But she does not always do so without hindrance. Let me recount one of the misadventures of this work of storage. There is in the neighbourhood of the burrows a plant which catches insects with glue. It is the Oporto silene (S. portensis), a curious growth, a lover of the sea-side dunes, which, though of Portuguese origin, as its name would seem to indicate, ventures inland, even as far as my part of the country, where it represents perhaps a survivor of the coastal flora of what was once a Pliocene sea. The sea has disappeared; a few plants of its shores have remained behind. This Silene carries in most of its internodes, in those both of the branches and of the main stalk, a viscous ring, two- to four-fifths of an inch wide, sharply delimited above and below. The coating of glue is of a pale brown.
Its stickiness is so great that the least touch is enough to hold the object. I find Midges, Plant-lice and Ants caught in it, as well as tufted seeds which have blown from the capitula of the Cichoriaceae. A Gad-fly, as big as a Blue bottle, falls into the trap before my eyes. She has barely alighted on the perilous perch when lo, she is held by the hinder tarsi!
The Fly makes violent efforts to take wing; she shakes the slender plant from top to bottom. If she frees her hinder tarsi she remains snared by the front tarsi and has to begin all over again. I was doubting the possibility of her escape when, after a good quarter of an hour's struggle, she succeeded in extricating herself.
But, where the Gad-fly has got off, the Midge remains. The winged Aphis also remains, the Ant, the Mosquito and many another of the smaller insects. What does the plant do with its captures? Of what use are these trophies of corpses hanging by a leg or a wing? Does the vegetable bird-limer, with its sticky rings, derive advantage from these death-struggles?
A Darwinian, remembering the carnivorous plants, would say yes. As for me, I don't believe a word of it. The Oporto silene is ringed with bands of gum. Why? I don't know. Insects are caught in these snares. Of what use are they to the plant? Why, none at all; and that's all about it. I leave to others, bolder than myself, the fantastic idea of taking these annular exudations for a digestive fluid which will reduce the captured Midges to soup and make them serve to feed the Silene. Only I warn them that the insects sticking to the plant do not dissolve into broth, but shrivel, quite uselessly, in the sun.
Let us return to the Tachytes, who is also a victim of the vegetable snare.
With a sudden flight, a huntress arrives, carrying her drooping prey. She grazes the Silene's lime-twigs too closely. Behold the Mantis caught by the abdomen. For twenty minutes at least the Wasp, still on the wing, tugs at her, tugging again and again, to overcome the cause of the hitch and release the spoil. The hauling-method, a continuation of the flight, comes to nothing; and no other is attempted. At last the insect wearies and leaves the Mantis hanging to the Silene.
Now or never was the moment for the intervention of that tiny glimmer of reason which Darwin so generously grants to animals. Do not, if you please, confound reason with intelligence, as people are too prone to do. I deny the one; and the other is incontestable, within very modest limits. It was, I said, the moment to reason a little, to discover the cause of the hitch and to attack the difficulty at its source. For the Tachytes the matter was of the simplest. She had but to grab the body by the skin of the abdomen immediately above the spot caught by the glue and to pull it towards her, instead of persevering in her flight without releasing the neck. Simple though this mechanical problem was, the insect was unable to solve it, because she was not able to trace the effect back to the cause, because she did not even suspect that the stoppage had a cause.
Ants doting on sugar and accustomed to cross a foot-bridge in order to reach the warehouse are absolutely prevented from doing so when the bridge is interrupted by a slight gap. They would only need a few grains of sand to fill the void and restore the causeway. They do not for a moment dream of it, plucky navvies though they be, capable of raising miniature mountains of excavated soil. We can get them to give us an enormous cone of earth, an instinctive piece of work, but we shall never obtain the juxtaposition of three grains of sand, a reasoned piece of work. The Ant does not reason, any more than the Tachytes.
If you bring up a tame Fox and set his platter of food before him, this creature of a thousand tricks confines himself to tugging with all his might at the leash which keeps him a step or two from his dinner. He pulls as the Tachytes pulls, exhausts himself in futile efforts and then lies down, with his little eyes leering fixedly at the dish. Why does he not turn round? This would increase his radius; and he could reach then the food with his hind-foot and pull it towards him. The idea never occurs to him. Yet another animal deprived of reason.
Friend Bull, my Dog, is no better-endowed, despite his quality as a candidate for humanity. In our excursions through the woods, he happens to get caught by the paw in a wire snare set for rabbits. Like the Tachytes, he tugs at it obstinately and only pulls the noose tighter. I have to release him when he does not himself succeed in snapping the wire by his hard pulling. When he tries to leave the room, if the two leaves of the door are just ajar, he contents himself with pushing his muzzle, like a wedge, into the too narrow aperture. He moves forward, pushing in the direction which he wishes to take. His simple, dog-like method has one unfailing result: the two leaves of the door, when pushed, merely shut still closer. It would be easy for him to pull one of them towards him with his paw, which would make the passage wider; but this would be a movement backward, contrary to his natural impulse; and so he does not think of it.
Yet another creature that does not reason.
