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In the genus
usually on a moveable footstalk; their palpige- six legs; a head distinct from the body, and fur rous mandibles ; and their four antennæ, at least nished with two antennæ: they are all produced in the great majority. But the principal difference from eggs. Some undergo no metamorphosis, consists in the internal organisation and the others but a partial change, whilst the remainder fountains of vitality; for the crustacea have a pass through three stages of existence, after have double circulation, the fountain of which is a ing been hatched from the egg. heart in the middle of their thorax. They have Genus 1. Lepisma.-Gmelin, to whom the too a kind of gizzard and liver, at least the decu- admirers of Linné are indebted for one of the pods, and their respiration is by gills. Genuine best editions of the Systema Naturæ, defines insects terminate their existence after they have this genus as having four palpi, two of which are laid their eggs; but the crustacea live longer and setaceous, and two capitated; the lip membralay more than once.' See our articles Cancer, naceous, roundish, and emarginated ; antenna seMONOCULUS, ONISCUS, &c.
taceous; body imbricated with scales ; tuilending Although the adjective apterous is frequently in setaceous bristles ; legs six, and formed for applied more generally, no insect, it should be running. observed, can be included in the aptera of the This character combines the more essential Linnæan system, unless both sexes, when arrived parts of that of Fabricius. Lamarck proposes at their last state of being, are destitute of wings. further alteration; and Latreille, in whose arNoinsect of this order, except the common fiea, rangement they form the first family (lepisis supposed to undergo those successive changes menæ) of the order thysanoura, divides them into which are usual in most other insects. They are two distinct genera: lepisma and machilis. The almost entirely produced from the egg in their true lepisma, according to the new definition, perfect form, and cannot therefore be said to has the antenna inserted between the eyes, the have any larva. In the flea, however, the small body flat, and the tail ending in three equal worm which corresponds with the larva in other bristles. insects is clearly ascertained ; and if we may This genus walks and runs. place sufficient reliance on the evidence of certain machilis (which moves by skipping) the annaturalists, one or two more of the apterous ge- tennæ are seated under the eyes, the body connera exist for a short period in a state somewhat vex, and the middle bristle of the tail larger than analogous either to the larva or pupa. Leu- those at the sides. All the species, except the wenhoek observed that the mite was oviparous, L. saccharinum, are natives of Europe. In their laying very small oval whitish eggs, from which various states of growth they prey on decayed proceeded the young animals, resembling their wood, and moist or rotten substances; and are parents in all respects, except in the number of most commonly found in damp cellars, neglected their legs, these being only six in number, instead water-courses, and similar situations. of eight; and after they cast their skin, another L. saccharinum is scaly, silvery ; tail triple, pair of legs appear, a fact that evidently implies and originally a native of America, whence two periods of transformation, the first of which it has been introduced and naturalised in Europe. may be compared with that of larva. An ad- The antenna are as long as the body, which is vancement, or progressive increase in the number oblong and tapering; tail terminating in three of feet, is also well known to take place in species bristles, and two pairs of smaller ones beneath. both of the julus and scolopendra genera, after It secretes itself among books, old furniture, &c., they are produced from the egg state. The julus and runs, when disturbed, with great agility : it fabulosus, when first excluded, is furnished with is often found in sugar, and is thus supposed to three pairs of legs, which are situated at each side have found its way to Europe. In some places Dear the head; some days after about fourteen of this country it is common under stones ; its become visible, and the remainder, to the amount eight pairs of strings (one on each ventral segof 120 on each side, are gradually acquired af- ment of the abdomen) give it, says Kirby, a terwards. The same remark will apply to cer- wonderful power of leaping. The L. polypoda tain species, if not the whole of the scolopendra also, inhabiting among stones and rubbish on genus. Scorpions are produced by the female sandy sea-shores, possesses the faculty of leaping parent in a living state ; they are at first very in the same way to a prodigious height. Linné small and white, and become of a darker hue in only described another species, viz. L. terrestris: a few days; these, like the spiders cast their naked, tail triple. skin as they increase in size.
