Bramble-Bees and Others

by Jean-Henri Fabre

The Carpenter-bee gives us the same answer. When with her joiner's wimble she has patiently bored the beam to a depth of nine inches, would she be able to cut out and place in position the thousand and one pieces which the Silky Leaf-cutter employs for her nest? Time would fail her, even as it would fail a Megachile who, lacking the Capricorn's chamber, had herself to dig a home in the trunk of the oak. Therefore the Carpenter-bee, after the tedious work of boring, gets the installation done in the most summary fashion, simply running up a sawdust partition.

The two things, the laborious business of obtaining a lodging and the artistic work of furnishing, seem unable to go together. With the insect as with man, he who builds the house does not furnish it, he who furnishes it does not build it. To each his share, because of lack of time. Division of labour, the mother of the arts, makes the workman excel in his department; one man for the whole work would mean stagnation, the worker never getting beyond his first crude attempts. Animal industry is a little like our own: it does not attain its perfection save with the aid of obscure toilers, who, without knowing it, prepare the final masterpiece. I see no other reason for this need of a gratuitous lodging for the Megachile's leafy basket or the Anthidia's cotton purses. In the case of other artists who handle delicate things that require protection, I do not hesitate to assume the existence of a ready-made home. Thus Reaumur tells us of the Upholsterer-bee, Anthocopa papaveris, who fashions her cells with poppy-petals. I do not know the flower-cutter, I have never seen her; but her art tells me plainly enough that she must establish herself in some gallery wrought by others, as, for instance, in an Earth-worm's burrow.

We have but to see the nest of a Cotton-bee to convince ourselves that its builder cannot at the same time be an indefatigable navvy. When and newly-felted and not yet made sticky with honey, the wadded purse is by far the most elegant known specimen of entomological nest-building, especially where the cotton is of a brilliant white, as is frequently the case in the manufacturers of the Girdled Anthidium. No bird's-nest, however deserving of our admiration, can vie in fineness of flock, in gracefulness of form, in delicacy of felting with this wonderful bag, which our fingers, even with the aid of tools, could hardly imitate, for all their dexterity. I abandon the attempt to understand how, with its little bales of cotton brought up one by one, the insect, no otherwise gifted than the kneaders of mud and the makers of leafy baskets, manages to felt what it has collected into a homogeneous whole and then to work the product into a thimble-shaped wallet. Its tools as a master-fuller are its legs and its mandibles, which are just like those possessed by the mortar-kneaders and Leaf-cutters; and yet, despite this similarity of outfit, what a vast difference in the results obtained!

To see the Cotton-bees' talents in action seems an undertaking fraught with innumerable difficulties: things happen at a depth inaccessible to the eye; and to persuade the insect to work in the open does not lie in our power. One resource remained and I did not fail to turn to it, though hitherto I have been wholly unsuccessful. Three species, Anthidium diadema, A. manicatum and A. florentinum—the first-named in particular—show themselves quite ready to take up their abode in my reed-apparatus. All that I had to do was to replace the reeds by glass tubes, which would allow me to watch the work without disturbing the insect. This stratagem had answered perfectly with the Three-horned Osmia and Latreille's Osmia, whose little housekeeping-secrets I had learnt thanks to the transparent dwelling-house. Why should it not answer for its Cotton-bees and, in the same way, with the Leaf-cutters? I almost counted on success. Events betrayed my confidence. For four years I supplied my hives with glass tubes and not once did the Cotton-weavers or the Leaf-cutters condescend to take up their quarters in the crystal palaces. They always preferred the hovel provided by the reed. Shall I persuade them one day? I do not abandon all hope.

Meanwhile, let me describe the little that I saw. More or less stocked with cells, the reed is at last closed, right at the orifice, with a thick plug of cotton, usually coarser than the wadding of the honey-satchels. It is the equivalent of the Three-horned Osmia's barricade of mud, of the leaf-putty of Latreille's Osmia, of the Megachiles' barrier of leaves cut into disks. All these free tenants are careful to shut tight the door of the dwelling, of which they have often utilized only a portion. To watch the building of this barricade, which is almost external work, demands but a little patience in waiting for the favourable moment.

The Anthidium arrives at last, carrying the bale of cotton for the plugging. With her fore-legs she tears it apart and spreads it out; with her mandibles, which go in closed and come out open, she loosens the hard lumps of flock; with her forehead she presses each new layer upon the one below. And that is all. The insect flies off, returns the richer by another bale and repeats the performance until the cotton barrier reaches the level of the opening. We have here, remember, a rough task, in no way to be compared with the delicate manufacturer of the bags; nevertheless, it may perhaps tell us something of the general procedure of the finer work. The legs do the carding, the mandibles the dividing, the forehead the pressing; and the play of these implements produces the wonderful cushioned wallet. That is the mechanism in the lump; but what of the artistry?

