486 Dr. Wallace on some Variations 
which assume a yellower tint as the season advances and the leaf- 
lets grow older. 
Some specimens, bred late in the season, were small and evi- 
dently weakly ; their coloration was very deficient. No. 5 is a 
specimen. ‘These were greatly deficient in vigour, and if able to 
effect copulation and fertilize eggs, their progeny would doubtless 
be a very feeble race, whereas the richly-coloured specimens 
were very vigorous and wild, and produced healthy and fine off- 
spring. 
There are two specimens fed one on plum and the other on 
laburnum, both defective in size and coloration, and evidently 
weakened by an unnatural diet. 
But the most curious specimens are the dwarfs, These were 
from the cocoons of a second brood, which were fed later in the 
autumn, after the Ailanthus leaves had failed, on celery leaves, in- 
doors. They are very diminutive in size, some only measuring 
3 inches in expanse, whereas the finer specimens measure some 
6 inches from tip to tip; the dwarfs are also deficient in depth of 
coloration, their markings are less clearly defined, the shape of 
the wings is rounder and blunter at the tip, and the abdomen is 
covered with white prominent tufts. But what seemed to me the 
most singular point about them is, that although they spun up 
several months after the first brood, they were the first to emerge. 
On the 30th May a $ emerged from the small cocoons strung 
up; this was so unexpected, that I had failed to examine for 
several days some baskets wherein other small cocoons of the 
second brood had been placed; on searching in them I found 
another g out, rather worn. On June Ist two 2 emerged of the 
first brood; on the 2nd, one ¢ emerged of the first brood and 
three of the second brood; and so on, the dwarfs coming out 
rapidly. 
I believe this will throw some light on the question of the prior 
appearance of males or females. It seems to me that in propor- 
tion as the individual is finer, so the time required for its meta- 
morphosis is longer ; and for this reason the female, which is the 
larger and heavier insect, from having to carry her numerous 
eggs, will be preceded by the male, which is smaller and has less 
to mature. Thus the dwarfs, carrying few eggs and those small, 
required less time for their metamorphosis and appeared as early 
as their uncles and aunts. If this idea be correct, and it has been 
suggested to me by the observations made on Bombyx Cynthia, 
and also on B. Yamamai, it will follow that, though we may as a 
