The next active means of defence with which Creative Wisdom has endowed these busy tribes, are thoselimbsorweaponswith which they are furnished. The insect lately mentioned, the puss-moth, besides the syringes just described, is remarkable for its singular forked tail, entirely dissimilar to the anal termination of the abdomen of most other caterpillars. This tail is composed of two long cylindrical tubes moveable at their base, and beset with a great number of short stiff spines. When the animal walks, the two branches of the tail are separated from each other, and at every step are lowered so as to touch the plane of position; hence we may conclude that they assist it in this motion and supply the place of hind legs. If you touch or otherwise incommodeit, from each of the above branches there issues a long, cylindrical, slender, fleshy, and very flexible organ of a rose colour, to which the caterpillar can give every imaginable curve or inflection, causing it sometimes to assume even a spiral form. It enters the tube, or issues from it, in the same manner as the horns of snails or slugs. These tails form a kind of double whip, the tubes representing the handle, and the horns the thong or lash with which the animal drives away the ichneumons and flies that attempt to settle upon it. Touch any part of the body, and immediately one or both the horns will appear and be extended; and the animal will, as it were, lash the spot where it feels that you incommode it. De Geer, from whom this account is taken, says that this caterpillar will bite very sharply[366].—Several larvæ of butterflies, distinguished at their head by a semicoronet of strong spines, figured by Madame Merian, are armed with singular anal organs[367], which may have a similar use. Rösel when he first saw the caterpillar of the puss-moth, stretched out his hand with great eagerness, so he tells us, to take the prize; but when in addition to its grim attitude he beheld it dart forth these menacing catapults, apprehending they might be poisonous organs, his courage failed him. At length, without touching the monster, he ventured to cut off the twig on which it was, and let it drop into a box[368]! The caterpillar of the gold-tail moth (Arctia chrysorhœa) has a remarkable aperture, which it can open and shut, surrounded by a rim on the upper part of each segment. This aperture includes a little cavity, from which it has the power ofdarting forth small flocks of a cottony matter that fills it[369]. This manœuvre is probably connected with our present subject, and employed to defend it from its enemies. It also ejects a fluid from its anus.
There is a moth in New Holland, the larva of which annoys its foes in a different way: from eight tubercles in its back it darts forth, when alarmed, as many bunches of little stings, by which it inflicts very painful and venomous wounds[370].
The caterpillar of the moth of the beech (Stauropus Fagi), called the lobster, is distinguished by the uncommon length of its anterior legs. Mr. Stephens, an acute entomologist, relates to me that he once saw this animal use them to rid itself of a mite that incommoded it. They are probably equally useful in delivering it from the ichneumon and its other insect enemies.—Dr. Arnold has made a curious observation (confirmed by Dr. Forsström with respect to others of the genus) on the use of the long processes or tails that distinguish the secondary wings ofThecla Iarbas. These processes, he remarks, resemble antennæ, and when the butterfly is sitting it keeps them in constant motion; so that at first sight it appears to have a head at each extremity; which deception is much increased by a spot resembling an eye at the base of the processes. These insects, perhaps, thus perplex or alarm their assailants.—Goedart pretended that the anal horn with which the caterpillars of so many hawk-moths (Sphingidæ) are armed, answers the end of a sting instilling a dangerous venom: but the observations of modern entomologists have provedthat this is altogether fabulous, since the animal has not the power of moving them[371]. Their use is still unknown.
Whether the long and often threatening horns on the head, thorax, and even elytra, with which many insects are armed, are beneficial to them in the view under consideration, is very uncertain. They are frequently sexual distinctions, and have a reference probably rather to sexual purposes and the economy of the animal, than to any thing else. They may, however, in some instances deter enemies from attacking them, and therefore it was right not to omit them wholly, though I shall not further enlarge upon them.—Their mandibles or upper jaws, though principally intended for mastication,—and in the case of theHymenoptera, as instruments for various economical and mechanical uses,—are often employed to annoy their enemies or assailants. I once suffered considerable pain from the bite of the common water-beetle (Dytiscus marginalis), as well as from that of the great rove-beetle (Goerius olens); but the most tremendous and effectual weapon with which insects are armed—though this, except in the case of the scorpion, is also a sexual instrument, and useful to the females in oviposition—is their sting. With this they keep not only the larger animals, but even man himself, in awe and at a distance. But on these I enlarged sufficiently in a former letter[372].
These weapons, fearful as they are, would be ofbut little use to insects if they had not courage to employ them: in this quality, however, they are by no means deficient; for, their diminutive size considered, they are, many of them, the most valiant animals in nature. The giant bulk of an elephant would not deter a hornet, a bee, or even an ant, from attacking it, if it was provoked. I once observed a small spider walking in my path. On putting my stick to it, it immediately turned round as if to defend itself. On the approach of my finger, it lifted itself up and stretched out its legs to meet it.—In Ray's Letters mention is made of a singular combat between a spider and a toad fought at Hetcorne near Sittinghurst[373]in Kent; but as the particulars and issue of this famous duel are not given, I can only mention the circumstance, and conjecture that the spider was victorious[374]! Terrible as is the dragon-fly to the insect world in general, putting to flight and devouring whole hosts of butterflies, may-flies, and others of its tribes, it instills no terror into the stout heart of the scorpion-fly (Panorpa communis), though much its inferior in size and strength. Lyonnet saw one attack a dragon-fly of ten times its own bigness, bring it to the ground, pierce it repeatedly with its proboscis; and had he not by his eagerness parted them, he doubts not it would have destroyed this tyrant of the insect creation[375].
When the death's-head-hawk-moth was introducedby Huber into a nest of humble-bees, they were not affected by it, like the hive-bees, but attacked it and drove it out of their nest, and in one instance their stings proved fatal to it[376].—A black ground-beetle devours the eggs of the mole cricket, orGryllotalpa. To defend them, the female places herself at the entrance of the nest—which is a neatly smoothed and rounded chamber protected by labyrinths, ditches, and ramparts—and whenever the beetle attempts to seize its prey, she catches it and bites it asunder[377].
I know nothing more astonishing than the wonderful muscular strength of insects, which in proportion to their size exceeds that of any other class of animals, and is likewise to be reckoned amongst their means of defence. Take one of the common chafers or dung-beetles (Geotrupes stercorarius, orCopris lunaris), into your hand, and observe how he makes his way in spite of your utmost pressure; and read the accounts which authors have left us of the very great weights that a flea will easily move, as if a single man should draw a waggon with forty or fifty hundred weight of hay:—but upon this I shall touch hereafter, and therefore only hint at it now.
