Contributions to the theory of natural selection. A series of essays ... By Alfred Russel Wallace ...

202 Oy iNSTIYCT IN MAN AND ANIMALS.
animals not very far removed from ourselves, before
we pronounce positively as to the nature of the mental
operations in creatures so radically different from us
as insects. We have not yet even been able to ascertain what are the senses they possess, or what relation
their powers of seeing, hearing, and feeling have to
ours. Their sight may far exceed ours both in delicacy
and in range, and may possibly give them knowledge
of the internal constitution of bodies analogous to that
which we obtain by the spectroscope; and that their
visual organs do possess some powers which ours do
not, is indicated by the extraordinary crystalline rods
radiating from the optic ganglion to the facets of the
compound eye, which rods vary in form and thickness
in different parts of their length, and possess distinctive characters in each group of insects. This complex
apparatus, so different from anything in the eyes of
vertebrates, may subserve some function quite inconceivable by us, as well as that which we know as
vision. There is reason to believe that insects appreciate sounds of extreme delicacy, and it is supposed
that certain minute organs, plentifully supplied with
nerves, and situated in the subcostal vein of the wing
in most insects, are the organs of hearing. But besides these, the Orthoptera (such as grasshoppers,
&c.) have what are supposed to be ears on their fore
legs, and Mr. Lowne believes that the little stalked
balls, which are the sole remnants of the hind wings
in flies, are also organs of hearing or of some analogous sense. In flies, too, the third joint of the