The Descent of Man

ut Dr. Wallace is sure that most collectors take
all the specimens which they can find of the
rarer kinds, which alone are worth the trouble
of rearing. Birds when surrounded by caterpillars
would probably devour the largest; and
Professor Canestrini informs me that in Italy
some breeders believe, though on insufficient
evidence, that in the first broods of the Ailanthus
silk-moth, the wasps destroy a larger number
of the female than of the male caterpillars.
Dr. Wallace further remarks that female caterpillars,
from being larger than the males, require
more time for their development, and consume
more food and moisture: and thus they
would be exposed during a longer time to danger
from ichneumons, birds, etc., and in times
of scarcity would perish in greater numbers.
Hence it appears quite possible that in a state of
nature, fewer female Lepidoptera may reach
maturity than males; and for our special object
we are concerned with their relative numbers at