Part 9

An elegant little gnat, frequenting the margins of ponds and ditches during the spring months. The larva (Fig. 3a) is bright green, ornamented with numerous yellow spots; it is very sluggish, living in the green slime weed which floats on the water in such large masses during that season. Not being very common it is difficult to find, as its colour so closely resembles that of the weed which it always frequents. The pupa (Fig 3b), is not very agile, and is nearly always observed suspended from the surface by its thoracic air-tubes and caudal fins, the abdomen being directed upwards and thus bringing the two pairs of organs close together. In its metamorphosis and general appearance this insect forms a convenient link between the present family and the Culicidæ.

Family TIPULIDÆ.

Chironomus zealandicus, n.s. (Plate IV., fig. 2, 2a larva, 2b pupa).

This is the common midge of New Zealand, and is extremely abundant throughout the country. Its larva (Fig. 2a) inhabits the soft mud at the bottom of stagnant ponds and streams, and is very conspicuous, being of a brilliant crimson colour and thus much resembling the well-known "Bloodworm" of English anglers, which is the larva of a closely allied European species (C. plumosus). It may be readily kept in an aquarium, and if supplied with a little soil and green weed will rapidly cover the {44}walls of its glass prison with numerous tubular galleries. These take their rise from the mud at the bottom, and, extending upwards to a distance of three or four inches, afford the larva a convenient retreat from all enemies. These insects are occasionally seen swimming laboriously through the water with a peculiar zigzag motion. When out of their burrows they have considerable difficulty in keeping beneath the surface, and may be often observed floating helplessly with their exposed portions quite dry; in fact the whole integment of the insect appears to have a peculiar power of resisting the water. The pupa (Fig. 2b), is a most beautiful object, its anterior extremity being obtusely thickened and the limbs of the future insect quite discernible. On each side of the thorax the gills form a set of graceful plumes, a much smaller group being also situated at the extremity of its abdomen. In this state the insect remains almost entirely concealed in the burrows previously constructed by the larva, its gills imbibing sufficient air from the surrounding medium, and thus rendering ascension to the surface unnecessary. The water is periodically circulated in the tunnels by violent movements on the part of the pupa. About a day before emergence the insect assumes a peculiar silvery appearance, which is occasioned by the presence of a large quantity of air between the imago and its pupa skin. This air has been first imbibed by the gills and afterwards expelled through the spiracles of the enclosed gnat, thus inflating the skin of the pupa, and helping to buoy it up during its last and most important transformation. Leaving its tunnel the insect rises to the surface, the thorax is lifted above the water which retreats from it on all sides, the skin cracks open at the back and the insect slowly extricates itself in a similar manner to the mosquito. In about ten minutes' time the wings are sufficiently hardened for use and the insect then flies ashore, but we may occasionally notice, {45}beside their old pupa-skins, drowned individuals which have failed to effect a successful emergence. The perfect insect is extremely common in all swampy situations throughout the summer; it has a great partiality for light, and may be occasionally noticed in vast numbers round the street lamps on a hot summer's night, especially if rain is impending. It is a most graceful insect, and will amply repay a minute examination (Fig. 2).

Family TIPULIDÆ.

Ceratopogon antipodum, n.s. (Plate IV., fig. 4, 4a larva, 4b pupa).

Very plentiful in the forest throughout the year, often enlivening the winter sunshine by its merry gambols. The larva (Fig. 4a), is found under the bark of newly fallen trees, feeding on the sap which exudes in large quantities from the logs whilst drying. When first discovered it often has a curiously spangled appearance, owing to the minute beads of moisture retained by numerous bristles clothing the larva. When about to change, these insects assemble in large companies of thirty or forty, firmly affixing their basal segments to the wood, their heads all pointing inwards and forming a small circle. In some cases, where an unusually large gathering has occurred, a number arrange themselves into an outer row, their heads being immediately behind the extremities of the inner group, the whole thus bearing a rough likeness to the radiations of a star-fish. The pupa is very short, and is furnished with two clubbed horns on the thorax for respiration. Its abdominal portions are retained within the old larval skin, thus keeping it firmly anchored to the log. The perfect insect emerges from a rent in the thorax of the pupa, groups of exuviæ being of common occurrence under the bark. The sexes differ considerably, the individual figured {46}(Fig. 4) being a male; the female is slightly larger, and much more stoutly built; her antennæ are filiform, and the limbs generally shorter. Both are equally common, but the male is more often noticed, owing to his greater activity.

Family TIPULIDÆ.

Psychoda conspicillata (Plate IV., fig. 6).

A common species, occurring plentifully on window panes during August, and bearing a great superficial resemblance to a small moth of the Tineina group, often deceiving the novice in consequence. It is a beautiful object for the microscope, the figure being a careful drawing of the insect, seen with a power of about ten diameters. I regret to say that its transformations are at present unknown.

Family TIPULIDÆ.

Mycetophila antarctica, n.s. (Plate IV., fig. 5, 5a larva, 5b pupa).

Tolerably common in the vicinity of forest during the major part of the year. The larva (Fig. 5a), is a small elongate maggot of a pinkish colour; it is a social insect, inhabiting rotten pine logs, which it perforates with numerous cylindrical burrows. These larvæ, entirely confine their attention to damp wood of a "pappy" consistency, leaving the harder logs for the wood-boring Coleoptera, which are provided with much stronger jaws. They consequently do not injure the rafters and boards of houses, or other valuable timbers. The pupa (Fig. 5b) is very elongate, reposing in one of the burrows, previously constructed by the larva. It probably breathes by means of its spiracles, as no special organs of respiration are visible. The perfect insect appears in a short time, flying sluggishly in the sunshine, the female possessing an enormous abdomen, which {47}almost incapacitates her for aerial locomotion; in other respects she resembles the male, which is the sex figured (Fig. 5).

