The larvæ of a small beetle (Clytra longimana) reside in oviform cases apparently of a calcareous or earthy substance, joined by a gummy cement and covered with red hairs, the origin of which, Hübner, who first discovered them, could not account for: and from the observations of Amstein and the French translator of Fuessly'sArchives, it seems probable that the larvæ of all the species ofClytra, and according to Zschorn, at least of one species of Cryptocephalus, (C. duodecimpunctatus) differing in this respect from all other knownColeoptera, live in moveable cases[804]. I have however found a speciesofLimnius(L. æneus) inhabiting a fixed case made of particles of stone or sand.
Wax is the principal substance employed in the habitations of the larvæ before mentioned[805], occasionally so destructive to bee-hives. These insidious depredators, which are mentioned by Aristotle[806], tying together, with silk, grains of wax (which, and not honey, forms their food), construct galleries of a considerable length, and thus concealed from the sight, and protected from the stings of the armed people whom they have attacked, push their mines into the very heart of the fortress, and pursue their robberies in perfect safety[807].
As many of the habitations which I have been describing, fit the body of the insects as close as a coat, they might perhaps with more propriety be calledclothes. This is certainly the most appropriate designation of the abodes of some species of Tineæ (the clothes' moths), which not only cover themselves with a coat, but employ the very same material in its composition as we do in ours, forming it of wool or hair curiously felted together. Like us, they are born naked, but not like us helpless at that period, scarcely have they breathed before they begin to clothe themselves; thus contradicting Dr. Paley's assertion, that "thehumananimal is the only one which is naked, and the only one which can clothe itself[808]:" and wisely inattentive to change of fashion, the same suit serves them from their birth to mature age. The shape of their dress is adapted to that of their body—a cylindrical case open at both ends. The stuff of which it is composed is the manufacture of the larva ofthe moth (Tinea), which incorporates wool or hair artfully cut from our clothes or furniture, with silk drawn from its own mouth, into a warm and thick tissue: and as this would not be soft enough for its tender skin, it also lines the inside of its coat with a layer of pure silk. Since this suit of clothes during the earliest age of the insect accurately fits its body, you will readily conceive that it will frequently require enlarging. This the little occupant accomplishes as dexterously as any tailor. If the case merely requires lengthening, the task is easy. All that is needful is to add a new ring of hair or wool and silk to each end. But to enlarge it in width is not so simple an affair. Yet it sets to work precisely as we should, slitting the case on the two opposite sides, and then adroitly inserting between them two pieces of the requisite size. It does not, however, cut open the case from one end to the other at once: the sides would separate too far asunder, and the insect be left naked. It therefore first cuts each side about half way down, and then after having filled up the fissure proceeds to cut the remaining half: so that, in fact, four enlargements are made, and four separate pieces inserted.—The colour of the habit is always the same as that of the stuff from which it is taken. Thus, if its original colour be blue, and the insect previously to enlarging it be put upon red cloth, the circles at the end and two stripes down the middle will be red. If placed alternately upon cloths of different hues, its dress will be parti-coloured like that of a Harlequin.—The injury occasioned to us by these insects is not confined to the quantity of materials consumed in clothing and feeding themselves. In moving from place to place they seem to be as muchincommoded by the long hairs which surround them, as we are by walking amongst high grass; and accordingly, marching scythe in hand, with their teeth they cut out a smooth road, from time to time reposing themselves, and anchoring their little case with small silken cables.
If, as I hope, you are induced to investigate the manners of these insects, you have but to leave an old coat for a few months undisturbed in a dark closet, and you may be pretty certain of meeting with an abundant colony.
Not merely wool or hair, but another substance analogous to one employed in our dress, is adopted for their clothing by other insects. The larva of a fly which lives on the seeds of willows, makes itself a very beautiful case of their cottony down, not only impervious to wet and cold, but serving, if accidentally blown into the water, which from the situation of these trees frequently happens, as a buoyant little barge which is wafted safely to the shore[809].
The habitations which we have hitherto been considering, are formed by larvæ that live on land, but others equally remarkable are constructed by aquatic species, the larvæ of the variousPhryganeæL., a tribe of four-winged insects which an ordinary observer would call moths, but which are even of a distinct order (Trichoptera), not having their wings covered by the scales which adorn the lepidopterous race. If you are desirous of examining the insects to which I am alluding, you have only to place yourself by the side of a clear and shallow pool of water, and you cannot fail to observe at the bottom little oblong moving masses resembling piecesof straw, wood, or even stone. These are the larvæ in question, well known to fishermen by the title ofCaddis-worms, and which, if you take them out of the water, you will observe to inhabit cases of a very singular conformation. Of the larva itself, which somewhat resembles the caterpillars of manyLepidoptera, nothing is to be seen but the head and six legs by means of which it moves itself in the water, and drags after it the case in which the rest of the body is inclosed, and into which on any alarm it wholly retires. The construction of these habitations is very various. Some select four or five pieces of the leaves of grass, which they glue together into a shapely polygonal case; others employ portions of the stems of rushes, placed side by side so as to form an elegant fluted cylinder; some arrange round them pieces of leaves like a spirally-rolled ribband[810]; others inclose themselves in a mass of the leaves of any aquatic plants united without regularity; and others again form their abode of minute pieces of wood either fresh or decayed[811]. One, like theSabellæ[812], forms a horn-shaped case composed of grains of sand, so equal in size, and so nicely and regularly gummed together, the sides throughout being of the thickness of one grain only, that the first time I viewed it I could scarcely persuade myself it could be the work of an insect. The case ofLeptocerus bimaculatus, which is less artificially constructed of a mixture of mud and sand, is pyriform, and has its end curiously stopped by a plate formed of grains of sand, with a central aperture[813]. Other species construct houses which may be called alive, forming them of the shells of various aquaticsnails of different kinds and sizes even while inhabited, all of which are immoveably fixed to it, and dragged about at its pleasure—a covering as singular as if a savage, instead of clothing himself with squirrels' skins, should sew together into a coat the animals themselves. However various may be the form of the case externally, within it is usually cylindrical and lined with silk; and though seldom apparently wider than just to admit the body of the insect, some species have the power of turning round in it, and of putting out their head at either end[814]. Some larvæ constantly make their cases of the same materials; others employ indifferently any that are at hand; and the new ones which they construct as they increase in size (for they have not the faculty, like the larva of the moth, of enlarging them) have often an appearance quite dissimilar to that of the old. Even those that are most careless about the nature of the materials of their house, are solicitously attentive to one circumstance respecting them, namely, their specific gravity. Not having the power of swimming, but only of walking at the bottom of the water by aid of the six legs attached to the fore part of the body which is usually protruded out of the case, and the insect itself being heavier than water, it is of great importance that its house should be of a specific gravity so nearly that of the element in which it resides, as while walking neither to incommode it by its weight, nor by too great buoyancy; and it is as essential that it should be so equallyballastedin every part as to be readily moveable in any position. Under these circumstances our Caddis-worms evince their proficiency in hydrostatics, selecting the most suitablesubstances; and, if the cell be too heavy, glueing to it a bit of leaf or straw; or, if too light, a shell or piece of gravel. It is from this necessity of regulating the specific gravity, that to the cases formed with the greatest regularity we often see attached a seemingly superfluous piece of wood, leaf, or the like.
