fact of
two
distinctly
defined
castes of
sterile
workers
existing
in the
same nest,
both
widely
different
from each
other and
from their
parents,
has
originated.
We can see
how useful
their
production
may have
been to a
social
community
of
insects,
on the
same
principle
that the
division
of labour
is useful
to
civilised
man. As
ants work
by
inherited
instincts
and by
inherited
tools or
weapons,
and not by
acquired
knowledge
