh air, their several actions may be observed. They may be thus seen to lay their eggs, &c. They do not lay their eggs all at once, but by ten or twelve in a day, for several days successively, which eggs will be afterwards found to hatch successively, in the same order. The flea may easily be dissected in a drop of water; and thus the stomach and bowels, with their peristaltic motion, may be discovered very plainly, with the veins and arteries, though minute beyond all conception. This bloodthirsty insect, which fattens at the expense of the human species, prefers the more delicate skin of women, but preys neither upon epileptic persons, nor upon the dead or dying. It loves to nestle in the fur of dogs, cats, and rats. The nests of river-swallows are sometimes plentifully stored with them. Fleas are apterous, walk but little, but leap to a height equal to two hundred times that of their own body. This amazing motion is performed by means of the elasticity of their feet, the articulations of which are so many springs. Thus it eludes, with surprising agility, the pursuit of the person on whom it riots. Mercurial ointment, brimstone, a fumigation with the leaves of pennyroyal, or fresh-gathered leaves of that plant, sewed up in a bag, and laid in the bed, are remedies pointed out as destructive of fleas.

In the Athenian Oracle, a lady desires to know whether fleas have stings, or whether they only suck or bite, when they draw blood from the body? To which an ingenious author returns the following humorous answer:

"Not to trouble you, madam, with the Hebrew or Arabic name of a flea, or to transcribe Bochart's learned dissertations on the little animal, we shall, for your satisfaction, give such a description thereof as we have yet been able to discover.--

"Its skin is of a lovely deep red colour, most neatly polished, and armed with scales, which can resist any thing but fate, and your ladyship's unmerciful fingers: the neck of it is exactly like the tail of a lobster, and, by the a.s.sistance of those strong scales it is covered with, springs backwards and forwards much in the same manner, and with equal violence: it has two eyes on each side of its head, so pretty, that I would prefer them to any, madam, but yours; and which it makes use of to avoid its fate, and flee from its enemies, with as much nimbleness and success, as your s.e.x manage those fatal weapons, lovely basilisks as you are, for the ruin of your adorers. Nature has provided it six substantial legs, of great strength, and incomparable agility, jointed like a cane, covered with large hairs, and armed each of them with two claws, which appear of a h.o.r.n.y substance, more sharp than lancets, or the finest needle you have in your needle-book. It was a long while before we could discover its mouth, which, we confess, we have not yet so exactly perceived as we could wish, the little bashful creature always holding up its two fore-feet before it, which it uses instead of a fan or mask, when it has no mind to be known; and we were forced to be guilty of an act both uncivil and cruel, without which we could never have resolved your question. We were obliged to unmask this modest one, and cut off its two fore-legs to get to the face; which being performed, though it makes our tender hearts, as well as yours, almost bleed to think of it, we immediately discovered what your ladyship desired, and found Nature had given it a strong proboscis, or trunk, as a gnat or muschetto, though much thicker and stouter, with which we may very well suppose it penetrates your fair hand, feasts itself on the nectar of your blood, and then, like a little faithless fugitive of a lover, skips away, almost invisibly, n.o.body knows whither."

We close our remarks on this well-known insect, with the following interesting particulars on the DURATION OF THE LIFE OF A FLEA; by Borrichius; from the Acts of Copenhagen.--"Pliny represents to us a Greek philosopher, whose chief occupation, for several years together, was to measure the s.p.a.ce skipped over by fleas. Without giving in to such ridiculous researches, I can relate an anecdote, which chance discovered to me in regard to this insect.

"Being sent for to attend a foreign lady, who was greatly afflicted with the gout, and having staid, by her desire, to dine with her, she bade me take notice of a flea on her hand. Surprised at such discourse, I looked at the hand, and saw indeed a plump and pampered flea sucking greedily, and kept fast to it by a little gold chain. The lady a.s.sured me, she had nursed and kept the little animal, at that time, full six years, with exceeding great care, having fed it twice every day with her blood; and when it had satisfied its appet.i.te, she put it up in a little box, lined with silk. In a month's time, being recovered from her illness, she set out from Copenhagen with her flea; but having returned in about a year after, I took an opportunity of waiting upon her, and, among other things, asked after her little insect. She answered me with great concern, that it died through the neglect of her waiting-woman. What I found remarkable in this story was, that the lady, being attacked by chronical pains in her limbs, had recourse in France to very powerful medicines during six weeks; and all this time the flea had not ceased to feed upon her blood, imbued with the vapours, and yet was not the worse for it."