A larva of one of the aquaticTipulariælives in cases somewhat similar to those of somePhryganeæ. Several of these of a fusiform shape and brown colour, composed partly of silk and partly perhaps of fragments of leaves, and inhabited by a red larva apparently of aChironomus, were found by Reaumur upon dead leaves in a pool of water in the Bois de Boulogne[815].
In concluding this head I may observe, that here might have been described the various abodes which solitary larvæ prepare for themselves previously to assuming the pupa, and intended for their protection in that defenceless stage of existence; but as I shall have occasion again to refer to them in speaking of the larva state of insects, I shall defer their description to that letter, to which they more strictly belong.
From the next division of the habitations of insects—those formed by solitaryperfectinsects for their own accommodation—I shall select for description only two, both the work of spiders, and alluded to in a former letter, which indeed, with the exception of the inartificial retreats made by theGrylli,Cicindelæ, and perhaps a few others, are the only ones properly belonging to it.
The habitation of one of these (Cteniza cæmentaria) is subterraneous, not a mere shallow cavity, but a tubeor gallery upwards of two feet in length and half an inch broad. This tunnel, so vast compared with the size of the insect, it digs by means of its strong jaws in a steep bank of bare clay, so that the rain may readily run off without penetrating to its dwelling. Its next operation is to line the whole from top to bottom with a web of fine silk, which serves the double purpose of preventing the earth that composes the walls from falling in, and, by its connexion with the door of the orifice, of giving information to the spider of what is passing above. You doubtless suppose that in sayingdoorI am speaking metaphorically. It could never enter into your conception that any animal, much less an insect, could construct any thing really deserving of that name—any thing like our doors, turning upon a hinge, and accurately fitted to the frame of the opening which it is intended to close. Yet such a door, incredible as it may seem, is actually framed by this spider. It does not indeed, like us, compose it of wood, but of several coats of dried earth fastened to each other with silk. When finished, its outline is as perfectly circular as if traced with compasses; the inferior surface is convex and smooth, the superior flat and rough, and so like the adjoining earth as not to be distinguishable from it. This door the ingenious artist fixes to the entrance of her gallery by a hinge of silk, which plays with the greatest freedom, and allows it to be opened and shut with ease; and as if acquainted with the laws of gravity, she invariably fixes the hinge at thehighestside of the opening, so that the door when pushed up shuts again by its own weight. She has not less sagaciously left a little edge or groove just within the entrance, upon which the door closes, and to which it fitswith such precision, that it seems to make but one surface with it. Such is the astonishing structure of this little animal's abode; nor is its defence of its subterraneous cavern less surprising. If an observer adroitly insinuates the point of a pin under the edge of the door, and elevates it a little, he immediately perceives a very strong resistance.—What is its cause?—The spider, warned by the vibrations of the threads which extend from the door to the bottom of her gallery, runs with all speed to the door, fastens its legs to it on one side, and on the other to the walls, and, turning upon its back, pulls with all its might. Thus the door is alternately shut or opened, as the exertions of the observer or of the spider prevail. It is easy to guess which will in the end conquer; and the spider, when it finds all resistance ineffectual, betakes itself to flight, and retreats. If, to make a further experiment, the observer fastens down the door so that it cannot be forced open, the next morning he will find a new entrance, with a new door formed at a small distance; or, if he take the door entirely away, another will be constructed in less than twelve hours.
The habitation thus singularly formed and defended is not at all used as a snare, but merely as a safe abode for the spider, which hunts its prey at night only; and, when caught, devours it in security at the bottom of its den, which is generally strewed with the remains of coleopterous insects[816].—From some curious observations of M. Dorthes on this species in the second volume of theLinnean Transactions, it appears that both the maleand female spider and as many as thirty young ones occasionally inhabit one of these galleries.—Mygale Sauvagesiiof Rossi, which is a distinct species found in Corsica, forms a similar habitation[817].
The galleries just described are the work of an European species not uncommon in the south of France; but similar ones are fabricated byThomisus venatorius, an inhabitant of the West India islands, as well as by many other tropical species. I have seen one of these, which had been dug out of the earth, in the cabinet of Thomas Hall, Esq. F.L.S., that was nearly a foot in length, and above an inch in diameter, forming a cylindrical bag of dark-coloured silk, closed at the bottom, and accurately fitted at the top by a door or lid.
The habitation ofArgyroneta aquatica, the other spider to which I alluded, is chiefly remarkable for the element in which it is constructed and the materials that compose it. It is built in the midst of water, and formed, in fact, of air! Spiders are usually terrestrial, but this is aquatic, or rather amphibious; for though she resides in the midst of water, in which she swims with great celerity, sometimes on her belly but more frequently on her back, and is an admirable diver, she not unfrequently hunts on shore, and, having caught her prey, plunges with it to the bottom of the water. Here it is she forms her singular and unique abode. She would evidently have but a very uncomfortable time were she constantly wet, but this she is sagacious enough to avoid; and by availing herself of some well-known philosophical principles, she constructs for herself an apartment in which, like the mermaids and sea-nymphs of fable, she resides in comfort and security.The following is her process. First she spins loose threads in various directions attached to the leaves of aquatic plants, which may be called the frame-work of her chamber, and over them she spreads a transparent varnish resembling liquid glass, which issues from the middle of her spinners, and which is so elastic that it is capable of great expansion and contraction: and if a hole be made in it, it immediately closes again. Next she spreads over her belly a pellicle of the same material, and ascends to the surface. The precise mode in which she transfers a bubble of air beneath this pellicle is not accurately known; but from an observation made by the ingenious author of the little work from which this account is abstracted, he concludes that she draws the air into her body by the anus, which she presents to the surface of the pool, and then pumps it out from an opening at the base of the belly between the pellicle and that part of the body, the hairs of which keep it extended. Clothed with this aërial mantle, which to the spectator seems formed of resplendent quicksilver, she plunges to the bottom, and, with as much dexterity as a chemist transfers gas with a gas-holder, introduces her bubble of air beneath the roof prepared for its reception. This manœuvre she repeats ten or twelve times, until at length in about a quarter of an hour she has transported as much air as suffices to expand her apartment to its intended extent, and now finds herself in possession of a little aërial edifice, I had almost said an enchanted palace, affording her a commodious and dry retreat in the very midst of the water. Here she reposes unmoved by the storms that agitate the surface of the pool, and devours her prey at ease and in safety. Both sexes formthese lodgings. At a particular season of the year the male quits his apartment, approaches that of the female, enters it, and enlarging it by the bubble of air that he carries with him, it becomes a common abode for the happy pair[818].—The spider which forms these singular habitations is one of the largest European species, and in some countries not uncommon in stagnant pools.
