434 Mr Edwards, On the Procession and Pupation 



immediately before burrowing for pupation : but at other times 

 it may result from a variety of causes, amongst which may be 

 mentioned fatigue and external interference, and sometimes for 

 no apparent reason at all. Fabre suggests cold and darkness as 

 influences. 



When I caused a small procession to circulate in a closed 

 orbit, a circulating mass was formed after 2^ revolutions by the 

 gradual diminishing of the diameter of the circle, a process which 

 tended to crowd out some of the larvae. From this mass a pro- 

 cession was subsequently reformed. When formed from a straight 

 procession the method of procedure is somewhat complicated. 

 The primite appears to start the formation by assuming a zig-zag 

 mode of progression, which is followed for a time by the satellites. 

 The arrangement soon becomes obscure and difficult to follow, 

 but there are certain noteworthy features in the behaviour of the 

 satellites. 



On entering the mass the larvae do not come to rest, but 

 continue to move slowly and in a very characteristic way, all the 

 time moving their heads rapidly from side to side and depositing 

 their threads. If the procession be a large one, the satellites 

 entering into the newly-forming mass soon begin to crowd one 

 another out in their efforts to reach it, until ranks of four or five 

 deep are formed. The thread in these places takes a similar 

 course. During the day the circulating mass formation may be 

 maintained for an hour or two ; but if at the end of that period 

 the larvae have not begun to burrow, it is usually abandoned in 

 favour of the procession. 



The manner in which the procession is reformed is of consider- 

 able interest. By marking alternate larvae (by means of fine sand 

 or flour scattered over the dorsal papillae) I found that the 

 original order of the procession was not retained ; but in every 

 case I observed (five different processions *) the primite of the 

 resulting procession tuas the same as that which went into the 

 circulating mass. 



Shortly before the primite sets out a rough kind of arrange- 

 ment is sometimes to be observed in the mass, many of the larvae 

 being arranged with their heads directed towards the point at 

 which the procession is to start. The whole process of reformation 

 is a very orderly one, though the order in which the larvae "fall in'*' 

 is not in every case obvious. 



In the case of a large procession which I photographed in the 

 act of reforming the single-file formation, there was an arrange- 

 ment of larvae four or five abreast in the neighbourhood of the 

 mass, similar to that observed during its formation. 



* The largest a procession numbering 57 larvae. 



