minutes) she begins to deposit her eggs regularly, one every few minutes, until there are from twelve to twenty laid, when she rests awhile, brings her legs back to normal posture and flies away. The eggs when first laid are very light in colour but do not glitter as they do when a few hours old. The female prefers a shaded part of the tank in which to deposit her eggs, as for instance under a piece of asbestos partly covering a tank I was observing, away from wind and sunlight. If there is no wind to disturb the water, the eggs will remain in their little clusters of twelve to twenty, but do not adhere to each other by any glutinous substance as in Culex species, but simply by surface tension. The writer has on many occasions observed females depositing their batches of eggs, which can be discerned with the naked eye once one knows what to look for, the whole cluster not covering more than the space of a shilling piece.

I have had tanks where this species has been breeding during the past ten months under close observation both during the night as well as the day, spending many hours in so doing; but in no instance have I found eggs being deposited during the hours of darkness; in fact, when I have gone to the tank after 5 p.m. or after dusk, no mosquitoes could be seen. On the other hand, from the last week in October until the last week in May, I have on numerous occasions seen females depositing eggs in daylight, especially from noon until just before dusk, after which they flew away. The females begin to oviposit in October and continue to May, more eggs being seen on the water during April than in any other month.

They do not seem to be so easily disturbed as the females of other species, for on many occasions I have lifted the lid of the tank (i.e., a piece of asbestos covering two-thirds of the top) to take observations of either the larvae or adults, and they were in no way per turbed, but continued ovipositing apparently quite oblivious of my presence, this being directly opposite to C. pervigilans or A. notoscriptus.

On one occasion while I was observing females ovipositing (some short time before dusk in the month of April) one flew up from the water and alighted on my hand and, after a little wandering about, began to insert her lancets into my skin. This is the first occasion on which I have been aware of being bitten by a mosquito. She began to suck blood, continuing for exactly two minutes; almost immediately two more females arose and alighted on my bare arm and also began to suck blood, the time being two minutes and two minutes and five seconds respectively. While the lancets were inserted the hind legs were performing peculiar movements, being lifted up in the air and turned about in a rotary motion and down again.

Rachionotomyia argyropus seems to prefer tanks in secluded localities surrounded by native bush and partly covered for oviposition. I have in mind two tanks in the bush at Titirangi, one almost wholly covered by a piece of asbestos and shaded by ponga and native trees, the other more open and exposed to wind; these tanks are not more than sixty yards apart. The secluded and almost covered one has an abundant supply of eggs during the months mentioned above, while the wind-swept one has only odd eggs, and no females have been observed on the water. I have frequently found this species

breeding in galvanised iron tanks but not in the several square ungalvanised ones to be found in the district, and twice only in barrels. In every case their presence seemed to be conditioned by the shelter of native bush, for I have examined many galvanised iron tanks not far from native bush, and surrounded by exotic trees, without finding signs of the species, although they were breeding freely in tanks sheltered by native bush not more than a hundred yards away. This preference for a shaded tank situated among native bush is rather puzzling, for I have carefully searched pools, streams, rot- and knot-holes in trees in the heart of the bush, such as one might expect to be the natural habitat, without finding any signs of the breeding of this species. I have placed tins of water containing dead leaves round about these tanks in various heights and positions with and without a covering over them, and even placed one on the piece of asbestos which partly covers the tank mentioned above, trying to induce the female to deposit her eggs therein, but with no avail. On the other hand, eggs have been found in shallow dishes of water in the observation cage at the Museum where I have kept adults of this species during the month of April.

Fig. 59.—Dorsal view of egg of R. argyropus.
Fig. 60.—Lateral view of egg.
Fig. 61.—Showing dehiscence of egg.

Eggs: The eggs of this species are quite different from those of the other New Zealand species, i.e., Culex pervigilans and Aedes (Finlaya) notoscriptus, not only in form and structure, but also in colour and dehiscence. Seen in the ventral and dorsal view (Fig. 59) the egg is elliptical, the ends being rather pointed, but not acutely. Seen laterally (Fig. 60) the lower edge is only slightly convex, the upper considerably so, thus giving a dome-shaped appearance.

