THE MASTERY OF THE AIR 239 



greatly increases their safety, their chances of 

 getting food, their possibilities of trekking and 

 migrating, and their opportunities so plain in 

 the wasp's hanging nest of laying their eggs 

 or nurturing their young ones in places of 

 comparative security, far from the ground, 

 where danger always lurks. 



The second part of the answer is that insects 

 have an extraordinarily successful make-up. 

 Thus they have met the difficulty of capturing 

 oxygen by developing a system of branching 

 air-tubes (trachece), carrying oxygen to every 

 hole and corner of the body. The perfect 

 aeration is part of the secret of the insect's 

 intense activity and success. The blood never 

 becomes impure. Moreover, the beating of 

 the wings helps to drive the used air out, 

 letting fresh air in. Just as in birds, which 

 are also very successful, the flying helps the 

 breathing. 



The third reason for the great success of 

 insects is to be found in their remarkable 

 development of instinctive behaviour. Along 

 a line which is quite different from intelligence, 

 they have been able to acquire a repertory of 

 ready-make tricks, an inborn ability to do 

 effective things right away without learning. 



