Part 11

M. Réaumur differs from our English naturalists, White, and Kirby and Spence, with respect to the materials employed by the hornet for building. The latter say that it employs decayed wood; the former, that it uses the bark of the ash-tree, but takes less pains to split it into fine fibres than wasps do; not, however, because it is destitute of skill; for in constructing the suspensory columns of the platforms, a paste is prepared little inferior to that made by wasps. We cannot, from our own observations, decide which of the above statements is correct, as we have only once seen a hornet procuring materials, at Compton-Bassett, in Wiltshire; and in that case it gnawed the inner bark of an elm which had been felled for several months, and was, consequently, dry and tough. Such materials as this would account for the common yellowish-brown colour of a hornet's nest. (J. R.)

When hornets make choice of a tree for their domicile, they select one which is in a state of decay, and already partly hollowed; but they possess the means, in their sharp and strong mandibles, of extending the excavation to suit their purposes; and Réaumur frequently witnessed their operations in mining into a decayed tree, and carrying off what they had gnawed. He observed, also, that in such cases they did not make use of the large hole of the tree for an entrance, but went to the trouble of digging a gallery, sufficient for the passage of the largest hornet in the nest, through the living and undecayed portion of the tree. As this is perforated in a winding direction, it is no doubt intended for the purpose of protecting the nest from the intrusion of depredators, who could more easily effect an entrance if there were not such a tortuous way to pass through.

Hornets are in one sense more industrious than wasps. When night falls, the wasps betake themselves to their home, and sleep throughout the night. But, if the moon be up, the hornet is sure to work throughout the entire night, and will often do so, even when no moon is visible.]

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One of the most remarkable of our native social wasps is the tree-wasp (Vespa Britannica), which is not uncommon in the northern, but is seldom to be met with in the southern parts of the island. Instead of burrowing in the ground like the common wasp (Vespa vulgaris), or in the hollows of trees like the hornet (Vespa crabro), it boldly swings its nest from the extremity of a branch, where it exhibits some resemblance, in size and colour, to a Welsh wig hung out to dry. We have seen more than one of these nests on the same tree, at Catrine, in Ayrshire, and at Wemyss Bay, in Renfrewshire. The tree which the Britannic wasp prefers is the silver fir, whose broad flat branch serves as a protection to the suspended nest both from the sun and the rain. We have also known a wasp's nest of this kind in a gooseberry-bush, at Red-house Castle, East Lothian. The materials and structure are nearly the same as those employed by the common wasp, and which we have already described. (J. R.)

A singular nest of a species of wasp is figured by Réaumur, but is apparently rare in this country, as Kirby and Spence mention only a single nest of similar construction, found in a garden at East-Dale. This nest is of a flattened globular figure, and composed of a great number of envelopes, so as to assume a considerable resemblance to a half-expanded Provence rose. The British specimen mentioned by Kirby and Spence had only one platform of cells; Réaumur had two; but there was a large vacant space, which would probably have been filled with cells, had the nest not been taken away as a specimen. The whole nest was not much larger than a rose, and was composed of paper exactly similar to that employed by the common ground-wasp.

There is another species of social-wasp (Epipone nidulans, Latr.) meriting attention from the singular construction of its nest. It forms one or more terraces of cells, similar to those of the common wasp, but without the protection of an outer wall, and quite exposed to the weather. Swammerdam found a nest of this description attached to the stem of a nettle. Réaumur says that they are sometimes attached to the branch of a thorn or other shrub, or to stalks of grass;--peculiarities which prove that there are several species of these wasps.

The most remarkable circumstance in the architecture of this species of vespiary is, that it is not horizontal, like those formerly described, but nearly vertical. The reason appears to be, that if it had been horizontal, the cells must have been frequently filled with rain; whereas, in the position in which it is placed, the rain runs off without lodging. It is, besides, invariably placed so as to face the north or the east, and consequently is less exposed to rains, which most frequently come with southerly or westerly winds. It is another remarkable peculiarity, that, unlike the nests of other wasps, it is covered with a shining coat of varnish, to prevent moisture from soaking into the texture of the wasp's paper. The laying on this varnish, indeed, forms a considerable portion of the labour of the colony, and individuals may be seen employed for hours together spreading it on with their tongues.

