Volume 1 — LETTER XXX. (continued 2)

Hemiptera. The larvæ of this order, which in general resemble the perfect insect, except that they have no wings, seem most commonly to belong to the Anopluriform type[402]; but the Aphides, Chermes, and Thrips may, I think, be regarded as more analogous to the genera Podura and Sminthurus in the Thysanura[403]. I have some suspicion that the Nepidæ, Naucoris, and the remipedes, Notonecta, Sigara, &c. may find their prototypes amongst the Crustacea; but my confined knowledge of the latter does not enable me to point to any individual genera or tribes that they may be presumed to represent.

Neuroptera. As the kinds of larvæ of the different tribes composing this order, as it now stands, are very various, it is to be expected that the analogical forms they represent are equally so. The Libellulina MacLeay (whose metamorphosis that gentleman has denominated subsemicomplete, a term warranted by their losing in their perfect state the mask before described[404]) in their oral organs, particularly by their galeate maxilla and distinct ligula[405], have some relation to the Orthoptera, the prototypes of whose larvæ we have found amongst the Crustacea: probably, therefore, those of the tribe in question lurk in that class; a suspicion that receives strong confirmation from the larva of Agrion[406], which in its tapering body and anal natatorious laminæ represents a shrimp. The larvæ of that very peculiar and distinct tribe, the Ephemerina, appear to be intermediate between the Stomapodiform and Thysanuriform types. Their natatory respiratory abdominal laminæ seem copied from the former, and their anal diverging setæ from the latter[407]. The Myrmeleonina, as well in their general form as in their motions and habits, present a most singular analogy with the tribe of spiders, as does also in some respect that of Cicindela. With regard to Panorpa, which Mr. MacLeay remarks is related to Myrmeleon[408], and is a most ferocious insect[409], as its larva has not yet been discovered, nothing certain respecting its analogical form can be asserted; but should it, like the male fly, represent the scorpion, both orders of Arachnida will have their representatives in the class we are considering. The Corydalina, as far as the larva of Hemerobius instructs us, is Chilopodiform, but with a tendency to the Araneidiform Type. The Ametabola also furnish the prototype of the next tribe, the Termitina, which, as is evident both from Psocus and Termes, are perfectly Anopluriform. The Sialina, or Plicipennes of Latreille, excluding Trichoptera Kirby, appear to me to be intermediate between the Chilopodiform and Stomapodiform Types, and not without some relation to the Thysanuriform. Their pediform, jointed, respiratory abdominal appendages, their head and falcate mandibles, seem copied from the first tribe. The same appendages considered as organs of respiration, and their taper forks, are moulded upon the plan of the Stomapodiform Crustacea, and the long seta which terminates the abdomen is upon the Thysanuriform plan[410].

Trichoptera. The larvæ of this order appear also to be constructed upon a double plan. The respiratory threads observable in both the upper and under sides of the abdomen connect it with the Stomapoda, and its cylindrical elongate body with Chilognathiform types in the Lepidoptera[411].

Lepidoptera. The great majority of larvæ in this order are Chilognathiform, but there are exceptions to this remark. Those of the Geometræ recede from this type, both in their motions and the distance and number of their legs. In both these respects they represent the Læmodipoda in the Crustacea[412]. Other caterpillars are Onisciform; and a third sort seem to leave the Annulose type, and imitate that of the Mollusca, and one is figured by Madame Merian[413] which appears to tend even to the Chilopodiform type.

Hymenoptera. In this order the larvæ of the saw-flies, Tenthredo L., are in general Chilognathiform, though some are Onisciform, others Limaciform, and those of Lyda F. (Cephaleia Jur.) and Sirex[414] have a Vermiform tendency, and are a stepping-stone to those of the rest of the order, which are all Vermiform and apods.

Diptera. The majority of this order may be set down as Vermiform, though it is not improbable that some of them bear an analogy to animals that appear far removed from the Annulosa. Thus, the larva of Stratyomis Chameleon seems to exhibit no small resemblance to some of the Polypi vaginati in the Acrita subkingdom of Mr. W. MacLeay[415]. That of Culex and some others is constructed on a quite different type from the rest, and seems to possess some analogy to the Branchiopod Crustacea.

Though some of these analogies are more striking than others, yet in almost all that I have stated there is that kind of resemblance that could not be the result of what is called mere chance; and Mr. MacLeay, by first pointing out this plan of the All-wise Creator, and by laying down the doctrine of analogies in general, as distinguished from affinities in the animal kingdom, has furnished the believer with a new argument against those attacks of the infidel, that would render null those proofs of the wisdom and goodness of the Author of nature with which the animal and vegetable creation furnish us; by affirming most absurdly, and under the most stultifying blindness of mind, that the creatures were in a manner their own creators, their wants under local circumstances stimulating them to efforts that in a long course of years produced all the different forms and organizations that are now to be found in our globe. The affinities and close connexion of beings with each other, so that the ascent from low to high is usually by the most gentle gradations, is the circumstance on which they build this strange and impious theory. But the fact, that certain animals of one tribe were created with a view to certain animals of another, so as to present a striking aspect of correspondence, parallel almost with that of type and antitype, without any real affinity or approximation;—this triumphantly proves a Power above and without them, who has associated them not only in a complex chain of affinities, but has caused them to represent and figure each other, even when evidently far removed, so as to give a mutual correspondence and harmony to the whole, which could be produced only by a Being infinite in power and wisdom, who made all things after a general preconceived plan and system.

iv. We are now to consider the clothing with which larvæ are furnished. Many are quite naked, and smooth or rough only with granular elevations or tubercles orderly arranged; but a very considerable number, especially of the Lepidoptera order, are clothed with hair or bristles of different kinds, in greater or less abundance, and arranged in different modes; and a proportion still smaller have their skin beset with spines or a mixture of spines and hairs. Lyonnet found that the hairs of the caterpillar of the great goat-moth (Cossus ligniperda) were hollow, though not to the apex: probably this is the case with those of other larvæ, as well as with their spines. In this instance they were set, he observes, in a corneous ring, or very short cylinder, elevated a little above the skin. The hair passes through this ring, and appears to be rooted in a soft integument, which clothes the skin within, and upon which the nerves form a reticular tissue, some of which he thinks he has even seen enter the root of the hairs, which perhaps are organs of touch[416].

Of the pilose larvæ, some, like most of those of the smaller moths (Geometra, Tortrix, Pyralis, &c.), have merely a few scattered short hairs, scarcely perceptible except through a lens: others (Odenesis potatoria, Lasiocampa Rubi) are covered with down more or less thick: in others (Eriogaster lanestris, Lasiocampa Neustria) the hair is slenderer, and more like wool; the body of two species which I purchased from the collection of Mr. Francillon is covered with woolly hairs, so long as to give them the appearance of a shock-dog; and Madam Merian has figured a similar one, which she could not bring to the perfect state[417]. The hairs of many Bombycidæ, known commonly by the name of hairy caterpillars, as Arctia erminea, &c. are stiffer, resembling bristles; sometimes, as in Arctia chrysorhea, mixed with shorter ones. The hairs either spring immediately from the skin (Noctua Aceris, leporina), or, as is more general, proceed only from certain tubercular elevations, usually subhemispherical, but sometimes conical; of which a number varying from four to twelve are found on each segment of different species. They seem to issue from these tubercles, as little diverging streams from the rose of a watering-pot. In both cases, they form a coating usually so dense as to conceal the body, but sometimes more thinly set, and admitting the skin to be seen more or less between them. In a caterpillar of the beautiful Arctia ocularia, the hairs are set upon tubercles alternately nearer the anterior and posterior margin of each segment, so as to form a dense band, the rest being naked; and in the lovely green and black one of Saturnia Pavonia, each tubercle bears but six hairs, diverging like a star, the central one being the longest and capitate, so that the chief part of the body appears naked. This diverging position of the hairs is most common in the thick-clothed larvæ also, but many have them placed differently: thus, in those of Callimorpha Caja and Arctia villica[418] they are all directed towards the tail, like the quills of a porcupine: in some others the anterior ones point towards the head: in that of Eriogaster Quercus half of the tuft of hairs of each tubercle is directed downwards, the other half upwards: in that of Arctia Salicis all the hairs point downwards, so that the belly is thickly covered, while the back is bare. Another variation is, that the hairs of half the tubercle are sometimes very long, while those of the other half are very short, and even of a different colour[419]. In the larva of Tussuck moths (Laria pudibunda, fascelina, &c.) the hairs are collected into tufts of a singular appearance, those on the intermediate segments of the back being quite level at the top, so as to resemble so many brushes; while those on the first and last segments are longer, and composed of feathered hairs converging to a point at their extremity, like a common camel-hair-pencil[420]. This last mode of arrangement prevails also in the larva of Noctua Aceris; but in this the pencils are shorter, exactly wedge-shaped, and distinguished by another particularity, that of springing directly from the skin, and not from a tubercle. This is also the case with the large caterpillars of Odenesis potatoria, which has a double row of short bundles of black hairs on the back, intermixed with larger ones: at each end of the body is a pencil of converging hairs, and the sides are spotted with bundles of white ones, which with longer tawny ones are bent downwards, so as to cover the sides of the creature[421]. Some have the anterior aigrettes disposed like the arms of a cross, of which the body of the caterpillar is the stem[422]. But not only is there considerable variety in the general arrangement of the hairs that clothe our little larvæ, the hairs themselves differ much in their kind and structure, of which I will now, before I proceed to consider spines, give you some account. Several of them are feathered like the plumes of a bird: this is the case with those of Morpho Idomeneus, on each segment of the body of which are three blue tubercles, like so many little turquois beads, from each of which proceeds a long black plume[423]. Other hairs terminate in a club; those of the larva of Noctua Alni, a specimen of which I possess taken in England, are flat and incrassated at the apex, something like the antennæ of some Sphingidæ. Mad. Merian has figured the caterpillar of another moth which feeds upon the Papaw-tree (Carica Papaya) with similar hairs[424]. But the most remarkable larva for the shape of its hairs is that of Anthrenus Musæorum, the little pest of our cabinets, which I noticed in a former letter[425]. All the hairs of its body are rough with minute points; but those of six diverging long tufts or aigrettes, laid obliquely on the anal extremity of the body, which the animal when alarmed erects as a porcupine does its quills, are of a most singular structure: every hair is composed of a series of little conical pieces, placed end to end, the point of which is directed towards the origin of each hair, which is terminated at the other extremity by a long and large conical mass, resembling somewhat the head of a pike[426].

