CATERPILLARS 53 



and large fatty bodies. It is not within our purpose to discuss 

 any of these things, but it is necessary to recognise that the 

 caterpillar is a very highly organised creature. 



Most caterpillars lead an active life, moving about in 

 search of food. Some rove by day and others by night. 

 In some dim way they are aware of the appropriate food- 

 plants, passing others by, and certain kinds may often 

 be seen exploring in a most business-like fashion. The 

 procession caterpillars of the genus Cnethocampa, which 

 rest together in a huge common web, go on the march in 

 large numbers, sometimes in single file, sometimes in broad 

 ranks. In the Italian Riviera one of the procession cater- 

 pillars (Cnethocampa pityocampa) makes a great silken 

 shelter on the branches of the Aleppo Pine, and often eats 

 them quite bare, doing great damage. They are checked a 

 little by the larva of a beautiful beetle (Calosoma) which 

 " forces its way into the silken nest and destroys the inmates. 

 So voracious is this grub that it kills many more of the 

 caterpillars than it can possibly eat. It is wisely protected 

 by those who are interested in the preservation of the pine 

 forests." These procession larvae may be seen on the 

 march about the date of the vernal equinox, forming long 

 lines on the road, the head of one almost touching the tail 

 of another. As they go they sometimes secrete a composite 

 thread, continuous to their headquarters on the tree. It 

 has been shown experimentally that they instinctively follow 

 the leader, and that he may abdicate his position in favour of 

 another. The experiment has been tried of making a circle 

 of the procession, the head of the leader being brought into 

 contact with the hind end of the last on the file, and such a 

 circle has been known to go on circling for days a fine 

 illustration of the non-intelligence of instinct. 



The biological significance of the procession is that the 

 caterpillars are seeking for a suitable soft place in which to 



