Title: Exotic Intruders

Author: Joan Druett

Publication details: Heinemann, 1983, Auckland

Digital publication kindly authorised by: Joan Druett

Part of: New Zealand Texts Collection

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Chapter Eleven
Little accidents: accidental intruders

The use of the word 'acclimatisation' implies, for most people, the introduction of those birds, beasts and fishes brought to New Zealand by acclimatisation societies. However many other importations arrived accidentally as a result of the colonisation of the country. The destruction of large areas of native vegetation, the sowing of alien seeds and the browsing of alien animals brought great changes to the land. None of the accidental introductions would have managed to make an impact on the environment if man and his animals had not created the opportunity.

'Acclimatisation began in New Zealand,' said James Drummond, 'when the Maoris brought their dog and their rat from Polynesia. The rat, which is a rather engaging little animal—for a rodent—is not plentiful now, except in some densely wooded districts.' These native rats, or kiore, were reddish-brown, with white underneath, quite a small size, similar to the Norwegian rat, and smaller than the black rat. The Maoris relished their flavour and, as they fed mainly on roots, berries and fruits, the taste was probably quite like rabbit. Colenso pronounced the native rat extinct in the 1930s. However a few members may be lurking in the bush, as some kiore are known to be surviving in small numbers in outlying islands, on Stewart Island and in a few localities in Fiordland. The kiore is identical to the Polynesian rat found on Pacific Islands, and its numbers could be augmented from time to time by illicit arrivals from trading vessels.

The black rat most probably came with Cook, as it was the prominent rat species in Britain in his day; after the eighteenth century the Norwegian, or brown, rat arrived in England and overran that country. According to Guthrie-Smith, it is highly unlikely that the black rat and the brown rat would share the same vessel, as the brown would make short work of the black.

Like all mariners at that time, Cook was plagued with rats. He kept ship's cats, and had the habit of anchoring close to shore and throwing out a hawser, so that as many rats as possible would quit his ship and reduce the problem for a period. When Cook arrived on his first voyage, Banks found the Maori rat 'so scarce, that I myself have not had an opportunity of seeing even one'; and then, on Cook's second voyage, Forster wrote, 'Our fellow voyagers (Furneaux and his men) found immense numbers of rats ... so that they were obliged to put some large jars in the ground ... into which these vermin fell during the night, by running backwards and forwards, and great numbers of them were caught in this manner.'

Obviously something had happened to change the state of the rat population in the meantime. These rats encountered in such great numbers must have been the descendents of black rats that got ashore during the first voyage.'Rats, like sparrows, are famous for their rate of reproduction. In 1872 von Fischer calculated that the progeny of a single pair of rats could, in ten years, amount to 48 319 698 843 030 334 720 individuals. Lantz thought that in three years a pair of rats would produce 20 155 392 offspring. Figures like these are purely theoretical, of course, with no allowance being made for accident or disease, but that they are based on a proven fecundity is shown by an experiment set up by Kolazy, where two female rats kept by him had 26 litters in 13 months, and produced 180 young. It is easy to believe, therefore, that page 214 where rats were introduced to a new land, where the food was abundant, where there were few predators, and where the competition was tame and slow-moving, then a few of these animals could succeed in overrunning the country with their progeny.

In any case, when the black rat made its entrance, the Maori rat disappeared. It could not compete with the aggressive and fertile intruder. But for the almost simultaneous arrival of the pig, the Maoris would have sorely missed the delicacy. The Maoris used to catch hundreds of kiore, trapping them in elaborate traps, and cooking and eating them whole, without gutting—presumably the intestines, full of berries, were tasty. The rats were very oily, and they used to extract a fat from them, for preserving food. The native laughing owl certainly missed them. The Maori rat was much tamer and slower than the European rat, so that the owl was hard put to it to catch a meal when its food suddenly became blacker, faster and more wily. Buller blamed the near extinction of this owl on the extinction of the Maori rat.

Although it is commonly believed that the black rat came with Cook, Yates in 1835 said that according to Maori tradition the black rat arrived with Tasman. As Tasman was unable to make a landfall, this seems most unlikely; however it is remotely possible that the rat may have come with one of the mysterious caravels that some historians think may have visited New Zealand in the seventeenth century: all ships, whatever their origin, were plagued with rats. By the time the whalers and sealers began to make regular calls to New Zealand shores, the brown rat had overrun the ports and wharves of Britain, so this was the rat that arrived on the sealing and whaling ships. Darwin first noted the establishment of the brown rat in the Bay of Islands in 1835. Like its black cousin, it quickly became very plentiful, and a great nuisance to early settlers, spreading in plague numbers to Canterbury and Otago.