Besides the one lately mentioned, other caterpillars are rendered striking by the brilliant colour of the tubercles from which their hairs emerge. A remarkable instance of this is the thick large caterpillar of a Bombyx, which feeds upon the Psidium pyriferum, or white Guava, figured by Madame Merian. This caterpillar, which is white, with transverse black stripes, and which has two singular long converging curved bunches of hairs near the tail, is splendidly adorned on each side with fifty red tubercles, shining like coral, from which proceed six or seven long diverging hairs. Leeuwenhoeck took these tubercles for eyes[427]. Another figured by the same lady, who mistakes it, with her usual inaccuracy, for the larva of a Lygæus F., and which seems by her description to be between the onisciform and limaciform types, has the apparently fleshy mamillæ that project from its sides and back crowned with little hairy red globes, which give the animal a most singular and unique appearance[428]. Having thus described some of the principal modes in which the All-wise Creator has decked and defended these creatures with hairs, I shall next give you a short account of the spines with which he has armed others. The spinous larvæ are principally lepidopterous, and more particularly conspicuous in some tribes of the genus Papilio L., though some saw-flies and Diptera are also distinguished by them. Vanessa Io[429], Atalanta and Urtica, Argynnis Paphia, Urania Leilus, and many other Butterflies, &c. are clothed with long sharp points, which claim the denomination of spines, rather than that of hairs or bristles; being horny and hard, and so stiff at the point as readily to pierce the skin. Those of the last-mentioned species, Madame Merian says, are as stiff as iron-wire[430]. They are sometimes entirely simple, and look like spikes rather than spines, as in the caterpillar of Nymphalis Amphinome and Morpho Menelaus[431]; but ordinarily they are beset with hairs, or more commonly with shorter spines, which often give them the appearance of plumes, as in Urania Leilus just mentioned: sometimes these lateral spines are so long as to have the appearance of a branch of a tree; this is strikingly the case with a small caterpillar which Captain Hancock brought from Brazil; its body is so thickly planted with spines of this description, that it absolutely wears the appearance of a forest or thicket in miniature. A singular circumstance attends the spines of this species: in many cases a smaller and very slender hair-like spine issues from them, resembling a sting; and this accounts for an observation of Abbott's, that many American caterpillars sting like a nettle, raising little white blisters on the skin when accidentally or slightly touched[432]. Lewin has described the caterpillar of a moth found in New Holland, which he names Bombyx vulnerans, that, like these Americans, has also the power of wounding, but in a different way. It darts out, he says, when alarmed by the approach of any thing, from as many knobs or protuberances in its back eight bunches of little stings, with which it inflicts a very painful and venomous wound[433]. The caterpillar of Papilio Protesilaus F., if Madame Merian's account and figure of it are correct, has its body armed with hairy spines, the extreme point of which is surmounted by a star-shaped appendage[434]. Those of a few saw-flies (Tenthredo Pruni L.), and another figured by Reaumur[435], are covered with a little forest of spines without lateral branches, but divided into a fork at the apex. Some spines are merely rough, with very short points, as those round the head, which give so terrific an appearance to the caterpillar of the Bombyx regalis, of some proceedings of which I gave you an account in one of my former letters[436].

I must now say something upon the arrangement of these spines. Though in a few instances so thickly set as entirely to conceal the body of the animal, as in the case of the Brazil one lately mentioned, yet generally speaking, even when they are most numerous, they permit the skin to be distinctly seen. Their arrangement is various, though always orderly: in the majority they are planted singly, but in some caterpillars in bundles. In that of Saturnia Io, on each segment there are six bundles of longish, quill-shaped, sharp, slender, diverging spines, which also appear to sheath aculei. Madame Merian has figured this larva, or one very near it, as the grub of a Euglossa[437], with which, though she affirms she traced it to the fly, it can have no connection. With regard to number, some larvæ have only four spines on each segment; others five, others again six, and others seven, or even eight: they are planted on the sides and back only, never on the belly. They are often more numerous on the intermediate than on the anterior and posterior segments; but sometimes the reverse of this takes place; in that of Attacus Erythrinæ only the head and tail are armed with spines, the rest of the body being without any[438]; and in that of Morpho Teucer there is only a single spine on the four intermediate segments[439]. They are usually all nearly of equal length; but in some cases those of the head and tail are much longer than the rest, and remarkably so in the caterpillar of Urania Leilus, also beautifully plumose, and gracefully waved[440]. Those in the second and third segments are much longer than any of the rest in that of Bombyx regalis; which circumstance gives it the terrific appearance lately alluded to. In the family to which Argynnis Paphia belongs, the larva is adorned with two on the back of the first segment twice as long as the rest, and resembling at first sight two antennæ.

The spines, as well as the hairs of the new skin, are concealed under the old one, and not incased in its spines; but Bonnet ascertained, that if cut off very closely, the larva sometimes died in consequence, whilst no such result followed a similar operation on hairy larvæ. We learn from Reaumur[441], that some spinous larvæ of saw-flies (Tenthredo L.) lose their spines at the last change of their skin; and from Madame Merian, that that of Attacus Erythrinæ before mentioned loses also at the same period the six tremendous black spikes that arm its black and yellow larvæ. The grubs of ants that are destined to pass the winter in the larva state are hairy, but are not so in summer[442]. The spines found in the grubs of some gad-flies (Œstrus L.) are of a different kind from those above described, being very minute triangular flat plates, arranged in different and contrary directions[443], and serving the insect merely to change its place and fix itself[444].

Two other kinds of clothing, if so they may be called, neither coming under the description of hairs nor spines, are found in some other larvæ, not only amongst the Lepidoptera, but also in some of the other orders. Nymphalis Populi and others of the same family have larvæ furnished on the back of each segment with cylindricoconical processes of a fleshy substance, obtuse at the apex and surrounded with capitate hairs. In that of N. Sybilla, which has on each segment two fleshy protuberances, they are bifurcate or trifurcate, and also encircled at the base with a hairy tuft[445]. Others, as those of Melitæa Artemis, Cynthia, &c. have each segment beset on the back with from seven to nine fleshy, pubescent, wedge-shaped protuberances; two larger ones projecting over the head. Under this head, too, may be noticed, the glutinous secretion which clothes the grub of Cionus Scrophulariæ, a little weevil; and of Tenthredo Cerasi L. a saw-fly, and that waxy or powdery substance which transpires through the skin of the larvæ of several Aphides, Chermes, Cocci, Hylotoma ovata F., &c. The Aphis, whose extensive ravages of our apple-trees (A. lanata) were before described to you[446], is covered and quite concealed by this kind of substance, so that the crevices in the bark which they inhabit look as if they were filled, not with animals, but with cotton. The insect, also, that forms those curious galls produced upon the spruce fir, and which imitate its cones (Chermes Abietis L., Aphis De Geer) secretes a similar substance. In these and other cases of the same kind, this matter seems to be, if I may so speak, wire-drawn through numerous pores in certain oval plates in the skin, more depressed than the rest of the back, arranged regularly upon the segments, and exhibiting minute tuberosities. When young, these animals have more of this secretion than when more advanced: it then hangs from their anal extremity in locks[447].

But the insects most remarkable for a covering of this nature are those Coccidæ of which Bosc has made a genus under the name of Dorthesia. De Geer is the first author that notices them, and has given a description and figure of one species under the name of Coccus floccosus[448]. It was discovered by Modeer upon some sere fir-leaves in a thick bed of moss. Panzer has figured a second found upon Geranium sanguineum, which from the figure appears distinct from De Geer's, under the name of Coccus dubius[449]. Fabricius regards this as synonymous with the Dorthesia characias of Bosc, inhabiting Euphorbia characias in South Europe[450]. Olivier found a species upon the bramble[451]. I once took one, which appears to differ in some respects from the preceding species, upon Melampyrum cristatum, and our indefatigable friend Mr. Sheppard has sent me another, on what plant found I do not remember, which does not agree with any that I have mentioned. The body of the animals of this genus is covered by a number of cottony or waxy laminæ which partly cover each other, and are arranged usually in a triple series: in De Geer's figure the series appears quadruple, the lateral ones being placed obliquely. The anterior one in my specimen covered the head, and they are all canaliculate. Above the anus are four diverging ones: the whole are of the most dazzling whiteness. When these laminæ are removed, the body appears divided into segments.