We are next to consider the modes ofconcealmentto which insects have recourse in order to escape the observation of their enemies. One is by covering themselves with various substances. Of this description is a little water-beetle (Elophorus aquaticus), which is always found covered with mud, and so when feeding at the bottom of a pool or pond can scarcely be distinguished,by the predaceous aquatic insects, from the soil on which it rests. Another very minute insect of the same order (Limnius æneus) that is found in rivulets under stones and the like, sometimes conceals its elytra with a thick coating of sand, that becomes nearly as hard as stone. I never met with these animals so circumstanced but once; then, however, there were several which had thus defended themselves, and I can now show you a specimen.—A species of a minute coleopterous genus (Georyssus areniferus[378]), which lives in wet spots where the toad-rush (Juncus bufonius) grows, covers itself with sand; and another nearly related to it (Chætophorus cretiferus, K.) which frequents chalk, whitens itself all over with that substance. As this animal, when clean, is very black, were it not for this manœuvre, it would be too conspicuous upon its white territory to have any chance of escape from the birds and its other assailants.—No insect is more celebrated for rendering itself hideous by a coat of dirt than theReduvius personatus, a kind of bug sometimes found in houses. When in its two preparatory states, every part of its body, even its legs and antennæ, is so covered with the dust of apartments, consisting of a mixture of particlesof sand, fragments of wool or silk, and similar matters, that the animal at first would be taken for one of the ugliest spiders. This grotesque appearance is aided and increased by motions equally awkward and grotesque, upon which I shall enlarge hereafter. If you touch it with a hair-pencil or a feather, this clothing will soon be removed, and you may behold the creature unmasked, and in its proper form. It is an insect of prey; and amongst other victims will devour its more hateful congener the bed-bug[379]. Its slow movements, combined with its covering, seem to indicate that the object of these manœuvres is to conceal itself from observation, probably, both of its enemies and of its prey. It is therefore properly noticed under my present head.
As Hercules, after he had slain the Nemean lion, made a doublet of its skin, so the larva of another insect (Hemerobius Chrysops, a lace-winged fly with golden eyes,) covers itself with the skins of the luckless Aphides that it has slain and devoured. From the head to the tail, this pygmy destroyer of the helpless is defended by a thick coat, or rather mountain composed of the skins, limbs, and down of these creatures. Reaumur, in order to ascertain how far this covering was necessary, removed it, and put the animal into a glass, at one time with a silk cocoon, and at another with raspings of paper. In the first instance, in the space of an hour it had clothed itself with particles of the silk: and in the second, being again laid bare, it found the paper so convenient a material, that it made of it a coat of unusual thickness[380].
Insects in general are remarkable for their cleanliness;—however filthy the substances which they inhabit, yet they so manage as to keep themselves personally neat. Several, however, by no means deserve this character; and I fear you will scarcely credit me when I tell you that some shelter themselves under an umbrella formed of their own excrement! You will exclaim, perhaps, that there is no parallel case in all nature;—it may be so;—yet as I am bound to confess the faults of insects as well as to extol their virtues, I must not conceal from you this opprobrium. Beetles of three different genera are given to this Hottentot habit. The first to which I shall introduce you is one that has long been celebrated under the name of the beetle of the lily (Lema merdigera,Cantaride de' Gigli, Vallisn.) The larvæ of this insect have a very tender skin, which appears to require some covering from the impressions of the external air and from the rays of the sun; and it finds nothing so well adapted to answer these purposes, and probably also to conceal itself from the birds, as its own excrement, with which it covers itself in the following manner. Its anus is remarkably situated, being on the back of the last segment of the body, and not at or under its extremity, as obtains in most insects. By means of such a position, the excrement when it issues from the body, instead of being pushed away and falling, is lifted up above the back in the direction of the head. When entirely clear of the passage, it falls, and is retained, though slightly, by its viscosity. The grub next, by a movement of its segments, conducts it from the place where it fell to the vicinity of the head. It effects this by swelling the segment on which the excrementis deposited, and contracting the following one, so that it necessarily moves that way. Although, when discharged, it has a longitudinal direction, by the same action of the segments the animal contrives to place every grain transversely. Thus, when laid quite bare, it will cover itself in about two hours. There are often many layers of these grains upon the back of the insect, so as to form a coat of greater diameter than its body. When it becomes too heavy and stiff, it is thrown off, and a new one begun[381].—The larvæ of the various species of the tortoise-beetles (Cassida, L.) have all of them, as far as they are known, similar habits, and are furnished besides with a singular apparatus, by means of which they can elevate or drop their stercorarious parasol so as most effectually to shelter or shade them. The instrument by which they effect this is an anal fork, upon which they deposit their excrement, and which in some is turned up and lies flat upon their backs; and in others forms different angles, from very acute to very obtuse, with their body; and occasionally is unbent and in the same direction with it[382]. In some species the excrement is not so disgusting as you may suppose, being formed into fine branching filaments. This is the case withC. maculata, L.[383].—In the cognate genusImatidium, the larvæ also are merdigerous; and that ofI. Leayanum, Latr., taken by Major-General Hardwicke in the East Indies, also produces an assemblage of very long filaments, that resemble a dried fucus or a filamentous lichen.—The clothing of theTineæ, clothes-moths and others, and alsoof the case-worms, having enlarged upon in a former letter[384], I need not describe here.
Some insects, that they may not be discovered and become the prey of their enemies when they are reposing, conceal themselves in flowers. The male of a little bee (Heriades[385]Campanularum), a true Sybarite, dozes voluptuously in the bells of the different species ofCampanula—in which, indeed, I have often found other kinds asleep. Linné named another speciesflorisomnison account of a similar propensity. A third, a most curious and rare species (Andrena[386]spinigera), shelters itself when sleeping, at least I once found it there so circumstanced, in the nest-like umbel of the wild carrot. You would think it a most extraordinary freak of Nature, should any quadruped sleep suspended by its jaws, (some birds however are said, I think, to have such a habit, andSus Babyroussaone something like it,)—yet insects do this occasionally. Linné informs us that a little bee (Epeolus[387]variegatus) passes the night thus suspended to the beak of the flowers ofGeranium phæum: and I once found one of the vespiform bees (Nomada[388]Goodeniana) hanging by its mandibles from the edge of a hazel-leaf, apparently asleep, with its limbs relaxed and folded. On being disengaged from its situation it became perfectly lively.
