124 THE WONDERS OF INSTINCT 



evening, when the weather permits, the building has to 

 be strengthened and enlarged. It is indispensable, there- 

 fore, that the corporation of workers should not be dis- 

 solved while the stormy season continues and the insects 

 are still in the caterpillar stage. But, without special 

 arrangements, each nocturnal expedition at grazing-time 

 would be a cause of separation. At that moment of 

 appetite for food there is a return to individualism. The 

 caterpillars become more or less scattered, settling singly 

 on the branches around; each browses his pine-needle 

 separately. How are they to find one another afterwards 

 and become a community again? 



The several threads left on the road make this easy. 

 With that guide, every caterpillar, however far he may be, 

 comes back to his companions without ever missing the 

 way. They come hurrying from a host of twigs, from 

 here, from there, from above, from below ; and soon the 

 scattered legion reforms into a group. The silk thread 

 is something more than a road-making expedient: it is 

 the social bond, the system that keeps the members of 

 the brotherhood indissolubly united. 



At the head of every procession, long or short, goes a 

 first caterpillar whom I will call the leader of the march 

 or file, though the word leader, which I use for the want 

 of a better, is a little out of place here. Nothing, in fact, 

 distinguishes this caterpillar from the others : it just de- 

 pends upon the order in which they happen to line up; 

 and mere chance brings him to the front. Among the 

 Processionaries, every captain is an officer of fortune. 

 The actual leader leads ; presently he will be a subaltern, 



