It is a curious fact that the bees do not, on being put into a hive, or when working in a bell-glass, begin several combs at once; but, having thoroughly laid the foundation of one, and having made some progress with this, they then start one on each side of the first, and, after a time, one on the outer side of each of the last begun. Usually, therefore, the combs hang in parallel series. If any obstruction occurs, a deviation from the normal direction takes place, but, manifest intelligence is shown in surmounting the difficulty, whatever it may be. [Illustration: Fig. 18.--Arrangement of Combs in a Bell-Glass.] At first, the substance of the cells is of a dull, semi-transparent, white colour, soft, and very brittle. After a time, a yellow tinge spreads over the comb, and, with age, this hue deepens to brown, and if some years old, becomes almost black. The colour, therefore, furnishes a tolerably safe guide as to the age of comb. The darkening seems due, partly to a chemical change from contact with the air, but still more to the constant traffic of the bees over it, and its getting smeared with dirt and propolis. It occasionally happens that, owing to a great in-flow of honey, the weight of the combs endangers their security, and the bees, seeing the danger of their breaking down, resort to a most clever method of rendering their treasures safe. Gnawing away a small part of the topmost row of the combs on one side, they lay a broader foundation, and then, with a strongly glutinous mixture of wax and propolis, they fasten afresh the upper cells to their points of attachment. Having completed one side, they then proceed in the same way with the other, till they are satisfied of the firmness of the whole structure. Again, if the supply of food outruns the capacity of their store-houses as first made, they will often lengthen the cells, till, especially in the case of _supers_, they reach the length of even two inches--more than twice the normal size. [Illustration: Fig. 19.--The Queen Cell.] The _queen-cells_ are remarkably distinguished from those for workers or drones, in respect to size, direction, shape, and amount of material. They occupy at least as much space as half a dozen ordinary cells. They are directed downwards, instead of lying horizontally. They are irregularly oval or pyriform in shape, and are made up of a sort of mosaic of wax, which material, so sparingly used elsewhere, seems lavished on the royal nurseries. The reasons for this are, probably, to secure the young queens from danger while passing through the larval and pupal conditions, and to keep up the warmth necessary for their more rapid development. Wax being a very bad conductor of heat, the thick walls prevent the chilling of the brood, and, at the same time, allow of considerable clustering of nurse-bees, and consequent generation of warmth, without the danger of the cells being broken down by the pressure. [Illustration: Fig. 20.--Queen Cells in Situ.]