it—pumping, as it were, its life-blood through their rostra—a plant must of necessity suffer greatly.

Birds do not, as a rule, seem to care much about eating the Coccididæ, whose work is thus little interfered with by them. The "white-eye" (Zosterops) or "blight-bird" has been seen feeding on scale-insects; but its visits are few and far between, and its assistance to the gardener in this respect not great. The Coccididæ are, however, much subject to attacks from Hymenopterous parasites, of which some account will be found in a subsequent chapter (Chap. IV.).

The effects of the Coccididæ are not confined altogether to damage to plants: there are some species producing materials useful to man. For example, Coccus cacti produces cochineal; Carteria lacca produces shellac; Ericerus pé-la is used by the Chinese for candles: and others might be mentioned. But, so far, no New Zealand species appears to be of any commercial use. Dactylopius alpinus makes a rather rich red dye in alcohol; Cælostoma zealandicum constructs thick, waxy coverings, which might possibly be turned to some account; but even these are probably not worth much.

Groups.

The groups into which the Coccididæ are, in this work, divided are as follow:—

1. Female insects constructing for themselves shields composed partly of secretion, partly of the pellicles discarded from earlier stages; abdomen not cleft; legs lost at full growth.

Diaspidinæ.

2. Female insects naked, or covered with shields of secretion, either waxy, horny, cottony, or felted; abdomen in all stages cleft; legs either lost or retained at full growth.

Lecanidinæ.

3. Female insects naked, or covered with shields of waxy secretion; abdomen of larva ending in prominent processes, abdomen of adult cleft; legs either lost or retained at full growth.

Hemicoccidinæ.

4. Female insects naked, or covered with secretion either waxy, cottony, or felted; abdomen in all stages ending in prominent processes; legs either lost or retained at full growth.

Coccidinæ.

Life-history.

The life-history of the insects in the above groups is as follows:—

All of them pass through four stages of existence: 1, the egg; 2, the young larva; 3, the second stage of life, or "pupa;" 4, the adult, or full-grown insect.

1. The egg. This is, in all cases, of regularly-oval form, the colour varying from white to yellow or red (see Plate i, Fig. 1). It may be produced in great numbers, and in some cases several times in a year. As a general rule, the female ejects the eggs from her body; but there are some species, notably in the group Lecanidinæ, where the eggs are hatched within the body, the insect being thus, in a manner, viviparous.

2. The young larva (Plate I., Fig. 2). This is of precisely the same form both for the male and the female—or, rather, perhaps it should be said that no definite character has yet been discovered to show which are male and which are female larvæ. Neglecting slight variations of form, the larva is very minute—seldom more than about ¹/₃₀ in. long, often as small as ¹/₁₀₀ in.—oval, flattish, possessing a rostrum and accompanying bristles (setæ), six legs, and two antennæ: and in all species it is fairly active, travelling as soon as hatched over the plant in search of food.

3. The second stage. Here the first distinction is noticeable between the male and the female in most cases; but this distinction usually depends not so much upon the form of the insect as upon the character of the covering it makes for itself. Confining ourselves at present to the female, there are differences now noticeable between the groups. In the Diaspidinæ the insect begins by slipping out of the skin of the larva; but it does not cast it aside altogether: it makes use of the old skin as part of its covering. Adding to it a small portion of fibrous secretion—produced by organs called "spinnerets," which will be noticed presently—it attaches itself to the plant by its rostrum and setæ, and lies, inert and stationary, under a little shield composed half of its old skin and half of secretion. As it also, in entering this stage, loses its legs altogether, it must remain in the position it has chosen for the rest of its life. In the Lecanidinæ and in the Coccidinæ the skin of the larva is thrown away altogether, and the female in her second stage takes up a new position, in which she may be either naked or covered with a thin coat of secretion, active or stationary, retaining her legs in most cases, or losing them in some instances. In all the groups there is almost always some approach to the form of the full-grown insect noticeable in this second stage.

4. The full-grown insect. Here there is almost unlimited variety of form, colour, and habits. The insects may be naked or covered, active or stationary. In the Diaspidinæ the process just described is repeated: the female slips out of her second skin, but still keeps both it and the first over her, adding more fibrous secretion from the spinnerets; so that, in fact, she lies an inert, legless, slug-like object, under a covering composed partly of the two skins, partly of secretion. (See Plate I., Fig. 3: a is the discarded larval skin, b the discarded skin of the second stage, both being used as part of the shield. In the genus Aspidiotus these skins would be in the centre instead of at one end.) In the Lecanidinæ (except in one single genus) and the Coccidinæ the second skin is discarded altogether; but the insect may either construct a new shield or remain naked, may be either with or without legs, either active or stationary. Once this last stage of her existence entered upon, the female prepares for laying her eggs. In most species the services of a male are needed; in some, as far as can be made out after investigation of many years, no males are found. The female, if naked, either hatches her eggs in her own body or lays them on the plant; if covered, she fills her shield with the eggs. The naked insects often cover the eggs themselves—e.g., Lecanium hemisphæricum; or, again, deposit them in an ovisac, a mass of cottony secretion—e.g., Pulvinaria camellicola or Icerya