36 "LE RAIL SOYEUX" 



says, the larvae find their way back to the nest. 

 But, as regards the processionary march, the 

 leader can have nothing to guide him, nor 

 would the thread serve when crossing a dusty 

 high-road or wind-swept sandy ground. 



Were these caterpillars solely dependent on 

 " le rail soyeux," as Fabre terms it, they would 

 soon become disbanded and so lose touch of one 

 another. Le fit luisant, however, is an invalu- 

 able safeguard against falling from sUppery 

 situations — ^the narrow rim of a flower-pot, for 

 instance ; for it ensures secure footing, and, 

 moreover, it is a natural precaution which is 

 common to most arboreal larvae, especially in 

 their younger stages ; were it not so, they 

 would risk being blown or washed from the 

 trees. 



That this thread is instrumental in guiding 

 the larvae to the nest is hardly probable, seeing 

 that the whole of the branch is matted with it. 

 When a larva has fallen from the leaf and is 

 left suspended in the air the thread is useful 

 in helping it up again, but on gaining the leaf 

 the creature must depend on its sense of 

 direction. 



Though none quite so remarkable as the 

 processionary larvae, there are many other 

 species of gregarious caterpillars who " follow 

 the leader " in mtich the same way. For 



