| Fig. 275.—Antithesia salicana. | Fig. 276.—Pœdisca occultana | Fig. 277.—Argyrolepia æneana. |
| Fig. 278.—Sericoris Zinkenana. | Fig. 279.—Sarrothripa revayana. |
| Fig. 280.—Cochylis francilana. | Fig. 281.—Choreutes dolosana. |
We have just alluded to the tube formed of a rolled leaf, in which the caterpillar takes refuge, and in which it lives. This tube it constructs itself. Réaumur has devoted a magnificent chapter of his Memoirs to observations on the skill with which divers species of caterpillars fold, roll, and bind the leaves of plants and trees, especially those of the oak. Let us listen to the great observer:—"If one looks attentively at the leaves of the oak tree towards the middle of the spring, many of them will be seen to be rolled in different ways. The exterior surface of the end of one of these leaves has, it appears, been rolled back towards the interior surface, in order to describe the first turn of a spiral, which is then covered by many other turns ([Fig. 282]). Some leaves are rolled towards their exterior surfaces, others are rolled towards their interior surfaces, but in a totally different direction. The length or axis of the first roll is perpendicular to the principal rib and to the stalk of the leaf, the axis of the latter parallel to the same rib ([Fig. 283]). Work of this kind would not be very difficult to perform for those who had fingers; but caterpillars have neither fingers nor anything equivalent to fingers. Moreover, to have rolled the leaves is only to have done half the work: they must be retained in a position from which their natural spring tends constantly to draw them. The mechanism to which the caterpillars have recourse for this second part of their work is easily perceived. We see packets of threads attached by one end to the surface of the roll, and by the other to the flat surface of the leaf. They are so many bands, so many little cords which hold out against the spring of the leaf. There are sometimes more than from ten to twelve of these bands arranged nearly in the self-same straight line. Each band is a packet of threads of white silk, pressed one against the other, and yet we must remember all are separate." [75]
| Fig. 282.—Oak leaf rolled perpendicularly. | Fig. 283.—Oak leaf rolled sideways. |
Réaumur made the oak-leaf rollers work in his house. He has admirably described all their little manœuvres, but we lack the space to convey to the reader the result of his minute observations. In fact, the leaf-rollers construct for themselves a sort of cylindrical cell, which receives light only through the two extremities. The convenience of this green fresh habitation is, that its walls furnish food to the animal which inhabits it. The caterpillar, thus sheltered, sets to work to gnaw away at the end of the leaf which it rolled first; it then eats all the rolls it has made, up to the very last.
Fig. 284.—Leaf of sorrel, a portion of which is cut and rolled perpendicularly to the leaf.
Réaumur found also rolls which had been formed of two or three leaves rolled lengthwise, and he saw that the leaves which had occupied the centre had been almost entirely eaten. He saw also caterpillars which continued to eat while they were making their habitation. Let us add that one of the ends of the roll is the opening through which the caterpillar casts its excrement; that the caterpillar can prepare itself a fresh roll if it is turned out of the first; and, lastly, that it is in a rolled leaf that the caterpillar undergoes its metamorphoses into a chrysalis and into a moth.