IN TOUCH WITH NATURE.

Otago Witness, Issue 3870, 15 May 1928, Page 5

IN TOUCH WITH NATURE.

THE GRASSHOPPERS.

By

J. Drummond, F.L.S., F.Z.S.

A specimen of a large species of native grasshopper, sent by Mrs N. Whitmore, Wairoa, Hawke’s Bay, with an inquiry as to its identity, brings to mind the astonishing decrease in the numbers of these insects in New Zealand since foreign birds were introduced. In the ’sixties and the ’seventies the grasshopper was a burden in the land indeed. It was present in its millions in almost all open country. In these days it has to be looked for. Near large towns it is almost extinct. Native grasshoppers seem to shun cultivated fields and introduced plants, and to keep to native vegetation on land that the plough has not disturbed.

There is some confusion in applying the names of grasshoppers and locusts. The insects commonly called locusts in New Zealand are neither locusts nor grasshoppers. They are cicadas, and they provide the stridulating summer choruses sent out from innumerable trees and shrubs when the sun is shining. Entomologists do not clearly distinguish between grasshoppers and locusts, using other names, which they find to be more precise, and which the public regard as formidable. The rule, apparently, is to call grasshoppers locusts when they swarm and become a pest. New Zealand’s grasshoppers, although very plentiful once, never seem to have developed the migratory swarming habits that entitle them to rank as locusts. They never swarmed devastatingly, created terror by their arrival, and left in their wake the abomination of desolation.

The commonest New Zealand grasshopper is a somewhat small insect, reddish or yellowish-brown, which in former years, when conditions were more favourable for it rose before people’s footsteps in swarms on hot summer days. It was—may be is—one of the last insects to leave at this season, and it often was found in warm places in the middle of winter. Some of New Zealand’s grasshoppers are in the shorthorn class, distinguished from the long horns by the length of their feelers. New Zealand has about 1G species of them, while her next-door neighbour, the Commonwealth, has no fewer than 354, and amongst these arc species that plague dry areas ii> the interior of the continent. Australia has pygmy grasshoppers, about half an inch long, with a very bizarre appearance. They frequent moist mossy places, and sometimes are found under water in still ponds.

Classed with the grasshoppers are the fantastic wetas. Amongst these are the cave-wetas, extraordinary insects with neither ears nor sound producing apparatus, and absolutely wingless They are characterised by vary short bodies and prodigiously long legs and feelers. In an old tunnel near Wellington are found many individuals of a species of cave-wetas which measure Bin or 9in from the tips of their feelers to the ends of their hind legs. A species discovered in the \Vaitakere Ranges, north of ~nd, in recent times, has a total length of about 14in, and feelers with more than 550 segments, some of them armed with small spines.

In short-horned grasshoppers, the apparatus that produces sound, the stridulating mechanism, usually consists of a row of raised knobs, on the inner service of the shanks of the hind legs, and a vein on a tegument of the upper wings. The vein is raised and prominent, and has a sharp edge. When it is drawn across a row of bead-like knobs it throws the tegument into vibration, and the grasshopper’s song is produced. It was believed once that with the grasshoppers, as with the cicadas, only the males stridulated, but it is now known that the females also produce sounds. Organs have been found in grasshoppers that are believed to be kinds of ears. Minute examination has shown that the important part of a grasshopper’s ear is a drum, connected with the nervous system. Its purpose, probably, is to detect vibrations made by other grasshoppers.

