PHYSICAL ANTECEDENTS OF SCIENCE 129

Ichneumon flies will lay their eggs within the bodies of

aterpillars, that they may find abundant suitable food when

hey are hatched, but we cannot believe they foresee the

>urpose and practical utility in their action.

A kind of wasp, called sphex, provides for the nutrition of

icr unhatched young in an analogous but yet more remark-

ble manner. She will hunt about till she finds a suitable

:aterpillar, grasshopper, or spider, which she adroitly stings

on the spot which induces, or in the several spots which in-

duce, complete paralysis, so as to deprive it of all power of

motion, but not to kill it, as to kill it would defeat her purpose.

This done, she stores away the helpless victim along with

icr eggs, in order that when her eggs are hatched the grubs

vhich issue from them may find living animal food ready for

hem and in a suitable state of helplessness ; for were they

not in such a state, the grubs would be utterly unable to

catch, retain, and prey upon them. The species of sphex

vhich preys on the grasshopper first stings it and then

throws it on its back, so as to get at the delicate membrane

which unites the pieces of its hard armour at their joints.

This it bites through to reach a specially enlarged portion

of nervous tissue there concealed, by mutilating which it

attains its practical but surely unforeseen end.

But if the adult insect cannot reasonably be supposed to

understand the future conditions of its unborn young which

t will never see, still less can the poor grub be expected to

understand what will be the future conditions of its own life

when it is a grub no longer conditions so utterly different

from those of which it has had any experience. Yet many

species of caterpillar form cocoons in modes and in places

most suitable for their protection and for their own easy

emergence when they have changed into the adult form.

The caterpillars of a moth found in Africa will unite their

efforts to form a great, as it were, common cocoon, within

K

Ichneumon flies will lay their eggs within the bodies of

aterpillars, that they may find abundant suitable food when

hey are hatched, but we cannot believe they foresee the

>urpose and practical utility in their action.

A kind of wasp, called sphex, provides for the nutrition of

icr unhatched young in an analogous but yet more remark-

ble manner. She will hunt about till she finds a suitable

:aterpillar, grasshopper, or spider, which she adroitly stings

on the spot which induces, or in the several spots which in-

duce, complete paralysis, so as to deprive it of all power of

motion, but not to kill it, as to kill it would defeat her purpose.

This done, she stores away the helpless victim along with

icr eggs, in order that when her eggs are hatched the grubs

vhich issue from them may find living animal food ready for

hem and in a suitable state of helplessness ; for were they

not in such a state, the grubs would be utterly unable to

catch, retain, and prey upon them. The species of sphex

vhich preys on the grasshopper first stings it and then

throws it on its back, so as to get at the delicate membrane

which unites the pieces of its hard armour at their joints.

This it bites through to reach a specially enlarged portion

of nervous tissue there concealed, by mutilating which it

attains its practical but surely unforeseen end.

But if the adult insect cannot reasonably be supposed to

understand the future conditions of its unborn young which

t will never see, still less can the poor grub be expected to

understand what will be the future conditions of its own life

when it is a grub no longer conditions so utterly different

from those of which it has had any experience. Yet many

species of caterpillar form cocoons in modes and in places

most suitable for their protection and for their own easy

emergence when they have changed into the adult form.

The caterpillars of a moth found in Africa will unite their

efforts to form a great, as it were, common cocoon, within

K