The diners, all motionless, all poking their heads forward, nibble in silence, placidly. Their broad black foreheads gleam in the [[36]]rays of the lantern. A shower of granules drops on the sand below. These are the residues of easy-going stomachs, only too ready to digest their food. By to-morrow morning the soil will have disappeared under a greenish layer of this intestinal hail. Yes, indeed, it is a sight to see, one far more stimulating than that of the Silk-worms’ mess-room. Young and old, we are all so much interested in it that our evenings almost invariably end in a visit to the greenhouse caterpillars.
The meal is prolonged far into the night. Satisfied at last, some sooner, some later, they go back to the nest, where for a little longer, feeling their silk-glands filled, they continue spinning on the surface. These hard workers would scruple to cross the white carpet without contributing a few threads. It is getting on for one or even two o’clock in the morning when the last of the band goes indoors.
My duty as a foster-father is daily to renew the bunch of sprigs, which are shorn to the last leaf; on the other hand, my duty as an historian is to enquire to what extent the diet can be varied. The district supplies me with Processionaries on the Scotch pine, the maritime pine and the Aleppo pine indifferently, [[37]]but never on the other Coniferæ. Yet one would think that any resin-scented leaf ought to suit. So says chemical analysis.
We must mistrust the chemist’s retort when it pokes its nose into the kitchen. It may succeed in making butter out of tallow-candles and brandy out of potatoes; but, when it tells us that the products are identical, we shall do well to refuse these abominations. Science, astonishingly rich as it is in poison, will never provide us with anything fit to eat, because, though the raw substance falls to a large extent within its domain, that same substance escapes its methods the moment that it is wanted organized, divided and subdivided indefinitely by the process of life, as needed by the stomach, whose requirements are not to be met by measured doses of our reagents. The raw material of cell and fibre may perhaps be artificially obtained, some day; cell and fibre themselves, never. There’s the rub with your chemical feeding.
The caterpillars loudly proclaim the insurmountable difficulty of the problem. Relying on my chemical data, I offer them the different substitutes for the pine growing in my enclosure: the spruce, the yew, the thuja, the [[38]]juniper, the cypress. What! Am I asking them, Pine Caterpillars, to bite into that? They will take good care not to, despite the tempting resinous smell! They would die of hunger rather than touch it! One conifer and one only is excepted: the cedar. My charges browse upon its leaves with no appreciable repugnance. Why the cedar and not the others? I do not know. The caterpillar’s stomach, fastidious as our own, has its secrets.
Let us pass to other tests. I have just slit open longitudinally a nest whose internal structure I want to explore. Owing to the natural shrinkage of the split swan’s-down, the cleft reaches two fingers’ breadth in the centre and tapers at the top and bottom. What will the spinners do in the presence of such a disaster? The operation is performed by day, while the caterpillars are slumbering in heaps upon the dome. As the living-room is deserted at this time, I can cut boldly with the scissors without risk of damaging any part of the population.
My ravages do not wake the sleepers: all day long not one appears upon the breach. This indifference looks as though it were due [[39]]to the fact that the danger is not yet known. Things will be different to-night, when the busy work begins again. However dull they may be, the caterpillars will certainly notice that huge window which freely admits the deadly draughts of winter; and, possessing any amount of padding, they will crowd round the dangerous gap and stop it up in a trice. Thus do we argue, forgetting the animal’s intellectual darkness.
What really happens is that, when night falls, the indifference of the caterpillars remains as great as ever. The breach in the tent provokes not a sign of excitement. They move to and fro on the surface of the nest; they work, they spin as usual. There is no change, absolutely none, in their behaviour. When the road covered chances to bring some of them to the brink of the ravine, we see no alacrity on their part, no sign of anxiety, no attempt to close up the two edges of the slit. They simply strive to accomplish the difficult crossing and to continue their stroll as though they were walking on a perfect web. And they manage it somehow or other, by fixing the thread as far as the length of their body permits. [[40]]
Having once crossed the gulf, they pursue their way imperturbably, without stopping any more at the breach. Others come upon the scene and, using the threads already laid as foot-bridges, pass over the rent and walk on, leaving their own thread as they go. Thus the first night’s work results in the laying over the cleft of a filmy gauze, hardly perceptible, but just sufficient for the traffic of the colony. The same thing is repeated on the nights that follow; and the crevice ends by being closed with a scanty sort of Spider’s web. And that is all.
There is no improvement by the end of the winter. The window made by my scissors is still wide open, though thinly veiled; its black spindle shape shows from the top of the nest to the bottom. There is no darn in the split texture, no piece of swan’s-down let in between the two edges to restore the roof to its original state. If the accident had happened in the open air and not under glass, the foolish spinners would probably have died of cold in their cracked house.