With respect to those larvæ which imitate slugs by the viscid covering that besmears them and issues from their pores, we learn from Professor Peck that this exudation takes place as soon as they are hatched; that the animal retains its humidity although exposed to the fiercest heat of the sun, and that at the last moult the skin becomes quite clean, and free from all viscidity[452]. It is probable that the other limaciform larvæ are similarly circumstanced. Madame Merian has figured an onisciform one, the legs of which, she says, are covered with a viscid skin: this produced a Noctua. Those of Papilio Anchises also are slimy, and adhere to each other[453].

v. Amongst other qualities which attach to larvæ, we must not omit to say something concerning their Colour. For though those which live in darkness, in the earth, in wood, in fruits, &c. are, with few exceptions[454], of an uniform whitish colour, yet such as are exposed to the influence of the light are usually adorned with a vast variety of tints, sometimes the most vivid that can be imagined. That the white colour of the former may be attributed to the absence of light is proved by an experiment of M. Dorthes, who having forced some to live under glasses, exposed to the light, found that they gradually became brown[455]. To attempt any classification of coloured larvæ would be in vain, since they are tinged with almost every possible shade that can be conceived, of many of which it would be difficult to find examples elsewhere; and infinitely diversified as to the arrangement and figure of their multiform markings and spots. A few general remarks, therefore, are all that you will expect on this head. Many are of one uniform colour; while a variety of tints, very different, and very vivid and distinct, ornament others. Sometimes they are distributed in longitudinal rays or bands, at others in transverse ones. Sometimes they are waved or spotted, regularly or irregularly; at others they are sprinkled in dots, or minute streaks, in every possible way. Various larvæ are of the colour of the plant on which they feed, whence they are with difficulty discovered by their enemies. Thus, a large proportion of Lepidoptera are green of different shades, sometimes beautifully contrasted with black bands; a circumstance which renders the caterpillars of two of our finest insects of this order as lovely as the fly: I mean that of Papilio Machaon and Saturnia Pavonia. Very frequently the larvæ of quite different species resemble each other so exactly, in colour as well as shape, as scarcely to be distinguishable: this sometimes takes place even where they belong to different genera, as in those of Bombyx versicolor a moth, and Smerinthus Populi a hawk-moth. And it sometimes happens, very fortunately for distinguishing allied species, that where the perfect insects very nearly resemble each other, the larvæ are altogether dissimilar. Thus, the female of Pieris Rapæ is so much like the same sex of Pieris Brassicæ, that it might be taken for a variety of it, did not the green caterpillar of the one, and the spotted one of the other, evince the complete distinction of these butterflies. Noctua Lactuca, N. umbratica, and several other species of the same tribe, which includes N. Absinthii, Verbasci, Chamomillæ, Abrotani, are so extremely alike, that the most practised eye can scarcely discover a shade of difference between them, though their larvæ in colour and markings are constantly distinct[456]. The markings of species belonging to the same family are usually different; but in some cases the latter may be prejudged from the former. The larvæ of many of the genus Sphinx L., for example, have their sides marked by oblique streaks running from the back in a direction towards the head; and by this last circumstance they are distinguished from those of Bombyx versicolor, Attacus Tau, and others of the same tribe, which have also lateral oblique striæ, but running from the back towards the tail[457]. The colours of individual larvæ of the same species are usually alike, but in Sphinx Elpenor and some others they vary exceedingly. Many, like those of Lasiocampa Rubi, Saturnia minor, &c., are of one colour when first disclosed, and assume others quite different in riper age. Just previously to changing their skin, the tints of most larvæ become as dull and obscure, as they are fresh and vivid when the change has fully taken place; and in some instances the new skin is quite differently marked from the old one. This is remarkably the case with the last skin of some of the larvæ of the genus Tenthredo L., which is entirely different from all the preceding ones. As people when they advance far in years usually become more simple in their dress than when they were young, so the larvæ in question change an agreeably variegated skin for one of a uniform and less brilliant colour[458]. Madame Merian has observed with respect to Attacus Erythrinæ, that its caterpillar is at first yellowish, with nine black striæ on each side: when arrived at one third of its size, they become orange; the striæ are obliterated, and in their place a round black spot appears on each of the eight intermediate segments[459]. Mr. Sheppard has remarked to me, that the skin of that of Sphinx Ligustri, after being under ground four days, was changed from a vivid green to a dull red. Very rarely, however, it becomes of a more brilliant hue just before entering the pupa state: thus, that of another hawk-moth (Smerinthus Tiliæ) changes to a bright violet; and the yellow hairs of that of Laria pudibunda then become of a lovely rose colour. And here I may observe, that the hairs and spines also, of larvæ, vary greatly in colour. They are to be met with brown, black, red, yellow, violet, white, &c. De Geer found, that in the larva of Cimbex nitens the two sides of the body were of a different colour, the left being of a deep green, whilst the right side and the rest of the body were paler[460]; but as he saw only a single individual, this was probably an accidental circumstance. Though the caterpillars, as I lately said, of one of the most beautiful butterflies and moths that inhabit Britain contend with the perfect insect in loveliness, yet in general no judgement can be formed of the beauty of the future fly from the colour of the larva; and the young Aurelian must not flatter himself always with the hope, because the caterpillar excites admiration by its colours and their arrangement, that the butterfly or moth it is to produce will do the same; nor ought he to despise and overlook a sombre or plain-coloured individual of the former, under the idea that it will produce one equally plain of the latter, for it often happens that the splendid caterpillar gives a plain butterfly or moth, and vice versâ. De Geer, however, gives us two instances of conformity between the colours of the caterpillar and those of the future moth; the one is that of the common currant-moth (Phalæna G. grossulariata L.), the caterpillar of which is white, ornamented with several black spots varying in size. At the two extremities it is yellowish, with a longitudinal ray of the same colour on each side, the head and legs being black. These colours are all to be found in the fly, the ground of its wings being white ornamented with many black spots of different sizes. Its upper wings are traversed by a yellowish band; and towards their base is a spot of the same colour. Its body is yellowish, with black spots; but the head and legs are black[461]. The other is that of a green caterpillar, which gives a green moth, figured by Reaumur (Pyralis prasinaria Fab.)[462]. Sometimes, also, the sex of the future perfect insect may be predicted from the colour it exhibits in its first state: thus, the brown caterpillars of Noctua Pronuba produce males, and the green ones females[463]. The sexes, also, of N. exoleta and Persicariæ differ in that state.

vi. To the full account of the Food of insects given in a former letter[464], which had reference chiefly to their larva state, it is only necessary in this place to add a few particulars not there noticed. Many larvæ when first excluded, as those of Pieris Cratægi, &c. devour the shells of the eggs from which they have proceeded[465]; and others (Cerura Vinula, Sphinx Euphorbiæ, Noctua Verbasci), though their usual food is of a vegetable nature, eat with great apparent satisfaction the skins which they cast from time to time, not leaving even the horny legs. This strange repast seems even a stimulating dainty, which speedily restores them to vigour, after the painful operation by which they are supplied with it. Under this head it will not be out of place to mention, that some larvæ of insects, which feed only on the juices of animals, or the nectar and ambrosia of flowers, have no anal passage, and of course no feces. This is said to be the case with the grubs of bees, wasps, the larvæ of Myrmeleon, &c.[466]

vii. You will require no stimulus to induce you to attend to the subject I am next going to enter upon,—the Moulting, namely, of Larvæ; or their changes of skin. This, indeed, is a subject so replete with interest, and which so fully displays the power, wisdom, and goodness of the Creator, affording at the same time such large occasion for nice investigation, that a pious and inquisitive mind like yours cannot but be taken with it. In the higher orders of animals, though the hairs of quadrupeds and the feathers of birds are in many cases annually renewed, the change, or scaling and increment of the skin, is gradual and imperceptible; no simultaneous rejection of it, in which it is stripped off by the animal itself like a worn shirt, being observable, till you descend in the scale to the Serpent tribe[467], which at certain periods disengage themselves from their old integument, and start forth with that new and deadly beauty so finely described by the Mantuan bard:—

In these the new skin, I imagine, is formed under the old from the rete mucosum; but in insects, as I formerly stated[469], since the time of Swammerdam it has generally been believed by entomologists, that the larva includes a series of cases or envelopes, one within the other, containing in the centre the germe of the future perfect insect, whose development and final exclusion take place only when these cases have been successively cast off. This hypothesis, as was explained to you on a former occasion[470], has been controverted by a late writer, Dr. Herold; who affirms that the skins of caterpillars are also successively produced out of the rete mucosum. I have however, I hope, satisfied you that the old system is most consonant to nature and probability: but as we are now to enter at large upon the Moults of insects, it will not be without use if I add a few additional reasons which seem to me still further to prove the correctness of Swammerdam's system, as far as it relates to that subject. With regard to the mere formation of the skin from the rete mucosum, were this the whole question few would hesitate to adopt the sentiments of M. Herold; but when we come to consider further—that the number of moults of individuals of the same species is always the same, and that it varies in different species, and takes place at certain periods,—we begin to suspect that something more than the mere formation of a new skin upon an old one being cast is to be accounted for; and that the law which prescribes its own definite number of skins to each species, must begin to act in the primordial formation of the larva. Again, the hairs observable in the higher animals do not take their origin from the epidermis solely, but are planted below it in the rete mucosum, or deeper[471]; so that the change of skin does not affect them; but in the larvæ of insects they are a continuation of that integument, since, when the moult takes place, they always remain on the rejected skin[472]: this is the case, also, even with spines. If you shave a caterpillar ready to change its skin, either partially or generally, you will find that the parts in the new skin that correspond with those that are denuded, are equally hairy with those that were not[473]; and if you pay attention to the new-clad animal, you will find further, that the hairs never grow after a moult. From hence it follows, that the hairs have their place and take their whole growth between the new skin and the old[474]. Whether the spines, simple or compound, lately described to you, that arm some larvæ are similarly circumstanced, seems not as yet to have been ascertained; but as the spinous ones of certain Tenthredines L. and Lepidoptera at their last moult have no spines, the presumption is, that, whether incased or not, they are mere appendages of the skin on which they appear. A new set of hairs, therefore, and probably of spines in spinous larvæ, accompanying each skin, and these varying very much in size, composition, &c. though a new membrane may be admitted to be formed from an action in the rete mucosum without a pre-existent germe of it, it seems not easy to conceive how these hairs and spines can spring up and grow there, each according to a certain law, without existing previously as a kind of corculum or punctum saliens; and that the germes of the tubercles, in which the hairs are so generally planted, according to a certain arrangement and in a given number, should also pre-exist, seems most consonant to reason. These and the several skins may all co-exist in their primordial germes, and remain beyond the discovery of our highest powers of assisted vision, till a certain period when they may first enter the range of the microscope-aided eye. It does not therefore follow, because these primordia semina rerum are not discoverable, that therefore they may not exist. Our faculties and organs are too limited and of too little power to enable us to see the essences of being.

