Insect life: Souvenirs of a naturalist

by Jean-Henri Fabre

After choosing a boulder, she comes with a pellet of mortar in her mandibles, and arranges it in a ring on the surface of the pebble. The forefeet, and above all the mandibles, which are her most important tools, work the material, which is kept plastic by the gradually disgorged saliva. To consolidate the unbaked clay, angular pieces of gravel, as large as a small bean, are worked in singly on the outside of the still soft mass. This is the foundation of the edifice. Other layers are added until the cell has the required height of three or four centimetres. The masonry is formed by stones laid on one another and cemented with lime, and can stand comparison with our own. True, to economise labour and mortar, the bee uses coarse materials,—large bits of gravel, which in her case answer to hewn blocks. They are chosen singly—very hard ones, almost always with angles which, fitted together, give mutual support, and add solidity to the whole. Layers of mortar, sparingly used, hold them together. The outside of the cell thus assumes the look of a piece of rustic architecture, in which stones project with their natural inequalities; but over the inside, which requires a smoother surface in order not to wound the tender skin of the larva, is spread a wash of pure mortar—artlessly, however, as if by broad sweeps of a trowel; and when it has eaten up its honey paste, the grub [[282]]takes care to make a cocoon and hang the rude wall of its abode with silk. The Anthophora and Halictus, whose larvæ spin no cocoon, varnish the inside of their earthen cells delicately, giving them the polish of worked ivory.

The construction, the axis of which is always nearly vertical, with an orifice opening upward, so that the fluid honey may not run out, differs a little in form, according to its basis. On a horizontal surface it rises like a little oval tower; on a vertical or slanting one it resembles half a thimble cut down its length. In this case the support—the pebble itself—completes the surrounding wall. The cell completed, the bee sets to work at once to store it. The neighbouring flowers, especially those of Genista scorpius, which in May turn the alluviums of the torrents golden, furnish sugared liquid and pollen. She comes with her crop swelled with honey, and all yellow underneath with pollen dust, and plunges head first into the cell, where for some moments one may see her work her body in a way which tells that she is disgorging honey. Her crop emptied, she comes out, but only to go in again at once—this time backwards. With her two hind feet she now frees herself from her load, of pollen by brushing herself underneath. Again she goes out, and returns head first. She must stir the materials with her mandibles for a spoon, and mix all thoroughly together. This labour of mixing is not repeated after every journey, but only from time to time, when a considerable quantity has been collected. When the cell is half full, it is stored; an egg must be laid on the honey paste, and the door [[283]]has to be closed. This is all done without delay. The orifice is closed by a cover of undiluted mortar, worked from the circumference to the centre. Two days at most seem required for the whole work, unless bad weather or a cloudy day should interrupt it. Then, backing on the first cell, a second is built and stored in the same way, and a third and fourth, etc., follow, each one with honey and an egg, and closed before another is begun. Work once begun is continued until it is completed, the bee never building a new cell until the four acts required to perfect the preceding one are performed—namely, construction, provisioning, an egg, and sealing the cell.

As Chalicodoma muraria always works alone on her chosen boulder, and shows great jealousy if her neighbours alight there, the number of cells clustered on one pebble is not great—usually six to ten. Are some eight larvæ her whole progeny, or will she establish a more numerous family on other boulders? The surface of the stone would allow of more cells if she had eggs for them, and the bee might build there very comfortably without hunting for another, or leaving the one to which she is attached by habit and long acquaintance. I think, therefore, that most probably all her scanty family are settled on the same stone—at all events when she builds a new abode.

The six or ten cells composing the group are certainly a solid dwelling, with their rustic covering of gravel, but the thickness of their walls and lids—two millimetres at most—hardly seems sufficient against rough weather. Set on its stone in the open [[284]]air, quite unsheltered, the nest will undergo the heat of summer suns which will turn every cell into an oven; then will come the autumn rains which will slowly eat away the masonry, and then winter frosts which will crumble what the rain may have respected. However hard the cement may be, can it resist all these attacks, and if it can, will not the larvæ, sheltered by so thin a wall, suffer from over-heat in summer and too keen cold in winter?

