GENERAL CHARACTERISTICS. 31 
flight. The reader may have noticed that if they are fright- 
ened, or even touched with the finger, they will occasionally 
move only by slight jumps. This temporary inability to 
fly, is due to the small quantity of air that their tracheal 
sacs contain. They were at rest, their blood circulated 
slowly, their body was comparatively heavy ; but when their 
wings were expanded, the tracheal bags, that were as flat as 
ribbons, were soon filled with air, and they were ready to 
take wing. 
Practical Apiarists well know that bees may be shaken off 
the comb, and gathered up, with a shovel, with a spoon, or 
even with the hands, to be weighed or measured in open ves- 
sels, like seeds. The foregoing remarks give the explana- 
tion of this fact. 
73. When the tracheal bags are filled with air, bees, 
owing to their peculiar structure, can best discharge the 
residue contained in their intestines. 
The queen is differently formed, her ovaries occupying 
part of the space belonging to the air-sacks in the worker, 
hence her discharges, like those of the drones (190), take 
place in the hive. (40.) 
V4. “The tracheous bags of the abdomen, which we would 
be tempted to name abdominal lungs, hold in reserve the air need- 
ed to arterialize the blood and to produce muscular strength 
and heat. in connection with the powerful flight of the insect. 
Heat is indispensable, to keep up the high temperature of the 
hive, for the building of comb and rearing of brood. The aerial 
vesicles increase, by their resonance, the intensity of the hum- 
ming, and are used also like the valve of a baltoon, to slacken or 
increase the speed of the flight, by the variation of density, ac- 
cording to the quantity or weight, of the air that they contain. 
This accumulated air is also the means of preventing asphyxy, 
which the insects resist a long time. Lastly, these air-bags help 
in the mating of the sexes, which takes place in the air; the 
swelling of the vesicles being indispensable tothe bursting forth 
of the male organs.”—(Girard.) 
75. The hum that is produced by the vibration of the 