Upon the supposition that the hypothesis of Swammerdam is the true one, we may imagine that the envelope that lies within all the rest is that which covers the insect in its pupa state. Above this are placed several others, which successively become external integuments. These changes or casting of the skin in larvæ, analogous, as before observed, to that of serpents, are familiar to every breeder of silk-worms, in which four such changes occur: the first at the end of about twelve days from its birth, and the three next each at the end of half that time from the moulting which preceded it. With some exceptions[475], similar changes of the skin take place in all larvæ, not however in the same number and at the same periods. Most indeed undergo this operation only three or four times; but there are some that moult oftener, from five up to eight (Arctia villica), nine (Callimorpha Dominula), or even ten times; for so often, M. Cuvier informs us, the caterpillar of the tiger-moth (Callimorpha Caja) casts its exuviæ. It has been observed that the caterpillars of the day-flying Lepidoptera (Papilio L.) usually change only three times, while those of the night-flying ones (Phalæna L.) change four[476]. The periods that intervene between each change depend upon the length of the insect's existence in the larva state. In those which live only a few weeks or months, they are from eight to twenty days; while in those that live more than a year, as the cockchafer, &c. they are probably proportionably longer: though we know very little with regard to the moult of any insects besides the Lepidoptera.

A day or two previously to each change of its skin, the larva ceases eating altogether; it becomes languid and feeble, its beautiful colours fade, and it seeks for a retreat in which it can undergo this important and sometimes dangerous and even fatal operation in security. Here, either fixing itself by its legs to the surface on which it rests, or, as is the case with many caterpillars, by its prolegs, to a slight web spun for this purpose, it turns and twists its body in various directions, and alternately swells and contracts its different segments. The object of these motions and contortions seems to be, to separate the exterior skin, now become dry and rigid, from the new one just below it. After continuing these operations for some hours, resting at intervals without motion, as if exhausted by their violence, the critical moment arrives: the skin splits in the back, in consequence of the still more violent swelling of the second or third segment: the opening thus made is speedily increased by a succession of swellings and contractions of the remaining segments: even the head itself often divides into three triangular pieces, and the inclosed larva by degrees withdraws itself wholly from its old skin. All larvæ, however, do not force their way through this skin in precisely the same place. Thus, those of the hawthorn butterfly (Pieris Cratægi), according to Bonnet[477] make their way out by forcing off what may be called their skull, or the horny part of their head, without splitting the skin, which remains entire; others have been observed to make their way out at the side and the belly. Reaumur noticed the larva of Zygæna Filipendulæ, previously to its last moult, actually biting off and detaching several portions of its old skin; and before this, drops of a fluid resembling water were seen to exude from it[478].

The skin when cast is often so entire, that it might be mistaken for the larva itself; comprising not only the covering of the main trunk with the hairs which clothed it, but of the very skull, eyes, antennæ, palpi, jaws, and legs; which, if examined from within, are now found to be hollow, and to have incased, like so many sheaths, similar parts in the new skin. That the feet of the newly-coated larva were actually sheathed, as fingers in a glove, in the same parts of the exuviæ, may be proved by a very simple experiment: if a leg of one just ready to cast its skin be cut off, the same limb will be found mutilated when that change has ensued. The anal horns, also, of the larvæ of the hawk-moth (Sphinx L.) and other similar protuberances, are incased in each other in like manner; but hairs are laid flat between the two skins, and contribute considerably towards their more easy separation. Thus, if you saved the skins cast by the larva of Callimorpha Caja, for instance, you would appear to have ten different specimens of caterpillars, furnished with every external necessary part, and differing only in size, and the colour perhaps of the hairs, and all representing the same individual.

But further changes than this take place. Swammerdam says, speaking of the moult of the grub of Oryctes nasicornis, a beetle common in Holland, but not satisfactorily ascertained to inhabit Britain, "Nothing in all nature is in my opinion a more wonderful sight than the change of skin in these and other the like worms. This matter, therefore, deserves the greatest consideration, and is worthy to be called a specimen of nature's miracles; for it is not the external skin only that these worms cast, like serpents, but the throat and a part of the stomach, and even the inward surface of the great gut, change their skin at the same time. But this is not the whole of these wonders; for at the same time some hundreds of pulmonary pipes within the body of the worm cast also each its delicate and tender skin. These several skins are afterwards collected into eighteen thicker, and, as it were, compounded ropes, nine on each side of the body, which, when the skin is cast, slip gently and by degrees from within the body through the eighteen apertures or orifices of the pulmonary tubes before described, having their tops or ends directed upwards towards the head. Two other branches of the pulmonary pipes that are smaller, and have no points of respiration, cast a skin likewise." ... "If any one separates the cast little ropes or congeries of the pulmonary pipes with a fine needle, he will very distinctly see the branches and ramifications of these several pipes, and also their annular composition[479]."—Bonnet makes a similar observation with regard to caterpillars; but he appears to have observed it more particularly, at least the change of the intestines, previously to the metamorphosis of the insect, when he says with the excrements it casts the inner skin of the stomach and viscera[480]. Both these great men appear to have recorded the result of their own actual observations with regard to the proceedings of two very different kinds of insects; the one the grub of a beetle, and the other the caterpillars of Lepidoptera. The account of the former is given quite in detail, as that of a person who is describing what he has actually seen: yet by a later and very able physiologist, Dr. Herold, it is affirmed that the inner skin of the intestinal canal is never cast, that canal constantly retaining its two skins. He further affirms, that they are only the large trunks of the Tracheæ that cast their skins, none being detached from their smaller ramifications[481]. When men so eminent for their anatomical skill and nicety, and for their depth and acumen, disagree, the question must be regarded as undecided till further observations throw sufficient weight into one scale or the other.

The larva which has undergone this painful process is at first extremely weak: all its parts are soft and tender; even the corneous ones, as the head and the legs, are then scarcely more than membranous, and are all bathed with a fluid, which, before the moult, intervenes between the two skins, and facilitates their separation[482]: and it is only after some hours, or in some cases even days, during which it lies without motion, that this humidity evaporates, all its parts become consolidated, and it recovers its strength sufficiently to betake itself to its wonted food. Its colour, too, is usually at first much paler than before, and its markings indistinct, until their tints have been enlivened by exposure to the air, when they become more fresh, vivid, and beautiful to appearance than ever. When a few meals have invigorated its languid powers, the renovated animal makes up for its long abstinence by eating with double voracity. . A similar preparatory fast, and succeeding state of debility, accompany every change of the larva's skin. Each time except the last, the old skin is succeeded by a new one, with few exceptions, similar to the one it has discarded. Previously to the final change, which discloses the pupa, it quits the plant or tree on which it had lived, and appears to be quite unsettled, wandering about and crossing the paths and roads, as if in quest of some new dwelling. It now abstains from food for a longer time than before a common moult, empties itself copiously, and as I have just said, if Swammerdam and Bonnet are to be depended upon, casts the skin that lines the stomach and intestines, as well as that of the Tracheæ.

I have observed above, that all larvæ, with few exceptions, change their skins in the manner that I have described. These exceptions are principally found in the order Diptera, of which those of the Linnean genera Musca, Œstrus, and probably all that, like the maggot of the common flesh-fly, have membranous contractile heads, never change their skin at all, not even preparatory to their becoming pupæ. The skin of the pupa, though often differing greatly in shape from that of the larva, is the same which has covered this last from its birth, only modified in figure by the internal changes that have taken place, and to which its membranous texture readily accommodates itself. The larvæ of the Dipterous genera Tipula, Culex, and those which have corneous heads, like other larvæ change their skins several times previously to becoming pupæ[483]. The grubs, also, of bees, wasps, ants? and probably many other Hymenoptera, do not change their skin till they assume the pupa, nor the larva of the female Coccus[484].

