The Descent of Man

and thus we see how ignorant we are of the
causes of the apparent discrepancy in the proportion
of the two sexes.
In the other classes of the Articulata I have been
able to collect still less information. With spiders,
Mr. Blackwall, who has carefully attended
to this class during many years, writes to me
that the males from their more erratic habits are
more commonly seen, and therefore appear
more numerous. This is actually the case with a
few species; but he mentions several species in
six genera, in which the females appear to be
much more numerous than the males. (91.
Another great authority with respect to this
class, Prof. Thorell of Upsala ('On European
Spiders,' 1869-70, part i. p. 205), speaks as if
female spiders were generally commoner than
the males.) The small size of the males in comparison
with the females (a peculiarity which is
sometimes carried to an extreme degree), and
their widely different appearance, may account