Tortricina
(from torqueo, to twist). A group of Moths, popularly known as Leaf-rollers, because of the habit exhibited by the larvae of many species of rolling up the leaves of their food-plants into tubes, in which they shelter themselves from birds and other foes. Inside the tubes the larvae live and feed in safety; but when the food-plant is shaken, each larva drops from its tube, and hangs suspended by a silken thread. When the danger is past, the larva climbs up the thread, and regains the shelter of the tube. Many larvae become pupae in the tubes. Some species live in roots or twigs (see Retinia), or in unripe fruits (see Apple or Codlin Grub). The Tortricina are all of small size, scarcely any of the moths reaching 1in. in spread of wings. The body is slender, but the wings are comparatively broad, and when at rest they slope like the roof of a house above the body. In many, the costa, or front margin, of the wings is peculiarly curved; so that the insect at rest is not unlike a bell in outline when seen from above. The front wings are, in most of the species, rather uniformly coloured; usually being some shade of brown, with darker markings, or bands and spots. Some show metallic spots; and others have the wings variegated with black and white, while others have them some uniform shade of green. The palpi, or feelers attached to the mouth-pieces, are short and inconspicuous. The larvae have never less than sixteen prolegs, or sucking feet, on the binder rings of the body.
A good many species of this group are injurious to cultivated plants, often by eating the leaves; e.g., Tortrix viridana sometimes strips Oak-trees bare. Roses are also much damaged by several species that live in the rolled leaflets, or inside the leaf-buds and flower-buds. Most fruit-trees are more or less liable to similar injuries; and the Coniferae often have the twigs pierced up the centre by the larvae. Herbaceous plants, though occasionally attacked, are far less often seriously damaged than woody plants or shrubs. Remedies. These vary according to the nature of the injury done. Larvae in tubes are best got rid of by beating the branches well over sheets, or over vessels tarred inside to prevent the escape of the larvae. The insects shaken off should be destroyed. Such as live in twigs are more difficult to dislodge; but sickly twigs should be cut off and burned. Fruits tenanted by larvae usually fall prematurely, and such windfalls should, without delay, be collected from the ground, and destroyed, or given to pigs, as the larvae very soon bore out of the fruits, and pass into the soil, there to remain all winter as pupae. Further information is given under Moths, Oak (INSECT PESTS), and Tortrix.