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The habitations of insects which I shall next proceed to describe, are those formed by the united labour of several individuals.
The societies which thus combine their operations may be divided into two kinds: 1st, those of which the object is simply the conservation of the individuals composing them; and 2dly, those whose object is also the nurture and education of their young. To the last head belong bees, wasps, &c.: to the former the larvæ of some species of moths, whose labours being the most simple I shall first describe.
You cannot fail to have observed in gardens the fruit-trees disfigured, as you would probably think them, with what at first view seem very strong and thick spiders' webs. If you have bestowed upon these webs the slightest attention, you must have likewise remarked that they differ very materially in their construction from those spun by spiders, inclosing on every side an angular space, and being besides filled with caterpillars. These are the larvæ ofArctia chrysorrhœa, and the web which contains them is spun by their united labour for the protection of the common society. As soon as the cluster ofeggs deposited by the parent moth is hatched, the young caterpillars, to the number of three or four hundred, commence their operations. At first they content themselves by forming a sort of hammock of the single leaf upon which they find themselves assembled, covering it with a roof composed of a number of silken threads drawn from one edge to the other; and under one or more of these temporary habitations they reside for a few days, until they are become large and strong enough to undertake a more solid and spacious building sufficient to contain the whole society. In constructing this new habitation, they spin a close silken web round the end of two or three adjoining twigs and the leaves attached to them, so as to include the requisite space. They are not curious in giving any particular form to the edifice: sometimes it is flat, often roundish, but always more or less angular. The interior is divided by partitions of silk into several irregular apartments, to each of which there is purposely left an appropriate door. Within these the caterpillars retire at night, or in rainy weather, quitting the nest on fine days, and dispersing themselves over the neigbouring leaves, upon which they feed. Here too they repose during the critical period of the change of their skins. On the approach of winter the whole community shut themselves up in the nest, which, by the addition of repeated layers of silk, has at this time become so thick and strong as to be impervious to the wind and rain. They remain in a state of torpidity during the cold months, but towards the beginning of April are awakened to activity by the genial breath of spring, and begin to feed with greediness upon the young leaves that surround their habitation, which, as they soon greatly increase in size,they find it necessary to enlarge. One might fear that a structure formed of such materials would at this period be sadly damaged by the growth of the young shoots and leaves of the twigs which it incloses; but the inhabitants, as if to guard against such an accident, have gnawed off all the buds within their dwelling, and thus secured themselves from this inconvenience[819].
The nest of the larvæ of another species of moth, theLasiocampa processionea, unfortunately not a native of this country, to which on account of their singular manners, that will be detailed to you in a subsequent letter, Reaumur has given the title ofprocessionarycaterpillars, is somewhat different in its construction from that just described, though formed of the same material. As the caterpillars which fabricate it feed upon the leaves of the oak, it is always found upon this tree, attached not to the branches but the trunk, sometimes at a considerable height from the ground. In shape it resembles an irregular knob or protuberance, and the silk which composes it being of a gray colour, at a distance it would be taken for a mass of lichens. Sometimes this nest is upwards of eighteen inches long, and six broad, rising in the middle about four inches from the surface of the tree. Between the trunk and the silken covering, a single hole is left which serves for the entrance and exit of the inhabitants. These differ in their manners from those last mentioned. While very young they have no fixed habitation, contenting themselves with a succession of different temporary camps until they have attained two-thirds of their growth. Then it is they unite their laboursin spinning the nest just described; and in this they continue to reside in harmony until they become perfect insects, assuming in it even the state of chrysalis[820].
Habitations similar, as to their general structure, to the above, though differing in several minute circumstances, are formed by the larvæ of several other moths, as ofArctia phæorrhœaof Curtis,Trichoda neustria, &c. as well as those ofVanessa Io,Melitæa Cinxia, and some other butterflies: and even of some saw-flies (serrifera), which, however, have each a separate silken covering. But as it would be tedious to describe these particularly, I pass on to the habitations formed by insects in their perfect state, which have in view the education of their young as well as self-preservation, describing in succession those ofants,bees,wasps, andwhite-ants.
Of these the most simple in their structure are the nests of different kinds ofants, many of which externally present the appearance of hillocks more or less conical, formed of earth or other substances.
The nest of the large red or horse ants (F. rufa,) which are common in woods, at the first aspect seems a very confused mass. Exteriorly it is a conical mount composed of pieces of straw, fragments of wood, little stones, leaves, grain; in short, of any portable materials within their reach. But however rude its outward appearance, and the articles of which it consists, interiorly it presents an arrangement admirably calculated at once for protection against the excessive heat of the sun, and yet to retain a due degree of genial warmth. It is wholly composedof numerous small apartments of different sizes, communicating with each other by means of galleries and arranged in separate stories, some very deep in the earth, others a considerable height above it: the former for the reception of the young in cold weather and at night, the latter adapted to their use in the day time. In forming these, the ants mix the earth excavated from the bottom of the nest with the other materials of which the mount consists, and thus give solidity to the whole. Besides the avenues which join the apartments together, other galleries varying in dimensions communicate with the outside of the nest at the top of the mount. These open doors would seem ill calculated for precluding the admission of wet or of nocturnal enemies: but the ants alter their dimensions continually according to circumstances; and they wholly close them at night, when all gradually retire to the interior, and a few sentinels only are left to guard the gates. On rainy days, too, they keep them shut, and when the sky is cloudy open them partially[821].