Gmelin notices the close affinity this species Our countryman, Dr. Leach, has contended bears to the podura tribe. It is entirely white that the first five of the Linnæan genera of this and cylindrical, with obtuse antenniæ half the order, are the only insects, properly speaking, length of the antenna. Fabricius adds L. vilto be found in it, i. e. the lepisma, podura, pe- losa, brown, with a triple, villous tail, a native diculus, pulex, and termes. The genera, acarus, of China; L. collaris, black, with a snowy band phalangium, aranea, and scorpio, he refers to his on the neck and end of the abdomen : tail triple class arachnoida. Genera cancer, monoculus, and villous, an inhabitant of the South American and oniscus, to the crustaccu ; scolopendra and Islands : and L. lineata, tail triple, body brown, julus, to myriapoda. We adopt the names of with two white fillets. Natives of Helvetia. these classes in our subdivision of this order, Genus 2. Podura.— Antenna filiform; palpi, but make no further alteration in the system of four, subclavate; lip bitid ; two eyes, composed Linné.
of eight facets; the body scaly; tail forked, bent Class 1.- INSECTA.
under the body and acting as a spring; from
which the genus has its name, podura or springDr. Leach defines this class as having uniform!. tailed: it has six legs, formed for running.
There are thirty species enumerated by Gmelin, same time entomologists, might easily mistake all comparatively small insects, found in general an acarus for a pediculus. Dr. Willan, in one in damp places, under stones, on the bark case of prurigo senilis, observed a small number of trees, &c. When disturbed they suddenly of small insects on the patient's skin and linen. spring to a small distance by the help of their They were quick in their motions, and so minute spring which is ordinarily doubled under the ab- that it required some attention to discover them. domen, and thrown out during the act of leaping. He took them at first for small pediculi; but They feed on the leaves of various plants. Their under a lens they appeared to him rather to be spring will even enable these animals to leap on a nondescript species of pulex ; yet the figure water. A minute species P. aquatica is sometimes he gives has not the slightest likeness to the found in boundless numbers on the water of latter genus, while it bears a striking resemblance hollows' and ruts. When disturbed they re to the former. It is not clear whether his semble in their leaping up the appearance of draughtsman meant to represent the insect with steel-filings or gunpowder suddenly thrown into six or eight legs : if it had only six, it was promotion. One species, sminthurus fuscus, Lat. bably a pediculus; but if it had eight, it would besides the caudal fork has another singular form a new genus between the acaride and the organ which seems designed to prevent its falling bexapod aptera. Dr. Bateman in reply to some off from a perpendicular surface. Between the queries put to him at my request, by our comends of the fork is an elevated cylinder or tube mon and lamented friend Dr. Reeve, relates that from which this little creature can protrude at he understood from Dr. Willan, in conversation, pleasure two long filiform transparent threads, that the insect in question jumped in its motion. covered with a slimy secretion.
This circumstance he regards as conclusive Genus 3. Pediculus (the louse). Antenna, against its being a pediculus; but such a conseleugth of the thorax; mouth with a retractile re- quence does not necessarily follow, since it not curved sucker without proboscis; no palpi; two seldom bappens that insects of the same genus eyes; the abdomen depressed ; six legs formed either have or have not this faculty; for instance, for running.
cyphon hemisphæricus, acarus scabiei, &c. Dr. The insects of this genus live by extracting Willan has quoted with approbation two cases animal juices. Some infest the bodies of quad- from Amatus Lusitanus, which he seems to think rupeds, others of birds, and some even of in- correctly described as phthiriasis. In one of sects themselves. It must, however, be observed, them, however, which terminated fatally, the cirthat many insects, infesting other animals, have cumstances seem rather hyperbolically statedsometimes been referred to the genus pediculus, I mean, where it is said that two black servants which, in reality, belong to those of acarus, mono- had no other employment than carrying baskets culus, &c. Gmelin enumerates sixty-six species. full of these insects to the sea !!
