Before coming to a conclusion, let us
try an experiment.
I deprive certain occupied peas of their skin, and I dry them with
abnormal rapidity, placing them in glass test-tubes. The grubs prosper
as well as in the intact peas. At the proper time the preparations for
emergence are made.
If the grub acts on its own inspiration, if it ceases to prolong its
boring directly it recognizes that the outer coating, auscultated from
time to time, is sufficiently thin, what will it do under the conditions
of the present test? Feeling itself at the requisite distance from the
surface, it will stop boring; it will respect the outer layer of the
bare pea, and will thus obtain the indispensable protecting screen.
Nothing of the kind occurs. In every case the passage is completely
excavated; the entrance gapes wide open, as large and as carefully
executed as though the skin of the pea were in its place. Reasons of
security have failed to modify the usual method of work. This open
lodging has no defence against the enemy; but the grub exhibits no
anxiety on this score.
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