If you feel disposed to investigate the reasons of that law of the Creator which has ordained that the skins of the higher animals shall be daily, and imperceptibly, and as it were piece by piece renewed, while those of insects are cast periodically and simultaneously,—the proximate cause must be sought for in the nature of the two kinds of skin, the one being more pliable and admitting a greater degree of tension than the other, and being so constructed as to scale off more readily. If, ascending higher, you wish to know why the skins of insects are so differently circumstanced from our own, the most apparent reason is, to accommodate the skin to the very rapid growth of these animals, which a gradual and slower change would have impeded too much, or the skin have suffered constant dilapidation and injury; therefore their Beneficent Creator has furnished them with one which will stretch to a certain point, and during a certain period, and then yield to the efforts of the inclosed animal, and be thrown aside as a garment that no longer fits the wearer.

viii. And this leads me to a subject to which I am desirous now to bespeak your attention,—the Growth, I mean, and size of Insects in this state. As to size, larvæ differ as much as insects in their perfect state: these last, however, never grow after their exclusion from the pupa, while larvæ increase in bulk in a proportion, and often with a rapidity, almost without a parallel in the other tribes of animals. Thus Lyonnet found, that the caterpillar of the great goat-moth (Cossus ligniperda F.) after having attained its full growth is at least 72,000 times heavier than when it was first excluded from the egg[485]; and of course had increased in size in the same proportion. Connected with the size of larvæ, is the mode in which their accretion takes place. This, with respect to the more solid parts, as the head, legs, &c., is not, as in other animals, by gradual and imperceptible degrees, but suddenly and at stated intervals. Between the assumption of a new skin and the deposition of an old one, no increase of size takes place in these parts, while the rest of the body grows and extends itself, till, becoming too big for these solid parts, nature restores the equilibrium between them by a fresh moult[486], in which the augmentation of bulk, especially in these parts, is so great, that we can scarcely credit the possibility of its being cased in so small an envelope. Malpighi declares, that the head of a silk-worm that has recently cast its skin is four times larger than before the change[487]. It is very probable, also, that when the outer skin becomes rigid, it confines the body of the larva within a smaller compass than it would expand to if unconfined, so that, when this compression is removed, the soft and elastic new integument immediately swells out, and the animal appears all at once much larger than it was before the moult. In fact, the proximate cause of the rupture and rejection of the old skin is the expansion of the included body, which at length becomes so distended as to split its envelope, aided, indeed, as before described, by the contortions of the creature itself.

The larvæ most notorious for the rapidity of their growth are those of Musca carnaria and other flesh-flies: some of which Redi found to become from 140 to more than 200 times heavier in twenty-four hours[488]: an increase of weight and size in so short a time truly prodigious, but essential for the end of their creation—the rapid removal of dead and putrescent animal matter. As the skins of these larvæ are never changed, we may conclude, if the cause of the change of skin in other larvæ above surmised be accurate, that their skins are more contractile and capable of a greater degree of tension than those of larvæ that are subject to moulting. And two peculiarities observable in them confirm this idea: in the first place, their head is not hard and corneous, as that of the others, but capable of being shortened or lengthened; and in the next, their breathing-pores are not in the sides, but at the extremities of the body, while in the moulting larvæ there are two in almost every segment, which must form so many callous points that impede the stretching of the skin to the utmost. The hairs, spines, and tubercles, that are so often found on caterpillars, must also form so many points of resistance that prevent that full extension of the integument which it might otherwise admit.

There is not always that proportion between the size of larvæ and of the insects that proceed from them that might have been supposed, some small larvæ often producing perfect insects larger than some of those proceeding from such as are of greater size.

ix. As insects often live longest in the state we are treating of, I shall say something next upon the age of larvæ, or the period intervening between their exclusion from the egg and their becoming pupæ. This is exceedingly various, but in every case nicely adapted to their several functions and modes of life. The grubs of the flesh-fly have attained their full growth, and are ready to become pupæ, in six or seven days; the caterpillar of Argynnis Paphia, a butterfly, in fourteen days; the larvæ of bees in twenty days; while those of the great goat-moth (Cossus ligniperda) and of the cockchafer (Melolontha vulgaris) live three years, or at least survive three winters, before the same change. That of another lamellicorn beetle (Oryctes nasicornis F.) is said to be extended to four or five; that of the wire-worm (Elater segetum) to five. That of the stag-beetle (Lucanus Cervus) is affirmed by Rösel to be extended to six years; but the most remarkable instance of insect longevity is recorded by Mr. Marsham in the Linnean Transactions[489]. A specimen of Buprestis splendida, a beautiful beetle never before found in this country, made its way out of a deal desk in an office in London in the beginning of the year 1810, which had been fixed there in the year 1788 or 1789; so that according to every appearance it had existed in this desk more than twenty years. Ample allowance being made for its life as a pupa, we may conclude that it had existed as a larva at least half the above period. The grubs of the species of the genus Cynips L. attain their full size in a short time; but they afterwards remain five or six months in the gall before they become pupæ[490].

With few exceptions it may be laid down, that those larvæ which live on dead animals, in fungi, in dung, and in similar substances, are of the shortest duration in this state; and that those which live under the earth, on the roots of grass, &c. and in wood, the longest: the former becoming pupæ in a few days or weeks, the latter requiring several months, or even years, to bring them to maturity. The larvæ which live on the leaves of plants seem to attain a middle term between the one and the other,—seldom shorter than a few weeks, and rarely longer than seven or eight months. Aquatic larvæ appear to be subject to no general rule: some, as the larvæ of Gnats, becoming pupæ in two or three weeks; and others, as those of the Ephemeræ, which are thus compensated for their short life as flies, in as many years[491]. The cause of all these differences is obviously dependent on the nature of the food, and the purposes in the economy of creation to which the larvæ are destined.

x. The last part of the history of larvæ relates to their Preparations for assuming the pupa state. When they have acquired their full size, after having ceased to take food, by a copious evacuation they empty the intestinal canal, even rejecting the membrane that lines it and the stomach[492]; their colours either change totally, or fade; and they make themselves ready for entering upon a new stage of their existence. Some merely rest in a state of inactivity in the midst of the substances in which they feed, as if conscious of their inability to select any safer abode. Of this description are most Coleopterous, Hymenopterous, and Dipterous larvæ, that feed under ground, or in the interior of trees, fruits, and seeds.

But a still larger tribe, those which feed on leaves, animals, &c. act as if more sensible of the insecurity of this to them important epoch. They are about to exchange their state of vigour and activity for a long period of deathlike sleep. The vigilant caution which was wont to guard them from the attack of their enemies will be henceforward of no avail. Destitute of all the means of active defence, their only chance of safety during their often protracted night of torpor must arise from the privacy of their place of repose. About this, therefore, they exhibit the greatest anxiety. Many, after wandering about as if bewildered, retire to any small hole on the surface of the earth, covering themselves with dead leaves, moss, or the like, or to the chinks of trees, or niches in walls and other buildings, or similar hiding-places. Many penetrate to the depth of several inches under ground, and there form an appropriate cavern by pushing away the surrounding earth; to which they often give consistence by wetting it with a viscid fluid poured from the mouth. The larvæ of other insects undertake long and arduous journeys in search of appropriate places of shelter. Those of flesh-flies, now satiated with the mass of putridity in which they have wallowed, leave it, and conceal themselves in any adjoining heap of dust. The grubs of the gad-fly (Œstrus) creep some of them out of the backs of cattle, in tumours of which they have resided, and suffer themselves to fall to the earth; while others, which have fed in the stomach of horses, quit their hold, and by a still more extraordinary and perilous route are carried through the intestines the whole length of their numerous circumvolutions, and are discharged at the anus. And without enumerating other instances, various aquatic larvæ, as that of a common fly (Elophilus pendulus), &c. leave the water, now no longer their proper element, and betake themselves to the shore, there to undergo their metamorphosis.

Most of these, having reached their selected retreat, require no other precaution; but another large tribe of larvæ have recourse to further manœuvres for their defence before they assume the pupa. Those of the aphidivorous flies (Syrphus F. &c.), of the various lady-birds (Coccinella L.), and tortoise-beetles (Cassida L.), &c. fix themselves by the anus with a gummy substance to the leaves or twigs under which they propose to conceal themselves during their existence in that state. Others previously suspend themselves by a silken thread fixed to the tail, or passing round the body; by which also, when become pupæ, they are afterwards pendent in a similar position; and lastly, a very great number of larvæ wholly inclose themselves in cases or cocoons, composed of silk and various other materials, by which during their state of repose they are protected both from their enemies and the action of the atmosphere. As these two last-mentioned processes are extremely curious and interesting, I shall not fear tiring you by entering into some further detail respecting them: explaining first the mode by which larvæ suspend themselves, both before and after they are become pupæ, by silken threads; and next, the various cases or cocoons in which others inclose themselves, and their manner of operating in the formation of them.

1. The larvæ which suspend themselves and their pupæ, with the exception of the tribe of Alucitæ, and some Geometræ of the family of G. pendularia, punctaria, &c. are almost all butterflies[493]. No others follow this mode. They may be divided into two great classes—those which suspend themselves perpendicularly by the tail, and those which suspend themselves horizontally by means of a thread girthed round their middle. In both cases it should be observed, that the suspension of the pupa is the object in view; but as the process is the work of the larva, this seems the proper place for explaining it. To begin with the first case.

You are aware that all lepidopterous larvæ have the faculty of spinning silk threads from their mouths, and it will readily occur to you that it is by means of these threads that they suspend themselves. But how? How is a caterpillar to hang itself by the tail to threads spun from the mouth? Even suppose this difficulty overcome, others still greater remain. Suppose the caterpillar to be suspended by its tail,—this is but a preparatory operation,—what is required is, that the pupa shall hang in the same position: now when you take into consideration that it is incased within the skin of the larva, and without feet or other external organs; that it has to extricate itself from this skin; to hang itself in its place, and to detach the skin from the threads which hold it—this will appear no trifling task. Indeed at first view it seems impossible. Country-fellows for a prize sometimes amuse the assembled inhabitants of a village by running races in sacks: take one of the most active and adroit of these, bind him hand and foot, suspend him by the bottom of his sack with his head downwards, to the branch of a lofty tree; make an opening in one side of the sack, and set him to extricate himself from it, to detach it from its hold, and suspend himself by his feet in its place. Though endowed with the suppleness of an Indian juggler, and promised his sack full of gold for a reward, you would set him an absolute impossibility: yet this is what our caterpillars, instructed by a beneficent Creator, easily perform. Their manœuvres I shall now endeavour to explain.