There is no period of their existence in which insects usually are less able to help themselves, than during that intermediate state of repose which precedes their coming forth in their perfect forms. I formerly explained to youhow large a portion of them during this state cease to be locomotive, and assume an appearance of death[389]. In this helpless condition, unless Providence had furnished them with some means of security, they must fall an easy prey to the most insignificant of their assailants. But even here they are taught to conceal themselves from their enemies by various and singular contrivances. Some seek for safety by burying themselves, previously to the assumption of the pupa, at a considerable depth under the earth; others bore into the heart of trees, or into pieces of timber; some take their residence in the hollow stalks of plants; and many are concealed under leaves, or suspend themselves in dark places, where they cannot readily be seen. But in this state they are not only defended from harm by the situation they select, but also by the covering in which numbers envelop themselves; for, besides the leathery case that defends the yet tender and unformed imago, many of these animals know how to weave for it a costly shroud of the finest materials, through which few of its enemies can make their way;—and to this curious instinct, as I long since observed, we owe one of the most valuable articles of commerce, the silk that gives lustre to the beauty of our females. These shrouds are sometimes double. Thus the larvæ of certain saw-flies spin for themselves a cocoon of a soft, flexible, and close texture, which they surround with an exterior one composed of a strong kind of net-work, which withstands pressure like a racket[390]. Here nature has provided that the inclosed animal shall be protected by the interior cocoon from the injury it might be exposed to from the harshness of the exterior, while thelatter by its strength and tension prevents it from being hurt by any external pressure.
But of all the contrivances by which insects in this state are secured from their enemies, there is none more ingenious than that to which the may-flies (Trichoptera) have recourse for this purpose. You have heard before that these insects are at first aquatic, and inhabit curious cases made of a variety of materials, which are usually open at each end[391]. Since they must reside in these cases, when they are become pupæ, till the time of their final change approaches, if they are left open, how are the animals, now become torpid, to keep out their enemies? Or, if they are wholly closed, how is the water, which is necessary to their respiration and life, to be introduced? These sagacious creatures know how to compass both these ends at once. They fix a grate or portcullis to each extremity of their fortress, which at the same time keeps out intruders and admits the water. These grates they weave with silk spun from their anus into strong threads, which cross each other, and are not soluble in water. One of them, described by De Geer, is very remarkable. It consists of a small, thickish, circular lamina of brown silk, becoming as hard as gum, which exactly fits the aperture of the case, and is fixed a little within the margin. It is pierced all over with holes disposed in concentric circles, and separated by ridges which go from the centre to the circumference, but often not quite so regularly as the radii of a circle or the spokes of a wheel. These radii are traversed again by other ridges, which follow the direction of the circles of holes; so that the two kinds of ridges crossing eachother form compartments, in the centre of each of which is a hole[392].
Under this head I shall call your attention to another circumstance that saves from their enemies innumerable insects:—I mean their coming forth for flight or for food only in the night, and taking their repose in various places of concealment during the day. The infinite hosts of moths (Phalæna, L.),—amounting in this country to more than a thousand species,—with few exceptions, are all night-fliers. And a considerable proportion of the other orders,—exclusive of theHymenopteraandDiptera, which are mostly day-fliers,—are of the same description. Manylarvæof moths also come out only in the night after their food, lying hid all day in subterraneous or other retreats. Of this kind is that ofFumea pullaandNycterobius, whose proceedings have been before described[393]. The caterpillar of another moth (Noctua subterranea, F.) never ascends the stems of plants, but remains, a true Troglodyte, always in its cell under ground, biting the stems at their base, which falling, bring thus their foliage within its reach[394].
The habitations of insects are also usually places of retreat, which secure them from many of their enemies:—but I have so fully enlarged upon this subject on a former occasion[395], that it would be superfluous to do more than mention it here.
I am now to lay before you some examples of the contrivances, requiring skill and ingenuity, by which our busy animals occasionally defend themselves from thedesigns and attack of their foes. Of these I have already detailed to you many instances, which I shall not here repeat; my history therefore will not be very prolix.—I observed in my account of the societies of wasps, that they place sentinels at the mouth of their nests. The same precaution is taken by the hive-bees, particularly in the night, when they may expect that the great destroyers of their combs,Galleria mellonellaand its associates[396], will endeavour to make their way into the hive. Observe them by moonlight, and you will see the sentinels pacing about with their antennæ extended, and alternately directed to the right and left. In the mean time the moths flutter round the entrance; and it is curious to see with what art they know how to profit of the disadvantage that the bees, which cannot discern objects but in a strong light, labour under at that time. But should they touch a moth with these organs of nice sensation, it falls an immediate victim to their just anger. The moth, however, seeks to glide between the sentinels, avoiding with the utmost caution, as if she were sensible that her safety depended upon it, all contact with their antennæ. These bees upon guard in the night, are frequently heard to utter a very short low hum; but no sooner does any strange insect or enemy touch their antennæ, than the guard is put into a commotion, and the hum becomes louder, resembling that of bees when they fly, and the enemy is assailed by workers from the interior of the hive[397].
To defend themselves from the death's-head hawk-moth, they have recourse to a different proceeding. In seasons in which they are annoyed by this animal, theyoften barricade the entrance of their hive by a thick wall made of wax and propolis. This wall is built immediately behind and sometimes in the gateway, which it entirely stops up; but it is itself pierced with an opening or two sufficient for the passage of one or two workers. These fortifications are occasionally varied: sometimes there is only one wall, as just described, the apertures of which are in arcades, and placed in the upper part of the masonry. At others many little bastions, one behind the other, are erected. Gateways masked by the anterior walls, and not corresponding with those in them, are made in the second line of building. These casemated gates are not constructed by the bees without the most urgent necessity. When their danger is present and pressing, and they are as it were compelled to seek some preservative, they have recourse to this mode of defence[398], which places the instinct of these animals in a wonderful light, and shows how well they know how to adapt their proceedings to circumstances. Can this be merely sensitive? When attacked by strange bees, they have recourse to a similar manœuvre; only in this case they make but narrow apertures, sufficient for a single bee to pass through.—Pliny affirms that a sick bear will provoke a hive of bees to attack him in order to let him blood[399]. What will you say, if humble-bees have recourse to a similar manœuvre? It is related to me by Dr. Leach, from the communications of Mr. Daniel Bydder—an indefatigable and well-informed collector of insects, and observer of their proceedings—thatBombus[400]terrestris, when labouring underAcariasis[401]from the numbers of a small mite (Gamasus Gymnopterorum) that infest it, will take its station in an ant-hill; where beginning to scratch, and kick, and make a disturbance, the ants immediately come out to attack it, and falling foul of the mites, they destroy or carry them all off; when the bee, thus delivered from its enemies, takes its flight.
