The Descent of Man

of the Cynipidae. (85. Walsh in 'The American
Entomologist,' vol. i. 1869, p. 103. F. Smith, 'Record
of Zoological Lit.' 1867, p. 328.) In all the
gall-making Cynipidae known to Mr. Walsh,
the females are four or five times as numerous
as the males; and so it is, as he informs me,
with the gall-making Cecidomyiidae (Diptera).
With some common species of Saw-flies
(Tenthredinae) Mr. F. Smith has reared hundreds
of specimens from larvae of all sizes, but
has never reared a single male; on the other
hand, Curtis says (86. 'Farm Insects,' pp. 45-46.),
that with certain species (Athalia), bred by him,
the males were to the females as six to one;
whilst exactly the reverse occurred with the
mature insects of the same species caught in the
fields. In the family of bees, Hermann Muller
(87. 'Anwendung der Darwin'schen Lehre,'
Verh. d. n. Jahrg., xxiv.), collected a large number
of specimens of many species, and reared
others from the cocoons, and counted the sexes.
He found that the males of some species greatly