An elementary manual of New Zealand entomology

by G. V. Hudson

Family Tipulidæ.

Corethra antarctica, n.s.[^[7]] (Plate [IV]., fig. 3, 3a larva, 3b pupa).

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 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, 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 (Fig. 4) being a male; the female is slightly larger, and much more stoutly built; her antennæ are filiform[^[8]], and the limbs generally shorter. Both are equally common, but the male is more often noticed, owing to his greater activity.

Family Tipulidæ.