English prose literature; Exposition (Rhetoric); Readers -- Science
A pretty invention, this little closed porthole, this barricade against
the invader, this trap-door raised by a push when the time has come for
the hermit to enter the world. Shall we credit it to the Bruchus? Did
the ingenious insect conceive the undertaking? Did it think out a plan
and work out a scheme of its own devising? This would be no small
triumph for the brain of a weevil. 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.
Neither is it thinking of the outer enemy when it bores down to the skin
when the pea is intact, and then stops short. It suddenly stops because
the innutritious skin is not to its taste. We ourselves remove the
parchment-like skins from a mess of pease-pudding, as from a culinary
point of view they are so much waste matter. The larva of the Bruchus,
like ourselves, dislikes the skin of the pea. It stops short at the
horny covering, simply because it is checked by an uneatable substance.
From this aversion a little miracle arises; but the insect has no sense
of logic; it is passively obedient to the superior logic of facts. It
obeys its instinct, as unconscious of its act as is a crystal when it
assembles, in exquisite order, its battalions of atoms.
Sooner or later during the month of August we see a shadowy circle form
on each inhabited pea; but only one on each seed. These circles of
shadow mark the doors of exit. Most of them open in September. The lid,
as though cut out with a punch, detaches itself cleanly and falls to the
ground, leaving the orifice free. The Bruchus emerges, freshly clad, in
its final form.
Public-domain text, read in full here on John Shaqi.
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