Three weeks later, new skin is forming, but is covered all over with painful little pimples. [[167]]The swelling diminishes; the redness persists and is still very marked. The effect of the infernal paper lasts a long time. At the end of a month, I still feel an itching, a burning irritation, which is intensified by the warmth of the bed-clothes. At last, a fortnight later, all has disappeared but the redness, of which I shall retain the marks for a long time yet, though it grows gradually fainter and fainter. It will take three months or more to vanish altogether.
We now have some light on the problem: the Processionary’s virus is certainly an offthrow of the organic factory, a waste product of the living edifice. The caterpillar discards it with his excrement. But the material of the droppings has a twofold origin: the greater part represents the digestive residuum; the rest, in a much smaller proportion, is composed of the urinary products. To which of the two does the virus belong? Before going farther, let us permit ourselves a digression which will assist us in our subsequent enquiries. Let us ask what advantages the Processionary derives from his urticating product.
I already hear the answer:
“It is a means of protection, of defence. [[168]]With his poisoned mane, he repels the enemy.”
I do not clearly perceive the bearing of this explanation. I think of the creature’s recognized enemies: of the larva of Calosoma sycophanta, which lives in the nests of the Processionary of the Oak and gobbles up the inhabitants with never a thought of their burning fleece; of the Cuckoo, another mighty consumer, so we are told, of the same caterpillars, who gorges on them to the point of implanting in his gizzard a bristling coat of their hairs.
I am not aware if the Processionary of the Pine pays a like tribute. I do know of at least one of his exploiters. This is a Dermestes,[1] who establishes himself in the silken city and feeds upon the remains of the defunct caterpillars. This ghoul assures us of the existence of other consumers, all furnished with stomachs expressly fashioned for such highly-seasoned fare. For every harvest of living creatures there is always a harvester.
No, the theory of a special virus, expressly prepared to defend the Processionary and his [[169]]emulators in urtication, is not the last word on the subject. I should find it difficult to believe in such a prerogative. Why have these caterpillars, more than others, need of protection? What reasons would make of them a caste apart, endowed with an exceptional defensive venom? The part which they play in the entomological world does not differ from that of other caterpillars, hairy or smooth. It is the naked caterpillars who, in default of a mane capable of striking awe into the assailant, ought, one would think, to arm themselves against danger and impregnate themselves with corrosives, instead of remaining a meek and easy prey. Is it likely that the shaggy, bristling caterpillar should anoint his fleece with a formidable cosmetic and his smooth-coated kinsman be unfamiliar with the chemical properties of the poison beneath his satin skin! These contradictions do not inspire confidence.
Have we not here, rather, a property common to all caterpillars, smooth-skinned or hairy? Among the latter, there might be some, just a few, who, under certain special conditions which will need to be defined, would be quick to reveal by urtication the [[170]]venomous nature of their organic refuse; the others, the vast majority, living outside these conditions, even though endowed with the necessary product, would be inexpert at the stinging business and would not produce irritation by contact. In all, the same virus is to be found, resulting from an identical vital process. Sometimes it is brought into prominence by the itching which it produces; sometimes, indeed most often, it remains latent, unrecognized, if our artifices do not intervene.
What shall these artifices be? Something very simple. I address myself to the Silkworm. If there be an inoffensive caterpillar in the world, it is certainly he. Women and children take him up by the handful in our Silkworm-nurseries; and their delicate fingers are none the worse for it. The satin-skinned caterpillar is perfectly innocuous to a skin almost as tender as his own.
But this lack of caustic venom is only apparent. I treat with ether the excretions of the Silkworm; and the infusion, concentrated into a few drops, is tested according to the usual method. The result is wonderfully definite. A smarting sore on the arm, similar in its mode of appearance and in its effects to [[171]]that produced by the droppings of the Processionary, assures me that logic was right.