But the spirit of the hive has taken its precautions, and the guards have received the necessary instructions. They know exactly what must be done, and when to do it. They are well aware that if the princesses were to come out of their lodging too soon, they would fall into the hands of their furious elder sister, who would destroy them one by one. To avoid this, therefore, the workers keep on adding layers of wax to the cells as fast as the princesses within are stripping it away; so that all their gnawing and eagerness are of no avail, and the captives must bide their time. One of them perhaps will hear the war-cry of her enemy; and although she has not yet come into contact with life, nor knows what a hive may be, she answers the challenge from within the depths of her prison. But her song is different; it is hollow and stifled, for it has to pass through the walls of a tomb; and when night is falling and noises are hushed, while high over all is the silence of the stars, the bee-keeper is able to distinguish, and recognize, this exchange of challenges between the restlessly wandering queen and the young princesses still in their prison. The young queens will have benefited by the long stay in their cradles, for when at last they come out they are big and strong, and able to fly. But this period of waiting has also given strength to the first-born queen, who is now able to face the perils of the voyage. The time has come, therefore, for the second swarm, called the "cast," to depart, with the eldest queen at its head. No sooner has she gone than the workers left in the hive will release one of the princesses from her cradle; she will at once proceed to show the same murderous desires, to send forth the same cries of anger, as her sister had done before her, till at last, after another three or four days, she will leave the hive in her turn, at the head of the third swarm, to build a new home far away. A case has been known where a hive, through its swarms and the swarms of its swarms, was able in a single season to send forth no less than thirty colonies. This excessive eagerness, which is known as "swarming-fever," usually follows a severe winter; and one might almost believe that the bees, always in touch with the secrets of nature, are conscious of the dangers that threaten their race. But at ordinary times, when the seasons have been normal, this "fever" will rarely occur in a strong and well-governed hive; many will swarm only once, and some, indeed, not at all.