Few circumstances are more striking, with regard to insects, as Kirby and Spence justly remark, than the great and incessant labour which maternal affection for their progeny leads them to undergo. Some of these exertions are so disproportionate to the size of the insect, that nothing short of ocular conviction could attribute them to such an agent. A wild bee, or a wasp, for instance, as we have seen, will dig a hole in a hard bank of earth some inches deep, and five or six times its own size, labouring unremittingly at this arduous task for several days in succession, and scarcely allowing itself a moment for eating or repose. It will then occupy as much time in searching for a store of food; and no sooner is this finished, than it will set about repeating the process, and, before it dies, will have completed five or six similar cells, or even more.

We shall have occasion more particularly to dwell upon the geometrical arrangement of the cells, both of the wasp and of the social-bee, in our description of those interesting operations, which have long attracted the notice, and commanded the admiration of mathematicians and naturalists. A few observations may here be properly bestowed upon the material with which the wasp-family construct the interior of their nests.

The wasp is a paper-maker, and a most perfect and intelligent one. While mankind were arriving, by slow degrees, at the art of fabricating this valuable substance, the wasp was making it before their eyes, by very much the same process as that by which human hands now manufacture it with the best aid of chemistry and machinery. While some nations carved their records on wood, and stone, and brass, and leaden tablets,--others, more advanced, wrote with a style on wax,--others employed the inner bark of trees, and others the skins of animals rudely prepared,--the wasp was manufacturing a firm and durable paper. Even when the papyrus was rendered more fit, by a process of art, for the transmission of ideas in writing, the wasp was a better artisan than the Egyptians; for the early attempts at paper-making were so rude, that the substance produced was almost useless, from being extremely friable. The paper of the papyrus was formed of the leaves of the plant, dried, pressed, and polished; the wasp alone knew how to reduce vegetable fibres to a pulp, and then unite them by a size or glue, spreading the substance out into a smooth and delicate leaf. This is exactly the process of paper-making. It would seem that the wasp knows, as the modern paper-makers now know, that the fibres of rags, whether linen or cotton, are not the only materials that can be used in the formation of paper; she employs other vegetable matters, converting them into a proper consistency by her assiduous exertions. In some respects she is more skilful even than our paper-makers, for she takes care to retain her fibres of sufficient length, by which she renders her paper as strong as she requires. Many manufacturers of the present day cut their material into small bits, and thus produce a rotten article. One great distinction between good and bad paper is its toughness; and this difference is invariably produced by the fibre of which it is composed being long, and therefore tough; or short, and therefore friable.

The wasp has been labouring at her manufacture of paper from her first creation, with precisely the same instruments and the same materials; and her success has been unvarying. Her machinery is very simple, and therefore it is never out of order. She learns nothing, and she forgets nothing. Men, from time to time, lose their excellence in particular arts, and they are slow in finding out real improvements. Such improvements are often the effect of accident. Paper is now manufactured very extensively by machinery in all its stages; and thus, instead of a single sheet being made by hand, a stream of paper is poured out, which would form a roll large enough to extend round the globe, if such a length were desirable. The inventors of this machinery, Messrs. Fourdrinier, it is said, spent the enormous sum of 40,000l.. in vain attempts to render the machine capable of determining with precision the width of the roll; and, at last, accomplished their object, at the suggestion of a bystander, by a strap revolving upon an axis, at a cost of three shillings and sixpence. Such is the difference between the workings of human knowledge and experience, and those of animal instinct. We proceed slowly and in the dark, but our course is not bounded by a narrow line, for it seems difficult to say what is the perfection of any art; animals go clearly to a given point--but they can go no further. We may, however, learn something from their perfect knowledge of what is within their range. It is not improbable that if man had attended in an earlier state of society to the labours of wasps, he would have sooner known how to make paper. We are still behind in our arts and sciences, because we have not always been observers. If we had watched the operations of insects, and the structure of insects in general, with more care, we might have been far advanced in the knowledge of many arts which are yet in their infancy, for nature has given us abundance of patterns. We have learnt to perfect some instruments of sound by examining the structure of the human ear; and the mechanism of an eye has suggested some valuable improvements in achromatic glasses.

