PEAR AND CHERRY SLUG, OR SAW-FLY(_Caliroa limacina_).--The slug-like larvæ of this insect are very abundant upon hawthorn foliage, and if not controlled do considerable damage to cherry, plum, pear, and peach. These larvæ (Fig. 11, 5b) are very often called leeches, and devour the epidermis, exposing the skeleton of the infested leaves; they are slimy, of a dark green, though orange-coloured immediately after a moult, and the head end is much enlarged, giving a clubbed shape to the body, along the under side of which are several false legs. Pupation takes place in the ground. The adult (Fig. 11, 5a) measures about a quarter of an inch long, is rather thickly set, black in colour, and possesses four transparent wings. The female deposits her eggs in the tissue of the foliage by means of a saw-like ovipositor--hence the name "saw-fly"--which is thrust through the lower epidermis of the leaf, when a pocket is formed to receive the egg; each egg pocket forms a little pimple on the upper surface. This insect is very easily controlled by spraying foliage infested by the larvæ with lead arsenate.
Another saw-fly closely related to the foregoing species is the willow saw-fly (_Pontania proxima_). This species has only recently appeared in New Zealand, and its larvæ live in galls, or swellings, on the foliage of willows.
PEAR MIDGE(_Perrisia pyri_).--A serious pest of pear trees, which for some years retarded the culture of pears, especially in the Auckland district, is the pear midge. This is a minute, delicate, two-winged fly (Fig. 11, 6), measuring about one-twenty-fifth of an inch long; it has a blackish head and thorax, and an orange-red to brownish abdomen. The female alights upon young leaves just burst from the bud; and, while they are yet curled, lays her eggs between the folds. The larvæ, on hatching, live protected in the curled leaves, which they attack, and which never unfold. The result is that the infested leaves eventually turn black and brittle, and cease to function. The fully-developed larvæ drop to the ground, which they enter, and there pupate. The midges become abundant in early spring, when the first young pear foliage develops, and they keep on producing generation after generation until the autumn. The winter is passed in the larval stage underground beneath the trees.