Some species of grasshoppers do not produce special sounds that can be detected by the human ear. The general belief now is that these species, apparently dumb, produce sounds that are easily heard by other members of the same species. A female grasshopper excavates a hole in the ground and deposits in it her , with a quantity of fluid. The fit:' dening, protects the eggs. The, e, e very nutritious. Some beetles . other insects live largely on them, and they are subject to attacks by several parasites. The development of New Zealand's grasshoppers from the egg to the perfect insect has not been studied in detail. In other countries, observation has shown that, as soon as a young grasshopper leaves its egg, it sheds its skin. It then is a clear green colour, but soon becomes brown. Later, it turns black. Six days later still, it moults again, and its coat then takes on a distinct pattern, , black, spotted and banded with white, and with a rose-coloured streak on each side of the hind body. After the third moult, the rose colour becomes more distinct, and the head takes on a brown tint, instead of a

black one. The fourth moult sees the rose colour replaced by citron yellow. The creature then -is very voracious, and shows the first signs of wings. Another moult, and there are further changes, and after the sixth moult the grasshopper takes its form as a perfect insect. These processes may not be common to all species, but the changing colour in the course of development is one of the features of the group. The movements of migratory grasshoppers, or locusts, when they 'make up their minds to swarm, depend largely on the wind. It is stated that trial flights are made to discover the direction of the wind. On the wing, probably, very little muscular effort is necessary.’ The creatures’ bodies contain elasuc airbags, which communicate with the breathing tubes. As at the time of flight, the bodies, probably, are comparatively empty, food being scarce, the air-bags have full room for expansion. With air-bags filled with air, a grasshopper becomes a living balloon. Exerting only slight efforts in their aerial movements, grasshoppers are borne mainly on the wings of the wind. When the wind is unfavourable, it is believed, they alight and wait for a change. A pestilential swarm often comes into a district suddenly, clears up all the vegetable food available, and leaves no green thing for man or beast. The weight of a swarm that swept over the Red Sea some years ago was estimated at 42,850,000,000 tons, on the ■basis of each member weighing onesixteenth of an ounce. In Cyprus in one year swarms of locusts deposited about 5,000,000,000 egg-cases, and each case contained a fairly large number of eggs.

Some years ago a correspondent described a grey warbler’s nest that had been torn. He concluded that a rat had raided the nest, and had destroyed the eggs or young inside. Mr J. B. Cumming, Ellerslie, Auckland, who has had a wide experience as a bushman in New Zealand, believes that the damage -was done by an escaping young cuckoo, not by a rat. His theory is that the nest was broken out of, not into. A close examination of the nest, he thinks, would show that the broken strands had been bent outward, that about the broken place the walls of the nest were thin and weak, and bore evidence of a strain. According to Mr Cunini'ug, a cuckoo parasitically placed its egg in the nest, the young cuckoo was hatched by the owners of the nest, the young cuckoo’s weight was somewhat greater than the nest was designed to bear, the young cuckoo was fed by the grey warblers through the wall, not through the porched entrance at the side, which, usually, is reinforced, and is the strongest part, and through the hole in the wall the young cuckoo escaped. Mr Cumming states that he has actually seen several young cuckoos fed in that way. He once, apparently, just missed seeing a cuckoo emerge; it was sitting on a branch within 2ft of a grey warbler’s torn nest.

Scores of insects that frequent a garden in Winter’s road, Papanui, are drone flies, whose interesting life history, from the egg to the strange rattail grub that lives in drains and gutters and in putrescent material, was sketched in this column a few weeks ago. The Winter’s road resident, who sent three specimens, mistook them for a species of bee. The drone fly's superficial resemblance to a bee is one of the most notable instances of mimicry in the animal world. It is quite on the surface, and does not deceive anybody who notes that a drone fly has only two wings, while a bee has four. A drone fly may be recognised in its true character while it is at work; to kill it and handle it is not necessary. It crawls slowly and deliberately over flower heads that attract it. Always its movements are leisurely. It never seems to be in haste. No' other insect, probably, was so plentiful during last month iii town and city gardens. March usually is the month in which the perfect drone flies appear, after having gone through their metamorphosis. They are most in evidence in April. Staying long on the wing, they often may be seen on their favourite flowers in May, when the conditions are somewhat wintry, and when insect life generally has greatly diminished to outward appearances, although many forms have prepared to pass the cold months in the shape of grubs or chrysalids. The Red Admiral butterfly is one of the insects that adorns bright sunny May days, and the Red Admiral’s cousin, the Painted Lady, expands her wings even in June’s frosty weather.