To return to Bevan. "The larva is no sooner perfectly inclosed than it begins to line the cell by spinning round itself, after the manner of the silk worm, a whitish silky film or cocoon, by which it is encased, as it were, in a pod. When it has undergone this change, it has usually borne the name of _nymph_ or _pupa_. The insect has now attained its full growth, and the large amount of nutriment which it has taken serves as a store for developing the perfect insect." "The _working bee nymph_ spins its cocoon in thirty-six hours. After passing about three days 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. On its belly six rings become distinguishable, which by slipping one over another enables the bee to shorten its body whenever it has occasion to do so. "When it has reached the twenty-first day of its existence, counting from the moment the egg is laid, it comes forth a perfect winged insect. The cocoon 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 may become so much diminished in size as not to admit of the perfect development of full sized bees." "Such are the respective stages of the working bee: those of the royal bee are as follows: she passes three days in the egg and is five a worm; the workers then close her cell, and she immediately begins spinning her cocoon, which occupies her twenty four hours. On the tenth and eleventh days and a part of the twelfth, as if exhausted by her labor, she remains in complete repose. Then she passes four days and a part of the fifth as a nymph. It is on the sixteenth day therefore that the perfect state of queen is attained." "The drone passes three days in the egg, six and a half as a worm, and changes into a perfect insect on the twenty-fourth or twenty-fifth day after the egg is laid." "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. Dr. Hunter has observed that the eggs, worms and nymphs all require a heat above 70° of Fahrenheit for their evolution." In the chapter on protection against extremes of _heat_ and _cold_, I have dwelt, at some length, upon the importance of constructing the hives in such a manner as to enable the bees to preserve, as far as possible, a uniform temperature in their tenement. In thin hives exposed to the sun, the heat is sometimes so great as to destroy the eggs and the larvæ, even when the combs escape from being melted; and the cold is often so severe as to check the development of the brood, and sometimes to kill it outright.