The habitations of these ants are much larger than those of any other species in this country, and sometimes as big as a small haycock; but they are mere molehills when compared with the enormous mounds which other species apparently of the same family, but much larger, construct in warmer climates. Malouet states, that in the forests of Guiana he once saw ant-hills which, though his companion would not suffer him to approach nearer than forty paces for fear of his being devoured, seemed to him to be fifteen or twenty feet high, and thirty or forty in diameter at the base, assuming the form of apyramid, truncated at one-third of its height[822], and Stedman, when in Surinam, once passed ant-hills six feet high, and at least one hundred feet in circumference[823].
The nest ofFormica brunneais composed wholly of earth, and consists of a great number of stories, sometimes not fewer than forty, twenty below the level of the soil, and as many above, which last, following the slope of the ant-hill, are concentric. Each story, separately examined, exhibits cavities in the shape of saloons, narrower apartments, and long galleries which preserve the communication between both. The arched roofs of the most spacious rooms are supported by very thin walls, or occasionally by small pillars and true buttresses; some having only one entrance from above, others a second communicating with the lower story. The main galleries, of which in some places several meet in one large saloon, communicate with other subterranean passages, which are often carried to the distance of several feet from the hill.—These insects work chiefly after sunset.—In building their nest they employ soft clay only, scraped from its bottom when sufficiently moistened by a shower, which, far from injuring, consolidates and strengthens their architecture. Different labourers convey small masses of this ductile material between their mandibles, and with the same instruments they spread and mould it to their will, the antennæ accompanying every movement. They render all firm by pressing the surface lightly with their fore feet; and however numerous the masses of clay composing these walls, and thoughconnected by no glutinous material, they appear when finished one single layer well united, consolidated, and smoothed. Having traced the plan of their structure, by placing here and there the foundations of the pillars and partition-walls, they add successively new portions: and when the walls of a gallery or apartment which are half a line thick are elevated about half an inch in height, they join them by springing a flattish arch or roof from one side to the other. Nothing can be a more interesting spectacle than one of these cities while building. In one place vertical walls form the outline, which communicate with different corridors by openings made in the masonry; in another we see a true saloon whose vaults are supported by numerous pillars; and further on are the cross ways or squares where several streets meet, and whose roofs, though often more than two inches across, the ants are under no difficulty in constructing, beginning the sides of the arch in the angle formed by two walls, and extending them by successive layers of clay till they meet; while crowds of masons arrive from all parts with their particle of mortar, and work with a regularity, harmony, and activity, which can never enough be admired. So assiduous are they in their operations, that they will complete a story with all its saloons, vaulted roofs, partitions and galleries, in seven or eight hours. If they begin a story, and for want of moisture are unable to finish it, they pull down again all the crumbling apartments that are not covered in[824].
Another species of ants (F. fusca) are also masons. When they wish to heighten their habitations, they begin by covering the top with a thick layer of clay whichthey transport from the interior. In this layer they trace out the plan of the new story, first hollowing out little cavities of almost equal depth at different distances from each other, and of a size adapted to their purposes. The elevations of earth left between them serve for bases to the interior walls, which, when they have removed all the loose earth from the floors of the apartments, and reduced the foundations to a due thickness, they heighten, and lastly cover all in. M. Huber saw a single working ant make and cover in a gallery which was two or three inches long, and of which the interior was rendered perfectly concave, without assistance[825].
The societies ofF. fuliginosamake their habitations in the trunks of old oaks or willow-trees, gnawing the wood into numberless stories more or less horizontal, the ceilings and floors of which are about five or six lines asunder, black, and as thin as card, sometimes supported by vertical partitions, forming an infinity of apartments which communicate by small apertures; at others by small light cylindrical pillars furnished with a base and capital which are arranged in colonnades, leaving a communication perfectly free throughout the whole extent of the story[826].
Two other tribes of carpenter ants (F. æthiopsandF. flava) use saw-dust in forming their buildings. The former applies this material only to the building of walls and stopping up chinks: the latter composes whole stages or stories of it made into a sort ofpapier mâché, with earth and spiders' web[827].
Some ants form their nests of the leaves of trees. One of these was observed by Sir Joseph Banks in NewSouth Wales, which was formed by glueing together several leaves as large as a hand. To keep these leaves in a proper position, thousands of ants united their strength, and if driven away, the leaves spring back with great violence[828].
The most profound philosopher, equally with the most incurious of mortals, is struck with astonishment on inspecting the interior of abee-hive. He beholds a city in miniature. He sees this city divided into regular streets, these streets composed of houses constructed on the most exact geometrical principles and the most symmetrical plan, some serving for store-houses for food, others for the habitations of the citizens, and a few, much more extensive than the rest, destined for the palaces of the sovereign. He perceives that the substance of which the whole city is built, is one which man, with all his skill, is unable to fabricate; and that the edifices in which it is employed are such, as the most expert artist would find himself incompetent to erect. And the whole is the work of a society of insects! "Quel abîme(he exclaims with Bonnet)aux yeux du sage qu'une ruche d'Abeilles! Quelle sagesse profonde se cache dans cet abîme! Quel philosophe osera le fonder!" Nor have its mysteries yet been fathomed. Philosophers have in all ages devoted their lives to the subject; from Aristomachus of Soli in Cilicia, who, we are told by Pliny, for fifty-eight years attended solely to bees, and Philiscus the Thracian, who spent his whole time in forests investigating their manners, to Swammerdam, Reaumur, Hunter, and Huberof modern times. Still the construction of the combs of a bee-hive is a miracle which overwhelms our faculties.
You are probably aware that the hives with which we provide bees are not essential to their labours, and that they can equally form their city in the hollow of a tree or any other cavity. In whatever situation it is placed, the general plan which they follow is the same. You have seen a honey-comb, and must have observed that it is a flattish cake, composed of a vast number of cells, for the most part hexagonal, regularly applied to each other's sides, and arranged in two strata or layers placed end to end. The interior of a bee-hive, consists of several of these combs fixed to its upper part and sides, arrangedverticallyat a small distance from each other, so that the cells composing them are placed in a horizontal position, and have their openings in opposite directions—not the best position one would have thought for retaining a fluid like honey, yet the bees find no inconvenience on this score. The distance of the combs from each other is about half an inch, that is, sufficient to allow two bees busied upon the opposite cells to pass each other with facility. Besides these vacancies, which form the high roads of their community, the combs are here and there pierced with holes which serve as posterns for easy communication from one to the other without losing time by going round.
