44 
THORAX, LEGS, AND WINGS, 
In Fig. 20 the marks made by the bee’s wing are 
shown at while a represents the curve produced by 
the tuning fork, which makes a double oscillation 250 
times a second. This enabled Marey to determine as 
190 the number of vibrations of the bee’s wings, as he 
found this number registered in the same space occu- 
pied by the 250 vibrations of the tuning fork. In his 
Fig. 20. — Graphic Representation of Vibration of Bee’s Wing. 
experiments he found that, by diminishing the contact 
of the wings on the cylinder, and thus reducing 
friction, the velocity was still greater, so that this 
number cannot be reckoned as the highest a bee is 
capable of attaining. The corroboration of this theory, 
Marey says, is found in the experiments which many 
naturalists have made. All these experiments prove 
that the insect needs for the due function of flight a 
rigid main rib and a flexible membrane. 
When treating of tracheae, we shall see how these 
are filled when the bee is preparing for flight, for at 
other times, when they are not so filled, they are 
not able to fly. Young bees do not fly, and it is 
not until they are several days old that their tracheae 
become sufficiently charged with air to enable them 
to do so. 
Wolff (170) has explained clearly how the air sacs 
in the thorax are filled with air during flight. 
