(iF.NEHAI. CIIAliAcrHRISTlCS. 31 



flight. The reader may ha\e noticed that If they are fright- 

 ened, or even touehed with the linjie'r, they will occasionally 

 move only by slight jumps. This temporary inability to 

 fly, is duo to the small quantity of aii- 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.) 



•74. " The traoheous 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 balloon, 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 to the bursting forth 

 of the male organs." — (Girard.) 



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



