BEES, 33 



The respiratory apparatus in insects is composed of tubes. 

 These tubes open down the sides of the abdomen, in val- 

 vular apertures, closely fring-ed with elastic hair, called 

 spiracles, or breathing-holes. The spiracle^ communicate 

 -vdth two large tubes that pass along- the sides of the abdo- 

 men, and from them other tubes spring, traversing every 

 portion of the body, serving as ligatures to keep the internal 

 organs in their proper places, and piercing to the extremities 

 even of the feet and antennse, so that an insect may be said 

 to breathe with every portion of its body. The cylindrical 

 form of the tubes, together with the necessary flexibility, 

 is preserved in a most wonderful manner. The breathing 

 tubes are composed of several membranes. Between these 

 a fine and very elastic thread is coiled, closely resembling 

 a wire bell-spring. This arrangement preserves the tube"?; 

 from being flattened, or contracted by any movement ; while 

 at the same time, so strong is this thread, that it can 

 easily be removed from the tubes without breaking. I have 

 removed two inches of the spiral thread of the breathing 

 tubes of the humble bee. Even when separated from the 

 tubes, the thread retains its elasticity, and when released 

 from the forceps, springs into a spiral form again. 



.rig. 11.) 



Anatomy of Hmnbie Bi-v.* 

 • From an original dissection. 