Family TIPULIDÆ.

Tipula holochlora (Plate V., fig. 1, 1a larva, 1b pupa).

This beautiful insect is very common in the forest throughout New Zealand. Its larva (Fig. 1a) inhabits various kinds of decaying wood, frequently occurring in vegetable refuse at the roots of trees. It is a large, sluggish-looking grub, and the anterior segments are very retractile. Its colour appears to vary according to its surroundings, those specimens found in red pine being of the dull reddish hue characteristic of that wood, while those taken from pukatea and henau are dark brown larvæ, resembling the illustration. These insects are very voracious, but their growth is gradual, each larva probably occupying at least six months to reach maturity. They mostly feed during the winter, but may be often taken at other times. The pupa (Fig. 1b) is enclosed in a small oval cell, previously excavated by the larva, which also constructs a ready means of escape for the future insect in the form of a small tunnel leading out of one end of its prison to the open air. Through this the pupa wriggles, assisted by the spines, which arm the edges of all the segments; the coronet of hooks at its extremity retaining the insect firmly at the mouth of its burrow while undergoing its final transformation. After numerous twistings and contortions on the part of the pupa, a rent is formed in the thoracic plates, and the imago draws itself out, standing on the log until its wings are sufficiently hardened for flight. In many old houses numbers of these exuviæ may be seen projecting from holes in the boards--a relic of the destruction that has taken place within. These insects naturally inhabit dead trees, but as they will devour unsound timber in any {48}form they are very injurious to old wooden buildings. The perfect insect chiefly frequents forest, where it is difficult to detect owing to its green colour harmonizing so closely with the leaves. The specimen figured (Fig. 1) is a male, the female being considerably smaller with a much stouter body and shorter legs.

Family TIPULIDÆ.

Tipula fumipennis, n.s. (Plate V., fig. 2, 2a larva, 2b pupa).

Another fine species, occurring in similar situations to the last, but not quite so commonly. The larva (Fig. 2a) may be found throughout the year under the bark of very rotten henau and pukatea, feeding on the moist decaying wood. It constructs in this material numerous burrows, which are lined with a viscous fluid constantly emitted from the mouth. Its movements in these are very rapid, frequently eluding the most careful searches. When divested of its slimy covering, it is anything but an offensive-looking larva, the great air-tubes, which run the whole length of the insect, being very conspicuous, and many of the other internal organs are easily detected owing to its partial transparency. The pupa (Fig. 2b) is enclosed in a small cocoon, having ready access to the air; it is chiefly remarkable for its very large thoracic horns, which are curiously toothed. The air-tubes connected with these are distinctly visible in the abdomen of the insect, where they may be seen branching in all directions. When about to emerge this pupa works its way to the surface of the log, the head and thorax are thrust outside, and the perfect insect escapes in the ordinary way. The illustration (Fig. 2) is taken from a female; the male differs in being less robust, and in being provided with longer legs.

{49}Family TIPULIDÆ.

The Glow-worm. Bolitophila luminosa, Skuse.

(Frontispiece, fig. 1).

Every one who has walked in the forest at night has no doubt noticed, in many damp and precipitous situations, numerous brilliant points of greenish white light shining out from amongst the dense undergrowth. The animal which causes this light may be seen at Fig. 1a on the Frontispiece, and is probably one of the most interesting insects we have in New Zealand. It inhabits irregular cavities, mostly situated in the banks of streams, where it hangs suspended in a glutinous web which is stretched across the cavity and supported by several smaller threads running right and left, and attached to the sides and ends of the niche. On this the larva invariably rests, but when disturbed immediately glides back along the main thread and retreats into a hole which it has provided at the end of it. From the lower side of this central thread numerous smaller threads hang down, and are always covered with little globules of water, constituting a conspicuous, though apparently unimportant, portion of the insect's web. It should be mentioned that all these threads are constructed by the larva from a sticky mucus exuded from the mouth.

The organ which emits the light can easily be seen by referring to Fig. 1a. It is situated at the posterior extremity of the larva, and is a gelatinous and semi-transparent structure capable of a great diversity of form. It can be extended or withdrawn at the will of the larva, which, however, can shut off the light independently of this latter action. Larvæ cease to shine on very cold nights, in the daytime, and in a room which is artificially lighted. They gleam most brilliantly on dark, damp nights, with a light north-west wind. These larvæ appear to suffer great mortality in a state of nature, as the {50}young ones will always be found greatly in excess of those that are approaching maturity.

When full-grown this insect is transformed into the curious pupa shown at Fig. 1b. It is furnished with a large process on the back of the thorax which is attached to the web and holds the pupa suspended in the middle of the niche previously inhabited by the larva. The light is emitted from the posterior segment of the pupa, but is much fainter than in the larva, and a distinct organ is not apparent. It is frequently suppressed for days together.

The perfect insect is drawn at Fig. 1. It emits a strong light from the posterior segment of the abdomen, about half as bright as that emanating from a full grown larva. It has been recently described by Mr. Skuse, of Sydney, as Bolitophila luminosa.

During the whole course of my observations on this insect, extending over five years, I have only succeeded in bringing two specimens to maturity, and both of these were females.

The uses of the light and the web to the larva are at present quite unknown to me, as well as its food, which, however, possibly consists of fungi. It should also be mentioned that the larvæ are found in the greatest abundance in mining tunnels, many feet below the surface of the earth, as well as in caves.