between lepidopterous larve and their surroundings. 361 
June 26th. The 2 dark larve mature and removed. 
The 5th larva had now became a typical and distinct 
bright green form, the brown dorsal line having almost 
disappeared. 
July 2nd. The green larva mature and removed. 
CONCLUSIONS. 
This is a deeply interesting little set, showing the effect 
of the dark surroundings persisting unaltered in the 2 
larvee which were first to pupate, the green environment 
producing some effect in the greyness overspreading the 
next 2, and predominating altogether in the last. 
B. A. betularia. 
May 20th. The 51 betularia larvee remaining in the stock, 
with green leaves and shoots of Populus nigra, were care- 
fully examined. Two larvz had just entered the 3rd stage, 
having changed the 2nd skin, 5 were small in the 2nd 
stage, while all the rest were changing the 2nd skin, and 
-thus at the end of the 2nd stage. Twenty of these latter 
were transferred to a cylinder (B!) with an abundance of 
black twigs of the Turkish oak, while the remainder were 
put back into the green environment. From this date to 
the 25th all the larvee were fed on Balsam Poplar. 
May 25th, Thirty larvee counted at this date. Of these, 
15 changing the 3rd skin were transferred to a cylinder 
(B*) with black twigs. The remaining larvee were smaller, 
but even in the 3rd stage a small proportion of green in- 
dividuals had begun to appear among the brown. All 
the larvae were fed on Populus nigra from this date 
(May 25th) onwards. 
May 29th. The 15 larve remaining in the green environ- 
ments were mostly at the end of the 8rd stage and many 
were changing the 3rd skin. They were mostly lght 
brown but some were green. 
June 2nd, Six larve had reached the end of the 4th 
stage, although they were not changing their skins. Of 
these 5 were green with slight traces of brown, while the 
6th, although green, retained a larger amount of the darker 
shade. Six larvee were smaller, having reached various 
points in the 4th stage. Of these 2 were green with 
slight traces of brown, while four were brownish-green or 
light greenish-brown. Three larve were still in the 3rd 