The European rats became enormously abundant in the early days of settlement, moving around the country in huge armies. Taylor White, who arrived in Canterbury in 1855, reminisced in 1890 how the rats 'came in crowds around the dwelling, so much so that, having stored the flour—which was very precious ... on beams overhead, I made myself a lance by lashing a large packing-needle to a long stick, and, when lying in bed, having the light burning, would spear the rats as they frolicked about, scattering the flour-dust over me.' One winter's night Mr White went outside and was amazed to note that his birch tree was full of apples. 'I rubbed my eyes and looked again,' he said. Finally he picked up a long pole and poked at one of the apples. The apple squeaked, and all the fruit vanished in a twinkling.

Wherever Taylor White travelled, he found that in places where there were no mice, that animal would suddenly appear in great armies. He set up a small sheep run at the back of the Waimakariri River and there were no mice for months; then they suddenly appeared, having crossed the ice-cold rivers in their thousands.

Guthrie-Smith states that the first mice arrived in the 1830s, when vessels were beginning to reach the colony laden with cargoes suitable for mice to live in during the long journey. It can easily be imagined that shipments of books, clothes and grain would make it easy for this little animal to arrive hidden in packages and bales. Pastor Wohlers, a missionary working near Foveaux Strait, claimed that mice were first brought to that area when the Elizabeth Henrietta was wrecked there in 1824; for a long time mice there were nicknamed 'henriettas'.

Taylor White remarked many times how when the mice arrived in large numbers, the rats largely disappeared. Apparently rats do not like the company of mice, probably because of the mouse's habit of contaminating food supplies with its droppings. Both mice and rats were an enormous problem for the pioneers. Settlers living near Lake Te Anau in the 1850s killed and salted a lot of beef one autumn and hung the pieces up in the thatched roof. When White visited them in the winter he was told, wryly, to examine these stores. 'There seemed nothing unusual about them,' he said. But when he took a piece down it proved to be only a shell, as the whole centre had been eaten away by rats, which were too cunning to bite and sever the string from which the meat was hanging. One had to have a strong stomach to be a colonial housewife.

The rats moved in armies, often in such great numbers that many of their numbers died of starvation. In 1884 a plague of rats visited Nelson and Marlborough. Meeson wrote, 'Living rats are sneaking in every corner, scuttling across every path; their dead bodies in various states of decay, and in many cases more or less mutilated, strew the roads, fields and gardens, pollute the wells and streams in all directions ... Young and succulent crops, as of wheat and peas, are so ravaged as to be unfit for and not worth the trouble of cutting and harvesting. A young farmer the other day killed with a stout stick two hundred in a couple of hours in his wheatfield.' Thomson describes visiting a beach in Paterson Inlet in the 1870s, and finding the whole beach alive with rats which were feeding on the shellfish and stranded animals thrown up by the tide. He said that they were literally in their hundreds, a wave of them skittering into the bush as Thomson and his companion approached. The animals spread up mountains as well as along the beaches; Haast found rats in the Mount Cook range during a climbing expedition in 1862. He wrote about 'the host of rats by which we were sometimes much disturbed during the night. These rats all belong to the large grey Norwegian species, which thus had already reached the very heart of our Alps.'

Today the brown or Norwegian rat is found mostly in association with man, in his towns and cities, while the black rat is found more generally, in the bush as well as in settled areas. Brown rats infest rubbish dumps, abattoirs, pigsties and fowlhouses. Black rats are a nuisance in houses, factories and grain and seed stores. Both species are heartily disliked by the acclimatisation societies and bird and forest protection societies, because of their habit of eating eggs and young birds. There is much evidence that predation by rats has seriously affected some native bird species: in 1963 when black rats got ashore on some of the islets near Stewart Island, the saddlebacks, bushwrens and snipe virtually disappeared. The stitchbird is now found in appreciable numbers only on Little Barrier Island, where there are no rats because of the many wild cats. It must be admitted, however, that a recent programme to eradicate wild cats on this island has improved matters still further. A Ministry of Agriculture and Fisheries veterinarian, Mr Kearns, volunteered to catch cats in his spare time, and told a Veterinarians' Conference in May 1982 that he had caught 121 cats and fluttering shearwaters had returned to the island; the stitchbird numbers have increased sixfold since the cats have gone.

