— 441 — 
their 4th skins were placed at a low spring temperature (about 
so” F., say 10% C.), pupating there in from 14 to about 30 days 
and being afterwards transferred to the room temperature ; not 
one has emerged, as they would certainly have done had the 
larvæ remained at summer temperature. I expect the whole will 
« go over » to the spring (1). 
A. levana, WINTER PHASE LARVÆ. 
Next as to winter phase larve. On August 18th and 25th, 1908, 
I received some hundreds, mostly about */; of an inch (say 1-2 cen- 
timetres) long. 25 were forced at 80° F. (27° C.); of these only 
5 emerged as summer phase, all of course of prorsa aspect. All the 
others of those received « went over », though placed at a spring 
temperature for various periods and then transferred to higher 
temperatures. 
A. levana, CONVERSION OF ONE PHASE INTO THE OTHER. 
These experiments, and many other published experiments both 
with the summer and the winter phase (2), show how difficult it is 
to convert the winter phase of A. /evana into the summer phase, 
even if it is by no means in a very advanced larval stage. But this 
last conversion can be readily effected if the transfer to the higher 
temperature is made in a very early larval stage; for some larve 
from eggs laid by the summer phase in the latter part of July 1909 
and which would therefore under normal circumstances have 
pupated late in August or in September as winterphase /evana, 
forced as larvæ at 80° F. (27° C.) from the time of hatching, and 
pupating in 16 to 20 days, all emerged in 2 to 3 weeks, at the 
outdoor temperature, as pure Prorsa. 
The particulars I have given afford, I submit, sufficient proof 
that either phase of A. levana can be made to assume the other 
(1) September 25th. All are still in pupa. 
(2) WEISMANN, Studies in the Theory of Descent (English translation by 
Prof. MELDOLA, vol. I, appendix 1, pp. 117-125); « New Experiments [in 1883- 
1884 and 1886] on the Seasonal Dimorphism of Lepidoptera » (English transla- 
tion by NICHOLSON) reprinted from « The Entomologist », January- August 1896. 
