Yung raised the percentage of females from 54 to 78: in the
second, with fish, the percentage rose from 61 to 81; while in
the third set, when the especially nutritious flesh of frogs
was supplied, the percentage rose from 56 to 92. That is to
say, in the last case the result of high feeding was that
there were 92 females and 8 males.[11]

Similarly, the experiments of Siebold on wasps show that the
percentage of females increases from spring to August, and
then diminishes. We may conclude without scruple that the
production of females from fertilized ova increases with
the temperature and food supply, and decreases as these
diminish.[12]

Nor are there many facts more significant than the simple and
well-known one that within the first eight days of larval
life the addition of food will determine the striking and
functional differences between worker and queen.[13]

It is certainly no mere chance, but agrees with other
well-known facts, that for the generation of the female organ
more favorable external circumstances must prevail, while
the male organ may develop under very much more unfavorable
conditions.[14]

These facts are not conclusive, but they all point in the same
direction, and are probably sufficient to establish a connection
between food conditions and the determination of sex. But behind the
mere fact that a different attitude toward food determines difference
of sex lies the more fundamental--indeed, the real--explanation of