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All, after filling the spiral staircase with two or three cells, closed the house with a thick earthen stopper on a level with the opening. It was a long and troublesome task, in which the Osmia displayed all her patience as a mother and all her talents as a plasterer. When the pupae are sufficiently matured, I proceed to examine these elegant abodes.
If their presence proved useful to the species which had seized them if it were more advantageous to this species to capture workers than to procreate them the habit of collecting pupae originally for food might by natural selection be strengthened and rendered permanent for the very different purpose of raising slaves.
Those below, on attaining the adult state, burst their swaddling-bands, demolish their resin partitions, pass through the gravel barricade and try to release themselves; those above, larvae still or budding pupae, prisoners in their shells until the following spring, completely block the way.
At any rate, these little creatures are alive, the batrachians also, and, as I found the next day, pupae and chrysales of one sort or another, for, to my deep emotion, I saw a little white butterfly staggering in the air over the flower-garden of a rustic station named Butley.
Yet there must have been something there for all these eager bills eggs or pupae. A jackdaw, with iron-grey patch on the back of his broad poll, dropped in my garden one morning, to the great alarm of the small birds, and made off with some large dark object in his beak some beetle or shell probably, I could not distinguish which, and should most likely have passed the spot without seeing it.
Two days later it stopped travelling, and pupated on the top of the now hardened earth in the bucket that contained the other two. It was the largest of the pupae when it emerged, a big shining greenish brown thing flattened and seeming as if it had been varnished. On the thin pupa case the wing shields and outlines of the head and different parts of the body could be seen.
But these latter defended themselves without animosity, merely knocking the aggressors head over heels, and then letting them alone. The pratenses could not make it out. As for the other pratenses, those belonging to the mixed community, they avoided their sometime sisters, would not fight with them, but carried the pupae into the nest. The hostility was all on the side of the newcomers.
A perfectly similar appendage, "a most delicate tube or ribbon," was found by Darwin in free-swimming pupae of Lepas australis on the last joints of the "prehensile antennae."
Four inches down, or thereabouts, the worms have found a quiet lodging, protected above by the layer through which they have passed and on every side by the thickness of the vessel's contents. Satisfied with the site, they have stopped there. It is a very different matter in the tube. The least buried of the pupae are half a yard down.
From this it follows that this appendage in Lepas australis can hardly be anything but a young cement-duct. If, therefore, the supposition that the appendages on the antennae of the pupae of Rhizocephala are young roots be correct, the roots of the Rhizocephala are homologous with the cement-ducts of the Cirripedia.
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