Réaumur has given a very interesting account of the wasps of Cayenne (Chartergus nidulans), which hang their nests in trees. Like the bird of Africa called the social grosbeak (Loxia socia), they fabricate a perfect house, capable of containing many hundreds of their community, and suspend it on high out of the reach of attack. But the Cayenne wasp is a more expert artist than the bird. He is a pasteboard-maker;--and the card with which he forms the exterior covering of his abode is so smooth, so strong, so uniform in its texture, and so white, that the most skilful manufacturer of this substance might be proud of the work. It takes ink admirably.

The nest of the pasteboard-making wasp is impervious to water. It hangs upon the branch of a tree, as represented in the engraving; and those rain-drops which penetrate through the leaves never rest upon its hard and polished surface. A small opening for the entrance of the insects terminates its funnel-shaped bottom. It is impossible to unite more perfectly the qualities of lightness and strength.

In the specimen from which we take our description, the length of which is nine inches, six stout circular platforms stretch internally across, like so many floors, and fixed all round to the walls of the nest. They are smooth above, with hexagonal cells on the under surface. These platforms are not quite flat, but rather concave above, like a watch-glass reversed; the centre of each platform is perforated for the admission of the wasps, at the extremity of a short funnel-like projection, and through this access is gained from story to story. On each platform, therefore, can the wasps walk leisurely about attending to the pupæ secured in the cells, which, with the mouths downward, cover the ceiling above their heads--the height of the latter being just convenient for their work.

Pendent wasps' nests of enormous size are found in Ceylon, suspended often in the talipot-tree at the height of seventy feet. The appearance of these nests thus elevated, with the larger leaves of the tree, used by the natives as umbrellas and tents, waving over them, is very singular. Though no species of European wasp is a storer of honey, yet this rule does not apply to certain species of South America. In the 'Annals and Magazine of Natural History' for June, 1841, will be found a detailed account, with a figure, of the pendent nest of a species termed by Mr. A. White Myrapetra scutellaris. The external case consists of stout cardboard covered with conical knobs of various sizes. The entrances are artfully protected by pent-roofs from the weather and heavy rains; and are tortuous, so as to render the ingress of a moth or other large insect difficult. Internally are fourteen combs, exclusive of a globular mass, the nucleus of several circular combs, which are succeeded by others of an arched form--that is, constituting segments of circles. Many of the uppermost combs were found to have the cells filled with honey of a brownish-red colour, but which had lost its flavour. After entering into some minute details, Mr. A. White makes the following interesting observations:--"Azara, in the account of his residence in various parts of South America, mentions the fact of several wasps of these countries collecting honey. The Baron Walchenaer, who edited the French translation of this work, published in 1809, thought that the Spanish traveller, who was unskilled in entomology, had made some mistake with regard to the insects, and regarded the so-called wasps as belonging to some bee of the genus of which Apis amalthea is the type (Melipona). Latreille (who afterwards corrected his mistake) also believed that they must be referred to the genera Melipona or Trigona--insects which in South America take the place of our honey-bee. These authors were afterwards clearly convinced of the correctness of Azara's observations, by the circumstance of M. Auguste de St. Hilaire finding near the river Uruguay an oval grey-coloured nest of a papery consistence, like that of the European wasps, suspended from the branches of a small shrub about a foot from the ground: he and two other attendants partook of some honey (contained in its cells) and found it of an agreeable sweetness, free from the pharmaceutic taste which so frequently accompanies European honey. He gives a detailed account of its poisonous effects on himself and his two men. Afterwards he procured specimens of the wasp, which was described by Latreille under the name of Polistes Lecheguana."

The material is probably the dung of the Capincha, an animal allied to the guinea-pig and the agouti. The natives, at all events, state that such is the case, and the aspect of the nest as seen through a magnifying glass carries out this assertion. The nest is hung to a branch, and is seldom more than four feet from the ground. The insect is a very little one in comparison with the size of the nest, which is sixteen inches in length, and twelve in width. The largest specimens of this insect are only one third of an inch long, while the generality scarcely exceed a quarter of an inch. Its colour is brown.

In the section is shown the very peculiar shape of the combs. At the upper part is seen the globular centre, surrounded with a comb that completely encircles it. Other combs follow in order, but are less curved as they approach the bottom of the nest. The insects obtain admission to the several tiers by means of apertures which are left between the extremities of the comb and the wall of the nest. The combs are made of the same material as the outer wall, but are very thin and paper-like. This nest may be seen in the British Museum.]

