580 ilfr Brindley, Further notes on the 



"evidence is required before we can feel certain that Fabre's 

 suggestion as to the function of the thread formed during 

 procession can stand. It may well be that his far more extensive 

 study of the larvae compared with other observers justifies his 

 conclusion, but he does not present the evidence in the Souvenirs. 

 As regards the thread being a less important aid to main- 

 taining the integrity of a procession than head-and-tail contact 

 of the larvae, all that I observed is in agreement with Edwards, 

 who made many experiments to test the point and came to the 

 general conclusion that in the case of breaks in a procession 

 joining occurs more readily if the thread is intact, though if 

 the interval is short the presence of the thread seems negligible. 

 Only in one instance of many did it appear to me that joining up 

 really resulted from the larvae finding and following a thread 

 secreted ahead of them. A procession of 6 larvae came across 

 a thread formed by a single larva, when the leader of the 

 6 closely followed it, a proceeding which was more obvious because 

 the single larva went round in a circle. At the same time 

 the distance was only a few inches, and sight may really have 

 been the guide. On all the other numerous occasions on which 

 two processions became one or single larvae joined processions 

 there was no suggestion that the thread was regarded, while 

 on several occasions the impression that sight was the chief aid 

 in effecting joining up was strong. Moreover, a single larva 

 joining a procession does not always make contact with the last 

 in the procession, but just as often comes parallel to the marshalled 

 larvae and quickly intercalates itself between any two, being 

 accepted without hesitation. 



In considering the value of the thread in maintaining the 

 integrity of a procession it is necessary to refer to the "circulating 

 mass," so frequently formed by larvae on the march. This con- 

 dition has been already described by Fabre (loc. cit. chap, xx, p. 332), 

 Edwards (loc. cit. p. 434), and myself (loc. cit. p. 100), and it is 

 enough to say here that the chain breaks up into a heap of larvae 

 walking over each other without the heap as a whole making 

 way over the sand. The mass formation was held by Fabre to 

 be encouraged by cold and darkness, and to be very likely a mode 

 of resting. Edwards has discussed the subject (loc. cit. p. 434). 

 It is certainly the usual condition of a procession about to burrow, 

 but it is frequently adopted temporarily, the procession reforming 

 sooner or later. Artificial interference with a procession will 

 often cause the formation of a mass, but it is quite unknown 

 why it is so frequent a condition of a group of larvae on the 

 mai'ch. While in a circulating mass the individuals continue to 

 secrete threads, but the continual crossing over each other by 

 the larvae necessarily prevents the fusion of the threads which 