Leuwenhoeck has proved that the nits or Genus 4. Puler (the flea).- Antenne projecteggs of ordinary lice are not hatched until the ing, and moniliform; no palpi or maxillæ ; a long, eighth day after they are laid; and that they inflected proboscis, covered at the base with two never commence laying them until a month old: ovate laminæ; the sheath two-valved, five-jointed, he also ascertained that a single louse may and containing one bristle; lip rounded, and in eight weeks witness the birth of 5000 de- fringed with reflected prickles; eyes two; abdoscendants. A pedicular disease (phthiriasis), is men compressed; legs six, formed for leaps. said to have carried off Antiochus Epiphanes, This genus is oviparous, and the common Sylla, two of the Herods, and the emperor species, P. irritans, deposits its nits on animals Maximian. Mr. Kirby, however, disputes that afford them a proper food; these, being this, because, as he contends, this genus is round and smooth, usually slip straight down, never subcutaneous, for which he quotes the unless detained by folds, or other inequalities of authority of Mead and Willan. If these ob- clothes, hairs, &c. They lay their eggs, not all servations be allowed their due weight, he con at once, but ten or twelve in a day for several tinues, it will follow, that a disease produced by days successively, which eggs will be afterwards animals residing under the cuticle cannot be a found to hatch 'successively in the same order, true phthiriasis, and therefore the death of the These eggs first produce a white worm, of a poet Alcman, and of Pherecydes Syrius the phi- shining pearl color, which feeds on the scurfy losopher, mentioned by Aristotle, must have been substance of the cuticle, the downy matter occasioned by some other kind of insect.' For gathered in the piles of clothes, or like substances. speaking of the lice to which he attributes these In a fortnight they come to a tolerable size, and catastrophes, he says that they are produced in the are very lively and active: if at any time disflesh in small pustule-like tumors, which have no turbed, they roll themselves into a kind of ball. pus and from which when punctured they issue. Soon after they creep, after the manner of silkFor the same reason, the disorder which Dr. He- worms, with a very swift motion. When arrived berden has described in his Commentaries, from at full size, they hide themselves as much as posthe communications of Sir E. Wilmot, under the sible, and spin a silken thread out of their mouth, name of morbus pedicularıs, must also be a dif- wherewith they form a small round bag, or case, ferent disease, since, with Aristotle, he likewise white within as paper, but without always dirty. represents the insects as inhabiting tumors, from Here, after a fortnight's rest, the animalcule which they may be extracted when opened by a bursts out, transformed into a perfect tea; learneedle. He says, indeed, that in every respecting its exuviæ in the bag. While it remains in they resemble the common lice, except in being the bag it is milk-white, till the second day bewhiter ; but medical men, who were not at the fore its eruption; when it becomes colored, grows
hard, and gets strength; so that, upon its first its piercer, except at the time of feeding, but delivery, it springs nimbly away.—Phil. Trans. keeps it folded inwards; and the best way of No. 249.
