32 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
would not care to deny that great, prolonged, and equable 
cold, might even for very considerable periods retard the 
emergence of imagines from pup, but not destroy pupal 
vitality, such retardation would be caused by a complete 
cessation of organic development while the cold lasted, 
and the cold would probably require to be applied before 
development reached a certain point, at or beyond which 
vitality would not be arrested but destroyed. Now I think 
I am right in saying that no approach even to the neces- 
sary conditions can be afforded by any possible state of 
our sandhills, besides which the moth is equally erratic 
and appears in exactly the same years in places where no 
sandhills exist as it does at Wallasey or Deal. It may 
be admitted however that the supporters of this retarded 
emergence explanation derive some small support from 
cases which have occurred with other Lepidopterous 
pupa, which have been known to “lay over”’ for several 
years at atime, but what evidence of fact we have avail- 
able in the case of this species goes in quite the opposite 
direction. There is no doubt that many thousands of gala 
have been bred from the pupe by collectors, but there is 
not one instance on record of a single pupa having ever 
deferred its emergence a single year. ‘Take this special 
year 1888 although the larve swarmed in that autumn, 
not a moth or larva was seen in 1889. Due say these 
theorists to deferred emergence; the pupz remained as 
it were dormant and presumably are dormant still. How 
came it then, that of the great numbers taken by ento- 
mologists, every one either emerged the next year or died, 
while of those left to nature the majority have deferred 
their emergence for at least four years? It is I think 
difficult for the supporters of this idea to furnish a satis- 
factory reply. 
I should perhaps not omit to mention that one well 
