ii)Air enters the spiracles during inspiration and comes to the trachea, then it comes to the tracheoles which contain tissue fluids. The oxygen dissolves in these fluids and reaches the cells of tissues.
(ii) This supplies sufficient oxygen for normal respiratory needs of the insect
(iv) in expiration, some carbon dioxide may pass out through the spiracles, but the major part in the plasma diffuses out through the cuticular ar covering af the body.
(v) When active movement takes place in the insect, as in running or flying, the metabolic rate is high, the osmotic pressure of the tissue increases, as a result of which the tissue fluid is withdrawn from the tracheoles into the cells. This withdrawal makes it possible for the column of air to extend deeper into the tracheoles and directly reach the cells, and oxygen is taken up from air by the fuids of the cells.
(vi) In active movement, abdominal segments the expand and relax. These movements are termed respiratory movements and they cause more air to be taken in through the spiracles.
vii) During mouiting, the cuticle of trachea, but not of tracheoles, is shed. After moulting. new trachea are joined to old tracheoles by a glue of unknown composition Trocha al cos