The eggs ([Fig. 10], 7b) are bottle-shaped, and stand erect upon the leaf surface, where they are laid singly, and not in batches; they are visible to the naked eye. The eggs hatch within a week after being laid. There are several generations each year.

The cabbage butterfly can be controlled by the use of lead arsenate. It has been found effective when planting out to first dip the seedlings in lead arsenate at the rate of 1lb. in 50 gallons of water, to which 1lb. of laundry soap is added as a spreader. During the growth of the crop the same strength of arsenate and soap can be applied as a spray.

Magpie Moth (Nyctemera annulata).—​One of the commonest and most conspicuous day-flying insects of the garden and field is the magpie moth. It is black in colour, relieved by an orange-banded abdomen and whitish spots on the wings, two on each of the front wings and one on each hind one. Its black, hairy caterpillars, commonly called “woolly bears,” have narrow brick-red lines along the body, and very often do some considerable damage to cinerarias; they also attack weeds, such as ragwort and groundsel.

The small globular eggs are laid in clusters on the leaves of the food plant. At first they are pale green, later becoming dark yellow, and just before the young caterpillars emerge from them they change to a leaden colour. When fully fed, the caterpillar seeks a sheltered place (beneath stones, under, bark, etc.), and there spins a loose cocoon, in which it transforms to the chrysalis; the latter becomes blackish or brownish in colour, with yellow markings. There are several generations during the year.

Cinerarias can be protected by spraying with lead arsenate, or, better, by removing the caterpillars by hand and destroying them.

Cabbage Tree Moth (Venusia verriculata).—​The foliage of the cabbage tree is frequently holed on the surface and notched along the edges—​this is the work of the cabbage tree moth caterpillars. The history of the insect is as follows:—​The nocturnal moth measures about an inch and a-half across the expanded wings, which are characteristically coloured by alternating chocolate-brown and yellowish-white lines running from wing-tip to wing-tip across the body, so that the insect merges into the general pattern and colour of a dead leaf, upon which it usually rests. The eggs are green, and at first blend with the green leaf, on which they are often laid in batches; when on dead leaves they become conspicuous. Later the eggs change colour to brown, and finally red. The caterpillars congregate in the unopened foliage, and their injury becomes apparent as the leaves open. The larvæ transform to chrysalids in silken cocoons, loosely spun in any suitable crevice upon the trees. If it was necessary and practicable to protect ornamental cabbage trees from the attacks of this insect, it could be done by removing dead leaves from the crown and spraying with arsenate of lead to which laundry soap had been added.

Bag Moth (Œceticus omnivorus).—​This is an insect that never fails to attract attention on account of its cigar-shaped bags ([Fig. 10], 8), constructed by the larvæ, and are to be found attached to a variety of plants, upon the foliage of which the larvæ feed, though they are not serious pests. Each caterpillar spins its own tough silken bag, which it never leaves, and to the outside of which it frequently attaches fragments of leaves and twigs. Though the male is a normal moth, and flies about (it is practically black, and densely haired, with translucent smoky-black wings having an expanse of about an inch and a-quarter), the female develops in an abnormal manner, and assumes a grub-like form, never leaving the bag woven by its caterpillar.

If it should be found necessary, as sometimes happens, the only satisfactory way of controlling the bag-moth is to remove by hand and destroy.

Beetles.

Unlike the caterpillars of moths, there are very few beetles in New Zealand that are important leaf-feeders. Though few in numbers, however, the outstanding ones are very destructive. The beetles themselves, as well as their larvæ, according to the species, may attack foliage, but in other cases it is only the beetles that feed on foliage while their larvæ live underground on roots. The following species are outstanding:—