The arrangement of the combs is well adapted for its purpose, but it is the construction of the cells which is most admirable and astonishing. As these are formed of wax, a substance secreted by the bees in no great abundance, it is important that as little as possible ofsuch a precious material should be consumed. Bees, therefore, in the formation of their cells have to solve a problem which would puzzle some geometers, namely, a quantity of wax being given, to form of it similar and equal cells of a determinate capacity, but of the largest size in proportion to the quantity of matter employed, and disposed in such a manner as to occupy in the hive the least possible space. Every part of this problem is practically solved by bees. If their cells had been cylindrical, which form seems best adapted to the shape of a bee, they could not have been applied to each other without leaving numberless superfluous vacuities. If the cells were made square or triangular, this last objection, indeed, would be removed; but besides that a greater quantity of wax would have been required, the shape would have been inconvenient to a cylindrical-bodied animal. All these difficulties are obviated by the adoption of hexagonal cells, which are admirably fitted to the form of the insect, at the same time that their sides apply to each other without the smallest vacant intervals.—Another important saving in materials is gained by making a common base serve for two strata of cells. Much more wax as well as room would have been required, had the combs consisted of a single stratum only. But this is not all. The base of each cell is not an exact plane, but is usually composed of three rhomboidal or lozenge-shaped pieces, placed so as to form a pyramidal concavity. From this form it follows that the base of a cell on one side or stratum of the comb is composed of portions of the bases ofthreecells on the other. You will inquire, Where is the advantage of this arrangement? First, a greater degree ofstrength; and secondly, precisely the same as results from the hexagonal sides—a greater capacity with less expenditure of wax. Not only has this been indisputably ascertained, but that the angles of the base of the cell are exactly those which require the smallest quantity of wax. It is obvious that these angles might vary infinitely; but by a very accurate admeasurement Maraldi found, that the great angles were in general 109° 28', the smaller ones 70° 32'. Reaumur ingeniously suspecting that the object of choosing these angles from amongst so many was to spare wax, proposed to M. Kœnig, a skilful geometrician, who was ignorant of Maraldi's experiments, to determine by calculations what ought to be the angle of a hexagonal cell, with a pyramidal bottom formed of three similar and equal rhomboid plates, so that the least matter possible might enter into its construction. For the solution of this problem the geometrician had recourse to the infinitesimal calculus, and found that the great angles of the rhombs should be 109° 26', and of the small angles 70° 34'[829]. What a surprising agreement between the solution of the problem and the actual admeasurement[830]!
Besides the saving of wax effected by the form of thecells, the bees adopt another economical plan suited to the same end. They compose the bottoms and sides of wax of very great tenuity, not thicker than a sheet of writing-paper. But as walls of this thinness at the entrance would be perpetually injured by the ingress and egress of the workers, they prudently make the margin at the opening of each cell three or four times thicker than the walls. Dr. Barclay has recently discovered that though of such excessive tenuity, the sides and bottom of each cell are actuallydouble, or, in other words, that each cell is a distinct, separate, and in some measure an independent structure, agglutinated only to the neighbouring cells, and that when the agglutinating substance is destroyed, each cell may be entirely separated from the rest[831].
You must not imagine that all the cells of a hive are of precisely similar dimensions. As the society consists of three orders of insects differing in size, the cells which are to contain the larvæ of each proportionally differ, those built for the males being considerably larger than those which are intended for the workers. The abode of the larvæ of the queen bee differs still more. It isnot only much larger than any of the rest, but of a quite different form, being shaped like a pear or Florence flask, and composed of a material much coarser than common wax, of which above one hundred times as much is used in its construction as of pure wax in that of a common cell. The situation, too, of these cells (for there are generally three or four, and sometimes many more, even up to thirty or forty, in each hive) is very different from that of the common cells. Instead of being in a horizontal they are placed in a vertical direction, with the mouth downwards, and are usually fixed to the lower edge of the combs, from which they irregularly project like stalactites from the roof of a cavern.—The cells destined for the reception of honey and pollen, differ from those which the larvæ of the males and workers inhabit, only, by being deeper, and thus more capacious; in fact, the very same cells are successively applied to both purposes. When the honey is collected in great abundance, and there is not time to construct fresh cells, the bees lengthen the honey cells by adding a rim to them.
You will be anxious to learn the process which these ingenious artificers follow in constructing their habitations: and on this head I am happy that the recent publication of a new edition of the celebrated Huber'sNew Observations on Bees, in which this subject is for the first time elucidated, will enable me to gratify your curiosity.
But in the first place you must be told of an important and unlooked-for discovery of this unrivalled detector of the hidden mysteries of nature—that the workers or neuters, as they are called, of a hive, consist of two descriptions of individuals, one of which he callsabeilles nourrices,orpetites abeilles, the otherabeilles cirières.—The former, ornurse-bees, are smaller than the latter; their stomach is not capable of such distention; and their office is to build the combs and cells after the foundation has been laid by thecirières; to collect honey; and to feed the larvæ. Theabeilles cirièresare the makers of wax, which substance Huber has now indisputably ascertained to be secreted, as John Hunter long ago suspected, beneath the ventral segments, from between which it is taken by the bees when wanted, in the form of thin scales. The apparatus in which the wax is secreted consists of four pair of membranous bags orwax-pocketssituated at the base of each intermediate segment, one on each side, which can only be seen by pressing the abdomen so as to lengthen it, being usually concealed by the over-lapping of the preceding segments. It should be observed that this discovery was nearly made by our countryman Thorley, who in hisFemale Monarchy(1744) says that he has taken bees with six pieces of wax within the plaits of the abdomen, three on each side. In these pockets the wax is secreted by some unknown process from the food taken into the stomach, which in the wax-making bees is much larger than in the nurse-bees, and afterwards transpires through the membrane of the wax-pocket in thin laminæ. The nurse-bees, however, do secrete wax, but in very small quantities.—When wax is not wanted in the hive, the wax-makers disgorge their honey into the cells.