In this long detail, the first idea that will, I should hope, strike the mind of every thinking being, is the truth of the Psalmist's observation—that the tender mercies of God are over all his works. Not the least and most insignificant of his creatures is, we see, deprived of his paternal care and attention; none are exiled from his all-directing providence. Why then should man, the head of the visible creation, for whom all the inferior animals were created and endowed; for whose well-being, in some sense, all these wonderful creatures with their miraculous instincts, whose history I am giving you, were put in action,—why should he ever doubt, if he uses his powers and faculties rightly, that his Creator will provide him with what is necessary for his present state?—Why should he imagine that a Being, whose very essence isLove, unless he compels him by his own wilful and obdurate wickedness, will ever cut him off from his care and providence?
Another idea that upon this occasion must force itself into our mind is, that nothing is made in vain. When we find that so many seemingly trivial variations in the colour, clothing, form, structure, motions, habits, and economy of insects are of very great importance tothem, we may safely conclude that the peculiarities in all these respects, of which we do not yet know the use, are equally necessary: and we may almost say, reversing the words of our Saviour, that not ahairis given to them without our Heavenly Father.
I am, &c.
Amongst the means of defence to which insects have recourse, I have noticed theirmotions. These shall be the subject of the present letter. I shall not, however, confine myself to those by which they seek to escape from their enemies; but take a larger and more comprehensive survey of them, including not only every species of locomotion, but also the movements they give to different parts of their body when in a state of repose: and in order to render this survey more complete, I shall add to it some account of the various organs and instruments by which they move.
Whenever you go abroad in summer, wherever you turn your eyes and attention, you will see insects in motion. They are flying or sailing every where in the air; dancing in the sun or in the shade; creeping slowly, or marching soberly, or running swiftly, or jumping upon the ground; traversing your path in all directions; coursing over the surface of the waters, or swimming at every depth beneath; emerging from a subterranean habitation, or going into one; climbing up the trees, or descending from them; glancing from flower to flower;now alighting upon the earth and waters, and now leaving them to follow the impulse of their various instincts; sometimes travelling singly; at other times in countless swarms: these the busy children of the day, and those of the night. If you return to your apartment—there are these ubiquitaries—some flying about—others pacing against gravity up the walls or upon the ceiling—others walking with ease upon the glass of your windows, and some even venturing to take their station on your own sacred person, and asserting their right to the lord of the creation.
This universal movement and action of these restless little animals gives life to every part and portion of our globe, rendering even the most arid desert interesting. From their visitations every leaf and flower becomes animated; the very dust seems to quicken into life, and the stones, like those thrown by Deucalion and Pyrrha, to be metamorphosed into locomotive beings. In the variety of motions which they exhibit, we see, as Cuvier remarks[402], those of every other description of animals. They walk, run, and jump with the quadrupeds; they fly with the birds; they glide with the serpents; and they swim with the fish. And the provision made for these motions in the structure of their bodies is most wonderful and various. "If I was minded to expatiate," says the excellent Derham, "I might take notice of the admirable mechanism in those that creep; the curious oars in those amphibious insects that swim and walk; the incomparable provision made in the feet of such as walk or hang upon smooth surfaces; the great strength and spring in the legs of such as leap; the strong-made feetand talons of such as dig; and, to name no more, the admirable faculty of such as cannot fly, to convey themselves with speed and safety, by the help of their webs, or some other artifice, to make their bodies lighter than the air[403]."
Since the motions, and instruments of motion, of insects are usually very different in their preparatory states, from what they are in the imago or perfect state, I shall therefore consider them separately, and divide my subject into—motions of larvæ,—motions of pupæ,—and motions of perfect insects.
I. Amongstlarvæthere are two classes of movers—Apodouslarvæ, or those that move without legs,—andPedatelarvæ, or those that move by means of legs. I must here observe, that by the termlegs, which I use strictly, I mean only jointed organs, that have free motion, and can walk or step alternately; not those spurious legs without joints, that have no free motion, and cannot walk or take alternate steps; such as support the middle and anus of the larvæ of mostLepidopteraand saw-flies (Serrifera).
Apodouslarvæ seldom have occasion to take long journeys; and many of them, except when about to assume the pupa, only want to change their place or posture, and to follow their food in the substance, whether animal or vegetable, to which, when included in the egg, the parent insect committed them. Legs therefore would be of no great use to them, and to these last a considerable impediment. They are capable of three kinds ofmotion;—they either walk, or jump, or swim. I usewalkingin an improper sense, for want of a better term equally comprehensive: for some may be said to move by gliding; and others (I mean those that, fixing the head to any point, bring the tail up to it, and so proceed) by stepping.
The motion of serpents was ascribed by some of the ancients (who were unable to conceive that it could be effected naturally, unless by the aid of legs, wings, or fins,) to a preternatural cause. It was supposed to resemble the "incessus deorum," and procured to these animals, amongst other causes, one of the highest and most honourable ranks in the emblematical class of their false divinities[404]. Had they known Sir Joseph Banks's late discovery,—that some serpents push themselves along by the points of their ribs, which Sir E. Home has found to be curiously constructed for this purpose,—their wonder would have been diminished, and their serpent-gods undeified. But though serpents can no longer make good their claim to motionmore deorum, some insects may take their places; for there are numbers of larvæ, that having neither legs, nor ribs, nor any other points by which they can push themselves forward on a plane,glidealong by the alternate contraction and extension of the segments of their body. Had the ancient Egyptians been aware of this, their catalogue of insect divinities would have been wofully crowded. In this annular motion, the animal alternately supports each segment of the body upon the plane of position, which it is enabled to do by the little bundlesof muscles attached to the skin, that take their origin within the body[405].
