Let us speak now of eggs carefully deposited by other insects in galleries and excavations made into timber. The insects which thus act have been called by the fanciful title of carpenter-bees, in allusion to the drilling process by which they penetrate the wood. A highly interesting spectacle it is, in truth, to see one of these pigmy carpenters at her work, and, fortunately, some of the species are not very uncommon in our gardens. Spring is the season when she commences her labours. She reconnoitres about for a proper piece of timber for some time, and exhibits great discrimination in the selection of a suitable place for establishing herself and for the nurture of her progeny. Strange to say, she will not select living wood, such as the trunk of a tree, but generally prefers wood which has already begun to decay, as if fully aware that such wood was likely to give her much less trouble in boring than any other. She also selects a piece of wood placed in some sunny and genial position, with a view to the development and comfort of her progeny. This important point being settled to her mind, she next sets about the work. Well may Réaumur exclaim, "Truly the labour she has undertaken demands strength, courage, and patience!"
Carpenter-Bee.
Mandibles of the Carpenter-Bee.
The violet carpenter-bee is, perhaps, the most interesting example we can select. She begins by cutting out with her strong jaws small portions of the timber, and soon forms a little hole, which looks downwards and inwards into the wood. She then alters the direction of her drilling, and now perforates the timber perpendicularly downwards, and in a parallel direction to the sides of the wood. Long and hard does she thus labour, until she has actually scooped out a tunnel in the timber a foot or so in length, and half an inch in diameter. Sometimes she will drill several of these beautiful galleries in the wood. The task, however arduous, never seems to weary her; impelled by a heaven-bestowed influence, she works strenuously and cheerfully for weeks, or even sometimes for months. Our readers may be interested to know what she does with the saw-dust. If they can but get an opportunity of watching her they will soon see her mode of dealing with it. Standing by the side of the wood she is drilling, and keeping our eyes stedfastly fixed on the hole, we shall presently observe her head emerging from it, and immediately after she is seen to shovel out a little heap of the dust, which accumulates on the ground beneath into a pile. When her galleries are finished her labour is yet far from accomplished. She has now to deposit her eggs, and make provision for the prospective wants of her young ones. Now, her eggs must not be piled together, nor be scattered about in the same cavity. The larvæ which are to be produced by them must each live in separation from the others. How is this fresh difficulty to be overcome? The insect soon supplies us with the answer. She has not forgotten her heap of saw-dust. She first deposits an egg at the bottom of the tunnel, and then away she flies to the fields for a load of the fine yellow dust of flowers, called pollen, and also for honey. She mixes these up into a nice little mass of pollen-bread, or cake, which is intended for the food of the larva, when it comes out of the egg, and then piles it up in the gallery just over the first egg. She then, at a height of about three quarters of an inch, plasters a layer or ring of saw-dust made by her into a sort of mortar, and adds to this another and another ring of the same material until the ceiling is quite complete, and the cell thus formed is shut off from the rest of the excavation by a circular plate of this substance, which effectually excludes all intercourse between the occupants of this wooden nursery. Having completed this cell she proceeds in the same way to lay an egg, and to provide a store of food, and, finally, to close in the rest of the gallery, until she has subdivided it into ten or twelve separate apartments. The appearance of the circular ceilings formed on these ingenious principles is exhibited in the engraving annexed.
Cells of Carpenter-Bee.
Ceiling-plate.