THE MYSTERY OF THE SWARM 187 
renders her so heavy and bulky that often she can 
scarcely get on the wing. The object of this is 
that she may be all the more ready for laying 
when the new home is established. It is also 
well ascertained that all swarming bees have their 
honey-sacs well filled, and this loading up for the 
journey takes place just before the signal for 
departure is given. There is great variation in 
the behaviour of the different stocks in a bee- 
garden during the swarming season, and many 
close observers are unable to detect any sure signs 
that a particular hive is going to swarm. But it 
appears fairly well established that, when a swarm 
is imminent, nearly all the bees of that stock 
remain at home, even when all other hives in the 
garden are in full foraging activity. Such a hive 
gives out a peculiar throbbing note, which suggests 
the noise made by a powerful locomotive brought 
to a standstill, but with full steam up, and impatient 
to be gone. Just before the issue of the swarm 
there is often a curious lull in this pent-up, forceful 
sound, and probably this is the moment when the 
travellers are lading themselves up for the march. 
Immediately after—and here it is difficult not to 
believe that a definite, authoritative signal for the 
movement is given—a sudden stir and tumult 
begins in the centre of the crowded hive, much 
like that caused by a heavy stone cast into water. 
This radiates swiftly in all directions until it 
reaches the bees near the entrance, and then the 