I shall begin the list ofwalkers, the movements of which are aided by various instruments, with one which is well known to most people,—the grub of the nut-weevil (Balaninus Nucum). When placed upon a table, after lying some time, perhaps, bent in a bow, with its head touching its tail, at last it begins to move, which, though in no certain direction, it does with more speed than might be expected. Rösel fancied that this animal had feet furnished with claws; but in this, as De Geer justly observes, he was altogether mistaken, since it has not the least rudiment of them, its motion being produced solely by the alternate contraction and extension of the segments of the body, assisted, perhaps, by the fleshy prominences of its sides.—Other larvæ have this annular motion aided by a slimy secretion, which gives them further hold upon the plane on which they are moving, and supplies in some degree the place of legs or claws. That of the weevil of the common figwort (Cionus Scrophulariæ) is always covered with slime, which enables it,—though it renders its appearance disgusting,—to walk with steadiness, by the mere lengthening and shortening of its segments, upon the leaves of that plant[406].—Of this kind also are those larvæ, mentioned above[407], received by De Geer from M. Ziervogel, which, adhering to each other by a slimy secretion, glide along so slowly upon the ground as to be a quarter of an hour in going the breadth of the hand, whence the natives call their bandsGårds-drag[408].
As a further help, others again call in the assistance of their unguiform mandibles. These, which are peculiar to grubs with a variable membranaceous, or rather retractile, head[409], especially those of the fly tribe (Muscidæ), when the animal does not use them, are retracted not only within the head, but even within the segments behind it[410]; but when it is moving they are protruded, and lay hold of the surface on which it is placed. They were long ago noticed by the accurate Ray. "This blackness in the head," says he, speaking of the maggot of the common flesh-fly, "is caused by two black spines or hooks, which when in motion it puts forth, and fixing them in the ground, so drags along its body[411]."—The larvæ of the aphidivorous flies (Syrphus, &c.), the ravages of which amongst the Aphides I have before described to you[412], transport themselves from place to place in the same way, walking by means of their teeth. Fixing their hind part to the substances on which they are moving, they give their body its greatest possible tension; and, if I may so speak, thus take as long a step as they can: next, laying hold of it with their mandibles, by setting free the tail and relaxing the tension, the former is brought near the head. Thus the animal proceeds, and thus will even walk upon glass[413]. Some grubs, as the lesser house-fly (Anthomyia canicularis), have only one of these claw-teeth; and in some they have the form as well as the office of legs[414]. Bonnet mentions an apodous larva, that, before it can use its mandibles,is obliged to spin, at certain intervals, little hillocks or steps of silk; of which it then lays hold by them, and so drags itself along.
Besides their mandibular hooks, some of these grubs supply the want of legs by means of claws at their anus. Thus that of the flesh-fly, Ray tells us in the place just quoted, pushes itself by the protruded spines of its tail. The larva also of a long-legged gnat (Limnobia replicata), which in that state lives in the water, is furnished with these anal claws, which, in conjunction with its annular tension and relaxation, and the hooks of its mouth, assist it in walking over the aquatic plants[415].
A remarkable difference, according to their station, obtains in the bots of gad-flies (Œstridæ); those that are subcutaneous (Cuticolæ, Clark) having no unguiform mandibles; while those that are gastric (Gastricolæ, Clark), and those that inhabit the maxillary sinuses of animals (Cavicolæ, Clark), are furnished with them. In this we evidently see Creative Wisdom adapting means to their end. For the cuticular bots having no plane surface to move upon, and imbibing a liquid food, in them the mandibular hooks would be superfluous. But they are furnished with other means by which they can accomplish such motions, and in contrary directions, as are necessary to them; the anterior part of each segment being beset with numbers of very minute spines, not visible except under a strong magnifier, sometimes arranged in bundles, which all look towards the anus; and the posterior part is as it were paved with similar hooks, but smaller, which point to the head. Thus we may conceive, when the animal wants to move forward, thatit pushes itself by the first set of hooks, keeping the rest, which would otherwise impede motion in that direction, pressed close to its skin—or it may depress that part of the segment; and when it would move backwards that it employs the second[416]. The other descriptions of bots, not being embedded in the flesh but fixed to a plane, are armed with the mandibles in question, by which they can not only suspend themselves in their several stations, but likewise, with the aid of the spines with which their segments also are furnished, move at their pleasure[417]. Other larvæ of flies, as well as the bots, are furnished with spines or hooks—by which they take stronger hold—to assist them in their motions. Those mentioned in my last letter as inhabiting the nests of humble-bees[418], besides the six radii that arm their anus, and which perhaps may assist them in locomotion, have the margin of their body fringed with a double row of short spines[419], which are, doubtless, useful in the same way.
The next order of walkers amongst apodous larvæ are those that move by means of fleshy tuberculiform or pediform prominences,—which last resemble the spurious legs of the caterpillars of mostLepidoptera. Some, a kind of monopods, have only one of such prominences, which being always fixed almost under the head, may serve, in some degree, the purpose of an unguiform mandible. The grub of a kind of gnat (Chironomusstercorarius), and also another, probably of the Tipularian tribe (found by De Geer in a subputrescent stalk of Angelica which he was unable to trace to the fly), have each a fleshy leg on the underside of the first segment, which points towards the head and assists them in their motions[420].—Others again go a little further, and are supported at their anterior extremity by a pair of spurious legs. An aquatic larva of a most singular form, and of the same tribe, figured by Reaumur, is thus circumstanced. In this case the processes in question proceed from the head, and are armed with claws[421]. Would you think it—another Tipularian grub is distinguished bythreelegs of this kind? It was first noticed by De Geer under the name ofTipula maculata(Tanypus monilis, Meig.), who gives the following account of its motions and their organs:—It is found, he observes, in the water of swampy places and in ditches, is not bigger than a horse-hair, and about a quarter of an inch in length. Its mode of swimming is like that of a serpent, with an undulating motion of the body, and it sometimes walks at the bottom of the water and upon aquatic plants. The most remarkable part of it are its legs, called by Latreille, but it should seem improperly, tentacula. They resemble, by their length and rigidity, wooden legs. The anterior leg is attached to the underside, but towards the head, of the first segment of the body. It is long and cylindrical, placed perpendicularly or obliquely, according to the different movements the animal gives it, and terminates in two feet, armed at their extremity by a coronet of long moveable hooks.These feet, like the tentacula of snails, are retractile within the leg, and even within the body, so that only a little stump, as it were, remains without. The insect moves them both together, as a lame man does his crutches, either backwards or forwards. The two posterior legs are placed at the anal end of the body. They are similar to the one just described, but larger, and entirely separate from each other, being not, like them, retractile within the body, but always stiff and extended. These also are armed with hooks. In walking, this larva uses these two legs much as the caterpillars of the moths, calledGeometræ, do theirs. By the inflection of the anus it can give them any kind of lateral movement, except that it can neither bend nor shorten them, since like a wooden leg, as I have before observed, they always remain stiff and extended[422]. Lyonet had observed this larva, or a species nearly related to it; but he speaks of it as having four legs, two before and two behind. Probably, when he examined them, the common base, from which the feet are branches, was retracted within the body[423].
