IN TOUCH WITH NATURE

Otago Witness, Issue 4041, 25 August 1931, Page 74

IN TOUCH WITH NATURE

I’OWDEK WINGS. By J. Drummond, F.L.S.. F.Z.S. Unknown to the public on account of their smallness, inconspicuousness, and retiring disposition, are very plentiful insects that have interested entomologists for a long time. Their wings are short and rounded, and are covered with powder as fine as flour, instead of with the microscopic scales that beautify moths and butterflies’ wings. They look like tiny moths. “ The Illustrious Swede,” Linnarns, was excused for classifying them as moths, a mistake rectified years later, when the powder-wings, white-flies, or snow-flies, as they are called, were found to be allies of the plant lice and the scale insects in the Hemiptera, a vast order, in eluding many groups of diverse appearance, but all possessing sucking beaks and most of them vegetarians.

New Zealand has at least seven species of powder-wings. It harbours an introduced species, the greenhouse white fly, which damages plants in greenhouses. The possession of four wings shows that they are not flies, which have only two. Their early development is very different from the development of moths and butterflies. Their minute eggs, which only sharp eyes can see without a lens, have foot-stalks. These attach them to the underside of a leaf. A female, before laying, dusts a space with meal from her wings or body. She sometimes sprinkles her eggs with the same powder, which may have a disagreeable smell and in that way protect the eggs from enemies.

As observed by Mr E. Strep, an English entomologist, after 10, 12, or 14 days there comes out of an egg a little powderwings, with no wings at all and with a body so absurdly thin and colourless as to be almost diaphanous. At first it is difficult to trace any organs in the body. As the creature grows, the organs are trace-1 more easily. From the beginning one remarkable organ is noticeable. This is an opening on the upper side of the hindmost section of the body. It is fitted with a lid, which closes it or opens it, to allow a tongue-like instrument to be extruded. Using this equipment the insect produces a sweet, sticky fluid. The grub stage is followed by the chrysalis stage, and the chrysalis stage by the perfect stage, in which flip powder-wings congregate together. In England members of one species, in the grub stage, are found on the underside of cabbage leaves, doing some damage. That species has not come to New Zealand, apparently. The seven native species known have been found on native plants only. The greenhouse white fly is the only member of the group troublesome in New Zealand.

The life histories of these humble insects are highly specialised, not primitive. As in the case of all winged insects, they begin life in a wingless condition. Insects’ wings are never- developed until late in life. Described by Dr R. J. Tillyard, the wings at first are small bags filled with fluid. As they expand, the two sides of the bag come closer together. These finally fuse everywhere, except along the qourse of the veins, where channels are left for the passage of breathing tubes, nerves, and blood. The rate of expansion varies in different insects, but always is sufficiently rapid to- be watched with deep interest.

There are four episodes in the life cycle of a highly specialised insect like the powder wing. The complete life cycle usually is passed through in one year, but in many cases there are two or more complete broods in one year, and in other insects the life cycle occupies several years. The four episodes are: The egg, or embryo stage; the grub, or growing stage; the chrysalis, or resting stage, a stage or inertia; the perfect stage, usually winged, which alone is the sexually adult stage. The chrysalis stage is found in only highly specialised insects. These have complete metamorphosis. •

The grub stage usually is the longest in an insect’s life. In its turn, it is

divided into stages, separated by moults, sometimes three or four, sometimes more than 20. _ Hatching from the egg takes place rapidly. It is set in motion by pressure from the embryo’s swelling head, which forces the cap of the egg off. In all embryos, the head is formed first. In the pow’der wings, the dragon flies, the moths and butterflies, the embryo is formed head downwards on the lower side of the egg. Later, it turns to the top of the egg, and moves forward until its head rests at the front end of the egg.

Some 40 years ago, Mr J. A. B. Johnston, Horotutu road, One Tree Hill, Auckland, lived for two years on the Warrego River, Central Queensland, and in times of drought he often fished for Murray cod, using frogs for bait. Instead of seeking the help of natives to catch the frogs, or seeking for them in sand on the plains, his mates and he simply clambered down to the water, filled a meat-tin or a jam-tin, and returned to the bank, the clay in which was criss-crossed with innumerable sun-cracks. They poured the contents of the tin into a crack, and up came a frog to see if it was raining. Every crack seemed to have its frog, and the supply of bait never failed. A species of frog Mr Johnston knew in Central Queensland had a habit of diming trees. In the evening they often could be heard croaking from 10 to 15 feet up a mulga tree.

People who see in their gardens or orchards a beetle only about one-sixth of an inch long, handsome in its coats of yellow, green, or bronzy black should know that they have met a serious little pest. It lives on the leaves of apple trees, pear trees, and vegetables, and extends its operations to trees of the forest, notably the totara, the acia, and all species of eucalyptus. When present in large numbers it may completely deprive a tree of the leaves. A few years ago females were induced to lay eggs in earth in an insectary. Grubs that hatched from the eggs were obtained, but the insect’s life history is unknown. It is a native of New Zealand, is called popularly the bronze beetle, and is known to entomologists as Eucolaspis brunneus. It belongs to the immense cosmopolitan family of the leafeaters.

Seeking respite from the strain of devising schemes to help the unborn millions, Sir George Grey often walked from his mansion on Kawau Island to a small promontory, looked down on a shelly beach of exquisite beauty, fringed with crimsonflowered pohutukawa trees, and watched black shags fishing in the clear water, coursing like greyhounds under the surface, energetically using wings and tails. He reared a young black shag taken from a nest on the island. It was given its freedom, but never left the island, fishing iu the small bays, or resting and sunning its wings on the stone pier or on rocks strewn in the cove. It became so tame that whenever Sir George Grey went out in his boat it followed him and occasionally uttered a peculiar note to attract his attention. It was missed one day. The caretaker, after searching, found its dead body on the beach, without any sign of injury. In New Zealand, as in England, black shags are easily tamed, and. in their captivity, show affection and intelligence.

Tt seems bad taste to publish anything likely to destroy the grace, dignity, stateliness, and haughty bearing of the white heron, as bad almost as showing up famous men and women in tantrums and ill-humours, and prying into their private lives, which cannot be justified. A resident of the Thames has done this for a white heron he kept in his garden years ago. At first it slept in a box in an outhouse. After a fight with a hen that had chickens running in the garden it slept about 20 feet up a karaka tree. As one of its wings had been clipped, it climbed by passion flower vines that grew up the tree trunk. In doing this its actions were by no means graceful, quite an unpleasant contrast to its dignified stride in shallow pools and lagoons. It was completely hidden amongst the boughs while asleep, but it came out early in the morning and, especially after a frost, went to the extreme edge of the boughs, where it sunned itself for hours. It seldomcame down for breakfast until the meal was well advanced, and, strangely, preferred beef or sheep’s liver to fish. In its fights with the hen it again abandoned all . dignity, throwing itself on its back and thrusting its long bill so vigorously that it usually was the victor. In spite of all this, it was dazzlingly beautiful, particularly when it put on its long filamentous plumes, as white as snow, springing from the shoulders and extending all down the back.