procession of Cnethocampa pinivora. 587 



Reaumur and all subsequent authors observed the larvae to a 

 considerable extent under somewhat artificial conditions. Even 

 in Fabre's glass-houses containing pine saplings and sand at 

 S^rignan the larvae could not wander as much as in the woods. 

 The really satisfactory method would be to follow day and night 

 the proceedings of the occupants of a nest in the woods. This 

 would throw light on how far they can range and yet find their 

 nest again and to what extent the integrity of a family is 

 maintained. The meaning of processions which do not end by 

 burying and the advantage obtained by continuous secretion of 

 the thread remain puzzles. So also does the frequent formation 

 of a "circulating mass" by a procession. It seems certain that 

 contact between larvae is of much importance and that though 

 there is no permanent leadership the leader for the time being 

 does really determine the behaviour of a procession because all 

 its followers endeavour to maintain head-and-tail contact. This 

 is seen well when the leader checks its march, for the larvae 

 always endeavour to maintain head-and-tail contact by bending 

 their bodies : overlapping ensues only if the leader stops for some 

 little time. Thus mass formation is always incepted by the leader, 

 as sometimes also is burrowing. 



In my previous paper I suggested that the procession may be 

 compared with a chain of salps or polychaetes, save that organic 

 union is absent, in the sense that they probably all respond 

 fairly equally to the same stimulus, hunger, sunlight, desire to 

 pupate and so on. The observations made since this was written 

 seem to emphasise the comparative importance of the leader for 

 the time being. 



I am indebted to Mr Edwards for much information on various 

 matters referred to in his paper and to my wife for continuous 

 assistance during the observations made this year. 



LITERATURE. 



Reaumur, 1736, Memoires pour I'histoire des Insectes, ii. pp. 149 — 161 



(Paris). 

 Ratzeburg, 1840, Forst-Insecten, ii. p. 128, and Taf. 8 (Berlin); also 



Stettiner Entomologische Zeitung, p. 40. 

 Lapaury, 1876, Ann. Soc. Ent. de France, xvi. p. 244 (Paris). 

 Fabre, circa 1898, Souvenirs Entomologiques, Ser. vi. pp. 298 — 392 



(Paris). 

 Brindley, 1906, Proc. Cambridge Phil. Soc. xiv. Pt. i. p. 97. 

 Edwards, 1910, Proc. Cambridge Phil. Soc. xv. Pt. v. p. 431. 