Generally speaking, however, in these apodous walkers the place of legs is supplied by fleshy and often retractile mamillæ or tubercles. By means of these and a slimy secretion, unaided by mandibular hooks, the caterpillar of a little moth (Apoda Testudo,) moves from place to place[424].—A subcutaneous larva belonging to the same order, that mines the leaves of the rose, movesalso by tubercular legs assisted by slime. It has eighteen homogeneous legs, with which, when removed from its house of concealment, it will walk well upon any surface, whether horizontal, inclined, or even vertical[425]. But the greatest number of legs of this kind that distinguish any known larva, is to be observed in that of a two-winged fly (Syrphus Pyrastri) that devours the Aphides of the rose. This animal has six rows of tubercular feet, with which it moves, each row consisting of seven, making in all forty-two[426].—The grub of the weevil of the dock (Hypera Rumicis) has twenty-four tubercular legs; but, what is remarkable, the six anterior ones, being longer than the rest, seem to represent the real legs, while the others represent the spurious ones, of lepidopterous larvæ. These legs, however, are all fleshy tubercles, and have no claws, the place of which is supplied by slime which covers all the underside of the body, and hinders the animal from falling[427]. Another weevil (Lixus paraplecticus,) produces a grub inhabiting the water-hemlock, which has only six tubercles that occupy the place and are representatives of the legs of the perfect insect[428].
Some larvæ have these tubercles armed with claws. The maggot of a fly described by De Geer (Volucella plumata,) has six pair of them, each of which has three long claws. This animal has a radiated anus, and seems related to those flies that live in the nests of humble-bees[429].
Insects in the peculiarities of their structure, as we have seen in many instances, sometimes realize the wildestfictions of the imagination. Should a traveller tell you that he had seen a quadruped whose legs were on its back, you would immediately conclude that he was playing upon your credulity, and had lost that regard to truth which ought to distinguish the narratives of persons of his description. What then will you say to me, when I affirm, upon the evidence of two most unexceptionable witnesses, Reaumur and De Geer, that there are insects which exhibit this extraordinary structure? The grub of a little gall-fly, appearing to beCynips Quercus inferusof Linné—which inhabits a ligneous gall resembling a berry to be met with on the underside of oak-leaves—was found by the former to have on its back, on the middle of each segment, a retractile fleshy protuberance that resembled strikingly the spurious legs of some caterpillars. A little attention will convince any one, argues Reaumur, that the legs of insects circumstanced like the one under consideration, if it has any, should be on its back. For this grub—inhabiting a spherical cavity, in which it lies rolled up as it were in a ring—when it wants to move, will be enabled to do so, in this hollow sphere, with much more facility, by means of legs on the middle of its back, than if they were in their ordinary situation[430]. So wisely has Providence ordered every thing.—Another similar instance is recorded by De Geer, which indeed had previously been noticed, though cursorily, by the illustrious Frenchman[431]. There is a little larva, he observes, to be found at all seasons of the year, the depth of winter excepted, in stagnant waters, which keeps its body always doubled as it werein two, against the sides of ditches or the stalks of aquatic plants. If it is placed in a glass half full of water, it so fixes itself against the sides of it, that its head and tail are in the water while the remainder of the body is out of it; thus assuming the form of a siphon, the tail end being the longest. When this animal is disposed to feed, it lifts its head and places it horizontally on the surface of the water, so that it forms a right angle with the rest of the body, which always remains in a situation perpendicular to the surface. It then agitates, with vivacity, a couple of brushes, formed of hairs and fixed in the anterior part of the head, which producing a current towards the mouth, it makes its meal of the various species of animalcula, abounding in stagnant waters, that come within the vortex thus produced. As these animals require to be firmly fixed to the substance on which they take their station, and their back is the only part, when they are doubled as just described, that can apply to it,—they are furnished with minute legs armed with black claws, by which they are enabled to adhere to it. They have ten of these legs: the four anterior ones, which point towards the head and are distant from each other, are placed upon the fourth and fifth dorsal segments of the body; and the six posterior ones, which point to the anus and are so near to each other as at first to look like one leg, are placed on the eighth, ninth, and tenth. When the animal moves, the body continues bent, and the sixth segment, which is without feet and forms the summit of the curve, goes first[432]. De Geer named the fly it producesTipula amphibia: it seems not clear, from his figure, to which of the modern generaof theTipulariæit belongs, nor is it referred to by Meigen.
I come now to the jumping apodes, and one of this description will immediately occur to your recollection,—that I mean which revels in our richest cheeses, and produces a little black shining fly (Tyrophaga Casei). These maggots have long been celebrated for their saltatorious powers. They effect their tremendous leaps—laugh not at the term, for they are truly so when compared with what human force and agility can accomplish—in nearly the same manner as salmon are stated to do when they wish to pass over a cataract, by taking their tail in their mouth, and letting it go suddenly. When it prepares to leap, our larva first erects itself upon its anus, and then bending itself into a circle by bringing its head to its tail, it pushes forth its unguiform mandibles, and fixes them in two cavities in its anal tubercles. All being thus prepared, it next contracts its body into an oblong, so that the two halves are parallel to each other. This done, it lets go its hold with so violent a jerk that the sound produced by its mandibles may be readily heard, and the leap takes place. Swammerdam saw one, whose length did not exceed the fourth part of an inch, jump in this manner out of a box six inches deep; which is as if a man six feet high should raise himself in the air by jumping 144 feet! He had seen others leap a great deal higher[433]. The grub of a little gnat lately noticed (Chironomus stercorarius) has a similar faculty, though executed in a manner rather different. These larvæ, which inhabit horse-dung, though deprived of feet, cannot move by annular contractionand dilatation; but are able, by various serpentine contortions, aided by their mandibles, to move in the substance which constitutes their food. Should any accident remove them from it, Providence has enabled them to recover their natural station by the power I am speaking of. When about to leap, they do not, like the cheese-fly, erect themselves so as to form an angle with the plane of position; but lying horizontally, they bring the anus near the head, regulating the distance by the length of the leap they mean to take; when fixing it firmly, and then suddenly resuming a rectilinear position, they are carried through the air sometimes to the distance of two or three inches. They appear to have the power of flattening their anal extremity, and even of rendering it concave: by means of which it may probably act as a sucker, and so be more firmly fixable[434].—The grub of a fly whose proceedings in that state I have before noticed[435](Leptis Vermileo), will, when removed from its habitation, endeavour to recover it by leaping. Indeed this mode of motion seems often to be given to this description of larvæ by Providence, to enable them to return to their natural station, when by any accident they have wandered away from it.
