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Volume 16, 1883
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2. Rhizococcus fossor, sp. nov.
Figs. 36–38.

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Adult female (fig. 36) greenish yellow in colour, sometimes brown, almost circular in outline, flat beneath and slightly convex above: length about 1/15 inch. In the last stage, after gestation it becomes dark brown. The cephalic part is smooth; the remainder segmented. The abdomen ends in two very small anal tubercles, which are nevertheless somewhat conspicuous on account of their brown colour. Between them there protudes a long thick pencil of white cotton, which is resolvable into six. Antennæ (fig. 37) short, with six joints, the last joint bearing several long hairs. Feet very small; the femur rather thick: the tibia is shorter than the tarsus by about one-third: the four digitules are long fine hairs. The anal tubercles have not terminal setæ; and I can only make out four hairs on the anal ring. A row of a few conical spines, set far apart, runs round the edge of the body, but I can see none elsewhere, nor any circular spinnerets. There is no sign of a sac in any stage.

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In the second stage the insect is oval, flatter than the adult, and of a rich golden colour: length about 1/40 inch. The segments of the body are somewhat more distinct than in the adult. The anal tubercles are proportionately larger, and bear terminal setæ. Antennæ longer than in the adult, with six joints. Feet also longer. All round the edge runs a row of conical spines, set more closely than in the adult; and from each of these springs a long curly tube of white cotton, making a kind of fringe to the body; each tube is a little dilated at the end, and then tapers to a narrow point (fig. 38). The base of each conical spine is a somewhat large tubercle.

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The young insect has the general form of the young Eriococcus hoheriæ: colour yellow; length about 1/60 inch. Antennæ as in adult, with six joints. The feet are somewhat large. Anal tubercles thick, bearing a terminal seta and one shorter hair. Along the edge of the body is the usual row of conical spines, set somewhat far apart, and four other longitudinal rows are seen on the surface. The mentum is large and, I think, di-merous.

This insect is viviparous. The females are often full of young larvæ, and, as these are born, they are sheltered in a cavity beneath the mother, as in some of the Lecanidæ. They do not remain there long, but soon begin their travels, and move rapidly.

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The male insect is red in colour, about 1/30 inch in length, undergoing its last transformation in a minute, white, cottony, oval sac. Antennæ of nine joints: the first two short and thick, the third very long and slender, the fourth, fifth, sixth, and seventh about half as long as the third, thicker and rounder, the eighth rather shorter, and the ninth very short and nearly globular. All the joints have hairs. Legs slender: the tarsus

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Coccidæ.

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rather less than half as long as the tibia: the four digitules are fine hairs. The usual hairs and spine on the tibia, and two spines on the lower edge of the tarsus, not far from the claw. There are three pairs of eyes. The abdominal spike is short and thick, and exhibits a curved appendage similar to, but rather longer than, that of Acanthococcus multispinus, mihi (Trans., vol. xi., pl. viii., fig. 18 f). This appendage is, indeed, common to the three genera Eriococcus, Acanthococcus, and Rhizococcus. At the base of the spike are two rather strong setæ, one on each side.

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Rhizococcus fossor does not construct a cottony sac (for the female), but, instead, buries itself usually in a circular hole or pit, in the leaf it lives on. Many adult insects may be found simply resting on the leaf, accompanied by a number of young larvæ and females in the second stage. But in most cases they pass their last stage in a pit. The young insect is very active: the female of the second stage moves about sluggishly; in the last stage it is fixed and stationary. At first it appears simply to lie on the leaf (on the under-side), but in a short while, whether from some chemical action produced by it or by mechanically compressing the cells of the plant, a circular elevation or wall on the leaf is raised up round the insect. At the same time the portion of the leaf beneath the body is pressed downwards, and a corresponding elevation appears on the other side: this elevation assumes a brown tint. As the depression continues and the wall grows the insect sinks deeper in the leaf, becoming more and more buried, and the wall curls over it a little, so that in fact the orifice of the pit is somewhat smaller than the cavity below. The insect lies in the pit (which may average about 1/18 inch in diameter at the opening, and is circular) with the head downward, and the anal tubercles and pencil of white cotton appearing over the wall, I presume to attract the male. Afterwards, as gestation proceeds, the whole body disappears in the pit, where the young larvæ are born. These cavities in the leaf look like small volcanic craters, and the corresponding brown elevation on the other side of the leaf is quite conspicuous.

Sometimes two insects may be found in the same pit, one lying over the other. I suppose the upper one simply took advantage of a ready-made domicile. The insects which are not in pits are generally darker in colour than the others.

On leaves of maire, Santalum cunninghamii, from the North Island, sent to me by C. P. Winkelmann, Esq., of Te Aute.

This is an interesting and peculiar insect, certainly differing from any that I know of in the genus. The curious mode adopted by it of burrowing into the leaf is, I think, unique. Ctenochiton viridis, mihi, produces a certain depression in the leaf it lives on, but by no means so complete a shelter for itself as does this little Rhizococcus.