3a¢ Professor E. B. Poulton on colowr-relation 
the 5th still small in the 3rd stage. The black twigs were 
removed at this date, and the 5 larve by this means 
re-transferred to green surroundings. 
June 2nd. Four in 4th stage, and 1 nearly at the end 
of 8rd stage. Four distinct medium brown colour; 1 very 
black. 
June 5th. One changing 4th skin and light reddish- 
brown; 2 in 4th stage, both darkish brown ; lat beginning 
of 5th stage and medium brown; the 5th small one was 
only 9:0 mm. long. 
June 14th. One small in 6th stage, and dark brown 
with distinct grey markings prominent on it; 1 changing 
5th skin and hght brown with ventral surface rather 
greenish ; 2 at end of 5th stage, 1 imtermediate and 1 
similar to but rather darker than the larva changing its 
skin. 
June 20th. Four in 6th stage, 2 dark, overspread with 
greyish, 1 green with brown dorsal line and_ lateral 
patches, 1 dark form becoming greenish on the sides, 
June 26th. One dark larva mature and removed. 
July 2nd. The green larva and the one with greenish 
sides mature and removed. ‘The remaining larva was very 
dark, with distinct sharply-marked pale yellowish spots on 
its sides, and one on each side of the dorsal surface of each 
segment. 
July 12th. The larva described above had _ been 
accidentally drowned. 
CONCLUSIONS. 
The effect of the dark surroundings is evident. The 
green environment of the three last stages was doubtless 
the cause of the greyish tint, the oreenish sides, and the 
yellowish spots on the 3 dark larve. In the case of the 
4th larva the effects of the latter surroundings were pre- 
dominant, although the larva still retained strong traces of 
its earlier environment in the brown markings. Comparing 
this result with that of A‘, the relative unimportance of 
environment in stage IT becomes clear. 
Al. A, betularia. 
May 20th. The 10 betularia larvee re-transferred from 
black into green at the end of the 2nd stage, changing the 
2nd skin, and 8:3 mm, long. 