When seen on the surface of the water, these eggs appear to the naked eye to be of a greyish-blue colour, and when the sun shines on them at certain angles they give the appearance of floating diamonds, in other lights they look like tiny bubbles. Under a low power microscope (twelve diameters) they are found to be lavender-coloured. This lavender coloration is really due to the film-like roughened covering forming an air sac round each egg; this acts as a float to the individual eggs. When the eggs are numerous they give a frosted appearance to the surface of the water. When the epidermis is lost through agitation of the water, the eggs assume a brownish hue and sink to the bottom, but this does not interfere with their successful hatching. On the surface of the water of the tanks, sheltered from all winds,

frost-like clusters can be seen scattered about, but a very slight wind causes the eggs to skip about over the surface; again, when endeavouring to pick them up I find they skip away, and it is very difficult to secure them. The only successful method the writer has found for collecting them (and this needs careful manipulation) is partly to submerge one end of a wooden match in the water at an angle of 45°, working the submerged part under the egg and drawing the match up with the egg adhering to the rough and wet surface; one has to be very gentle, and to see that the match is wet, for the slightest jar will send the egg skidding away. When the eggs are floating about and come to within about a quarter of an inch of one another they immediately run together and form scum-like masses like those of aquatic Collembola leaves.

In dehiscence (Fig. 61) a split runs full length along the lateral margin. The eggs usually take from two to three days to hatch with the water at 60° F.

Larva: The larva of R. argyropus can be easily distinguished from that of other New Zealand species by the coloration of the segments, the four posterior ones being of a bright golden yellow colour while the anterior ones are pure white, both colours being due to the presence of fat globules. The siphon has five simple pecten spines, while the anal gills are long and broad with a decided tracheal ramification which makes it conspicuously different from any other species in the same container.

Head (Fig. 62) strongly chitinised, almost circular, slightly broader than long. Front margin slightly rounded; a notch at the insertion of the antennae. Pre-clypeal hairs short, close to the centre

Fig. 62.—Head of larva of R. argyropus.
Fig. 63.—Antennae of larva.

and turned inwards, almost touching across. Pre-antennals absent. Outer anterior hairs consist of three 4- to 6-branched setae each on a short stem; these hairs, which are simple, extend to half the length of the antennae. Midway between the antennae and the eye on each side is a quadruple tuft on a pedunculate stem. A single simple anterior-ocular bristle stands immediately above the eye.

Antennae (Fig. 63) jointed, movable, straight or slightly tapered. Antennal tuft consists of two bristles situated at the apical two-thirds and extends a distance half way to the apex. Terminal-antennal hairs two long and two shorter hairs.

Mouth brushes of a deep golden brown, simple not bushy. The mandible (Fig. 64) is quadrangular, one long recurved elongated spine on the outer ridge, one short stumpy spine immediately below; premandible has one strong tooth and three minor ones below; there is a series of strong recurved spines along the outer ridge or margin. Maxilla (Fig. 65) roughly sub-ovate with conical apex invested with a number of long hairs; four spines on the margin. Palpus quite rudimentary, terminated by four short hairs on a stout spine-like protuberance on the inner margin. Mentum (Fig. 66) triangular, index 4.8: 3.4, one large tooth in centre, 13 strongly curved and pointed teeth on the left, 12 on the right, lower margin crenulated.

Thorax from above (Fig. 67) cuneiform, slightly wider than head. On the latero-dorsal margin are three groups of setae borne on distinct golden-tipped papillae; on the dorsal surface more tufts are to be seen; all hairs finely pubescent. For vestiture of ventral surface see Fig. 68.

Abdominal segments with bifid hairs on lateral margins and short minute hairs on each side of them. Lateral comb of eighth segment (Fig. 69) in the form of a semi-lunar patch of 100 to 140 spines, the posterior ones being more spatulate, carrying a fringe on the widest end of the free margin (Fig. 70). The anterior spines are shorter. Adjacent to the lateral comb is a tuft of palmate setae comprising 12 to 16 black hairs which show up conspicuously on the yellow segment. Siphonal plume a tuft of 6 to 8 pubescent hairs on a short stem, reaching to half the length of the anal segment. Sub-siphonal plume one bifid tuft slightly longer than the anal plume. Anal plume a single bifid tuft. It will be noticed by a comparison of Figure 69 with Figs. 20 (p. 213) and 40 (p. 224) that the anal gills of the larva of R. argyropus are 2 ½ to 3 times longer, and correspondingly broader than those of the larvae of A. notoscriptus and C. pervigilans; moreover, in R. argyropus they have a very pronounced tracheal ramification (Fig. 72), which is barely discernible in the others. Obviously they are more strongly functional as respiratory organs in R. argyropus, and this no doubt explains the ability, to be referred to below, of this larva to remain below water for practically indefinite periods.

Siphon: Index 3: 1, strongly tapering after two-thirds, widest just beyond base. Pecten comb comprises five apparently simple spines, each one being larger and further apart proceeding apically, under a high power they appear finely serrated on the outer edge (Fig. 71). Terminal hairs consist of two delicate cirri, as long as, or longer than, the width of the apex; these are situated one-third