The process of building the combs in a bee-hive, as observed by Huber, is as follows:
The wax-makers having taken a due portion of honey or sugar, from either of which wax can be elaborated,suspend themselves to each other, the claws of the fore-legs of the lowermost being attached to those of the hind pair of the uppermost, and form themselves into a cluster, the exterior layer of which looks like a kind of curtain. This cluster consists of a series of festoons or garlands, which cross each other in all directions, and in which most of the bees turn their back upon the observer: the curtain has no other motion than what it receives from the interior layers, the fluctuations of which are communicated to it.—All this time thenurse-beespreserve their wonted activity and pursue their usual employments.—The wax-makers remain immoveable for about twenty-four hours, during which period the formation of wax takes place, and thin laminæ of this material may be generally perceived under their abdomen. One of these bees is now seen to detach itself from one of the central garlands of the cluster, to make a way amongst its companions to the middle of the vault or top of the hive, and by turning itself round to form a kind of void, in which it can move itself freely. It then suspends itself to the centre of the space, which it has cleared, the diameter of which is about an inch. It next seizes one of the laminæ of wax with a pincer formed by the posterior metatarsus and tibia[832], and drawing it from beneath the abdominal segment, one of the anterior legs takes it with its claws and carries it to the mouth. This leg holds the lamina with its claws vertically, the tongue rolled up serving for a support, and by elevating or depressing it at will, causes the whole of its circumference to be exposed to the action of the mandibles, so that the margin is soon gnawed into pieces, which drop as they aredetached into the double cavity, bordered with hairs, of the mandibles. These fragments, pressed by others newly separated, fall on one side of the mouth, and issue from it in the form of a very narrow ribband. They are then presented to the tongue, which impregnates them with a frothy liquor like abouillie. During this operation the tongue assumes all sorts of forms; sometimes it is flattened like a spatula; then like a trowel, which applies itself to the ribband of wax; at other times it resembles a pencil terminating in a point. After having moistened the whole of the ribband, the tongue pushes it so as to make it re-enter the mandibles, but in an opposite direction, where it is worked up anew. The liquor mixed with the wax communicates to it a whiteness and opacity which it had not before; and the object of this mixture ofbouillie, which did not escape the observation of Reaumur[833], is doubtless to give it that ductility and tenacity, which it possesses in its perfect state.
The foundress-bee, a name which this first beginner of a comb deserves, next applies these prepared parcels of wax against the vault of the hive, disposing them with the point of her mandibles in the direction which she wishes them to take: and she continues these manœuvres until she has employed the whole lamina that she had separated from her body, when she takes a second, proceeding in the same manner. She gives herself no care to compress the molecules of wax which she has heaped together; she is satisfied if they adhere to each other. At length she leaves her work, and is lost in the crowd of her companions. Another succeeds, and resumes the employment; then a third; all follow the same plan ofplacing their little masses; and if any by chance gives them a contrary direction, another coming removes them to their proper place. The result of all these operations is a mass or little wall of wax with uneven surfaces, five or six lines long, two lines high, and half a line thick, which descends perpendicularly below the vault of the hive. In this first work is no angle nor any trace of the figure of the cells. It is a simple partition in a right line without any inflection.
The wax-makers having thus laid the foundation of a comb, are succeeded by the nurse-bees, which are alone competent to model and perfect the work. The former are the labourers, who convey the stone and mortar; the latter the masons, who work them up into the form which the intended structure requires. One of the nurse-bees now places itself horizontally on the vault of the hive, its head corresponding to the centre of the mass or wall which the wax-makers have left, and which is to form the partition of the comb into two opposite assemblages of cells; and with its mandibles, rapidly moving its head, it moulds in that side of the wall a cavity which is to form the base of one of the cells to the diameter of which it is equal. When it has worked some minutes it departs, and another takes its place, deepening the cavity, heightening its lateral margins by heaping up the wax to right and left by means of its teeth and fore-feet, and giving them a more upright form. More than twenty bees successively employ themselves in this work. When arrived at a certain point, other bees begin on the yet untouched and opposite side of the mass; and commencing the bottom oftwocells, are in turn relieved by others. While still engaged in this labour, the wax-makersreturn and add to the mass, augmenting its extent every way, the nurse-bees again continuing their operations.—After having worked the bottoms of the cells of the first row into their proper forms, they polish them and give them their finish, while others begin the outline of a new series.
The cells themselves, or prisms which result from the re-union and meeting of the sides, are next constructed. These are engrafted on the borders of the cavities hollowed in the mass. The bees begin them by making the contour of the bottoms, which at first is unequal, of equal height: thus all the margins of the cells offer an uniformly level surface from their first origin, and until they have acquired their proper length. The sides are heightened in an order analogous to that which the insects follow in finishing the bottoms of the cells; and the length of these tubes is so perfectly proportioned that there is no observable inequality between them.—It is to be remarked, that though the general form of the cells is hexagonal, that of those first begun ispentagonal, the side next the top of the hive, and by which the comb is attached, being much broader than the rest; whence the comb is more strongly united to the hive than if these cells were of the ordinary shape. It of course follows that the base of these cells, instead of being formed like those of the hexagonal cells of three rhomboids, consists of one rhomboid and two trapeziums.
The form of a new comb is lenticular, its thickness always diminishing towards the edges. This gradation is constantly observable while it keeps enlarging in circumference; but as soon as the bees get sufficient space to lengthen it, it begins to lose this form and to assumeparallel surfaces: it has then received the shape which it will always preserve.
The bees appear to give the proper forms to the bottoms of the cells by means of their antennæ, which extraordinary organs they seem to employ as directors by which their other instruments are instructed to execute a very complex work. They do not remove a single particle of wax until the antennæ have explored the surface that is to be sculptured. By the use of these organs, which are so flexible and so readily applied to all parts, however delicate, that they can perform the functions of compasses in measuring very minute objects, they can work in the dark, and raise those wonderful combs the first production of insects.
Every part of the work appears a natural consequence of that which precedes it, so that chance has no share in the admirable results witnessed. The bees cannot depart from their prescribed route, except in consequence of particular circumstances which alter the basis of their labour. The original mass of wax is never augmented but by an uniform quantity; and what is most astonishing, this augmentation is made by the wax-makers, who are the depositaries of the primary matter, and possess not the art of sculpturing the cells.
The bees never begin two masses for combs at the same time; but scarcely are some rows of cells constructed in the first, when two other masses, one on each side of it, are established at equal distances from it and parallel to it, and then again two more exterior to these. The combs are always enlarged and lengthened in a progression proportioned to the priority of their origin; the middle comb being constantly advanced beyond thetwo adjoining ones by some rows of cells, and they beyond those that are exterior to them. Was it permitted to these insects to lay the foundation of all their combs at the same time, they could not be placed conveniently or parallel to each other. So with respect to the cells, the first cavity determines the place of all that succeed it.
A large number of bees work at the same time on the same comb; but they are not moved to it by a simultaneous but by a successive impulse. A single bee begins every partial operation, and many others in succession add their efforts to hers, each appearing to act individually in a direction impressed either by the workers who have preceded it, or by the condition in which it finds the work. The whole population of wax-makers is in a state of the most complete inaction till one bee goes forth to lay the foundations of the first comb. Immediately others second her intentions, adding to the height and length of the mass; and when they cease to act, a bee, if the term may be used, of another profession, one of the nurse-bees, goes to form the draught of the first cell, in which she is succeeded by others.
