In many parts of New Zealand the European earwig (Forficula auricularia) causes considerable damage in gardens, while in Central Otago it sometimes ruins the stone fruits. During the winter this insect lies underground, where the female will be found with her cluster of eggs. In the spring these eggs hatch, and the small whitish young earwigs ([Fig. 4], 2) emerge from the ground to feed largely upon the pollen and pistils of flowers. At that time the insects and the injury they do are not very noticeable, but as the earwigs grow in size they become conspicuous and extend their depredations to the foliage of plants and to fruit. Earwigs are nocturnal in their habits, and during the day take shelter among fallen leaves, under stones, sacking, or boards, etc., lying on the ground, and may even burrow into the soil itself.
In the control of the earwig, a great deal can be done by what may be called clean gardening—that is, the removal of all places likely to shelter the insect above ground during the day. Another important means is systematic trapping, one of the simplest methods being to place crumpled newspapers on the ground at nightfall, in which many of the insects will seek shelter, the papers being collected and burned next day. But the best method is the use of the following poison bait:—With 12lb. of bran mix 6 quarts of water, to which has been added 5oz. of glycerine and 6oz. of sodium fluoride; to this mash add 4lb. of treacle, taking care to thoroughly mix the whole.
This bait is spread at nightfall in places frequented by earwigs, and should be repeated regularly, especially after wet weather. It is obvious, if satisfactory results are to be secured, that there should be a co-operative campaign organised among the residents of an earwig-infected district.
Crickets and Grasshoppers.
Fortunately, neither crickets nor grasshoppers ([Fig. 10], 1 and 2) are a serious menace to the New Zealand horticulturist, though at times, especially in the warmer parts of the country, crickets may do some extensive damage. The control of these pests is a difficult matter, since they are mobile insects, and breed in places outside the boundaries of the horticulturist’s activities. Some benefits can be secured, however, by thorough cultivation, which breaks up the egg-masses which are placed in the ground. In the case of serious outbreaks, the use of a poisoned bait would have to be resorted to, and the following is recommended from the several recipes in use:—With 25lb. of bran mix 3 or 4 gallons of water in order to make a thin mash; to this, add 2 quarts of molasses and 1lb. of Paris green, thoroughly mixing the whole. If crickets alone are to be dealt with, then use a little more of the Paris green. This mash is spread on the ground invaded by the insects.
Caterpillars.
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.