After this second moult, the hairs on the middle of the back are of a dull reddish colour, which is made paler still by the interposition of numerous long white hairs. But this faded costume is accompanied by the singular organs which attracted the attention of Réaumur, who was greatly perplexed as to their function. In the place originally occupied by the scarlet mosaic, eight segments of the caterpillar are now cleft by a broad transversal gash, a sort of thick-lipped mouth, which opens and gapes wide at the caterpillar’s will, or closes without leaving a visible trace. From each of these expanding mouths rises a tumour with a fine, colourless skin, as though the creature were exposing its tender inside and inflating it, for the appearance is almost that which would be presented by the viscera protruding through skin incised by the scalpel. Two large dark-brown dots occupy the front face of the protuberance. At the back are two short, flat tufts of russet bristles, which in the sunlight shine with a rich brilliancy. All around is a radiating border of long white hairs, spread almost flat. This protuberance is extremely sensitive. At the slightest irritation it goes in again and disappears under the dark integument. In its place opens an oval crater, a sort of huge stoma, which swiftly brings its lips together, closes and entirely disappears. The long white hairs that form a moustache and imperial around this mouth follow the movements of the contracting lips. After first radiating from a centre and lying flat, these hairs rise like levelled wheat which the wind has caught from beneath and meet to form a transversal crest, perpendicular to the creature’s back. This hairy erection produces a sudden modification in the caterpillar’s aspect. The red shiny bristles have disappeared, buried under the dark skin; the white hairs, now standing on end, form a hirsute mane; an ashy tinge has crept into the general colour of the costume. When calm is restored, as soon happens, the slits open and yawn afresh; the sensitive protuberances emerge, quick to disappear once more should any cause for alarm occur. These alternate expansions and contractions are rapidly repeated. I provoke them at will in various ways. A slight puff of tobacco-smoke immediately causes the stomata to yawn and the protuberances to emerge. One would think that the insect was putting itself on its guard and displaying some special apparatus of information. Before long the protuberances go in again. A second puff of smoke brings them out once more. But, if the smoke is too abundant, too acrid, the caterpillar wriggles and writhes without opening his apparatus.