The diameters of the cells intended for the larvæ of workers is always 2-2/5 lines, that of those meant for the larvæ of the males or drones 3-1/3 lines. The male cells are generally in the middle of the combs, or in their sides; rarely in their upper part. They are never insulated, but form a corresponding group on both sides the comb. When the bees form male cells below those of neuters, they construct many rows of intermediate ones, the diameter of which augments progressively till it attains that of a male cell; and they observe the same method when they revert from male cells to those of neuters.It appears to be the oviposition of the queen which decides the kind of cells that are to be made: while she lays the eggs of workers, no male cells are constructed; but when she is about to lay the eggs of males, the neuters appear to know it and act accordingly.—When there is a very large harvest of honey, the bees increase the diameter and even the length of their cells. At this time many irregular combs may be seen with cells of twelve, fifteen, and even eighteen lines in length. Sometimes also they have occasion to shorten the cells. When they wish to lengthen on old comb, the tubes of which have acquired their full dimensions, they gradually diminish the thickness of its edges, gnawing down the sides of the cells till it assumes the lenticular form: they then engraft a mass of wax round it, and so proceed with new cells.
Variations, as has been already hinted, sometimes take place in the position and even form of the combs. Occasionally the bees construct cells of the common shape upon the wood to which the combs are fixed, without pyramidal bottoms, and from them continue their work as usual. These cells with a flat bottom, or rather with the wood for their bottom, are more irregular than the common ones; some of their orifices are not angular, and their dimensions are not exact, but all are more or less hexagonal. Once when disturbed, Huber observed them to begin their combs on one of the vertical sides of the hive instead of on the roof. When particular circumstances caused it, as, for instance, when glass was introduced, to which they do not like to fix their combs, he remarked that they constantly varied their direction; and by repeating the attempt, he forced them to formtheir combs in the most fantastic manner. Yet glass is an artificial substance, against which instinct merely cannot have provided them: there is nothing in hollow trees, their natural habitation, resembling it.—When they change the direction of their combs, they enlarge the cells of one side to two or three times the diameter of those of the other, which gives the requisite curve.
To complete the detail of these interesting discoveries of the elder Huber, I must lay before you the following additional observations of his son.
The first base of the combs upon which the bees work holds three or four cells, sometimes more.—The comb continues of the same width for three or four inches, and then begins to widen for three quarters of its length. The bees engaged at the bottom lengthen it downwards; those on the sides widen it to right and left; and those which are employed above the thickest part extend its dimensions upwards. The more a comb is enlarged below, the more it is necessary that it should be enlarged upwards to the top of the hive. The bees that are engaged in lengthening the comb, work with more celerity than those which increase its width; and those that ascend or increase its width upwards, more slowly than the rest. Hence it arises that it is longer than wide, and narrower towards the top than towards the middle.—The first formed cells are usually not so deep as those in the middle; but when the comb is of a certain height, they are in haste to lengthen these cells so essential to the solidity of the whole, sometimes even making them longer than the rest.—The cells are not perfectly horizontal; they are almost always a little higher towardstheir mouth than at their base, so that their axis is not perpendicular to the partition that separates the two assemblages. They sometimes vary from the horizontal line more than 20°, usually 4° or 5°. When the bees enlarge the diameter of the cells preparatory to the formation of male cells, the bottoms often consist of two rhomboids and two hexagons, the size and form of which vary, and they correspond with four instead of three opposite cells.—The works of bees are symmetrical less perhaps in minute details than considered as a whole. Sometimes, indeed, their combs have a fantastic form; but this, if traced, will be found to be caused by circumstances: one irregularity occasions another, and both usually have their origin in the dispositions which we make them adopt. The inconstancy of climate, too, occasions frequent interruptions, and injures the symmetry of the combs; for a work resumed is always less perfect than one followed up until completed.
At first the substance of the cells is of a dead white, semitransparent, soft, and though even, not smooth: but in a few days it loses most of these qualities, or rather acquires new ones; a yellow tint spreads over the cells, particularly their interior surface: their edges become thicker, and they have acquired a consistence, which at first they did not possess. The combs also when finished are heavier than the unfinished ones: these last are broken by the slightest touch, whereas the former will bend sooner than break. Their orifices also have something adhesive, and they melt less readily; whence it is evident that the finished combs contain something not present in the unfinished ones. In examining the orifice of the yellow cells, their contour appeared to theyounger Huber to be besmeared with a reddish varnish, unctuous, strong-scented, and similar to, if not the same as,propolis. Sometimes there were red threads in the interior, which were also applied round the sides, rhombs, or trapeziums. This solder, as it may be called, placed at the point of contact of the different parts, and at the summit of the angles formed by their meeting, seemed to give solidity to the cells, round the axis of the longest of which there were sometimes one or two red zones. From subsequent experiments, M. Huber ascertained that this substance was actuallypropolis, collected from the buds of the poplar. He saw them with their mandibles draw a thread from the mass of propolis that was most conveniently situated, and breaking it by a sudden jerk of the head, take it with the claws of their fore-legs, and then, entering the cell, place it at the angles and sides, &c. which they had previously planished. The yellow colour, however, is not given by the propolis, and it is not certain to what it is owing.—The bees sometimes mix wax and propolis and make an amalgam, known to the ancients and called by themMitysandPissoceros, which they use in rebuilding cells that have been destroyed, in order to strengthen and support the edifice[834].
We know but little of the proceedings of the species of bees not indigenous to Europe, which live in societies and construct combs like that cultivated by us. A traveller in Brazil mentions one there which builds a kind of natural hive: "On an excursion towards upper Tapagippe," says he, "and skirting the dreary woods whichextend to the interior, I observed the trees more loaded with bees' nests than even in the neighbourhood of Porto Seguro. They consist of a ponderous shell of clay, cemented similarly to martins' nests, swelling from high trees about a foot thick, and forming an oval mass full two feet in diameter. When broken, the wax is arranged as in our hives, and the honey abundant[835]."
Humble-beesare the only tribe besides the hive-bee, that in this part of the world construct nests by the united labour of the society. The habitations composing them are of a rude construction, and the streets are arranged with little architectural regularity. The number of inhabitants, too, is small, rarely exceeding two or three hundred, and often not more than twenty. The nests of some species, as ofBombus[836]lapidaria,B. terrestris, &c. are found under ground at the depth of a foot or more below the surface; but as the internal structure of these does not essentially differ from that of the more singular habitations ofB. Muscorum, and as some of the subterranean species occasionally adopt the same situation, I shall confine my description to the latter.
