148 BEES AND BEE-KEEPING. 



quire. As DA (the wing-depressors) contract, they pull 

 the mesophragma (mp, and page 88) forwards and up- 

 wards, and away from the metathorax. The separation 

 of the two walls of the air sac lying behind the 

 mesophragma draws in a supply of air, which, at the 

 relaxation of the depressors, is distributed to the 

 tracheae, as the antagonist muscles (A) replace the 

 mesophragma, and rapidly drive all the air from the 

 air sacs. Other movements aid in the work, so that 

 the initial efforts of flying, as a natural result, distend 

 the body, and bring about all the conditions the absence 

 of which we just now noticed as making soaring im- 

 possible. We shall presently see that the bee has 

 perfect control over the spiracles, closing them at 

 pleasure. When on the wing, then, with the air sacs 

 fully filled, if the spiracles be shut, the power is 

 gained for discharging the contents of the bowels by 

 simple pressure, the latter being applied by con- 

 traction of those muscles which govern the abdominal 

 rings. That bees labour without weariness in banish- 

 ing every vestige of impurity from their hives, which, 

 under natural and healthy conditions, they never soil, 

 has frequently been remarked. But these most cleanly 

 creatures are, in this latter respect, structurally com- 

 pelled so to be, from the above-given curious arrano- e - 

 ment. The queen is an exception, so far as her 

 capability of removing the intestinal residua is con- 

 cerned, as her ovaries occupy the space taken by a 

 pair of large air sacs in the worker and drone ; so 

 that she on foot, and for an obvious reason, possesses 

 the power (pages 71 and 84) the others only acquire 

 when on the wing-. 



