Gum Tree Weevil (Gonipterus scutellatus).—Both the adults and larvæ of this Australian weevil attack eucalyptus foliage, particularly bluegum, in most parts of New Zealand, the adult weevils eating from the leaf margin, as well as devouring tender shoots, while the larvæ cut elongated holes from the leaf surface.
The weevil ([Fig. 11], 3a), which is of a tawny to brownish-black colour, and clothed with yellowish-white and golden hairs, measures from a quarter to one-third of an inch in length; it possesses a short snout on the head. The eggs are yellowish, and are packed in a hard, black capsule ([Fig. 11], 3b), attached mainly to the surface of young leaves. The larvæ ([Fig. 11], 3c) are legless, like those of all weevils, and yellowish at first, when they are studded with small black dots, and have a dark stripe along each side. Frequently these young larvæ are seen with a tail-like thread of blackish excrement projecting from the posterior end. The plump, fully-developed grub is yellowish-green, with a wrinkled skin, and is slug-like in general appearance. Pupation takes place in the ground. This insect over-winters in the adult stage, and large numbers of the weevils are very often to be found beneath loose bark on the tree trunks during the winter. Control depends upon the use of an egg parasite which has been established in certain localities of the Dominion. In the case of small ornamental trees, spraying with lead arsenate to which laundry soap has been added should be effective.
Eucalyptus Tortoise Beetle (Paropsis dilatata).—This is another Australian insect restricted so far to the East Coast districts of the South Island, where it attacks eucalyptus foliage in company with the weevil. The beetle ([Fig. 11], 4) is tortoise-shaped, varies in colour from reddish-yellow to reddish-brown, with darker markings on the back, which is pitted by minute depressions, and has a length of from one-third to half an inch. Like the weevil, this beetle passes the winter beneath loose bark.
The eggs are conspicuous and cigar-shaped, being laid in clusters, lying more or less on their sides, upon the foliage. The larva is rather plump, and pointed posteriorly; it possesses legs, while at the tip of the body is a sucker-like false foot. The general colour is yellowish, varying to a rosy-pink, there being a darker stripe down the back, while along each side is a similar one above a row of black dots.
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.
A parasite has been established against the pest, and is doing good work. The insect can be reduced to a large extent by thorough winter cultivation, especially beneath the trees. The insect’s larvæ, being protected within the curled-up leaves, are not reached by ordinary sprays, but Dr. R. H. Makgill, of Henderson, secured some excellent results on young trees by the use of nicotine.