Many apodous larvæ inhabit the water, and therefore must be furnished with means of locomotion proper to that element. To this class belongs the common gnat (Culex pipiens), which being one of our greatest torments, compels us to feel some curiosity about its history. Its larva is a very singular creature, furnished with a remarkable anal apparatus for respiration, by which it usually remains suspended at the surface of the water.If disposed to descend, it seems to sink by the weight of its body; but when it would move upwards again, it effects its purpose by alternate contortions of the upper and lower halves of it, and thus it moves with much celerity. The laminæ or swimmers, which terminate its anus[436], are doubtless of use to it in promoting this purpose. It does not, that I ever observed, move in a lateral direction, but only from the surface downwards, andvice versa.—Another dipterous larva (Corethra culiciformis), which much resembles that of the gnat in form, differs from it in its motions and station of repose. For, instead of being suspended at the surface with its head downwards, it usually, like fishes, remains in a horizontal position in the middle of the water. When it ascends to the surface, it is always by means of a few strokes of its tail, so that its motion is not equable,sed per saltus. It descends again gradually by its own weight, and regains its equilibrium by a single stroke of the tail[437].—A well known fly (Stratyomis Chamæleon), in its first state an aquatic animal, often remains suspended, by its radiated anus, at the surface of the water, with its head downwards. But when it is disposed to seek the bottom or to descend, by bending the radii of its tail so as to form a concavity, it includes in them a bubble of air, in brilliancy resembling silver or pearl; and then sinks with it by its own weight. When it would return to the surface it is by means of this bubble, which is, as it were, its air-balloon. If it moves upon the surface or horizontally, it bends its body alternately to the right and left, contracting itself into the form of the letter S; and then extending itself again into astraight line, by these alternate movements it makes its way slowly in the water[438].
I have dwelt longer upon the apodous larvæ, or those that are without what may be called proper legs, analogous to those of perfect insects, because the absence of these ordinary instruments of motion is in numbers of them supplied in a way so remarkable and so worthy to be known; and because in them the wisdom of the Creator is so conspicuously, or, I should rather say, so strikingly manifested—since it is doubtless equally conspicuous in the ordinary routine of nature. But aberrations from her general laws, and modes, and instruments of action, often of rare occurrence, impress us more forcibly than any thing that falls under our daily observation.
I come now topedatelarvæ, or those that move by means of proper or articulate legs. These legs (generally six in number, and attached to the underside of the three first segments of the body) vary in larvæ of the different orders: but they seem in most to have joints answering to the hip (coxa); trochanter; thigh (femur); shank (tibia); foot (tarsus), of perfect insects, the legs of which they include. Cuvier, speaking ofColeopteraand someNeuroptera, mentions only three joints. But many in these orders (amongst which he included theTrichoptera) have the joints I have enumerated. To name no more, theLamellicornia,Dytisci,Silphæ,Staphylini,Cicindelæ, andGyrini, &c. amongst coleopterous larvæ; and theTrichoptera, as well as theLibellulinaandEphemerina, amongst Cuvier'sNeuroptera,—have these joints, and in many the last terminates in a doubleclaw[439]. In some coleopterous genera the tarsus seems absent or obsolete. The larva of the lady-bird (Coccinella) affords an example of the former kind, and that ofChrysomelaof the latter[440]. These joints are very visible in the legs of caterpillars ofLepidoptera, and their tarsus is armed with a single claw[441]. The larvæ that have these legs walk with them sometimes very swiftly. In stepping they set forward at the same time the anterior and posterior legs of one side, and the intermediate one of the other; and so alternately on each side.
Pedate larvæ are of two descriptions: those that to perfect legs add spurious ones with or without claws, and those that have only perfect legs. I begin with the former—those that have both kinds of legs. But first I must make a few remarks uponspuriouslegs. Because their muscles, instead of the horny substance that protects them in perfect legs, are covered only by a soft membrane, they have been usually denominatedmembranaceous legs: since, however, they are temporary, vanishing altogether when the insect arrives at its perfect state,—are merely used, for they do not otherwise assist in this motion, as props to hinder its long body, when it walks, from trailing on the ground; to push against the plane of position; and, by means of their hooks or claws, to fix itself firmly to its station when it feeds or reposes,—I shall therefore call them prolegs (propedes[442]). Theseorgans consist of three or four folds, and are commonly terminated, though not always, by a coronet or semicoronet of very minute crooked claws or hooks. These claws, which sometimes amount to nearly a hundred on one proleg, are alternately longer and shorter. They are crooked at both ends, and are attached to the proleg by the back by means of a membrane, which covers about two-thirds of their length, leaving their two extremities naked. Of these the upper one is sharp, and the lower blunt. The sole, or part of the prolegs within the claws, is capable of opening and shutting. When the animal walks, that they may not impede its motion, it is shut, and the claws are laid flat with their points inwards; but when it wishes to fix itself, the sole is opened, becoming of greater diameter than before, and the claws stand erect with their points outwards. Thus they can lay stronger hold of the plane of position[443].
The number of these prolegs varies in different species and families. In the numerous tribes of saw-flies (Serrifera), the larvæ of which resemble those ofLepidoptera, and are called by Reaumur spurious caterpillars (fausses chenilles), one family (Lophyrus) has sixteen prolegs; a second (Hylotoma, &c.) fourteen; another (Tenthredo, F.) twelve; and a fourth (Lyda) none at all, having only the six perfect legs. The majority of larvæ ofLepidopterahave ten prolegs, eight being attached, a pair on each, to the sixth, seventh, eighth, and ninth segments of the body, and two to the twelfth or anal segment[444]. The caterpillar of the puss-moth(Cerura Vinula) and some others, instead of the anal prolegs, have two tails or horns. A hemigeometer, described by De Geer, has only six intermediate prolegs, the posterior pair of which are longer than the rest, to assist the anal pair in supporting the body in a posture more or less erect[445]. Other hemigeometers, of which kind is the larva ofPlusia Gamma[446], have only six prolegs, four intermediate and two anal. The true geometers or surveyors (Geometræ) have only two intermediate and two anal prolegs. Many grubs ofColeoptera, especially those ofStaphylinidæ,Silphidæ, &c. which are long and narrow, are furnished with a stiff joint at the anus, which they bend downwards and use as a prop to prevent their body from trailing. This joint, though without claws, may be regarded as a kind of proleg, which supports them when they walk[447]; and probably may assist their motion by pushing against the plane of position.