When the caterpillar has selected the under-side of the leaf or other object to which it purposes suspending itself, its first process is to spin upon it a little hillock of silk consisting of numerous loosely interwoven threads; it then bends its body so as to insinuate the anal pair of prolegs amongst these threads, in which, by a slight exertion, the little crochets which surround them[494] become so strongly entangled as to support its weight with ease. It now suffers the anterior part of the body to fall down, and it hangs perpendicularly from its silken support with its head downwards. In this position it remains often for twenty-four hours, at intervals alternately contracting and dilating itself. At length the skin is seen to split on the back near the head, and a portion of the pupa appears, which by repeated swellings acts like a wedge, and rapidly extends the slit towards the tail. By the continuance of these alternate contractions and dilatations of the conical pupa, the skin of the caterpillar is at last collected in folds near the tail, like a stocking which we roll upon the ancle before withdrawing it from the foot. But now comes the important operation. The pupa, being much shorter than the caterpillar, is as yet at some distance from the silken hillock on which it is to be fastened; it is supported merely by the unsplit terminal portion of the latter's skin. How shall it disengage itself from this remnant of its case, and be suspended in the air while it climbs up to take its place? Without arms or legs to support itself, the anxious spectator expects to see it fall to the earth. His fears, however, are vain; the supple segments of the pupa's abdomen serve in the place of arms. Between two of these, as with a pair of pincers, it seizes on a portion of the skin; and bending its body once more, entirely extricates its tail from it. It is now wholly out of the skin, against one side of which it is supported, but yet at some distance from the leaf. The next step it must take is to climb up to the required height. For this purpose it repeats the same ingenious manœuvre, making its cast-off skin serve as a sort of ladder, it successively with different segments seizes a higher and a higher portion, until in the end it reaches the summit, where with its tail it feels for the silken threads that are to support it. But how can the tail be fastened to them? you ask. This difficulty has been provided against by Creative Wisdom. The tail of the pupa is furnished with numerous little hooks pointing in different directions[495], as well adapted to the end in view as the crochets of the larva's prolegs, and some of these hooks are sure to fasten themselves upon the silk the moment the tail is thrust amongst it. Our pupa has now nearly completed its labours; it has withdrawn its tail from the slough, climbed up it, and suspended itself to the silken hillock—manœuvres so delicate and perilous, that we cannot but admire that an insect which executes them but once in its life, should execute them so well: nor could it, as Reaumur has well and piously observed, had it not been instructed by a Great Master. One more exertion remains: it seems to have as great an antipathy to its cast-off skin, as one of us should, when newly clothed after a long imprisonment, to the filthy prison garments we had put off. It will not suffer this memento of its former state to remain near it, and is no sooner suspended in security than it endeavours to make it fall. For this end—it seizes, as it were with its tail, the threads to which the skin is fastened, and then very rapidly whirls itself round, often not fewer than twenty times. By this manœuvre it generally succeeds in breaking them, and the skin falls down. Sometimes, however, the first attempt fails: in that case, after a moment's rest, it makes a second, twirling itself in an opposite direction; and this is rarely unsuccessful. Yet now and then it is forced to repeat its whirling, not less than four or five times: and Reaumur has seen instances where the feet of the skin were so firmly hooked, that after many fruitless efforts the pupa, as if in despair, gave up the task and suffered it to remain[496]. After these exertions, it hangs the remainder of its existence in this state until the butterfly is disclosed.

We are now to consider the second mode of suspension, in which larvæ by means of a silken girth round their middle, fix themselves horizontally under leaves, &c. These follow the same process with that of those last described, in spinning a small hillock of silk to which they fasten their hind legs; and if the operation concerned the larva state alone, this would be sufficient, as by means of this support, and of their prolegs, they could easily retain themselves in a horizontal position. But these larvæ act as if they foresaw the assumption of a state in which they will be deprived of legs. It is the suspension of the forthcoming pupa that is the object in view; and though this can be hung by the tail in the same way with those of the first class, yet it is plain that it cannot be retained in a horizontal position, which for some unknown reason is essential to it, without some support to its anterior extremity. It is necessary for the larva, therefore, not only to fix its posterior legs amongst a collection of silken fibres, but to spin a girth of the same material round its body. This girth, though apparently of a single thread, will be found on examination to be composed of several, often as many as fifty or sixty; and is fastened on each side of the body of the larva about the middle, to the surface under which it is placed. Three different modes of fixing these girths are adopted by the caterpillars of different butterflies. Some, as those of the common cabbage-butterfly (Pieris Brassicæ), which have remarkably pliable bodies, bend them almost double on one side, then fix the thread and carry it over to the other in the same position, repeating this operation as often as is necessary. Others, as that of Lycæna Argus and many more of the Papiliones Rurales and Urbicolæ L., which have a short and more rigid body, after having bent the head on one side so as to fix one end of the thread, bring themselves into a straight position, and, by a manœuvre not easily described, contrive to introduce the head under the thread, which they then bend themselves to fasten on the other side, pushing it to its proper situation by the successive tension and contraction of their segments. But the most curious mode, though indeed that which seems most natural, is adopted by the caterpillar of the beautiful swallow-tail butterfly (Papilio Machaon) and others of the same family. This first forms the loop which is to serve for its girth, and then creeps under it. But the difficulty it has to surmount is, to keep itself from being entangled in the fifty or sixty fine distinct threads of which the girth is composed, and to preserve them all extended so as to be able to introduce its body beneath them. For this purpose it makes use of the two first pair of its fore-legs, employing them as a woman does her hands in winding a skein of cotton, to collect and keep all the threads of its card unentangled and properly stretched; and it is often with great difficulty, towards the end of the process, that it prevents them from slipping off. When a sufficient number of threads is completed, the animal bends its head between its legs, and insinuates it under the collected loop, which by its annular contraction it easily pushes to the middle of the body.

In about thirty hours after the larvæ which girth themselves have finished their operations, the skin splits, and the pupa disengages itself from it by those contractions and dilatations of its segments which have been before described, pushing the exuviæ in folds to the tail, by different motions of which it generally succeeds in detaching them. One would have thought there would be considerable difficulty in slipping the skin past the girth; but this, according to Reaumur, seems to be easily effected[497].

If you are desirous of witnessing for yourself the manœuvres by which these curious modes of suspension are effected, you may be readily gratified. It is only necessary to collect and feed until their metamorphosis the black spinous caterpillars of the common peacock-butterfly (Vanessa Io), which in most places may be found upon nettles, or those of the Pieris Brassicæ, which swarm in cabbages or brocoli in every garden. The former will exhibit to you a specimen of vertical, the latter of horizontal suspension. It should be observed, however, that to hit the precise moment when these processes are going on, it is necessary to feed a considerable number of the larvæ of each kind; some one of which, if you watch them narrowly when they have attained their full growth, you will scarcely fail to surprise in the act.

I must observe here, that although the vertical and horizontal are the two principal positions in which caterpillars suspend themselves, yet that others are inclined at various angles; and some are attached with less art, appearing only to be fastened by some part of their abdomen to the body upon which they are fixed[498].

2. The larvæ whose procedures I am in the next place to describe, are those which, previously to assuming the pupa state, inclose themselves in cases or cocoons of different materials. For the sake of method, I shall divide these into two great classes: First, those which form their cocoons entirely or principally of silk; and secondly, those which form them chiefly of other substances.

To begin with the first. The larvæ which inclose themselves in silken cocoons are chiefly of the Lepidopterous tribes of Bombycidæ and Noctuidæ; but a few Geometræ (G. papilioniaria, lactearia, &c.); most of the Hymenoptera; some Coleoptera, as certain of the weevil tribe (Hypera Arator, Rumicis Germ.), and those brilliant beetles frequenting aquatic plants constituting the genus Donacia F.; the Neuropterous genera Hemerobius and Myrmeleon; Mycetophila and a few others in the Diptera; and Pulex in the Aphaniptera fabricate coverings of the same material. In all, with the exception of Myrmeleon and Hemerobius (and perhaps Hypera Rumicis, &c.?) which have their spinning apparatus at the extremity of the abdomen, the silken thread employed in forming these coverings proceeds from the middle part of the under-lip, as before explained; and is in fact composed of two threads gummed together as they issue from the two adjoining orifices of the spinner.

