NATURE NOTES.

New Zealand Herald, Volume LXVI, Issue 20306, 13 July 1929, Page 1 (Supplement)

NATURE NOTES.

THE WATER-BEETLES.

DI J. DIWMMOND, T.I/.9., F.Z.B.

A peculiarity with the water-beetle, which Mr. C. Tattersall, Rotorua, is studying, and about which ho has asked for information, is that it breathes air by tiny holes 011 its body. The air is taken in between the wing-cases and tho body. As tho body is convex, tho water-beetle takes sufficient air to meet its needs for about half-an-hour. These beetles are seen with the extremities of their wingcases standing out above tho surface of the water whilo fresh supplies of air are obtained. Mr. Tattersall does not state tho species of water-beetle he is studying. N'ew Zealand has at least 18 species of this family, tho Dyticidoe, which belongs to the group Hydra-dephaga, " gluttons of tho water."

tf Mr. Tattersall's species is Colymbettos rufimanus, it is a fairly large beetle, with blackish-brown wing-cases, and a pair of hind-legs fringed with hairs, shaped like paddles and used as oars. In tli summer it may bo found in most still waters. Mr. G. V. Hudson has 6een it on very hot days flying rapidly far away from its nativo ponds. When it does this it makes a loud humming noise, and is much more conspicuous than when it is in tho water. In the grub stage, as described by Mr. Hudson, it is soft and yellow, and has six slender legs and a pair of powerful mandibles. At tho end of its body there aro two strange appendages. On the point of each there is a hole. Air is taken in through the holes, Tho air is sent to all parts of tho body by two main air tubes. Ono of these springs from each hole and branches in every direction through tho grub's body. Mr. Hudson has found tho grubs to bo voracious. They devour fresh-water shrimps and tho grubs of may-flies. Hard pressed by hunger they becoino cannibals. They catch members of their own species by their mandibles, retain a firm hold until all the fleshy parts are eaten, and then throw away the rest and look for more.

A grub kept by Mr. Hudson remainod concealed all tho time in a small patch of weed that grew in the middle of the aquarium. It soon was surrounded by tho skeletons of small water shrimps, seized by it as they passed close to its hiding-place. The crustaceans did not discover their enemy's presenco until too late. The water-beetle may be described as handsome in its perfect insecthood As a grub it is ugly; and 'ts ugliness does not end with its appearance. Its life is an ugly affair. It is regarded as tho crocodile of the insect world Examined through the lens '"f a microscope, its jaws havo been found to be equipped with a hollow groove, closed by a membrane for the greater part of its length. ' but with an aperture at its base. By this effective structure, the grub plunges its mandibles deeply into the body of its prey, and sucks the juices through its hollow jaws.

In England—in New Zealand, also, probably—a grub, when it feels the mysterious impulse to change into a chrysalis, goes to the bank of its pond, climbs up, burrows into tho damp earth, makes a cell, and there passes tne time of inertia, until another impulse calls it to a higher stage 3 more varied life, wider activities. If tho grub retires to its cell in the summer, the chrysalis becomes a perfect insect in about a fortnight. If the grub retires in tho autumn, it remains dormant during the winter, appearing in perfect form in tho following spring. The water beetle is light in colour and soft in texture. Not until several days havo passed does it put on its hard, dark coat of mail.

The habits of New Zealand's waterbeetles, probably, are the same as the habits of water-beetles all the world over, for they are cosmopolitans. They are not good walkers, but scramble on the ground. If one of them falls on its back on a smooth surface, it spins round ludicrously. Tho front pair of legs belonging to water-beetles in tho Old Country are complex in structure. They aro equipped with a remarkable array of suckers, c>n the same principle as tho muckers of tho cuttle-fish. A waterbeetle's wonderful method of breathing lias been noted with care in England. Wishing to breaihe, tho water-beetle comes to the surface. This isjiot done in tho way a diver comes up. head first. Tho water-beetlo comes up head downward. It protrudes just the tip of its body above the surface In a vcrv short time, it expels air already used in breathing, and it takes in a fresh supply, and then dives to the bottom of its pond. There the air is passed from the reservoir between tho wing-cases and the body through tho insect's system. When a pond is approached quietly, water-beetles may bo seen floating near the surface head downward, the tips of their bodies in the air, their hind legs spread out in order to balance tho bodies. Tho humming noise mentioned by Mr. Hudson in tho "flight of tho species ho has observed seems to bo produced by plates which look like little wings, insido the wingcases and at their bases. The plates cannot bo seen when the insects are at rest, but aro exposed in tlight.

Mrs. F. N. Iladdow, Pukehau, Ngaruawahia, asks which is tho true New Zealand bellbird. When, a few years ago, she lived on the banks of tho Upper Waitotara River, Taranaki, sho saw there, nativo birds in their thousands. She often heard tuis. Ono day she thought that she heard a tui's song close to the back door. Sho went out to see it, but sho saw sitting on a silver birch a small greeny-brown bird, slightly larger than a sparrow, but built more slenderly. While sho was watching it sang again. They were beautifully liquid notes, much like a tui's. Later she saw dozens of birds of the same species. They did not always sing, but, in tho fruit trees, merely twittered. Ono of a flock occasionally sent out tho notes, and then all flew away. There was a big block of forest at the back of tho farm, and there Mr Iladdow, while away mustering, hear, many of tho songs, intermingled with twittering. These are tho true New Zealand bellbirds, sometimes called "mockies" or "mockers." A Ngaruawahia farmer told Mrs. Iladdow that tho native crow is the bellbird. Its uotes are bell-like but not so much so as tho bellbird'!! notes. A few peoplo in tho North Island know tho native crow as tho bellbird. It is a truo crow, although an aberrant member of tho great family of the crows, and, to prevent confusion, it should bo called by its proper name, leaving the true bellbird, the tui's relative, ono of tho honey-caters, tho Maori s makomako or korimako, in undisputed possession of ;i title it earns every time it sings.

The New Zealand crow's notes compare better with tho notes of a fluto than with tho sounds of a boll. It is hero that tho New Zealand member of tho family differs widely from tho better known crow of the Old Country, whoso notes are harsh. It is di/ibtful if, as a matter of variety, depth, quality, purity and beauty, tho bellbird's notes equal the nalivo crow's. [n tho nesting season the crow sings perhaps tho most varied and beautiful song heard in New Zealand's forests. It hardly can bo compared with tho exquisite song of tho song-thrush, which is heard in the garden rather than in the forest. Tho songs of these two songsters havo their own qualities. A New Zealander who has heard both tnaj feel inclined to give the prize to the native crow because it is a native, while tho song-thrush, although very charming, is a " how?."