578 Ml' Brindley, Further notes on the 



question as to how far the families remain separate after they 

 have commenced the processional habit. Continuous observa- 

 tion of the members of one nest from the first day of procession 

 is necessary to be certain on this point. Fabre does not deal 

 with this question definitely. He observed the larvae emerging 

 from the nest for a march, but does not say whether the in- 

 tegrity of the family was maintained from day to day. He states 

 however (p. 339) that daughter processions return to the nest 

 tree by wandering till they find the thread. The observations 

 by Edwards and myself suggest that this must very often fail to 

 happen. {Before the processional excursions begin it is probable 

 that the larvae remain in separate families, since it is rare to find 

 more than one nest in a tree.) In fact we remain in great 

 ignorance regarding the peculiar habit of forming processions 

 which return to the nest tree. That the larvae leave the tree 

 in a procession which may cover much ground and which ends in 

 burrowing for pupation is quite certain, but it remains uncertain 

 whether processions which return to the tree are the rule or only 

 exceptional. Fabre gives no statistics on this matter, but states 

 merely that in winter and early spring such processions do occur 

 on fine mild days, hazarding the suggestion that they represent 

 " une promenade hygienique, un pelerinage de reconnaissance aux 

 environs, peut-etre un examen des lieux oil se fera plus tard 

 I'ensevelissement dans le sable pour le metamorphose." Prima 

 facie such processions appear disadvantageous, for instance, apart 

 from other accidents such an exposed proceeding might be expected 

 to engender, oviposition by Tachinid flies is likely to occur, and 

 this event I observed in 1906, as described in my previous paper. 

 In spite of some degree of protection by the glandular hairs of 

 the larvae, which were obviously dreaded by the flies, the latter 

 succeeded every now and then in inserting their ovipositors. In 

 1909 and this year Edwards and myself saw no Tachinids, but 

 the sunless bleak days of my visit this year were probably un- 

 favourable to their activity. In the limited time at my disposal 

 and in the absence of opportunity of following a procession from 

 its departure from the nest till its return to it, I endeavoured this 

 year to obtain circumstantial evidence as to the occurrence of 

 processions which return to the nest tree. One step was the 

 examination of saplings bearing nests. In all cases the branches 

 near the nest were coated profusely, in fact matted, with the 

 aggregation of threads formed by the larvae, which is in accordance 

 with Fabre's statement that in their nocturnal excursions from 

 the nest to feed on the young leaves the larvae separate, each 

 spinning a thread which he holds is a guide to returning to 

 the nest towards sunrise. Below the nest the matting over with 

 threads becomes less profuse, and on the trunk of the sapling 

 threads are rare, though in places some are seen extending 