Of the larvæ which inclose themselves in silk, the most familiarly known is the silk-worm: the cocoon of this consists exteriorly of a thin, transparent, gauze-like coating, through the interstices of which can be seen an inner, smaller, oval ball of a more close and compact texture. The whole is in fact composed of one single thread, but arranged in two distinct modes. To form the exterior envelope, which is merely the scaffolding by means of which the inner and more solid covering is constructed, the caterpillar, after fixing upon a space between two leaves or twigs or angles suitable for its purpose, begins by glueing one end of its thread to one of the adjoining surfaces. This thread it next conducts to another part and then fastens, repeating this process and interlacing it in various directions, until it has surrounded itself with a slight and loosely spun netting. In the centre of this, when contracted into a space sufficiently small, it lays the foundation of the interior cocoon. Fixing itself by its prolegs to some of the surrounding threads, it bends its body, and by successive motions of its head from side to side spins a layer of silk on the side opposite to it: when this is of the requisite thickness, the larva shifts its position, and repeats the same process in another quarter, covering each layer in turn with a new one until the interior cavity is reduced to the size desired. Thus, the silken thread which forms this new cocoon is not, as might have been supposed, wound circularly as we wind the thread of a ball of cotton; but backwards and forwards in a series of zigzags, so as to compose a number of distinct layers. Malpighi could distinguish six of these layers[499], and Reaumur suspects there is often a greater number[500]. The former found the length of the thread of silk composing them when wound off, without including the exterior case, to be not less than 930 feet[501]; but others have computed it at more than a thousand[502]: consequently the threads of five cocoons united would be a mile in length. Estimating by the weight,—the thread of a pound of cocoons, each of which weighs about two grains and a half, would extend more than 600 miles[503], and such is its tenuity, that the threads of five or six cocoons require to be joined to form one of the thickness requisite in the silk manufacture. It is the continuous thread of the inner cocoon which is most valuable; the outer loose coating from its irregularity cannot be wound off, and is known in commerce by the name of floss silk.

Manœuvres in their general principle similar to those of the silk-worm are followed by most of those larvæ which inclose themselves in silken cocoons. Many species, however, adopt variations in the mode of procedure all of which it would be tedious to particularize, but some of them are worth mentioning. The larvæ of Tortrix prasinana, and other species of moths which form cocoons resembling a reversed boat, arrange their threads in layers, so as to construct two parallel walls gradually inclining towards the top and ends, where they finally force them to approach each other by means of an apparatus of silken cables[504]. And the larva of Saturnia Pavonia, though it forms the base of its flask-shaped cocoon by spinning like the silk-worm a number of interwoven zigzags, places the threads which compose the interior funnel-like opening of the apex nearly straight, parallel to each other, and converging towards the same point in the centre[505].

These last, as well as almost all larvæ, constantly remain in the inside of the cocoon during its construction. But De Geer has given us the history of a minute caterpillar of a species of moth (Tinea L.) which feeds on the under side of the leaves of the Rhamnus Frangula, or Black Alder, that actually weaves half of its cocoon on the outside. This cocoon, which is very small, is beautifully fluted, consisting of several longitudinal cords, with the intervals filled by fine net-work, and shaped like a reversed boat[506]. The animal begins by laying the foundations of one of the ends of her cocoon, she adds new threads to this small beginning, and so proceeds. As the work advances she retreats backwards, and her body is situated nearly in the same line with the cocoon she has begun, and quite out of it; she only touches with her head and legs its anterior margin. When half the cocoon, or rather of its exterior layer, is finished, she suspends her operations for some moments. She then for the first time introduces her head into this demi-cocoon, and turns herself in it by doubling her supple body, and passing one part over the other, so that at last she manages to bring her tail into the pointed end of the cocoon, the head and the anterior half of her body remaining without. Thus situated, she commences her operations afresh. At a distance from the margin of the demi-cocoon, equal to its length, she begins to spin the pointed end of the other moiety, the length of her body serving her as a measure that enables her to begin at the proper distance from it. This new portion she spins in the same manner as the other; but as she is prevented by the demi-cocoon in which the posterior part of her body is lodged from retreating backwards, she contracts her body more, which answers the same purpose. When the new work is so advanced that she can no longer contract her body, she bends the anterior part of it considerably, and reverses her head. When the distance between the margin of the two halves of the cocoon is very small, so as no longer to admit the head between them, in order to unite them she is obliged to have recourse to another manœuvre. Withdrawing her head, she extends silken longitudinal threads between the two margins, and thus unites them. This part is more clumsy, and not so regular as the rest of the cocoon, so that the point of union is always discoverable. These caterpillars do not always divide the cocoon into two equal portions, for often they will finish three quarters of the cocoon before they enter it, and begin at the other end[507].

The general rule is,—that each larva spins for itself a separate cocoon; but amongst those of Arctia chrysorhea and others which live in society, two or three sometimes begin their operations so close together that they are under the necessity of forming one common cocoon, which serves for a covering to the whole number. The same thing happens to silk-worms, the double or treble cocoons of which are called Dupions by the breeders. The larvæ of some Ichneumons, besides forming each its separate cocoon, spin a joint cottony covering for the whole[508], which is effected thus:—After they leave the caterpillar they have devoured, they fix themselves side by side at a little distance from it, and begin to spin each a cocoon; and in order to defend its end and side that is not covered by others, they spin further an envelope of loose silk, and thus this exterior covering is formed.

The size, figure, colour, substance, and texture of silken cocoons are extremely various. Their size indeed is usually proportioned to that of the included larva or pupa; yet it is by no means always so. Some large caterpillars spin cocoons so small, that the observer can hardly conceive how they can be contained in so narrow a compass: Eriogaster Catax is a moth of this description[509]. And others smaller in size lodge themselves in apartments apparently much more spacious than necessary. The transparent hammock-like cocoons of Hepialus Humuli and Arctia villica, two other moths, would contain several of their pupæ. I possess one in which the pupa is suspended in the centre, that is ten times its size, and not very short in dimensions of that of Attacus Paphia, a giant silk-moth. The largest cocoon I ever read or heard of, is that thus described by Mr. Hobhouse in his Travels: "Depending," says he, "from the boughs of the pines, near the Attic mountain Parnes, and stretching across from tree to tree so as to obstruct our passage, were the pods, thrice as big as a turkey's egg! and the thick webs of a chrysalis, whose moth must be far larger than any of those in our country."[510] If this statement is correct, and I am not aware that there is any reason for doubting it, the cocoon must be vastly larger than the pupa, or the moth it produced would far exceed in size any yet known. Perhaps, however, as this gentleman is probably no entomologist, what he took for a cocoon might be a nidus, in which many larvæ were associated, of the nature of those formerly described[511].

With regard to figure, the majority are like those of the silk-worm, of a shape more or less oval or elliptic: some, however, vary from this. That of Lasiocampa Rubi is oblong. I have one from New Holland somewhat resembling an acorn, fixed to the twigs of some tree or shrub, of a very close silk, and covered by a circular operculum, which the animal pushes off when it assumes the imago; this is ovate or conico-ovate; others again are globose[512]; others are conical[513], as that of Gastropacha quercifolia; others almost fusiform[514] (Odenesis potatoria). Reaumur received one from Arabia which was nearly cylindrical[515]. Those of T. prasinana before noticed, and many other Tortrices, are shaped like a reversed boat[516]; that of Saturnia Pavonia and others of the same tribe, like a Florence flask with a wide and short neck. The cocoon of Lygæna Filipendulæ resembles a grain of barley. Another cocoon in my cabinet, of very slight network, is shaped something like an air-balloon. But the most remarkable one for its form and characters, is one that I received from the rich cabinet above quoted. This, which is of an unusually close texture, is suspended by a thread more than two inches long from the point of a leaf; it then swells into a perfect cone, at the base about four-fifths of an inch in diameter and half an inch in length, and covered with scattered setiform appendages: from the centre of the base projects a large hemispherical protuberance, which terminates in a long stalk, much thicker than the thread that suspends the cocoon. There is commonly no difference between the shape of cocoons spun by larvæ which are to give birth to different sexes of the same species. The silk-worm cocoons, however, which will produce male moths, have more silk at the ends, and consequently are more round than those which are to produce females: but the difference is not striking.

The most usual colour of silken cocoons is white, yellow, or brown, or the intermediate shades. The whites are very pure in the general envelope of some species of Ichneumonidæ, and yellows often very brilliant. But besides these more general colours, some cocoons are black[517], some few blue or green, and others red[518]. Sometimes the same cocoon is of two different colours. Those of certain parasites of the tribe of Ichneumones minuti L. the motions of one of which I noticed on a former occasion[519], are alternately banded with black or brown and white, or have only a pale or white belt in the middle, which gives them a singular appearance. In both cases the difference in colour depends upon the different tints with which the silky gum is imbued in the reservoirs: the first portion of it is white, and with this the larva first sketches the outline of its cocoon, and then thickens the layers of silk considerably in those parts where the white bands appear: when these are finished, its stock of white silk is exhausted, and the remainder of the interior of the cocoon is composed of brown silk[520]. The circular operculum above mentioned as covering an acorn-shaped cocoon, is paler than the latter, and also ornamented by a zone within the margin of deep brown. The pale cocoon also of Attacus Paphia is veined with silk of a deep red.

I have very little to say on the substance of the silk of cocoons. Though that of the silk-worm is composed of such a slender thread, that of many others is still finer, scarcely yielding in tenuity to the spider's web. On the other hand, the silk of the cocoons of Saturnia Pavonia and of several foreign species is as thick as a hair.

With regard to the texture of their cocoons—in some, as in that of the silk-worm, the threads are so slightly glued to each other, as to separate with facility; but in that of the emperor-moth just mentioned they are intimately connected by a gummy matter, furnished, as Reaumur conjectures, from the anus[521], with which the whole interior of the cocoon is often plastered. Some, as that of the silk-worm, are composed of an exterior loose envelope, and an inner compact ball; others have no exterior covering, the whole cocoon being of an uniform and thick texture. The larva of Cossus Robiniæ Peck, in spinning its cocoon, makes the end next the opening to the air, by which the imago is to emerge, of a slighter texture than the rest of it[522]. The exterior case is sometimes, as in Laria pudibunda, very closely woven, so as to resemble a real cocoon[523]: its form is usually adapted to that of the inner one; but in some which fix them under flat surfaces (Laria fascelina, Callimorpha Caja,) it resembles a hammock[524]. Cocoons of a close texture have generally no orifice in any part; but that of Eriogaster lanestris is spun with openings, as if bored from without, the use of which, however, does not seem to have been ascertained[525].

