108 
Psyche 
[June-September 
Perhaps this is the 5000 Hz sound which Esch (19671 found superim¬ 
posed on the 500 Hz wing buzzes generated by buzz runners. 
In the final 3 min preceding lift-off, the swarm teemed with buzz 
runners scrambling over the clustered bees, vibrating their wings 
and boring through the interlocked nets of hanging bees. A loud 
humming noise radiated from the cluster, a mixture of the deep 
wing buzzes and shrill piping sounds. This climaxed as the once 
solid surface of the swarm appeared to melt as the chains of hanging 
bees began disintegrating, and within 50 more sec the entire swarm 
was airborne, filling the air with the roar of 11,000 bees tightly 
circling just overhead. 
3. Cross-Country Flight of the Swarm 
The movement of the airborne swarm began very slowly. Fig. 2 
shows that in both flights the island swarm traversed the first 30 m 
with an average velocity of just slightly over 1 km/h. This slow start 
may reflect the swarm’s checking for the airborne presence of the 
queen, signalled by the odor of (E)-9-oxodec-2-enoic acid (Avitabile 
et al. 1975), or the difficulty of getting the thousands of bees moving 
en masse in the proper direction, or both. Immediately after lift-off 
the swarm cloud was circular in horizontal cross-section, with a 
diameter of about 10 m, as estimated from the 30-m-spaced stakes 
along the flight path. Its vertical cross-section was roughly circular, 
though with the bottom somewhat flattened along an imaginary line 
about 2 m above the open ground. 
Not all the swarm’s bees stayed with the slow-moving swarm 
cloud; a few shot out ahead to the nest site where they settled at the 
nest entrance and began releasing assembly pheromones from their 
Nasanov glands (reviewed by Wilson 1971, Michener 1974). Fig. 3 
shows that there were 2 bees visible and scenting at the nest site 580 
m away even before the swarm cloud had crossed the 30 m marker. 
By the time the swarm had flown 60 m, its velocity had increased 
to over 4 km/h and it continued to increase through at least the 210 
m mark to 8.5 and 11.0 km/h maximum speeds on the first and 
second flights, respectively (see Fig. 2). Swarm shape also changed 
over the first 60 m. The swarm cloud became more flattened top-to- 
bottom so that its vertical cross-section was ovoid, about 10 m long 
and 3 m high. The swarm’s front was angled upward slightly, with 
the bottom of the swarm about 1 m above the tops of the bushes, 
