432 Mr Edwa7'ds, On the Procession and Pupation 



were alike in this respect. Yet — as Avill be seen later — it was 

 found that a particular larva, when once entrusted with this 

 position, usually retained it. On one occasion, however, I saw 

 a voluntar}' change of leader, the primite detaching himself and 

 becoming inserted at the fifth place. It seemed probable, too, 

 that the primite was capable of taking a real initiative in certain 

 cases, the remainder following him whether influenced by the same 

 stimuli or not. This was shown to be the case in 



(1) The selection of a path. 



(2) Burrowing for pupation. 



(3) Forming of a "circulating mass." (This term is explained 



later.) 



In the first case at least two external conditions seem to 

 influence his choice, viz. light and surface. This was suggested 

 in the case of a small procession of seven which came under my 

 observation, I threw the whole procession into the shade and 

 determined the path taken by the primite by causing a reflected 

 ray of light to be cast beneath his head. The procession followed 

 the reflected ray, although only the primite could have been 

 influenced by this stimulus. In the case of processions which 

 burrowed for pupation the primite was frequently observed to 

 test the ground Avith his mandibles before a circulating mass — 

 the formation always adopted before burying — was formed. 



The term " circulating mass " is used in Mr Brind ley's paper 

 to denote the assemblage of larvae moving among each other ; 

 but the assemblage, as a whole, remaining on the same spot. 



In the formation of the circulating mass, the primite seemed 

 to be taking the initiative by turning his body sharply round 

 into a position parallel to that of the second : and if a procession 

 was reformed without pupation the same larva usually took the 

 lead. Thus it appears that though any larva can take up the 

 duties of the primite, yet the primite does in a real sense lead the 

 procession, the satellites following whether influenced by identical 

 stimuli or not. At nightfall — according to Fabre — the procession 

 usually returns to the nest, the primite wandering round until 

 he strikes the outward-bound thread. I never observed this 

 proceeding, but if Fabre be correct it would seem that the primite 

 is capable of exercising choice in this respect. In all the cases 

 I examined the leader refused to walk along any foreign thread— - 

 whether artificial (e.g. silk thread frayed out) or that of another 

 procession — which I placed in his path. 



In addition to light and surface, the desire to pupate and 

 temperature might be suggested as factors influencing the primite 

 in his movements : and — as Fabre suggests — the occurrence of 

 processions at all is dependent upon atmospheric conditions ; for 

 in bad weather the larvae remain in their nests. 



