208 SECRETS OF ANIMAL LIFE 



delicate egg. So it is hung by a thread from the 

 roof of the cupola, and after the Eumenes grub 

 hatches, it makes the cast shell of the egg into a 

 flexible staircase so that it can reach the caterpillars 

 and bite them, yet retreat if they are too vigorously 

 recalcitrant. This is perfection. 



The second point which Fabre's observations 

 illustrate very finely is the frequently serial char- 

 acter of instinctive behavior. There is a particular 

 sequence, and that sequence is adaptive. The 

 Capricorn grub of the Cerambyx beetle burrows for 

 three years on end in the depths of an oak tree. 

 But when it is full-grown and the time of its meta- 

 morphosis draws near, it moves to the periphery 

 and makes a passage almost out, leaving only a 

 film-like screen, just as if it knew that the winged 

 beetle to emerge from the pupa-case would other- 

 wise be buried alive. It then draws back a little 

 in its gallery and makes an outer barricade of 

 particles of chopped wood, and inside that an 

 inner partition like a white skullcap or acorn-cup, 

 composed, strange to say, of carbonate of lime and 

 some organic cement. The next step is to make 

 on the side of the exit-way a transformation- 

 chamber. This is three or four inches long, and is 

 padded " with a fine swan's down, a delicate pre- 

 caution taken by the rough worm on behalf of the 

 tender pupa." The next step is to fall asleep and 

 dream of becoming a beetle. " The grub lays asiuc 

 its tools, molts its cuticle and becomes a pupa, 

 lying, weakness personified, on a soft couch. The 



