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The New Zealand Railways Magazine, Volume 6, Issue 2 (June 1, 1931)

A Fascinating New Zealander — (Chironomus Zealandicus.)

page 64

A Fascinating New Zealander
(Chironomus Zealandicus.)

The insect world of New Zealand has provided forms, not only indigenous to our islands, but new to the entomologist.

The subject of this article will be a fascinating New Zealander; small, slender, elegant, with a body barely one-quarter of an inch in size. To the casual observer, a common and insignificant midge; “a something with four wings and six legs that flies!” Yet, under the revealing lenses of the microscope, an insect of strange beauty as to structure and coloration!

Let us go one step further, and bring to bear the lenses of observation and study—our labours will be amply repaid.

Firstly, let us consider its relatives; these are the ubiquitous sandfly—so well and painfully known to many of us—the mosquito — that bloodsucking soloist daddy longlegs—beloved of childhood's fairy fancy—and, last but not least, our “living torch bearer,” the glow worm (completing life as a glow-moth) of our caves.

Delving further, we find the larva, inhabiting the soft mud at the bottom of stagnant pools, arrayed in conspicuous crimson vestments.

The chrysalid stage is even more elaborate in colouration. The abdominal segments still retain a crimson splendour; the blunt and rounded thorax is a warm rich brown. On either side of the thorax are white and feathery plume-like gills with a bright yellow sac at the base; and, at the tail end are another smaller set of gills—the whole of wondrous beauty!

The reader may say, if personal observation is suggested, “How am I to study an insect that secludes in mud?”

A glass jar as an aquarium—filled with water, a little soil and weeds, from the larval pool, thrown in.

The captives will lose no time before constructing their tube-galleries about the glass walls, starting from the mud and going upwards as high as four inches. Occasionally some may be seen swimming about slowly in zig-zags. Owing to their peculiar buoyant construction it is a feat to remain submerged; once the surface is reached, descent is impossible.

The pupa never emerges from its tube till about to make the final transformation; till then, the gills absorb a sufficient supply of air to make this possible. The tube-cells are kept fresh by a continuous circulation of water, driven through them by strong pupal movements.

Twenty-four hours before the final transformation the case assumes a distinctly silvery appearance brought about by the conservation of air around the coming perfect insect and inflating the pupal skin to give it the buoyancy necessary to float to the surface when the time arrives for the final change. Then, the case bursts across the thorax; the imago crawls slowly forth, releasing each pair of legs together to rest upon the surface. The wings follow, and, finally, the body is freed. Within the next ten minutes the wings are firm enough for use and the new-born midge flies away strongly and swiftly.