of the Larva of Cnethocampa pinivora. 433 



(b) The function of the Thread in the Procession. In the 

 case of a small procession, with the aid of a lens it was easy to 

 see that each larva secreted its own thread, which was passed 

 between the pro-legs of the terminal segment. When the path 

 of the procession became irregular the multiple nature of the 

 thread was occasionally observed. 



In the case of a large procession of 158 the thread became 

 very thick, in some places a band of silk some 2 or 3 mm. in 

 thickness being formed. In this case again the multiple nature 

 of the thread was clearly discernible. In spite of this it does not 

 seem that it is the thread which guides a satellite in procession 

 so much as the tail of the larva in front. The following observa- 

 tion supports this view. 



Two sections of a procession — each consisting of seven larvae — 

 were progressing in the same direction, separated by about 

 18 inches : the second eventually caught up the first and joined 

 it, though it did not at any time follow the silk thread laid down 

 by the latter. On the contrary that thread was crossed several 

 times, and joining up only occurred when the primite of the 

 second in his wanderings accidentally struck the sixth larva of the 

 first procession ; when he stopped immediately until the last larva 

 had passed and joined on in the right place. 



The evidence of artificial breaks is of interest in this connec- 

 tion. It appeared in all cases examined that touch rather than 

 sight was the chief guide to the satellites. When larvae were 

 removed from the middle of a procession, together with the 

 thread beneath them, joining-up always occurred if the leader 

 of the hinder portion actually came into contact with any part 

 of a larva in front. If the thread were left, joining-up was more 

 frequent, but if the break were small it occurred whether the 

 thread were removed or not. 



These observations tend to show that normally the chief factor 

 in keeping a procession together is the head-to-tail contact of the 

 larvae. The thread is of relatively small importance in this 

 connection, and serves rather as a guide to the primite on his 

 return journey to the nest. But the fact that joining-up occurs 

 more readily in the case of small breaks, when the thread is not 

 removed, would seem to indicate that the touch of the thread 

 may under certain conditions act as a guiding influence to the 

 satellites. 



Method of Formation of the " Circulating Mass." 



When on the march, processions were frequently observed to 

 form " circulating masses." This formation is usually adopted 