THE LOUSE.--This insect has six feet, two eyes, and a sort of sting in the mouth; the feelers are as long as the thorax; and the belly is depressed and sublobated. It is an oviparous animal. They are not peculiar to man alone, but infest other animals, as quadrupeds and birds, and even fishes and vegetables; but these are of peculiar species on each animal, according to the particular nature of each, some of which are different from those which infest the human body. Nay, even insects are infested with vermin, which feed on and torment them. Several kinds of beetles are subject to lice, but particularly that kind called by way of eminence the lousy beetle. The lice on this are very numerous, and will not be shook off. The earwig is often infested with lice, just at the setting on of its head: these are white and shining, like mites, but they are much smaller; they are round-backed, flat-bellied, and have long legs, particularly the foremost pair. Snails of all kinds, but especially the large naked sorts, are very subject to lice; which are continually seen running about them, and devouring them. Numbers of little red lice, with a very small head, and in shape resembling a tortoise, are often seen about the legs of spiders, and they never leave the animal while he lives; but if he be killed, they almost instantly forsake him. A sort of whitish lice is found on humblebees; they are also found upon ants; and fishes are not less subject to them than other animals. Kircher tells us, that he found lice also on flies, and M. de la Hire has given a curious account of the creature which he found on the common fly. Having occasion to view a living fly with the microscope, he observed on its head, back, and shoulders, a great number of small animals crawling very nimbly about, and often climbing up the hairs which grow at the origin of the fly's legs. He with a fine needle took up one of these, and placed it before the microscope used to view the animalcules in fluids. It had eight legs, four on each side; these were not placed very distant from each other, but the four towards the head were separated by a small s.p.a.ce from the four towards the tail. The feet were of a particular structure, being composed of several fingers, as it were, and fitted for taking fast hold of any thing, but the two nearest the head were also more remarkable in this particular than those near the tail; the extremities of the legs for a little way above the feet were dry, and void of flesh, like the legs of birds, but above this part they appeared plump and fleshy. It had two small horns upon its head, formed of several hairs arranged closely together; and there were some other cl.u.s.ters of hairs by the side of these horns, but they had not the same figure; and towards the origin of the hind-legs there were two other such cl.u.s.ters of hairs, which took their origin at the middle of the back. The whole creature was of a bright yellowish red; the legs, and all the body, except a large spot in the centre, were perfectly transparent. In size, he computed it to be about 1/4000th part of the head of the fly; and he observes, that such kind of vermin are rarely found on flies.

The louse which infests the human body, makes a very curious appearance through a microscope. It has such a transparent sh.e.l.l or skin, that we are able to discover more of what pa.s.ses within its body, than in most other living creatures. It has naturally three divisions, the head, the breast, and the tail part. In the head appear two fine black eyes, with a horn that has five joints, and is surrounded with hairs standing before each eye; and from the end of the nose, or snout, there is a pointed projecting part, which serves as a sheath or case to a piercer, or sucker, which the creature thrusts into the skin to draw out the blood and humours which are its destined food; for it has no mouth that opens in the common way. This piercer, or sucker, is judged to be seven hundred times smaller than a hair, and is contained in another case within the first, and can be drawn in or thrust out at pleasure. The breast is very beautifully marked in the middle; the skin is transparent, and full of little pits; and from the under part of it proceed six legs, each having five joints, and their skin all the way resembling s.h.a.green, except at the ends, where it is smoother.

Each leg is terminated by two claws, which are hooked, and are of an unequal length and size. These it uses as we would a thumb and middle finger; and there are hairs between these claws, as well as all over the legs. On the back part of the tail there may be discovered some ring-like divisions, and a sort of marks which look like the strokes of a rod on the human skin; the belly looks like s.h.a.green, and towards the lower end it is very clear, and full of pits: at the extremity of the tail there are two semicircular parts, all covered over with hairs. When the louse moves its legs, the motion of the muscles, which all unite in an oblong dark spot in the middle of the breast, may be distinguished perfectly; and so may the motion of the muscles of the head, when it moves its horns. We may likewise see the various ramifications of the veins and arteries, which are white, with the pulse regularly beating in the arteries. The peristaltic motion of the intestines may be distinctly seen, from the stomach down to the a.n.u.s.

If one of these creatures, when hungry, be placed on the back of the hand, it will thrust its sucker into the skin, and the blood which it sucks may be seen pa.s.sing in a fine stream to the fore part of the head; where, falling into a roundish cavity, it pa.s.ses again in a fine stream to another circular receptacle in the middle of the head; from thence it runs through a small vessel to the breast, and then to a gut which reaches to the hinder part of the body, where, in a curve, it turns again a little upward in the breast and gut; the blood is moved without intermission with great force, especially in the former, where it occasions a surprising contraction.

In the upper part of the crooked ascending gut above-mentioned, the propelled blood stands still, and seems to undergo a separation, some of it becoming clear and waterish, while other black particles are pushed forward to the a.n.u.s. If a louse is placed on its back, two b.l.o.o.d.y darkish spots appear; the larger in the middle of the body, the smaller towards the tail; the motions of which are followed by the pulsation of the dark b.l.o.o.d.y spot, in or over which the white bladder seems to lie. This motion of the systole and diastole is best seen when the creature begins to grow weak; and on p.r.i.c.king the white bladder, which seems to be the heart, it instantly dies. The lower dark spot is supposed to be the excrement.

CHAP. XXIX.

CURIOSITIES RESPECTING INSECTS.--(_Continued._)

In the vast, and the minute, we see Th' unambiguous footsteps of a G.o.d, Who gives its l.u.s.tre to an insect's wing, And wheels his throne upon the rolling worlds.

_Cowper._

THE APHIS.

This is an insect which has engaged the attention of naturalists for various reasons: their generation is equivocal, and their instinctive economy differs, in some respects, from that of most other animals.

Linnaeus defines the generic character of the aphis thus: beak inflected, sheath of five articulations, with a single bristle; antennae setaceous, and longer than the thorax; either four erect wings, or none; feet formed for walking; posterior part of the abdomen usually furnished with two little horns. Geoffrey says, the aphides have two beaks, one of which is seated in the breast, the other in the head; this last extends to, and is laid upon, the base of the pectoral one, and serves, as that writer imagines, to convey to the head a part of that nourishment which the insect takes or sucks in by means of the pectoral beak.