These nests, which do not exceed six or eight inches in diameter, are generally found in meadows and pastures, and sometimes in hedge-rows where the soil is entangled with roots. The lower half occupies a cavity in the soil, either accidentally found ready made, or excavated with great labour by the bees. The upper part or dome of the nest is composed of a thick felted covering of moss, having the interior ceiling coated with athin roof of coarse wax for the purpose of keeping out the wet. The entrance is in the lower part, and is generally through a gallery or covered way, sometimes more than a foot in length and half an inch in diameter, by means of which the nest is more effectually concealed from observation. On removing the coping of moss, the interior presents to our view a very different scene from that witnessed in a bee-hive. Instead of numerous vertical combs of wax, we see merely a few irregular horizontal combs placed one above the other, the uppermost resting upon the more elevated parts of the lower, and connected together by small pillars of wax. Each of these combs consists of several groups of pale-yellow oval bodies of three different sizes, those in the middle being the largest, closely joined to each other, and each group connected with those next it by slight joinings of wax. These oval bodies are not, as you might suppose, the work of the old bees, but the silken cocoons spun by the young larvæ. Some are closed at the upper extremity; others, which chiefly occupy the lower combs, have this part open. The former are those which yet include their immature tenants; the latter are the empty cases from which the young bees have escaped. On the surface of the upper comb are seen several masses of wax of a flattened spheroidal shape, and of very various dimensions: some above an inch and others not a quarter of an inch in diameter: which on being opened are found to include a number of larvæ surrounded with a supply of pollen moistened with honey. These, which are the true cells, are chiefly the work of the female, which after depositing her eggs in them furnishes them with a store of pollen and honey; and, when this is consumed, suppliesthe larvæ with a daily provision, as has been described in a former letter, until they are sufficiently grown to spin the cocoons before spoken of. Lastly, in all the corners of the combs, and especially in the middle, we observe a considerable number of small goblet-like vessels, filled with honey and pollen, which are not, as in the case of the hive-bee, the fabrication of the workers, but are chiefly the empty cocoons left by the larvæ. It falls to the workers, however, to cut off the fragments of silk from the orifice of the cocoon, which, after giving it a regular circular form, they strengthen by a ring or elevated tube of wax made in a different shape by different species; and to coat them internally with a lining of the same material. They even occasionally construct honey-pots entirely of wax[837].
The most curious circumstance in the construction of these nests, is the mode in which the bees transport the moss employed in forming the roof. When they have discovered a parcel of this material conveniently situated upon the ground, five or six insects place themselves upon it in a file, turning the hinder part of their bodies towards the quarter to which it is meant to be conveyed. The first takes a small portion, and with its jaws and fore-legs as it were felts it together. When the fibres are sufficiently entangled, it pushes them under its body by means of the first pair of legs; the intermediate pair receives the moss, and delivers it to the last, which protrudes it as far as possible beyond the anus. When by this process the insect has formed behind it a small ball of well-carded moss, the next bee pushes it to the third, which consigns it in like manner to that behind it; andthus the balls are conveyed to the foot of the nest, and from thence elevated to the summit, much in the same way that a file of labourers transfer a parcel of cheeses from a vessel or cart to a warehouse[838]. It is easy to perceive that a vast saving of time must ensue from this well contrived division of labour; the structure rising much more rapidly than if every individual had been employed first in carding his materials, and then in transferring them to the spot.
Wasps, though ferocious and cruel towards their fellow-insects, are civilized and polished in their intercourse with each other, and form a community whose architectural labours will not suffer on comparison even with those of the peaceful inhabitants of a bee-hive. Like these, the great object of their industry is the erection of a structure for their beloved progeny, towards which they discover the greatest tenderness and affection, and they even in like manner construct combs consisting of hexagonal cells for their reception; but the substance which they make use of is very dissimilar to the wax employed by bees, and the general plan of their city differs in many respects from that of a bee-hive.
The common wasp's nest, usually situated in a cavity under ground, is of an oval figure about sixteen or eighteen inches long by twelve or thirteen broad. Externally it is surrounded by a thick coating of numerous leaves of a sort of grayish paper, which do not touch each other, but have a small interval between each, so that if the rain should chance to penetrate one or two of them, its progress is speedily arrested. On removingthis external covering, we perceive that the interior consists of from twelve to fifteen circular combs of different sizes, not ranged vertically as in a bee-hive, but horizontally, so as to form so many distinct and parallel stories. Each comb is composed of a numerous assemblage of hexagonal cells formed of the same paper-like substance as the exterior covering of the nest, and according to a discovery of Dr. Barclay, each, as in those of bees, a distinct cell, the partition walls being double[839]. These cells, which, as wasps do not store up any food, serve merely as the habitations of their young, are not, like those of the honey-bee, arranged in two opposite layers, but in one only, their entrance being always downwards: consequently the upper part of the comb, composed of the bases of the cells, which are not pyramidal but slightly convex, forms a nearly level floor, on which the inhabitants can conveniently pass and repass, spaces of about half an inch high being left between each comb. Although the combs are fixed to the sides of the nest, they would not be sufficiently strong without further support. The ingenious builders, therefore, connect each comb to that below it by a number of strong cylindrical columns or pillars, having according to the rules of architecture their base and capital wider than the shaft, and composed of the same paper-like material used in other parts of the nest, but of a more compact substance. The middle combs are connected by a rustic colonnade of from forty to fifty of these pillars; the upper and lower combs by a smaller number.
The cells, which in a populous nest are not fewer than 16,000, are of different sizes, corresponding to that ofthe three orders of individuals which compose the community; the largest for the grubs of females, the smallest for those of workers. The last always occupy an entire comb, while the cells of the males and females are often intermixed.—Besides openings which are left between the walls of the combs to admit of access from one to the other, there are at the bottom of each nest two holes, by one of which the wasps uniformly enter, and through the other issue from the nest, and thus avoid all confusion or interruption of their common labours. As the nest is often a foot and a half under ground, it is requisite that a covered way should lead to its entrance. This is excavated by the wasps, who are excellent miners, and is often very long and tortuous, forming a beaten road to the subterranean city, well known to the inhabitants though its entrance is concealed from incurious eyes. The cavity itself which contains the nest is either the abandoned habitation of moles or field-mice, or a cavern purposely dug out by the wasps, which exert themselves with such industry as to accomplish the arduous undertaking in a few days.