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 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 of life subjects him to prolonged contact with his own ordure. Now consider the Hedgehog Caterpillar. Why is he harmless, despite his fierce and hirsute aspect? Because he lives in isolation and is always on the move. His mane, apt though it be to collect and retain irritant particles, will never give us the itch, for the simple reason that the caterpillar does not lie on his excretions. Distributed all over the fields and far from numerous, owing to the caterpillar’s solitary habits, the droppings, though poisonous, cannot transfer their properties to a fleece which does not come into contact with them. If the Hedgehog lived in a community, in a nest serving as a cesspit, he would be the foremost of our stinging caterpillars. At first sight, the barrack-rooms of the Silkworm-nurseries seem to fulfil the conditions necessary to the surface venom of the worms. Each change of litter results in the removal of basketfuls of droppings from the trays. Over this heaped-up ordure the Silkworms swarm. How is it that they do not acquire the poisonous properties of their own excrement? I see two reasons. In the first place, they are hairless; and a brushlike coat may well be indispensable to the collection of the virus. In the second place, far from lying in the filth, they live above the soiled stratum, being largely separated from it by the bed of leaves, which is renewed several times a day. Despite crowding, the population of a tray has nothing that can be compared with the ordinary habits of the Processionary; and so it remains harmless, in spite of its stercoral toxin.