It would seem that the nest described by Mr. White agrees with that of a wasp termed Chiguana by Azara (or Lecheguana), and is very different to the slight papery nest of the Polistes Lecheguana of Latreille. We may add that M. Auguste de St. Hilaire speaks of two species of wasps remarkable for storing honey in South America; the honey of one is white, of the other reddish. That the habits of these honey-wasps must differ considerably from those of any of our European species we may at once admit; perhaps in some points of their economy these insects may approach the bee.

In the accompanying illustration are shown the habitations of two remarkable insects, both belonging to the Hymenoptera. Indeed, the greater number of pensile nests made by insects are formed by members of this important order; and, if we were to exclude all the wasps, bees, and ants, we should find that we had excluded about ninety per cent. of the pensile architects.

The left-hand figure represents a nest made by a species of Polybia, inhabiting Brazil. It is made of a papery kind of substance, of rather slight texture, and is fixed to the stalk of a reed. The outside of the nest is seen to be marked with a series of horizontal ribs. These show the progressive stages of the nest, each rib marking a layer of paper as it was spread by the insect builder. The combs extend throughout the entire nest, the largest occupying the centre, and the smallest the ends. Each comb is firmly supported by a footstalk, which is fixed, not to the upper tier of cells, as is the case with the British wasps, but to the reed on which the nest is built.

Other species of Polybia build nests different in shape and arrangement, though still of the pensile character. One species builds a nearly globular nest, made in a rather curious manner. Carrying out still farther the principle on which the cardboard wasp enlarges its nest, the Polybia entirely covers the outer wall with cells, and then makes a new wall over them. When a nest has reached a tolerable size, it is composed of a whole series of concentric combs, the roof of each having been originally the outer wall of the nest. There are in the British Museum some admirable specimens of these nests, in some of which the process of enlargement can be very clearly traced. Patches of new cells are seen upon the external covering, while a few breaches in the structure show the concentric combs.

One very curious point about these cells is, that they are not uniform in their direction, as is generally the case with those of social hymenoptera. The greater part, such as the various wasps, hornets, and their kin, have the mouths of the cells downwards, while the cells of the hive-bee are nearly horizontal. But the cells of this insect are arranged without the least regard to their position, all the bases pointing towards the centre of the nest, and all the mouths radiating outwards.

There seems to be scarcely any bound to the variety which exists in the nests of the social hymenoptera. The insect which makes the nest which is represented in the illustration is a native of Brazil, and is known to entomologists as Synæca cyanea. The first of these names is given to it on account of its social habits, and the second, in reference to the bluish colour of its body. It is rather larger than the preceding insects, being about three quarters of an inch in length. Its wings are brown.

The shape and size of the nest are exceedingly variable, but it is almost invariably longer than wide, and is fixed to a branch or some similar object. Sometimes it attains considerable dimensions, and has been known to measure a full yard in length. Yet, however large it may be, there is only a single comb, which is set upon the side of the nest next the branch, and, in consequence, has almost all its cells placed in a horizontal direction. In the illustration, the right-hand figure represents the external appearance of the nest, and the central figure shows the manner in which the single comb is set upon the branch. The nest which occupies the left hand of the illustration is made by a species of Polybia, and is here given in order to show a remarkable example of similarity in the mode of building adopted by two different insects. In the one case, however, the cells are all fastened by their bases to the branch, but in the other the cells are attached to one common base which is prolonged into a footstalk.

There have been lately discovered some very remarkable social nests. Specimens of both these nests may be seen in the entomological department of the museum at Oxford.

The first is formed very much like a rather flattened Florence flask, and is hung by the neck from the branch of a tree. It is made of a strong, parchment-like substance, formed by innumerable silken threads woven and matted together into a kind of felt. When it was cut open a most singular sight was exhibited. Nearly the whole of the interior was covered with the pupæ of some butterfly, all hanging by their tails, and many of them suspended to a twig which projected downwards into the nest. Although the nest is barely eight inches in length, a great proportion of which is taken up by the neck, about one hundred pupæ were found in it. At the bottom of the nest is a small and nearly circular aperture, through which the insects could make their way as soon as they escaped from the pupal envelope, and before their wings became extended and hardened.

The butterfly which makes this singular nest is a native of Mexico, and is named Eucheira socialis. The colour of its wings is dark brown, with an ill-defined white band across them.