Insect Architecture - James Rennie

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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.

      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.

      It is a native of South Africa, and its name is Chalicodoma cœlocerus. The insect is about half an inch in length, and the colour of the head and body is black, that of the abdomen being brick red.

      

      The nest is made of mud, which is collected by the patient insect and stuck against walls, trunks of trees, and similar localities. In this lump of mud the insect excavates a small number of burrows, each of which contains several cells. If the reader will refer to the central burrow, he will see that it is divided into three cells. The specimen from which this drawing is taken may be seen in the British Museum.

      There is another South African insect which makes its mud nest, and fastens it against trees and walls. This is called Synagris calida, and its colour is almost dingy black, the only exception being the red tip to the abdomen. The holes seen in the engraving are the apertures through which the young brood has escaped into the world. The nest is represented of half its natural size.]

      Mining-Bees.

      A very small sort of bees (Andrenæ), many of them not larger than a house-fly, dig in the ground tubular galleries little wider than the diameter of their own bodies. Samouelle says, that all of them seem to prefer a southern aspect; but we have found them in banks facing the east, and even the north. Immediately above the spot where we have described the mason-bees quarrying the clay, we observed several holes, about the diameter of the stalk of a tobacco-pipe, into which those little bees were seen passing. The clay here was very hard; and on passing a straw into the hole as a director, and digging down for six or eight inches, a very smooth circular gallery was found, terminating in a thimble-shaped horizontal chamber, almost at right angles to the entrance and nearly twice as wide. In this chamber there was a ball of bright yellow pollen, as round as a garden pea, and rather larger, upon which a small white grub was feeding; and to which the mother bee had been adding, as she had just entered a minute before with her thighs loaded with pollen. That it was not the male, the load of pollen determined; for the male has no apparatus for collecting or transporting it. The whole labour of digging the nest and providing food for the young is performed by the female. The females of the solitary bees have no assistance in their tasks. The males are idle; and the females are unprovided with labourers, such as the queens of the hive command.

      Cell of Mining-Bee (Andrena).—About half the natural size.

      Réaumur mentions that the bees of this sort, whose operations he had observed, piled up at the entrance of their galleries the earth which they had scooped out from the interior; and when the grub was hatched, and properly provided with food, the earth was again employed to close up the passage, in order to prevent the intrusion of ants, ichneumon-flies, or other depredators. In those which we have observed, this was not the case; but every species differs from another in some little peculiarity, though they agree in the general principles of their operations.

      [The genus Andrena is an exceedingly large one, nearly seventy species being acknowledged in England alone. They choose various situations for their nest; a very favourite situation is a hard-trodden pathway; into this the bees burrow for some six or seven inches, and often drive their tunnels to a depth of ten inches. Digging up these habitations is not a very easy task, because the tunnel does not run straight, but turns aside when a stone or any similar obstacle comes in the way, and in getting out the stone the burrow is mostly broken. The only method of digging out the nest successfully is either by pushing a small twig up the hole, and using it as a guide, or by filling the entire hole with cotton wool, so as to prevent the earth from falling in.

      The commonest species is Andrena albicans. Its length is rather less than half an inch, and its colour is black, with a thick coating of rich red hair on the upper part of the thorax. This species is plentiful on the continent, and is found as far south as Italy. But it is equally capable of enduring great cold, as it has been captured in the Arctic regions. Sometimes the bee will not trouble itself to make a number of separate burrows, but will drive short supplementary tunnels from the side of the first burrow, so that they all open into one common entrance.

      The Andrenæ are remarkable for the parasites with which they are infested, the most curious of which is that tiny strepsipterous insect called the Stylops.

      One of the Andrenæ, called Colletes Daviesana, is remarkable for the character of its burrow. Like many of the insects which have already been described, it seems indifferent whether it burrows in sand-banks or into the mortar of walls, provided that in the latter case the mortar is soft and friable.

      The insect burrows a hole which is very deep in proportion to its size, the little bee being only the third of an inch in length, and the burrows some eight or ten inches in depth. When the mother Colletes has finished her tunnel, she lines the end of it with a thin kind of membrane, which has been well compared by Mr. F. Smith to goldbeater’s skin. This lining is intended to enable the bee to store honey in the cell, as, if there were no such protection, the honey would soak in the ground and be lost.

      Having stored up enough food for a single offspring, she shuts it off by a partition of the same membranous substance as the lining. Her next care is to make a thimble-like cup at the end, so as to have a double lining where the honey is to come, and then she puts a fresh supply in the new cell. This cell is then closed, and the bee proceeds with her work until she has made from six to eight cells in a single burrow. This insect suffers terribly from the depredations of the earwig, which completely empties the burrow both of food and of inhabitants. The colour of the insect is black, with a little reddish down on the upper part of the thorax, and some white on the legs. The abdomen is shining black, but each segment has a very narrow band of reddish down on its edge.

      In 1850, Mr. F. Smith, to whose works such constant reference has been made, undertook the study of a genus of mining-bees belonging to this family. The species which he chiefly watched is Halictus morio, and his observations are peculiarly valuable, as showing the wonderful manner in which the economy of the race is managed. It is known that in these and many other insects, the pregnant females pass the winter in a state of hibernation, and begin to work in the following spring, and that therefore some arrangement must be needful that a supply of such queens should be kept up.

      Mr. Smith found the case to stand thus. Early in April, the females appeared abundantly,

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