The Life of the Caterpillar 



anfmal; and it is expedient that they be filled 

 without delay with the aid of a special form of 

 nourishment. Then what shall the nature of 

 the first food be ? Vegetable matter, slow to 

 elaborate and niggardly in its yield, does not 

 fulfil the desired conditions at all well, for 

 time presses and we must trust ourselves 

 safely to the slippery leaf. An animal diet 

 \vould be preferable: it is easier to digest and 

 undergoes chemical changes in a shorter time. 

 The wrapper of the egg is of a horny nature, 

 as silk itself is. It will not take long to trans- 

 form the one into the other. The grub there- 

 fore tackles the remains of its egg and turns 

 it into silk to carry with it on its first journeys. 



If my surmise is well-founded, there is 

 reason to believe that, with a view to speedily 

 filling the silk-glands to which they look to 

 supply them with ropes, other caterpillars be- 

 ginning their existence on smooth and steeply- 

 slanting leaves also take as their first mouth- 

 ful the membranous sack which is all that re- 

 mains of the egg. 



The whole of the platform of birth-sacks 

 which was the first camping-ground of the 

 White Butterfly's family is razed to the 

 ground; naught remains but the round marks 



344 



