32 PHYSIOLOGY OP THE HONEY-BEE. 



with these, there is, on each side of the abdominal cavity, a 

 large tracheal bag, (fig. 17), variable in form and dimensions, 

 according to the quantity of air that it contains. Bees breathe 

 through holes, or spiracles, which are placed on each side of 

 the body, and open into the tracheal bags and tracheae. 



71. "The act of respiration consists in the alternate dila- 

 tation and contraction of the abdominal segments. By filling, 

 or emptying the air-bags, the bee can change her specific grav- 

 ity. When a bee is preparing herself for flight, the act of 

 respiration resembles that of birds, under similar circum- 

 stances. At the moment of expanding her wings, which is 

 indeed an act of respiration, the spiracles or breathing holes 

 are expanded, and the air, rushing into them, is extended into 

 the whole body, which by the expansion of the air-bags, is en- 

 larged in bulk, and rendered of less specific gravity; so that 

 when the spiracles are closed, at the instant the insect endeav- 

 ors to make the first stroke with, and raise itself upon, its 

 wings, it is enabled to rise in the air, and sustain a long and 

 powerful flight, with but little muscular exertion." f * » 

 ' ' Newport has shown that the development of heat in insects, 

 just as in vertebrates, depends on the quantity and activity of 

 respiration and the volume of circulation." — (Packard, Salem, 

 1869.) 



73. Mr. Cheshire notices that bees, even in full, vigorous 

 youth and strength, are not at all times able to take flight. 

 The reader may have noticed that if they are frightened, or 

 even touched vsdth 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 ex- 

 panded, 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 explanation 

 of this fact, 



