Cockchafers.—​These are the adults of the grass grubs, and there are several species, all native to New Zealand. The commonest and most destructive one ([Fig. 11], 1a) is the so-called brown beetle (Odontria zealandica), misnamed the “turnip fly,” which is on the wing for about six weeks each year, during November and early December as a rule. It swarms at dusk, creating a loud, droning sound, and is responsible for widespread damage by defoliating garden plants and field crops, as well as trees.

FIG. 11.

(1) a, Brown-chafer beetle; b, antenna of beetle, showing finger-like processes; c, larva or grass grub. (2) Bronze beetle. (3) a, Gum-tree weevil; b, egg capsule; c, larva. (4) Eucalyptus tortoise beetle. (5) a, Pear saw-fly; b, larva from the side; c, larva from above. (6) Pear midge.

This beetle is easily identified. It is rather plump-bodied, brownish, smooth, and measures about three-eighths of an inch long. Like all beetles, the front wings are hard, and form a cover over the body when closed; these hardened wings, or elytra, do not reach quite to the end of the abdomen, the tip of which remains uncovered. Another definite character is found in the antennæ, which terminate in finger-like processes ([Fig. 11], 1b). There are several species of cockchafers, to which all these characteristics, except the colour, might be referred, but none is so abundant as the species under review. There is one, however, that is on the wing about the same time as, or a little earlier than, the brown beetle. This species is somewhat larger, about half an inch long; it is sparsely clothed with hair, and the elytra are marked by broad brown stripes, alternated with very narrow darker ones.

The brown beetle lays its spherical eggs in the ground, preferably amongst the roots of grass, strawberries, etc. The grubs ([Fig. 11], 1c) are well known as grass grubs; they are whitish in colour, the swollen terminal segment of the abdomen being very often darker. These grubs are sometimes called “curl-grubs,” from their habit of lying doubled-up when at rest or feeding in the ground. Towards September each year the grubs of the brown beetle pupate prior to the beetles emerging in November. These grubs will be referred to later under the chapter dealing with subterranean insects.

In gardens and nurseries, the depredations of the beetles may be lessened by spraying with lead arsenate, or by the use of sulphur smudges. The use of smudges was developed very effectively as follows by Mr. D. J. Buchanan, forest ranger at the Tapanui State Forest nurseries. Sulphur is spread on strips of scrim, which are then rolled up and placed in containers, such as old paint pots. The latter are set about the nursery, and fired at evening, when they will burn throughout the night, the fumes acting as a deterrent to the beetles. When only a few plants are to be protected, such as bush roses, the beetles can be warded off by allowing a hose to play over the plants throughout the night.

Another common cockchafer which is on the wing most of the summer and autumn is the green manuka beetle (Pyronota festiva). This insect is capable of causing considerable damage as a defoliator. It is active both day and night. The general colour is bright green, with a dark stripe down the middle of the back, though some specimens are brown or coppery; the legs are orange-yellow, and the length of the insect is a little over a quarter of an inch.

Bronze Beetle (Eucolaspis brunneus).—​This insect ([Fig. 11], 2) is very often confused with the brown beetle, from which, however, it is easily distinguished. It is active during the day, and attacks the foliage and fruit of a great variety of plants, eating holes from leaves, so that the latter appear as if they had been subjected to a charge of shot, or devouring the epidermis from fruits and berries. This beetle is active during November to January; it measures about one-sixteenth of an inch long, is oval in outline, and varies in colour from yellowish, with darker markings, to greenish or bronzy-black; the antennæ are comparatively long, and do not terminate in any unusual manner, as do those of the cockchafers. A characteristic habit of the bronze beetle is to leap off the plant if disturbed; this habit has been responsible for the group to which this insect belongs being called “flea beetles.” The bronze beetle lays its eggs in the ground, where the larvæ feed, though they are not injurious in that stage. The beetles are to be controlled by the use of lead arsenate.