and long persisted in, alters its pattern so as to produce a close 
resemblance to that of the winter phase, which emerges in spring, 
and gives it a general darkness of colour resembling that phase, 
but of course cannot give it the much greater mass of the winter 
phase; and warming at the proper time the winter phase pupa 
gives it the characteristic colouring, and in a measure the 
pattern, of the ordinary summer form, but does not alter its 
habit of long pupal period or its great difference in mass. 
LARVAL STAGE. 
With these remarks on the insufficiency of temperature, brought 
to bear during the pupal stage alone, to alter the life-habit of 
the Insect, I pass on to the effect of temperature brought to bear 
during the larval stage. 
A. levana; SUMMER PHASE LARVA. 
And first as to the summer phase of A. levana, those individuals 
which under normal circumstances would have emerged in the 
summer as frorsa. It will be seen that in all but very advanced 
stages of larval growth these can readily be converted by a low 
temperature into the complete winter phase. 
On June 26th, 1908, I received from North Germany several 
hundred larva which I judged from their size to be in their 3rd, 
4th and sth instars. Between 150 and 200 were placed at a low © 
spring temperature, 50° F. (10° C.) as a mean. Half of them, which 
I will call A, were left there until they pupated, and were then 
moved to a warm room (about 67° F. 19-20° C.); the other half, 
which I will call B, were left there also as pupe. 
As to the A larve, 74 pupated, a first lot of 20, which I judged to 
be within 3 or 4 days of being full fed and to be in their sth skins, 
pupating in from 12 to 18 days; 15 emerged in 13 to 15 days, all in 
aspect porima or prorsa, except one of levana aspect and one 
nearly so, one died and 4 went over to the winter. Of a second lot 
of 20, which I judged to have been 6 or 7 days short of being 
full fed, probably in their 4th skins, and pupating in 20 to 26 days, 
4 only emerged, in rr to 12 days, all of porima aspect, 7 died and 
8 went over to the winter. Of the remaining or 3rd taking, 34 in 