Without having gone through all these arguments, the bee acts wisely. When all the cells are completed she builds a thick cover over the whole group, which, being of a material impermeable to water and almost a non-conductor, is at once a defence against heat and cold and damp. This material is the usual mortar, made of earth and saliva, only with no small stones in it. The bee lays it on,—one pellet after another, one trowelful and then a second,—till there is a layer a centimetre thick over all the cells, which disappear entirely under it. The nest is now a rude dome, about as big as half an orange; one would take it for a clod of mud, half crushed by being flung against a stone where it had dried. Nothing outside betrays its contents—no suggestion of cells—none of labour. To the ordinary eye it is only a chance splash of mud.

This general cover dries as rapidly as do our hydraulic cements, and the nest is almost as hard as a stone. A knife with a strong blade is needed to cut it. In its final shape the nest recalls in no degree the original work; one would suppose the elegant turrets adorned with pebble work, and the final dome, looking like a bit of mud, to be the work of [[285]]two different species. But scratch away the cover of cement and we recognise the cells and their layers of tiny pebbles. Instead of building on a boulder yet unoccupied, Chalicodoma muraria likes to utilise old nests which have lasted through the year without notable injury. The mortared dome has remained much as it was at the beginning, so solid was the masonry; only it is pierced by a number of round holes corresponding to the chambers inhabited by the larvæ of the past generation. Such dwellings, only needing a little repair to put them in good condition, economise much time and toil; so Mason Bees seek them, and only undertake new constructions when old nests fail them.

From the same dome come forth brothers and sisters—reddish males and black females—all descendants of the same bee. The males lead a careless life, avoiding all labour, and only returning to their clay dwellings for a brief courtship of their ladies; and they care nothing for the deserted dwelling. What they want is nectar from flower-cups, not mortar between their mandibles. But there are the young mothers, who have sole charge of the future of the family—to which of them will fall the inheritance of the old nest? As sisters they have an equal right to it—so would human justice decide, now that it has made the enormous progress of freeing itself from the old savage right of primogeniture; but Mason Bees have not got beyond the primitive basis of property—the right of the first comer.

So when the time to lay has come, a bee takes the first free nest which suits her and establishes herself [[286]]there, and woe to any sister or neighbour who thenceforward disputes possession of it. A hot reception and fierce pursuit would soon put the new-comer to flight; only one cell is wanted at the moment out of all which gape like little wells around the dome, but the bee calculates that by and by the rest will be useful, and she keeps a jealous watch on them all and drives away every visitor. I cannot remember having seen two Mason Bees working on the same pebble.

The work is now very simple. The bee examines the inside of the old cell to see where repairs are needed, tears down the rags of cocoon hanging on the walls, carries out the bits of earth fallen from the vault pierced by the inhabitant in order to get out, mortars any places out of repair, mends the orifice a little, and that is all. Then comes storage, laying an egg, and stopping up the cell. When these are successively completed, the general cover, the mortar dome, is repaired if necessary, and all is finished.

Chalicodoma sicula prefers a sociable life to a solitary one, and hundreds—nay, several thousands—will establish themselves on the under surface of the tiles on a hovel, or the edge of a roof. It is not a real society with common interests, dear to all, but merely a gathering where each works for herself and is not concerned for the rest—a throng recalling the swarm of a hive only by their number and industry. They use the same mortar as Chalicodoma muraria, equally resistant and waterproof, but finer and without pebbles. First the old nests are utilised. Every free cell is repaired, stored, and shut up. But the old ones are far from sufficing to the population, which increases rapidly year by year, and on the [[287]]surface of the nest, where the cells are hidden below the old general mortar covering, new ones are built as required. They are placed more or less horizontally, one beside another, with no kind of order. Every constructor builds as the fancy takes her, where and as she wills; only she must not interfere with her neighbour’s work, or rough treatment will soon call her to order. The cells accumulate in chance fashion in this workyard, where there is no general plan whatever. Their form is that of a thimble divided down the axis, and their enclosure is completed either by adjacent cells, or the surface of the old nest. Outside they are rough, and look like layers of knotted cords corresponding to the layers of mortar. Inside the walls are level but not smooth; a cocoon will replace the absent polish.