When the whole series of cells is completed, the bee closes up the entrance with little morsels of earth, bits of stick and little stones, all strongly glued together with some very adhesive substance. Another species (_Osmia parietina_) has much simpler habits, and is much easier satisfied with a dwelling. This insect merely looks out for a flattish stone lying on the ground, and crawls under it to see if there is any hollow. If so, it attaches the cocoons to the stone and leaves them. On one stone, seen in the British Museum, no less than two hundred and thirty cocoons were placed, although the stone is only ten inches in length by six in width. This insect is almost wholly confined to the north of England.] There was one circumstance attending the proceedings of this mason-bee which struck us not a little, though we could not explain it to our own satisfaction. Every time she left her nest for the purpose of procuring a fresh supply of materials, she paid a regular visit to the blossoms of a lilac-tree which grew near. Had these blossoms afforded a supply of pollen, with which she could have replenished her cells, we could have easily understood her design; but the pollen of the lilac is not suitable for this purpose, and that she had never used it was proved by all the pollen in the cells being yellow, whereas that of the lilac is of the same pale purple colour as the flowers. Besides, she did not return immediately from the lilac-tree to the building, but always went for a load of clay. There seemed to us, therefore, to be only two ways to explain the circumstance:--she must either have applied to the lilac-blossoms to obtain a refreshment of honey, or to procure glutinous materials to mix with the clay. When employed upon the building itself, the bee exhibited the restless disposition peculiar to most hymenopterous[P] insects; for she did not go on with one particular portion of her wall, but ran about from place to place every time she came to work. At first, when we saw her running from the bottom to the top of her building, we naturally imagined that she went up for some of the bricklayer's mortar to mix with her own materials; but upon minutely examining the walls afterwards, no lime could be discovered in their structure similar to that which was apparent in the nest found in the wall of Greenwich Park. Réaumur mentions another sort of mason-bee, which selects a small cavity in a stone, in which she forms her nest of garden-mould moistened with gluten, and afterwards closes the whole with the same material. [Illustration: Cells of _Chalicodoma_.] [In the accompanying illustration is shown a series of cells which are constructed by an insect which is closely related to the rose-cutter bee of our own country, to which it bears a close resemblance.