Of the leaf-feeding insects, the caterpillars of moths are the most commonly met with, there being a considerable number of destructive species. Caterpillars (Fig. 10, 3) can be readily distinguished by their structure from the grubs of other insects. They resemble short earthworms in shape, and in having the body divided into several segments, of which there are usually thirteen; but here the resemblance to worms stops. There is a distinct head--the first segment--provided with jaws, and on the under side of each of the next three segments, or thorax, is a pair of short feet. The remaining segments comprise the abdomen, and possess sucker-like feet, varying in number according to the kind of caterpillar; in some forms there may be as many as five pairs of such feet, in some three pairs, and in others two, but in all the pair on the terminal segment persists. Many caterpillars are more or less hairy, and others comparatively nude. The following are amongst the most injurious kinds:-- LEAF ROLLERS.--It is a common sight to see small greenish caterpillars sheltering between two or more leaves of plants that have been tied together by the silken threads spun by the caterpillars; protected thus, the insects feed more or less in security. These caterpillars belong to several species of the tortricid moths, which are themselves comparatively small and drab in colour. Of these species, the most abundant one, comprising over 84 per cent. of the leaf-roller population, is the Australian apple-leaf roller (_Tortrix postvittana_); the caterpillars of this insect by no means confine their attacks to the apple, but feed equally well upon pear, orange, grape, rose, insignis pine, oak, pelargoniums, etc. Apart from attacking the foliage, the caterpillars frequently tie a leaf to the surface of apple and stone fruits, and feed upon the skin of the latter, causing a blemish. The apple-leaf roller passes the winter in the caterpillar stage between two leaves. In the spring these caterpillars transform to pupæ, which give rise to moths from the end of August to about the end of October; there are at least two broods of caterpillars during the year, but the limits of these broods are not clearly defined. The caterpillars are attacked by several species of parasites. Leaf-rollers are easily controlled by the arsenical sprays used against codlin moth, but these sprays must be continued into the late summer after their need against codlin moth is past.