The Life of the Caterpillar

by Jean-Henri Fabre

Yes, the virus which makes one scratch so much, which blisters and eats away the skin, is not a defensive product vested in only a few caterpillars. I recognize it, with its invariable properties, even in a caterpillar which at first sight appears as though it could not possess anything of the kind.

The Silkworm’s virus, besides, is not unknown in my village. The casual observation of the peasant-woman has outstripped the precise observation of the man of science. The women and girls entrusted with the rearing of the Silkworm—the magnanarelles as they are called—complain of certain tribulations caused, they say, by lou verin di magnan, the Silkworms’ poison. This trouble consists of a violent itching of the eyelids, which become red and swollen. In the case of the more susceptible, there is a rash and the skin peels off the fore-arm, which the turned-up sleeves fail to protect during work.

I now know the cause of this little trouble, my plucky magnanarelles. It is not contact with the worm that afflicts you; you need have no fear of handling him. It is only the litter [[172]]that you need distrust. There, jumbled up with the remains of the mulberry-leaves, is a copious mass of droppings, impregnated with the substance which has just so painfully eaten into my skin; there and there only is lou verin, as you call it.

It is a relief merely to know the cause of one’s trouble; but I will provide you with another consolation. When you remove the litter and renew the leaves, you should raise the irritant dust as little as possible; you should avoid lifting your hands to your face, above all to your eyes; and it is just as well to turn down your sleeves in order to protect your arms. If you take these precautions, you will suffer no unpleasantness.

The successful result obtained with the Silkworm caused me to foresee a similar success with any caterpillar that I might come across. The facts fully confirmed my expectations. I tested the stercoral pellets of various caterpillars, not selected, but just as the hazard of collecting provided them: the Great Tortoiseshell, the Heath Fritillary, the Large Cabbage Butterfly, the Spurge Hawk-moth, the Great Peacock Moth, the Death’s-head Moth, the Puss-moth, the Tiger-moth and the Arbutus [[173]]Liparis. All my tests, with not a single exception, brought about stinging, of various degrees of violence, it is true. I attribute these differences in the result to the greater or lesser quantities of the virus employed, for it is impossible to measure the dose.

So the urticating excretion is common to all the caterpillars. By a very unexpected reversion of the usual order of things, the popular repugnance is well-founded; prejudice becomes truth: all caterpillars are venomous. We must draw a distinction, however: with the same venomous properties, some are inoffensive and others, far less numerous, are to be feared. Whence comes this difference?

I note that the caterpillars marked out as stinging live in communities and weave themselves dwellings of silk, in which they stay for long periods. Moreover, they are furry. Of this number are the Pine Processionary, the Oak Processionary and the caterpillars of various Lipares.

Let us consider the first-named in particular. His nest, a voluminous bag spun at the tip of a branch, is magnificent in its silky whiteness, on the outside; inside, it is a disgusting cesspit. The colony remains in it all [[174]]day and for the greater part of the night. It sallies forth in procession only in the late hours of twilight, to browse upon the adjacent foliage. This long internment leads to a considerable accumulation of droppings in the heart of the dwelling.

From all the threads of this labyrinth hang chaplets of these droppings; the walls are upholstered with them in all the corridors; the little narrow chambers are encumbered with them. From a nest the size of a man’s head I have obtained, with a sieve, over three-quarters of a pint of stercoral pellets.

Now it is in the midst of this ordure that the caterpillars live and have their being; in the midst of it they move, swarm and sleep. The results of this utter contempt for the rules of cleanliness are obvious. Certainly, the Processionary does not soil his coat by contact with those dry pellets; he leaves his home with his costume neat and glossy, suggesting not a suspicion of uncleanliness. No matter: by constantly rubbing against the droppings, his bristles are inevitably smeared with virus and their barbs poisoned. The caterpillar becomes irritant, because his manner [[175]]of life subjects him to prolonged contact with his own ordure.