The Life of the Caterpillar 



At the moment when contact occurs the ap- 

 paratus contracts and closes up. The recoil 

 of the Snail's horns, withdrawing the visual 

 and olfactory organs into their sheaths, is no 

 prompter. 



Everything seems to prove that these op- 

 tional tumours, appearing and disappearing 

 at the caterpillar's will, are instruments of 

 sensorial perception. The caterpillar exposes 

 them to obtain information ; he shelters them 

 under his skin to preserve their delicate func- 

 tions. Now what is it that they perceive? 

 This is a difficult question, in which the habits 

 of the Processionary alone can afford us a 

 little guidance. 



During the whole winter, the Pine Cater- 

 pillars are active only at night. In the day- 

 time, when the weather is fine, they readily 

 repair to the dome of the nest and there re- 

 main motionless, gathered into heaps. It is 

 the hour of the open-air siesta, under the pale 

 December and January sun. As yet none 

 leaves the home. It is quite late in the even- 

 ing, towards nine o'clock, when they set out, 

 marching in an irregular procession, to browse 

 on the leaves of the branches hard by. Their 

 grazing is a protracted affair. The flock re- 

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