584 Mr Brindley, Further notes on the 



should continue when the larvae are feeding and when they are 

 away from the nest tree remains obscure, and at present Fabre's 

 ingenious suggestions as to its value can be regarded only as 

 surmises. The great expenditure of material and energy which 

 its formation involves we have no right to call useless. It is 

 possible of course that it is to some extent an excretory process, 

 and we know that sericin and fibroin, which occur in silk, like the 

 other skeletins of invertebrate animals, contain nitrogen (Schafer, 

 Text Book of Physiology, 1898, i. p. 76). 



As far as I could ascertain a larva marching alone secretes 

 a thread almost invariably. That of a single larva is very fine, 

 but careful examination of the sand in its track with a lens shows 

 it : even this single thread is strong enough to be lifted for an 

 inch or two without breaking in spite of the particles of sand 

 adhering to it. A fairly extensive enquiry on this point revealed 

 only three or four cases of larvae marching without making the 

 thread. 



The details of processions given above are quite in agreement 

 with the original statement by Fabre and the observations of 

 Edwards that there is no special leader: when once a procession 

 is formed the leading larva may be removed without interference 

 with the progress of march. Leadership in a particular sense 

 exists only in the formation of a procession from a circulating 

 mass. All that therefore need be said on the subject here is to 

 quote an experiment I made to find out with some exactness 

 if the removal of the leader checked the progress of a procession 

 at all. In the case of a procession of 6 larvae I reversed each 

 larva, placing it with forceps as quickly and carefully as possible 

 in head-and-tail contact with its neighbours, thus effecting an 

 artificial countermarch. The procession proceeded at once in the 

 direction opposite to the original one. Immediately it was well 

 on the march I removed the leader and placed it in contact with 

 the last larva, repeating this each time immediately the march 

 was resumed. The times given below are those when the order 

 was changed as stated. 



The interval of five minutes between 5.9 and 5.14 was not due 

 to special hesitation of the leader, but because removing it was 

 delayed in order to watch the behaviour of the larvae to 

 sunlight, which at this time broke through the clouds. Each 

 time the leader was removed the new leader cast about with its 