seeing it is by cutting off first the head, and then The flea may easily be dissected in a drop of the fore-legs, when it is usually thrust out in water, and by this means the stomach and bowels, convulsions. with their peristaltic motion, may be discovered • Dear Miss,' said a lively old lady to a friend very plainly, as also their testes and penis, with of mine (says Mr. Kirby), who had the misforthe veins and arteries, though minute beyond all tune to be confined to her bed by a broken limb, conception. Mr. Leuwenhoeck affirms also, that and was complaining that the fleas tormented her, he has seen innumerable animalcules, shaped dont you like fleas? Well, I think they are the like serpents, in the semen masculinum of a fea. prettiest little merry things in the world. I never Baker's Micros. p. 191, and 194. On dissection, saw a dull flea in all my life.' The celebrated this animal is far from being a disagreeable ob- Willoughby kept a favorite flea; which used at ject. It is covered with curious black shelly stated times to be admitted to suck the palm of scales or plates, admirably jointed, and folded his hand; and enjoyed this privilege for three one over another in such a manner as to comply months, when the cold killed it. And Dr. Townwith all the nimble motions of the creature. son, from the encomium which he bestows upon They are all also curiously polished, and set round these vigilant little vaulters, as supplying the the edges with short spikes in a very regular man- place of an alarum and driving us from the bed ner. Its neck is finely arched ; the head also is of sloth, would seem to have regarded them with very extraordinary; for from the snout part of it feelings much more complacent than those of there proceed the two fore-legs, and between Dr. Clarke and his friends, when their hopes of these is placed the piercer or sucker, with which passing one night free from the attacks of verit penetrates the skin to obtain its nutriment. min,' were changed into despair by the informaIts eyes are large and handsome, and it has two tion of the laughing sheik, that the king of the short horns or feelers. It has four other legs fleas held his court at Tiberias:' or than those of joined all at the breast. These, when it leaps, M. M. Lewis and Clarke, who found them fold short one within another, and, then exerting more tormenting than all the other plagues of the their spring at the same instant, they carry the Missouri country, where they sometimes compel creature to a surprising distance. Aristophanes even the natives to shift their quarters. ridicules Socrates for having measured the leap P. penetrans, the chigoe of South America, has of a flea (Nubes, act i. sc. 2). Scientific men a proboscis as long as the body. The body is of a have however persevered in ascertaining the reddish-brown color; abdomen of the female, wonderful power and strength of this little crea- when gravid, orbicular, and swollen to nearly a ture, which will leap two hundred times the length hundred times its usual size. It is very troubleof its own body, unaided, as we see, by wings. sone in the sugar colonies, penetrating into the
Mr. Kirby (vol. iv. p. 188) furnishes us skin of the inhabitants, particularly of the negroes, with the following anecdotes of the strength of where it lodges its eggs, and causes malignant, this species.—Mouffet relates that an ingenious and often fatal, ulcers. English mechanic, named Mark, made a golden All disputes,' observe Messrs. Kirby and chain of the length of a finger, with a lock and Spence, concerning the genus of this insect, key, which was dragged by a flea ;-he had heard would have been settled long before Swartz's of another that was harnessed to a golden chariot, time (who first gave a satisfactory description and which it drew with the greatest ease. Another figure of it, proving it to be a puler, as has been English workman made an ivory coach with observed above), had success attended the
pa. six horses, a coachman on the seat with a dog triotic attempt of the Capuchin friar, recorded between his legs, a postilion, four persons in the by Walton in his History of St. Domingo, who coach, and four lacqueys behind- which also was brought away with him from that island a colony dragged by a single flea. At such a spectacle one of these animals, which he permitted to establish would hardly know which most to admire, the themselves in one of his feet; but unfortunately strength and agility of the insect, or the patience for himself, and for science, the foot entrusted of the workman. "Latreille mentions a flea, of a with the precious deposit mortified, was obliged moderate size, dragging a silver cannon on wheels, to be amputated, and with all its inhabitants that was twenty-four times its own weight, which, committed to the waves.' According to Ulloa, being charged with powder, was fired without the and his opinion is confirmed by Jussieu, there flea appearing alarmed.
are two South American species of this misThe legs have several joints, are very hairy, and chievous insect. It is described as generally atterminate in two long and hooked sharp claws. tacking the feet and legs, getting without being The flea lodges its piercer or sucker between its felt, between the skin and the flesh, usually under fore legs, and includes a couple of darts or lancets, the nails of the toes, where it nidificates and lays which, after the piercer has made an entrance, its eggs; and, if timely attention be not paid to are thrust farther into the flesh, to make the it, which, as it occasions no other uneasiness blood flow from the adjacent parts, and occasion than itching, (the sensation at first I am assured that red round spot, with a hole in the centre of is rather pleasing than otherwise), is sometimes it, vulgarly called a flea-bite This piercer, its neglected, it multiplies to such a degree, as to be sheath opening sideways, and the two lancets attended by the most fatal consequences, often, within it, are very difficult to be seen, unless the as in the above instance, rendering amputation two fore-legs, between which they are hid, be cut necessary, and sometimes causing death. The off close to the head : for the flea rarely puts out female slaves in the West Indies are frequently