A pretty invention, this little port-hole, this barricade against the invader, this trap-door lifted with a push of the hermit’s shoulder when the time has come. Shall we give the Bruchus the credit of it? Could the ingenious insect imagine the enterprise, ponder a plan and work upon a scheme of its own devising? This would be a fine triumph for the Weevil’s brain. Before deciding, let us hear what experiment has to tell us.
I skin some inhabited peas; I save them from drying too quickly by placing them in glass tubes. [[207]]The grubs do as well here as in the intact peas. The preparations for the deliverance are made at the proper time.
If the miner acts on its own inspiration, if it ceases to prolong its shaft as soon as it perceives, by sounding it now and again, that the ceiling is thin enough, what ought to happen under the present conditions? Feeling that it is as near the surface as it wishes to be, the grub will stop boring; it will respect the last layer of the bare pea and will thus obtain the indispensable defensive screen.
Nothing of the kind takes place. The well is excavated entirely; its mouth is open to the outside, as wide, as carefully finished as though the skin of the pea were still protecting it. Reasons of safety have in no way modified the usual work. The foe can enter this open lodging; the grub gives the matter not a thought.
Nor has it this in mind when it refrains from boring right through the pea still clad in its skin. It stops suddenly, because it does not like the non-farinaceous skin. We remove the skins before making our peas into soup: they have no culinary value; they are not good. The larva of the Bruchus appears to be like ourselves: it hates the tough outside of the pea. Warned by the unpleasant taste, it stops at the skin; and this aversion causes a little miracle. The insect has no logical sense of its own. It passively obeys a [[208]]higher logic; it obeys, but is as unconscious of its art as crystals are when assembling their battalions of atoms in exquisite order.
Sooner or later, in August, dark circles form on the peas, always one to each seed, with no exception. These mark the exit-hatches. Most of them open in September. The lid, which looks as though cut out with a punch, comes off very neatly and falls, leaving the opening of the cell free. The Bruchus issues, freshly clad, in her final form.
The weather is delightful. Flowers abound, awakened by the showers; the emigrants from the peas visit them in autumnal revelry. Then, when the cold sets in, they take up their winter-quarters in some retreat or other. Others, quite as numerous, are less eager to quit the native seed. They stay there, motionless, all through the frosty season, sheltered behind the trap which they are careful not to touch. The door of the cell will not open on its hinges, that is to say, along its line of least resistance, until the hot weather returns. Then the laggards leave their homes and rejoin the more forward; and all are ready for work when the peas come into flower.
The great attraction of the insect world for the observer is that he can obtain a more or less general survey of the instincts, in their inexhaustible variety; for nowhere do we see the wonderful order of life’s details more clearly revealed. Entomology, [[209]]I know, does not appeal to everybody from this point of view: people have a poor opinion of the artless person absorbed in the behaviour of insects. To the terrible utilitarian, a measure of peas saved from the Weevil is of more importance than any number of observations which bring no immediate profit.
And who has told you, O man of little faith, that what is useless to-day may not be useful to-morrow? If we learn the habits of animals, we shall be better able to protect our property. Do not despise disinterested ideas, lest you live to rue the day. It is by accumulating ideas, whether immediately applicable or not, that mankind has done and will continue to do better to-day than yesterday, better in the future than in the present. If we live by peas and horse-beans, which the Weevil disputes with us, we also live by knowledge, that mighty kneading-trough in which the dough of progress is mixed and fermented. Science is well worth a bean or two. Among other things, it tells us:
‘The corn-chandler need not trouble to wage war upon the Weevil. By the time that the peas are stored, the harm is done; it is irreparable, but not transmissible. The untouched seeds have nothing to fear from the proximity of the seeds attacked, however long they may remain together. The Bruchus will issue from the latter when her time comes; she will fly out of the granary, if escape be possible; if not, she will die without [[210]]in any way infesting the seeds that are still sound. No eggs, no new generation will ever be seen on the dried peas in our storehouse; nor will any damage be caused by the feeding of the adult.’