n of the mystery
of insect discrimination. The insect, in her then state, could have no
pleasure in the presence of certain plants, their modes of frequency
being out of sympathy with that particular Insect Life, and, it may be
conceived that, not only is there no inducement for the insect to
alight on that plant, but that even in its near proximity that insect
would feel discomfort or restlessness; when, however, a plant is
reached which is near akin to the one required, less antipathy or
unrest would be felt, and, when the true species of plant is reached,
all would be harmony, pleasure, and rest, the functions of Insect Life
would be vivified, and its life-work accomplished under the influences
of sympathetic action.

I have made several other investigations on this subject, but I must
only give one more to illustrate the higher form of Animal Life
appreciating Animal Life. There is a large class of insects, called
Ichneumonidae, which lay their eggs in the bodies of caterpillars, and,
as in the case of a moth laying its egg on the special food plant upon
which its caterpillar can feed, so does each species of these insects
unerringly lay its eggs in the body of a particular kind of
caterpillar. It must be a wonderful sense which can enable an
Ichneumon Fly to do this; it has never seen that caterpillar before,
as the egg, from which its own caterpillar was hatched, was laid
inside the body of one of those caterpillars, and the caterpillar upon
which it fed had been eaten up and disappeared at least six months
before the Ichneumon Fly had even made its way out of its own cocoon;
and yet this insect is not only forced, by some mysterious power, to
lay its egg in the body of a caterpillar, but there is only one
species which will serve its purpose, and it has to hunt up this
particular caterpillar from among thousands of other different
species.

Let me put before you what is, perhaps, the most mysterious
illustration which we have under this heading, wherein the Ichneumon
Fly cannot even get sight of its prey, nor employ any sense similar to
our own for its detection. There are several species of moths whose
caterpillars live in the very heart of trees. We will take the case of
the caterpillar of Zeuzera Aesculi, the Leopard Moth; the egg of this
Moth is laid in a crevice of the bark, and, when first hatched, the
small larva penetrates through the bark into the centre of an apple,
pear, or plum tree, and then comme