Insect Architecture

by James Rennie

"Several naturalists notice the irregularities in the cells of bees as so many defects. What would have been their astonishment had they observed that part of them are the result of calculation? Had they followed the imperfection of their organs, some other means of compensating them would have been granted to the insects. It is much more surprising that they know how to quit the ordinary route, when circumstances demand the construction of enlarged cells; and, after building thirty or forty rows of them, to return to the proper proportions from which they have departed by successive reductions. Bees also augment the dimensions of their cells when there is an opportunity for a great collection of honey. Not only are they then constructed of a diameter much exceeding that of the common cells, but they are elongated throughout the whole space admitting it. A great portion of irregular comb contains cells an inch, or even an inch and a half, in depth.

"Bees, on the contrary, sometimes are induced to shorten their cells. When wishing to prolong an old comb, whose cells have received their full dimensions, they gradually reduce the thickness of its edges, by gnawing down the sides of the cells, until they restore it to its original lenticular form. They add a waxen block around the whole circumference, and on the edge of the comb construct pyramidal bottoms, such as those fabricated on ordinary occasions. It is a certain fact, that a comb never is extended in any direction unless the bees have thinned the edges, which are diminished throughout a sufficient space to remove any angular projection.

"The law which obliges these insects partly to demolish the cells on the edges of the comb before enlarging it, unquestionably demands more profound investigation. How can we account for instinct leading them to undo what they have executed with the utmost care? The wonted regular gradation which may be necessary for new cells, subsists among those adjoining the edges of a comb recently constructed. But afterwards, when those on the edge are deepened like the cells of the rest of the surface, the bees no longer preserve the decreasing gradation which is seen in the new combs."[AW]

The Finishing of the Cells.

While the cells are building they appear to be of a dull white colour, soft, even, though not smooth, and translucent; but in a few days they become tinged with yellow, particularly on the interior surface; and their edges, from being thin, uniform, and yielding, become thicker, less regular, more heavy, and so firm that they will bend rather than break. New combs break on the slightest touch. There is also a glutinous substance observable around the orifices of the yellow cells, of reddish colour, unctuous, and odoriferous. Threads of the same substance are applied all around the interior of the cells, and at the summit of their angles, as if it were for the purpose of binding and strengthening the walls. These yellow cells also require a much higher temperature of water to melt them than the white ones.

It appeared evident, therefore, that another substance, different from wax, had been employed in varnishing the orifices, and strengthening the interior of the cells. M. Huber, by numerous experiments, ascertained the resinous threads lining the cells, as well as the resinous substance around their orifice, to be propolis; for he traced them, as we mentioned in our account of propolis, from the poplar buds where they collected it, and saw them apply it to the cells; but the yellow colour is not imparted by propolis, to which it bears no analogy. We are, indeed, by no means certain what it is, though it was proved by experiment not to arise from the heat of the hives, nor from emanations of honey, nor from particles of pollen. Perhaps it may be ascribed to the bees rubbing their teeth, feet, and other parts of their body, on the surfaces where they seem to rest; or to their tongue (haustellum) sweeping from right to left like a fine pliant pencil, when it appears to leave some sprinkling of a transparent liquid.

Besides painting and varnishing their cells in this manner, they take care to strengthen the weaker part of their edifice by means of a mortar composed of propolis and wax, and named pissoceros[AX] by the ancients who first observed it, though Réaumur was somewhat doubtful respecting the existence of such a composition. We are indebted to the shrewd observations of Huber for a reconcilement of the Roman and the French naturalists. The details which he has given of his discovery are perhaps the most interesting in his delightful book.

“Soon,” he says, "after some new combs had been finished in a hive, manifest disorder and agitation prevailed among the bees. They seemed to attack their own works. The primitive cells, whose structure we had admired, were scarcely recognizable. Thick and massive walls, heavy, shapeless pillars, were substituted for the slight partitions previously built with such regularity. The substance had changed along with the form, being composed apparently of wax and propolis. From the perseverance of the workers in their devastation, we suspected that they proposed some useful alteration of their edifices; and our attention was directed to the cells least injured. Several were yet untouched; but the bees soon rushed precipitately on them, destroyed the tubes, broke down the wax, and threw all the fragments about. But we remarked that the bottom of the cells of the first row were spared; neither were the corresponding parts on both faces of the comb demolished at the same time. The bees laboured at them alternately, leaving some of the natural supports, otherwise the comb would have fallen down, which was not their object: they wished, on the contrary, to provide it a more solid base, and to secure its union to the vault of the hive, with a substance whose adhesive properties infinitely surpassed those of wax. The propolis employed on this occasion had been deposited in a mass over a cleft of the hive, and had hardened in drying, which probably rendered it more suitable for the purpose. But the bees experienced some difficulty in making any impression on it; and we thought, as also had appeared to M. de Réaumur, that they softened it with the same frothy matter from the tongue which they use to render wax more ductile.

"We very distinctly observed the bees mixing fragments of old wax with the propolis, kneading the two substances together to incorporate them; and the compound was employed in rebuilding the cells that had been destroyed. But they did not now follow their ordinary rules of architecture, for they were occupied by the solidity of their edifices alone. Night intervening, suspended our observations, but next morning confirmed what we had seen.

“We find, therefore, that there is an epoch in the labour of bees, when the upper foundation of their combs is constructed simply of wax, as Réaumur believed; and that, after all the requisite conditions have been attained, it is converted to a mixture of wax and propolis, as remarked by Pliny so many ages before us. Thus is the apparent contradiction between these two great naturalists explained. But this is not the utmost extent of the foresight of these insects. When they have plenty of wax, they make their combs the full breadth of the hive, and solder them to the glass or wooden sides, by structures more or less approaching the form of cells, as circumstances admit. But should the supply of wax fail before they have been able to give sufficient diameter to the combs whose edges are rounded, large intervals remain between them and the upright sides of the hive, and they are fixed only at the top. Therefore, did not the bees provide against it, by constructing great pieces of wax mixed with propolis, in the intervals, they might be borne down by the weight of the honey. These pieces are of irregular shape, strangely hollowed out, and their cavities void of symmetry.”[AY]