The Insect World / Being a Popular Account of the Orders of Insects; Together with a Description of the Habits and Economy of Some of the Most Interesting Species

by Louis Figuier

Réaumur studied other leaf-rollers; for instance, those which roll the leaves of nettles and of sorrel. The last one works in a manner which deserves to be mentioned. Its roll is of no particular shape, but it is its position which is remarkable. It is set upon the leaf like a ninepin ([Fig. 284]). The caterpillar has not only to twist it up into a roll, but also to place it perpendicularly on the leaf.

Figs. 285 and 286.—Willow leaves rolled by a caterpillar, and section of a bundle of leaves drawn together by a caterpillar.

Next to the rolling caterpillars, let us mention those which are contented with folding the leaves. These caterpillars then lie in a sort of flat box. Besides the rolling and folding caterpillars, there are still those which bind up a good many leaves in one packet. These packets are to be found on nearly every tree and shrub, and the caterpillar, lying nearly in the middle of the packet, is well sheltered, and surrounded by a good supply of food. We will content ourselves by giving a drawing, after Réaumur, of the pretty arrangement of the leaves of a species of willow (Figs. [285], [286]). In the figures we see the parcel bound together by the caterpillar. In that to the right we see the transverse section of the packet of leaves magnified. At the two edges are seen the threads which keep the leaves together, and the cavity occupied by the caterpillar.

The Vine Pyralis is produced from a leaf-rolling caterpillar, which deserves our attention on account of the ravages which it has for some time committed, and which it still commits in vineyards. It was at the end of the sixteenth century that this pyralis first showed itself in the environs of Paris, in the territory of Argenteuil. "The inhabitants of this commune," writes the Abbé Lebœuf, "looked on the insects which spoiled their vines in the spring of 1562 as a visitation of God. The Bishop of Paris gave orders that they should offer up public prayers for the diminution of these insects, and that they should join to their prayers, exorcisms, without leaving the church." Prayers, processions, exorcisms, were again had recourse to in 1629, in 1717, and in 1733, to stop the ravages of this insect among the vines of Colombes, in the territory of Aï.

The country of the Mâconnais and the Beaujolais became in their turn the theatre of the ravages of the pyralis. These ravages very soon increased and spread. In 1836, 1837, 1838, this plague raged in the departments of the Saône-et-Loire, of the Rhône, of the Côte-d'Or, of the Marne, of the Seine-et-Oise, of the Charente-Inférieure, of the Haute-Garonne, of the Pyrénées-Orientales, and of the Hérault.

To give an idea of the losses which may be occasioned by the pyralis, in a period of ten years (1828-1837), twenty-three communes comprised in the two departments of the Saône-et-Loire and of the Rhône lost 75,000 hectolitres of wine a year, which may be valued at 1,500,000 francs. If we were to calculate the supply of articles of all sorts which this great number of casks of wine would have necessitated, the imposts on their transport, the duty, the taxes levied on their sale, the carriage by land and water, which would have brought receipts into the treasury, and lastly the diminution of taxes which had to be granted for seven years to the vine proprietors in the department of the Saône-et-Loire, and in 1837 in the department of the Rhône, and which amounted to a total of more than 100,000 francs, we shall find that the ravages of the pyralis caused in these two departments an annual loss of 3,408,000 francs, and as the visitation lasted ten years, we get the enormous sum total of 34,000,000 destroyed by the ravages of one species of insect. The moth of the pyralis ([Fig. 287]) shows itself from the 10th to the 20th of June. It is yellowish, more or less shot with gold. When at rest, its wings are folded back one over the other like a roof. Its flight is of short duration; it contents itself with going from one vine stock to another.

Fig. 287.—The Vine Pyralis.		Fig. 288.—Caterpillar of the Vine Pyralis.

It is at sunset mostly that you see the moths of the pyralis fluttering about. They remain quiet during the day, particularly when the sun is at its hottest. They live on an average for ten days. The females lay their eggs—which are at first green, then yellowish, then brown—on the lower surface of the leaves.