Mr Brindley, The procession of Cnethocampci pinivorci. 99 
abreast. In some cases he saw as many as twenty abreast, but in 
all the procession was headed by at least one single file and so was 
invariably triangular in its general arrangement. Kirby and 
Spence* follow this account and A. H. Nicolai + has written a 
short work on the procession of this species. Ratzeburgj in the 
main follows Nicolai, stating that he himself has never seen a 
procession. There is need for further enquiry on the remarkable 
form of the procession of this species and as to the causes which 
produce the different arrangements of the larvae §. 
Fabre’s observations on G. pinivorci were made on families 
kept in glass-houses floored with sand containing small pines at 
his laboratory near Avignon. He states that the imagos appear 
in July or August and deposit the eggs in cylindrical masses round 
the pine needles. Hatching occurs in September and the larvae 
soon commence to construct the silk nest which is so characteristic 
a feature of the pine woods in winter and spring. 
The Procession. 
The activities of the larvae on the nest tree are nocturnal, 
both the strengthening of the nest and the excursions therefrom 
being performed at night. The feeding expeditions are pro- 
cessional, the primite spinning a thread by the silk glands which is 
added to by the satellites in succession. On arrival at the food- 
branch the larvae separate, each continuing to lay down its thread. 
In winter and in early spring on fine mild days there are also 
occasional processions away from the nest tree over the neigh- 
bouring sand. The meaning of these expeditions is obscure, 
though Fabre hazards the fanciful suggestion that they represent 
“ une promenade hygienique, un pelerinage de reconnaissance aux 
environs, peut-etre un examen des lieux oil se fera plus tard 
l’ensevelissement dans le sable pour la metamorphose.” As 
originally recorded by Reaumur and confirmed by Fabre, the 
procession leaves the nest tree for the last time in the later weeks 
of March or early in April, in order to burrow for pupation. Fabre’s 
chief conclusions regarding the procession are that (1) guidance by 
a secreted thread has arisen as a means of return to the nest 
because the activities of the species are nocturnal, and so is 
presumably more efficient than visual guidance; (2) the sense 
of smell is poor and is not employed for guidance ; (3) there is 
never voluntary reversal by a larva on the thread, and artificial 
reversal results in entire loss of a sense of direction ; hence a 
* Introduction to Entomology, ed. 5, ix. 1828, p. 23. 
t Die Wander- oder-Prozessionsraupe in naturhistorischer, etc., Hinsicht. Berlin, 
1833. 40 pages. Unfortunately this work is not in Cambridge. 
X loc. cit. pp. 119 — 126. 
§ For further references to literature see W. F. Kirby, loc. cit. p. 591. 
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