Many silken cocoons are of so close a fabric, as, when finished, entirely to conceal the included insect; but a very considerable number are of a more open texture, composed of a much smaller quantity of silk, and that woven so loosely, that the larva or pupa may always be discovered through it. Of this description are the cocoons of Hypogymna dispar, Arctia Salicis, &c., which consist only of a few slight meshes. Those of some others resemble gauze or lace[526]. Of the first description is one in my cabinet before alluded to, shaped somewhat like an air-balloon; the meshes are large and perfectly square. The pupa hangs in the centre, fixed by some few slight threads which diverge from it to all parts of the cocoon—so that it looks as if it was suspended in the air, like Mahomet's coffin, without support. Of the second description is a black one with very fine and nearly circular meshes: the threads that form these are thick, and seem to be agglutinated. In our own country, the cocoons of some beetles, as of Hypera Arator, Galeruca Tanaceti, and of some little Tineæ, also resemble gauze. Many of the larvæ, however, which spin these cocoons, whose thinness is probably attributable to the smallness of their stock of silk, seem anxious for a more complete concealment; and therefore commonly either hide them between leaves tied together, in some with a certain regularity, in others without art[527]; or thicken their texture, and render it opaque, by the addition of grains of earth[528], or of other materials with which their bodies supply them. These are principally of two kinds. The larvæ of Lasiocampa Neustria, Arctia Salicis, &c. after spinning their cocoons, cast from their anus three or four masses of a soft and paste-like matter, which they apply with their head all round the inside of the cavity; and which, drying in a short time, becomes a powder that effectually renders it opake. This is not, as might be conjectured, an excrement, but a true secretion, evidently intended for this very purpose: and, according to Reaumur, a similar powder, but white, derived from the varicose intestines, is used by the caterpillars of Gastropacha quercifolia, &c.[529] The other material, which is still more frequently employed, and which is occasionally mixed with the former, is the hair which everyone has observed to cover so thickly the bodies of some caterpillars. This, after spinning a sufficient envelope, they tear, or in some instances cut off with their mandibles, and distribute all round them, pushing it with their head amongst the interstices of the silk, so as to make the whole of a regular thick texture. After this process, which leaves the body completely denuded, and often seems to give them great pain, they conclude by spinning another tissue of slight silk, in order to protect the forthcoming pupa from the surrounding prickly points. It should be observed, however, that though many hairy larvæ, as those of Noctua Aceris, Arctia Caja, and others, employ their hairs in the composition of their cocoons, the rule is not general, several never making any such use of them. Nor do all that do so employ them distribute them in the same manner as those above described, which rarely attempt to arrange them in any regular position. Reaumur has noticed a small hairy caterpillar that feeds on lichens, which is more methodical: this actually places its hairs upright, side by side, as regularly as the pales in a palisade, in an oval ring around its body, connecting them by a slight tissue of silk, which forces them to bend into a sort of roof at the top; and under this curiously-formed cocoon assumes its state of pupa[530]. Some larvæ make so much hair and so little silk enter into the composition of their cocoons, that on the first inspection they would be pronounced wholly composed of it[531]; others, thickening the interior of their cocoon with hair, line the whole with a viscid matter like varnish[532].

The larvæ of some saw-flies (Tenthredo L.) are remarkable for inclosing themselves in a double cocoon, in which the inner is not, as in the silk-worm &c., connected with the outer, but perfectly distinct from it. Some species, as T. Rosæ (Cryptus Jur.), which have but a small stock of silk, compose the outer cocoon of thick silken cords crossing at right angles, and forming an oval net; which at the same time that it protects them effectually from the ants, which are always ready to attack them, demands much less silk than a covering of a closer texture. But the tender nymph itself requires to be inclosed in a case of a softer and more delicate substance; and accordingly the inner cocoon is composed of fine silk, woven so closely that the threads are scarcely perceptible under a microscope[533]. Reaumur mentions a hymenopterous larva belonging to Latreille's Fossores (Sphex L.) which thickened its cocoon with the legs, wings, and other relics of the flies which it had devoured[534]: trophies—like the drinking-cups of some savages, made of the skulls of their enemies, or the skull pyramid near Ispahan—of its powers of devastation.

It is a general rule, that those larvæ which spin cocoons, never in ordinary circumstances become pupæ without having thus inclosed themselves. An exception, however, is met with in the larva of a species of ant noticed by De Geer (Formica fusca L.), some of the individuals of which inclose themselves in cocoons; while others neglect this precaution, and undergo their metamorphosis uncovered[535]. Rösel also made nearly the same observation on the larva of the flea[536].

I must say something with regard to the situation, often very remote from their place of feeding, in which larvæ fabricate their cocoons. A very considerable number, probably the majority, form them either partially (Arctia lubricipeda) or wholly under ground; others beneath dead leaves, moss, or in the chinks of the trees; others within the wood in substances on which they have fed; the larva of Cossus leaves in these a communication with the open air by which the imago emerges; and a large number attach them to the leaves and branches of trees and plants; the cocoon of Donacia fasciata(?) is fastened by one side to the roots or surculi of Typha latifolia. There is usually nothing very remarkable in the mode of fixing them, the exterior threads being merely gummed irregularly to different portions of the objects which support them. But some effect this with greater art. I have one from New Holland, very long, which is suspended from a twig by a long riband, as it were, which entirely girths the twig. The larva of the magnificent silk-moth, Attacus Paphia, actually forms a solid silken stalk to its cocoon, an inch and half in length and a line in diameter, fastened by the other extremity to a twig, which it closely surrounds as if with a ring, at first sight resembling a fruit of a very singular appearance[537]. I have specimens of this cocoon with both stalk and ring. A bell-shaped cocoon fastened by a foot-stalk, but of softer consistence, to a blade of grass, found by Mr. Sheppard, I can also show you; and my friend Mr. Wilkin had a similar one out of the late Mr. Hudson's collection. Most larvæ spin their cocoons in solitude: some of those, however, which live in society do it close together under their common tent.

There are other cocoons that should be noticed here, such as those formed by the larva of Zygæna Filipendulæ, and some Bombyces, saw-flies (Tenthredo L.), and beetles (Curculio, Donacia F.), &c. These are formed of a substance which seems more analogous to gum than silk, yet furnished from the silk reservoirs, and usually present the appearance externally of parchment or membrane. That of the insect first mentioned is coated, however, with a slight interior silken lining; as indeed are almost all cocoons, of whatever substance.

The second class, into which I have divided larvæ that inclose themselves in cocoons, includes those which form their coverings not solely or principally of silk, but in which other materials are mixed more or less. The cocoons of some of these larvæ are merely composed of a few leaves slightly tied together, either irregularly, or arranged, particularly when they are of a linear figure, with considerable symmetry. The grubs of many beetles, as of the rose-beetle, Cetonia aurata, &c., prepare themselves a cocoon, composed of earth, pieces of rotten wood, and any substances within their reach: which they fasten together with a glutinous secretion. The same material is employed by others in forming a cocoon wholly of earth; which is sometimes, as that of the stag-beetle, Lucanus Cervus, exceedingly hard; at others, as that of some moths, Noctua ambigua, &c., so slight as to fall to pieces as soon as touched[538]. Other cocoons are formed of grains of earth. Reaumur has given a very interesting account of the procedures of a larva in repairing one of these cocoons, from which he had broken off the top when just completed. Without quitting the interior of the walls that remained, it put out its head from the breach, and for more than an hour employed itself in selecting one by one grains of earth, which it conveyed with its mandibles and deposited within its case: it next spun all round the opening threads of silk, to which it attached grains of earth taken from the previously-stored heap, uniting them compactly by means of other silken threads. After employing three hours in this laborious process, the industrious little mason had reduced the diameter of the breach to a few lines. Reaumur was very curious to know how it would fill up this orifice, which would no longer admit the protrusion of its head outside the walls, as in its previous operations. He concluded, that while the rest of the cocoon was exteriorly formed of earth, this opening would be merely closed with silk. He was mistaken, however: the artist knew how to vary its manœuvres, and make its vault of one uniform texture. It spun across the opening a little net of silk, between the meshes of which it thrust grains of earth so dexterously that they projected as far as the outer surface, retained there probably by silken lines previously attached and fastened within. It then finished its habitation by fortifying the inside of the orifice with another layer of earth[539]. The ant-lion (Myrmeleon) spins a globular cocoon with its anus, which it covers with grains of sand[540]. One that I took in the forest of Fontainebleau, in the quarry that produces the crystallized sandstone called the Fontainebleau fossil, was covered with large and shining grains. Instead of the grains of earth or sand employed by these larvæ, those of another tribe substitute grains of stone detached from the softer walls, upon whose lichens they previously feed, which they unite into solid oval cocoons[541]. Those of a fourth form their cocoons of patches of short moss arranged with the roots downwards, and forming a vault, as it were, of verdant turf, admirably adapted for concealment[542]. The larvæ of some moths form their cocoons of irregular pieces of bark tied together with silk, and resembling when completed a knotty protuberance of the twig on which they are fixed. That of Pyralis tuberculana constructs a pannier-shaped one of the parenchyma of the leaves of plants[543].