[D] Kirby and Spence.
It may appear somewhat extraordinary that a creature which takes its food so voraciously prior to its assuming the pupa state, should live so long without food, after that assumption: but a little consideration will perhaps abate our wonder; for when the insect has attained the state of pupa, it has arrived at its full growth, and probably the nutriment, taken so greedily, is to serve as a store for developing the perfect insect.
The bee, when in its pupa state, has been denominated, but improperly, chrysalis and aurelia; for these, as the words import, are of a golden yellow colour and they are crustaceous; whilst the bee-nymphs appear of a pale, dull colour, and readily yield to the touch. The golden splendour, to which the above names owe their origin, is peculiar to a certain species only of the papilio or butterfly tribe. The higher class of entomologists, following the example of Linnæus, apply the term pupa to this state of the embryo bee, a term which signifies that the insect is enveloped in swaddling clothes like an infant, a very apt comparison. Kirby and Spence have remarked that it exhibits no unapt representation of an Egyptian mummy. Huber’s translator says that naturalists of the present day incline to use the name of larva, in all cases where the worm is not seen under its final aspect.
The working bee-nymph spins its cocoon in thirty-six hours. After passing a certain period in this state of preparation for a new existence, it gradually undergoes so great a change, as not to wear a vestige of its previous form, but becomes armed with a firmer mail, and with scales of a dark brown hue, fringed with light hairs. On its belly six rings become distinguishable, which by slipping one over another, enable the bee to shorten its body whenever it has occasion to do so; its breast becomes entirely covered with gray feather-like hairs, which as the insect advances in age assume a reddish hue.
When it has reached the twenty-first day of its existence, counting from the moment the egg is laid, it quits the exuviæ of the pupa state, comes forth a perfect winged insect, and is termed an imago. The cocoon or pellicle is left behind and forms a closely attached and exact lining to the cell in which it was spun: by this means the breeding-cells become smaller, and their partitions stronger, the oftener they change their tenants; and when they have become so much diminished in size, by this succession of pellicles or linings, as not to admit of the perfect development of full-sized bees, they are converted into receptacles for honey.
Such are the respective stages of the working bee; those of the royal bee are as follow. She passes three days in the egg and is five a worm; the workers then close her cell[E], and she immediately begins spinning the cocoon, which occupies her twenty-four hours. On the tenth and eleventh days, as if exhausted by her labour, she remains in complete repose, and even sixteen hours of the twelfth. Then she passes four days and one-third as a nymph. It is on the sixteenth day therefore that the perfect state of queen is attained.
[E] Instead of being nearly horizontal like the other brood-cells, those of the queens are perpendicular and considerably larger; in form they are oblong spheroids, tapering gradually downwards; their mouths being always at the bottom. Vide Part II. “[Architecture of Bees].”
The male passes three days in the egg, six and a half as a worm, and metamorphoses into a fly on the twenty-fourth or twenty-fifth day, after the egg is laid. The great epoch of laying the eggs of males may be accelerated or retarded by the state of the atmosphere promoting or impeding the collections of the bees. The development of each species likewise proceeds more slowly when the colonies are weak or the air cool, and when the weather is very cold it is entirely suspended. Mr. Hunter has observed that the eggs, maggots and nymphs, all require a heat above 70° of Fahrenheit for their evolution. The influence of temperature in developing embryo insects is very strongly illustrated in the case of the Papilio Machaon. According to Messrs. Kirby and Spence, “if the caterpillar of the Papilio Machaon becomes a pupa in July, the butterfly will appear in thirteen days; if it do not become a pupa till September, the butterfly will not make its appearance until the following June.” And this is the case, say they, with a vast number of other insects. Reaumur proved the influence of temperature, by effecting the regular changes in a hot-house, during the month of January. He also proved it conversely, by having recourse to an ice-house in summer, which enabled him to retard the development for a whole year.
“The larvæ of bees, though without feet, are not always without motion. They advance from their first station at the bottom of the cell, in a spiral direction: this movement, for the first three days, is so slow as to be scarcely perceptible; but after that it is more easily discerned. The animal now makes two entire revolutions, in about an hour and three quarters; and when the period of its metamorphosis arrives, it is scarcely more than two lines from the mouth of the cell. Its attitude, which is always the same, is a strong curve. This occasions the inhabitant of a horizontal cell to be always perpendicular to the horizon, and that of a vertical one to be parallel with it[F].”