Let us leave the unknown for facts within the scope of observation. I will question the Diadem Anthidium in particular, a frequent inmate of my reeds. I open a reed-stump about two decimetres long by twelve millimetres in diameter. (About seven and three-quarter inches by half an inch.—Translator's Note.) The end is occupied by a column of cotton-wool comprising ten cells, without any demarcation between them on the outside, so that their whole forms a continuous cylinder. Moreover, thanks to a close felting, the different compartments are soldered together, so much so that, when pulled by the end, the cotton edifice does not break into sections, but comes out all in one piece. One would take it for a single cylinder, whereas in reality the work is composed of a series of chambers, each of which has been constructed separately, independently of the one before, except perhaps at the base.

For this reason, short of ripping up the soft dwelling, still full of honey, it is impossible to ascertain the number of storeys; we must wait until the cocoons are woven. Then our fingers can tell the cells by counting the knots that resist pressure under the cover of wadding. This general structure is easily explained. A cotton bag is made, with the sheath of the reed as a mould. If this guiding sheath were lacking, the thimble shape would be obtained all the same, with no less elegance, as is proved by the Girdled Anthidium, who makes her nest in some hiding-place or other in the walls or the ground. When the purse is finished, the provisions come and the egg, followed by the closing of the cell. We do not here find the geometrical lid of the Leaf-cutters, the pile of disks tight-set in the mouth of the jar. The bag is closed with a cotton sheet whose edges are soldered by a felting-process to the edges of the opening. The soldering is so well done that the honey-pouch and its cover form an indivisible whole. Immediately above it, the second cell is constructed, having its own base. At the beginning of this work, the insect takes care to join the two storeys by felting the ceiling of the first to the floor of the second. Thus continued to the end, the work, with its inner solderings, becomes an unbroken cylinder, in which the beauties of the separate wallets disappear from view. In very much the same fashion, but with less adhesion among the different cells, do the Leaf-cutters act when stacking their jars in a column without any external division into storeys.

Let us return to the reed-stump which gives us these details. Beyond the cotton-wool cylinder wherein ten cocoons are lodged in a row comes an empty space of half a decimetre or more. (About two inches.—Translator's Note.) The Osmiae and the Leaf-cutters are also accustomed to leave these long, deserted vestibules. The nest ends, at the orifice of the reed, with a strong plug of flock coarser and less white than that of the cells. This use of closing-materials which are less delicate in texture but of greater resisting-power, while not an invariable characteristic, occurs frequently enough to make us suspect that the insect knows how to distinguish what is best suited now to the snug sleeping-berth of the larvae, anon to the defensive barricade of the home. Sometimes the choice is an exceedingly judicious one, as is shown by the nest of the Diadem Anthidium. Time after time, whereas the cells were composed of the finest grade of white cotton, gathered from Centaurea solsticialis, or St. Barnaby's thistle, the barrier at the entrance, differing from the rest of the work in its yellow colouring, was a heap of close-set bristles supplied by the scallop-leaved mullein. The two functions of the wadding are here plainly marked. The delicate skin of the larvae needs a well-padded cradle; and the mother collects the softest materials that the cottony plants provide. Rivalling the bird, which furnishes the inside of the nest with wool and strengthens the outside with sticks, she reserves for the grubs' mattress the finest down, so hard to find and collected with such patience. But, when it becomes a matter of shutting the door against the foe, then the entrance bristles with forbidding caltrops, with stiff, prickly hairs.

This ingenious system of defence is not the only one known to the Anthidia. More distrustful still, the Manicate Anthidium leaves no space in the front part of the reed. Immediately after the column of cells, she heaps up, in the uninhabited vestibule, a conglomeration of rubbish, whatever chance may offer in the neighbourhood of the nest: little pieces of gravel, bits of earth, grains of sawdust, particles of mortar, cypress-catkins, broken leaves, dry Snail-droppings and any other material that comes her way. The pile, a real barricade this time, blocks the reed completely to the end, except about two centimetres (About three-quarters of an inch.—Translator's Note.) left for the final cotton plug. Certainly no foe will break in through the double rampart; but he will make an insidious attack from the rear. The Leucopsis will come and, with her long probe, thanks to some imperceptible fissure in the tube, will insert her dread eggs and destroy every single inhabitant of the fortress. Thus are the Manicate Anthidium's anxious precautions outwitted.