GENERAL CHARACTERISTICS. 33 



73. When the tracheal bags are filled with air, bees, owing 

 to their peculiar structure, can best discharge the residue con- 

 tained in their intestmes. 



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.) The queen's air-sacks are much smaller than 

 those of the worker, hence comes a difficulty to take wing. 



74. ''The tracheous bags of the abdomen, which we would 

 be tempted to name abdominal lungs, hold in reserve the air 

 needed 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 humming, and are used also like the valve of a balloon, to 

 slacken or increase the speed of the flight, by the variation of 

 density, according to the quantity or weight, of the air that 

 they contain. This accumulated air is also the means of pre- 

 venting 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 

 to the bursting forth of the male organs." — (Girard.) 



75. The hum that is produced by the vibration of the 

 wings is different in each of the three kinds of inhabitants 

 of the hive, and easily recognizable to a practiced ear. The 

 hum of the drone is the most sonorous. But worker-bees, when 

 angry or frightened, or when they call each other, emit dif- 

 ferent and sharper sounds. On the production of these sounds, 

 bee-keepers and entomologists are far from being agreed. 



''Inside of every opening of the aerial tubes is a valvular 

 muscle, which helps to control the mechanism of respiration. 

 This can be opened or closed at will, by the bee, to prevent the 

 ingress, or egress, of air. It is by this means that the air is 

 kept in the large tracheous bags and decreases the specific grav- 

 ity of the insect. The main resonant organ of the bee is placed 

 in front of this stopping muscle, at the entrnnce of the 

 trachea. 



