The Descent of Man

all the species of the Odonatous group, there is
a great overplus of males: in the genus Hetaerina,
also, the males are generally at least four
times as numerous as the females. In certain
species in the genus Gomphus the males are
equally in excess, whilst in two other species,
the females are twice or thrice as numerous as
the males. In some European species of Psocus
thousands of females may be collected without
a single male, whilst with other species of the
same genus both sexes are common. (89. 'Observations
on N. American Neuroptera,' by H.
Hagen and B.D. Walsh, 'Proceedings, Ent. Soc.
Philadelphia,' Oct. 1863, pp. 168, 223, 239.) In
England, Mr. MacLachlan has captured hundreds
of the female Apatania muliebris, but has
never seen the male; and of Boreus hyemalis
only four or five males have been seen here.
(90. 'Proceedings, Ent. Soc. London,' Feb. 17,
1868.) With most of these species (excepting the
Tenthredinae) there is at present no evidence
that the females are subject to parthenogenesis;