With respect to the larvæ that have only perfect legs, having just given you an account of these organs, I have nothing more to state relating to their structure. I shall therefore now consider the motions of pedate larvæ, under the several heads of walking or running, jumping, climbing, and swimming.
Amongst those thatwalk, some are remarkable for the slowness of their motion, while others are extremely swift. The caterpillar of the hawk-moth of the Filipendula (Zygæna Filipendulæ) is of the former description, moving in the most leisurely manner; while that ofApatela leporina, a moth unknown in Britain, is named after the hare, from its great speed. The caterpillar ofanother moth, the species of which seems not to be ascertained, is celebrated by De Geer for the wonderful celerity of its motions. When touched it darts away backwards as well as forwards, giving its body an undulating motion with such force and rapidity, that it seems to fly from side to side[448].—Cuvier observes, that the grubs of some coleopterous and neuropterous insects, which have only the six perfect legs, by means of them lay hold of any surrounding object, and, fixing themselves to it, drag the rest of their body to that point; and that those of many capricorn beetles and their affinities (but that ofCallidium violaceumis an apode[449]) have these legs excessively minute and almost nothing; that they move in the sinuosities which they bore by the assistance of their mandibles, with which they fix themselves, and also of several dorsal and ventral tubercles, by which they are supported against the sides of their cavity, and push themselves along, in the same manner as a chimney-sweeper—by the pressure of his knees, elbows, shoulder-blades, and other prominent parts—pushes himself up a chimney[450]. The larva of the ant-lion (Myrmeleon)—with the exception of one species, which moves in the common way—always walks backwards, even when its legs are cut off.
Thejumpersamongst pedate larvæ, as far as they are known, are not very numerous, and will not detain you long. When the caterpillar ofLithosia Quadra, a moth not uncommon, would descend from one branch or leap to another, it approaches to the edge of the leaf on which it is stationed, bends its body together, andretiring a little backwards, as if to take a good situation, leaps through the air, and, however high the jump, alights on its legs like a cat. That of another moth (Herminia rostralis) will also leap to a considerable height[451].
Another species of motion, which is peculiar to larvæ,—their mode I mean ofclimbing,—as it merits particular attention, will occupy more time. I have already related so many extraordinary facts in their history, that I promise myself you will not disbelieve me if I assert that insects either use ladders for this purpose, or a single rope. You may often have seen the caterpillar of the common cabbage-butterfly climbing up the walls of your house, and even over the glass of your windows. When next you witness this last circumstance, if you observe closely the square upon which the animal is travelling, you will find that, like a snail, it leaves a visible track behind it. Examine this with your microscope, and you will see that it consists of little silken threads, which it has spun in a zigzag direction, forming a rope-ladder, by which it ascends a surface it could not otherwise adhere to. The silk as it comes from the spinners is a gummy fluid, which hardens in the air; so that it has no difficulty in making it stick to the glass.—Many caterpillars that feed upon trees, particularly the geometers, have often occasion to descend from branch to branch, and sometimes, especially previously to assuming the pupa, to the ground. Had they to descend by the trunk, supposing them able to traverse with ease its rugged bark, what a circuitous route must they take before they could accomplish their purpose! Providence, ever watchfulover the welfare of the most insignificant of its creatures, has gifted them with the means of attaining these ends, without all this labour and loss of time. From their own internal stores they can let down a rope, and prolong it indefinitely, which will enable them to travel where they please. Shake the branches of an oak or other tree in summer, and its inhabitants of this description, whether they were reposing, moving, or feeding, will immediately cast themselves from the leaves on which they were stationed; and however sudden your attack, they are nevertheless still provided for it, and will all descend by means of the silken cord just alluded to, and hang suspended in the air. Their name of geometer was given them, because they seem to measure the surface they pass over, as they walk, with a chain. If you place one upon your hand, you will find that they draw a thread as they go; when they move, their head is extended as far as they can reach with it; then fastening their thread there, and bringing up the rest of their body, they take another step; never moving without leaving this clue behind them; the object of which, however, is neither to measure, nor to mark its path that it may find it again; but thus, whenever the caterpillar falls or would descend from a leaf, it has a cord always ready to support it in the air, by lengthening which it can with ease reach the ground. Thus it can drop itself without danger from the summit of the most lofty trees, and ascend again by the same road. As the silky matter is fluid when it issues from the spinners, it should seem as if the weight of the insect would be too great, and its descent too rapid, so as to cause it to fall with violence upon the earth. The little animal knows how to preventsuch an accident, by descending gradually. It drops itself a foot or half a foot, or even less, at a time; then making a longer or shorter pause, as best suits it, it reaches the ground at last without a shock. From hence it appears that these larvæ have power to contract the orifice of the spinners, so as that no more of the silky gum shall issue from it; and to relax it again when they intend to resume their motion downwards: consequently there must be a muscular apparatus to enable them to effect this, or at least a kind of sphincter, which, pressing the silk, can prevent its exit. From hence also it appears that the gummy fluid which forms the thread must have gained a degree of consistence even before it leaves the spinner, since as soon as it emerges it can support the weight of the caterpillar.—In ascending, the animal seizes the thread with its jaws as high as it can reach it; and then elevating that part of the back that corresponds with the six perfect legs, till these legs become higher than the head, with one of the last pair it catches the thread; from this the other receives it, and so a step is gained: and thus it proceeds till it has ascended to the point it wishes to reach. At this time if taken it will be found to have a packet of thread, from which, however, it soon disengages itself; between the two last pairs of perfect legs[452]. To see hundreds of these little animals pendent at the same time from the boughs of a tree, suspended at different heights, some working their way downwards and some upwards, affords a very amusing spectacle. Sometimes, when the wind is high, they are blown to the distance of several yards from the tree, and yet maintain their threads unbroken. I witnessedan instance of this last summer, when numbers were driven far from the most extended branches, and looked as if they were floating in the air.