In the first rank of these free tenants, I will place an Osmia (Osmia cyanoxantha, PEREZ) and a Megachile, or Leaf-cutting Bee (Megachile apicalis, SPIN.) (Cf. "Bramble-dwellers and Others": chapter 8.—Translator's Note.), both of whom work in May, at the same time as the Mason, while both are small enough to lodge from five to eight cells in a single chamber of the Chalicodoma, a chamber increased by the addition of an outer hall. The Osmia subdivides this space into very irregular compartments by means of slanting, upright or curved partitions, subject to the dictates of space. There is no art, consequently, in the accumulation of little cells; the architect's only task is to use the breadth at her disposal in a frugal manner. The material employed for the partitions is a green, vegetable putty, which the Osmia must obtain by chewing the shredded leaves of a plant whose nature is still uncertain. The same green paste serves for the thick plug that closes the abode. But in this case the insect does not use it unadulterated. To give greater power of resistance to the work, it mixes a number of bits of gravel with the vegetable cement. These materials, which are easily picked up, are lavishly employed, as though the mother feared lest she should not fortify sufficiently the entrance to her dwelling. They form a sort of coarse stucco, on the more or less smooth cupola of the Chalicodoma; and this unevenness, as well as the green colouring of its mortar of masticated leaves, at once betrays the Osmia's nest. In course of time, under the prolonged action of the air, the vegetable putty turns brown and assumes a dead-leaf tint, especially on the outside of the plug; and it would then be difficult for any one who had not seen them when freshly made to recognize their nature.
The old nests on the pebbles seem to suit other Osmiae. My notes mention Osmia Morawitzi, PEREZ, and Osmia cyanea, KIRB., as having been recognized in these dwellings, although they are not very assiduous visitors. Lastly, to complete the enumeration of the Bees known to me as making their homes in the Mason's cupolas, I must add Megachile apicalis, who piles in each cell a half-dozen or more honey-pots constructed with disks cut from the leaves of the wild rose, and an Anthidium whose species I cannot state, having seen nothing of her but her white cotton sacks.
The Mason-bee of the Sheds, on the other hand, supplies free lodgings to two species of Osmiae, Osmia tricornis, LATR., and Osmia Latreillii, SPIN., both of whom are quite common. The Three-horned Osmia frequents by preference the habitations of the Bees that build their nests in populous colonies, such as the Chalicodoma of the Sheds and the Hairy-footed Anthophora. Latreille's Osmia is nearly always found with the Three-horned Osmia at the Chalicodoma's.
The real builder of the city and the exploiter of the labour of others work together, at the same period, form a common swarm and live in perfect harmony, each Bee of the two species attending to her business in peace. They share and share alike, as though by tacit agreement. Is the Osmia discreet enough not to put upon the good-natured Mason and to utilize only abandoned passages and waste cells? Or does she take possession of the home of which the real owners could themselves have made use? I lean in favour of usurpation, for it is not rare to see the Chalicodoma of the Sheds clearing out old cells and using them as does her sister of the Pebbles. Be this as it may, all this little busy world lives without strife, some building anew, others dividing up the old dwelling.
Those Osmiae, on the contrary, who are the self-invited guests of the Mason-bee of the Pebbles are the sole occupants of the dome. The cause of this isolation lies in the unsociable temper of the proprietress. The old nest does not suit her from the moment that she sees it occupied by another. Instead of going shares, she prefers to seek elsewhere a dwelling where she can work in solitude. Her gracious surrender of a most excellent lodging in favour of a stranger who would be incapable of offering the least resistance if a dispute arose proves the great immunity enjoyed by the Osmia in the home of the worker whom she exploits. The common and peaceful swarming of the Mason-bee of the Sheds and the two cell-borrowing Osmiae proves it in a still more positive fashion. There is never a fight for the acquisition of another's goods or the defence of one's own property; never a brawl between Osmiae and Chalicodomae. Robber and robbed live on the most neighbourly terms. The Osmia considers herself at home; and the other does nothing to undeceive her. If the parasites, so deadly to the workers, move about in their very ranks with impunity, without arousing the faintest excitement, an equally complete indifference must be shown by the dispossessed owners to the presence of the usurpers in their old homes. I should be greatly put to it if I were asked to reconcile this calmness on the part of the expropriated one with the ruthless competition that is said to sway the world. Fashioned so as to instal herself in the Mason's property, the Osmia meets with a peaceful reception from her. My feeble eyes can see no further.
I have named the provision-thieves, the grub-murderers and the house-grabbers who levy tribute on the Mason-bee. Does that end the list? Not at all. The old nests are cities of the dead. They contain Bees who, on achieving the perfect state, were unable to open the exit-door through the cement and who withered in their cells; they contain dead larvae, turned into black, brittle cylinders; untouched provisions, both mouldy and fresh, on which the egg has come to grief; tattered cocoons; shreds of skins; relics of the transformation.
If we remove the nest of the Chalicodoma of the Sheds from its tile—a nest sometimes quite eight inches thick—we find live inhabitants only in a thin outer layer. All the remainder, the catacombs of past generations, is but a horrible heap of dead, shrivelled, ruined, decomposed things. Into this sub-stratum of the ancient city the unreleased Bees, the untransformed larvae fall as dust; here the honey-stores of old go sour, here the uneaten provisions are reduced to mould.
Three undertakers, all members of the Beetle tribe, a Clerus, a Ptinus and an Anthrenus, batten on these remains. The larvae of the Anthrenus and the Ptinus gnaw the ashes of the corpses; the larva of the Clerus, with the black head and the rest of its body a pretty pink, appeared to me to be breaking into the old jam-pots filled with rancid honey. The perfect insect itself, garbed in vermilion with blue ornaments, is fairly common on the surface of the clay slabs during the working season, strolling leisurely through the yard to taste here and there the drops of honey oozing from some cracked pot. Notwithstanding his showy livery, so unlike the workers' sombre frieze, the Chalicodomae leave him in peace, as though they recognized in him the scavenger whose duty it is to keep the sewers wholesome.
Ravaged by the passing years, the Mason's home at last falls into ruin and becomes a hovel. Exposed as it is to the direct action of wind and weather, the dome built upon a pebble chips and cracks. To repair it would be too irksome, nor would that restore the original solidity of the shaky foundation. Better protected by the covering of a roof, the city of the sheds resists longer, without however escaping eventual decay. The storeys which each generation adds to those in which it was born increase the thickness and the weight of the edifice in alarming proportions. The moisture of the tile filters into the oldest layers, wrecks the foundations and threatens the nest with a speedy fall. It is time to abandon for good the house with its cracks and rents.
Thereupon the crumbling apartments, on the pebble as well as on the tile, become the home of a camp of gypsies who are not particular where they find a shelter. The shapeless hovel, reduced to a fragment of a wall, finds occupants, for the Mason's work must be exploited to the utmost limits of possibility. In the blind alleys, all that remains of the former cells, Spiders weave a white-satin screen, behind which they lie in wait for the passing game. In nooks which they repair in summary fashion with earthen embankments or clay partitions, Hunting Wasps—Pompili and Tripoxyla—store up small members of the Spider tribe, including sometimes the Weaving Spiders who live in the same ruins.