154 MY NATURE NOTEBOOK. 



when the enemy's face appears at one door, it escapes 

 by the other, and tumbles straight to the ground, 

 paying out a silken rope as it falls, to climb up again 

 by when danger is past. 



VERY LIKE HUMAN REASON. 



But the wasp, in its turn, is prepared for this, and 

 no action performed by any wild creature approaches 

 more nearly to the result of human reason than the 

 conduct of a wasp when it discovers that a caterpillar 

 has thus escaped. For it immediately descends in a 

 perpendicular line towards the ground, examining 

 each twig and leaf on its way, and if it fails to find 

 the caterpillar there or on the ground, it will often 

 ascend and descend several times, between the curled 

 leaf and the ground, before giving up the search. It 

 is just as if a man said to himself that the caterpillar 

 could only have fallen in a straight line, and must, 

 therefore, be either on the ground immediately below, 

 or on some intervening twig. He would in that case 

 refuse to give up the search after one failure, hunting 

 up and down the perpendicular line of descent several 

 times, just as the wasp does. What happens is, of 

 course, that the falling caterpillar glances from a leaf 

 or blade of grass into the mass of herbage, and there 

 lies snugly hidden till the coast is clear, and though 

 human reason would quickly learn to trace the run- 

 away by his silken rope, that is just where the limita- 

 tion of the wasp's intelligence enables the caterpillar 

 to survive. 



