ANATOMY AND PHYSIOLOGY. 139 
less, but that it ceases as soon as the current of air 
through the traches is stopped by pressure over the 
thoracic stigmata. Here is the chief cause of the 
sound; the vibration of the wings and _ halteres 
modifies it, but without a current of air through the 
trachea beneath there is no buzzing. 
Incidentally this experiment shows that the air 
which is expelled through the thoracic spiracles to 
make the buzzing sound is also drawn in through 
them. For the abdominal respiration is stopped 
during this time by the pressure of our finger, and 
no air can come in by that way. Though the air 
tubes communicate freely, yet the respiration is main- 
tained in them, as in ourselves, by a to-and-fro cur- 
rent along the same passages, not by a draught 
maintained in one direction, in at one and out at 
another set of spiracles, as in a coal-mine. 
Hunter,* for whose observation nothing was too 
small or insignificant, noticed that bees still buzzed 
though their wigs were rendered motionless by 
being smeared with honey; the tone was altered, but 
the sound continued. And when the bee was placed 
on water, with the buzzing, the water round the 
thoracic spiracles was thrown into vibration. Lan- 
doist has carried this branch of the inquiry still 
further. He found that the thorax of the honey-bee 
was still capable of buzzing, though in an altered 
tone, after it had been separated from all the rest of 
the body. And, that the sound was mainly produced 
during and by the emission of air from the spiracles, 
that is during expiration, was shown by the motion 
* * Works,’ Vol. IV, p. 459. 
t Op. cit. pp. 39, 62. 