Whatever the effect of cats, it is undeniable that rats and mice were most unwelcome accidental intruders to New Zealand. They are carriers of human and page 216 animal diseases; they have a serious effect on the agriculturalist and are the bane of the orchardist, fowl-farmer, pig-keeper, and the grain and seed merchant. In settled areas damage is widespread. Rats and mice gnaw holes in skirting boards and attack underground cables. As well as eating farm produce, they eat sheepskins and other types of skins, sacking, harness gear and fishing nets. But the greatest loss is caused by the fouling of food and water supplies.

Since the early days of settlement the population of rats and mice has been very much diminished. This is partly due to predators, of which the native predators, such as the harrier hawk and the morepork, played an important part. Taylor White reported that in the 1880s there was a plague of rats in Lincolnshire, England and that the locals blamed this on the large numbers of weasels being taken from that area and shipped to New Zealand: so it would appear that the mustelids and the domestic cat also helped in keeping down the numbers of these vermin. It is certain, however, that the initial huge population growth could not be sustained once the food supplies ran short: Thomson received many reports that in the huge migrations of rats and mice, which often seemed desperate for food, there were very few breeding females.

Today rat control is conducted under the supervision of the Health Department in all major ports of New Zealand. All ships are inspected, and those showing evidence of rat infestation are fumigated. Large cities have permanent rat catchers, under the control of the Sanitary Inspectors of the local City Council. Trapping, poisoning and fumigation are the main methods of rat destruction.

Another accidental intruder which arrived with Captain Cook was the flea. During Cook's second voyage, Forster wrote, 'We were told that the people from the Adventure had found the native huts exceedingly full of vermin and particularly fleas.' And yet neither Cook nor Banks had mentioned fleas at all during the first voyage, which is remarkable, as Banks had made particular mention of the lice which infested the natives' hair. Consequently the sad truth is probably that there were no fleas in New Zealand until the Endeavour arrived. There is a rather amusing explanation of why the Maori called the European the 'pakeha'. Apparently this name was first given to the flea, in the form of 'e pakeha nohinohi', or 'little stranger', and then was transferred to the European, as he was the agent that introduced the stranger into the land.

'Fleas increased at an astounding rate, spreading rapidly from one end of the country to the other. The Maori pas and villages became full of them, and they persisted even after the settlements were abandoned. The pupae of fleas can remain dormant in dry conditions for a very long time, hatching only when there are unfamiliar vibrations; when people return to old sheds and whares, making a commotion with their feet, the fleas all hatch at once and immediately begin to hop high, so that the very ground looks as if it is jumping.

So the various animal fleas—dog and cat fleas, rat fleas—were accidentally introduced into the country in the fur of their hosts. Other insects in later years also arrived in this way. Bot flies arrived on stock: the horse bot fly was first recorded by Captain Hutton in 1892, and for two or three years after that it was very abundant and caused quite a scare. The American horse bot fly was brought in on some Mexican page 217 circus horses from San Francisco in 1889; this fly became immediately common in the North Island, and common in the South Island after it spread there in 1891.

Flukes and tapeworms, including the dreaded hydatid tapeworm, arrived with their hosts—in the bellies and organs of sheep, dogs, pigs, cats, rabbits, fowls, horses, cattle and man. Accidental importations also came in food and merchandise. The cabbage white butterfly was released in Napier in 1929, flocking out of the vegetable bins of a trading vessel when the holds were opened. It, like so many of our importations, accidental and otherwise, spread with extraordinary speed and throughness, becoming a serious pest in a very short time. A much earlier accidental intruder was the clothes moth, which arrived in cloth and paper cargoes. This too is now very common and attacks a great range of materials, being particularlv destructive in museums and rice stores. The cottony cushion scale was first described in 1878, in Auckland, where it had nearly destroyed an acacia hedge. By 1883 it had spread widely, attacking orchards, rose gardens, cypresses and wattles. The earwig and cockroach also appeared early on, arriving in merchandise such as fruit and fodder.

Houseflies were introduced in blown meat and on blown sheep and cattle, in the very early years of settlement. These insects are particularly disgusting; they can only take in liquid food, so anything they eat has to be dissolved before they can absorb it. They have taste-buds on their feet, so they scuttle around on food to savour it and then vomit the contents of the stomach onto the food—this contains digestive enzymes as well as the remains of the last meal—mopping up the liquefied food with the sponge-like proboscis and leaving a proportion of it as a memento of the visit. It can easily be seen why flies are well-known disease carriers, spreading the bacteria of typhoid fever, typhus, cholera, tuberculosis and dysentery. Definitely not a popular accidental intruder.

The codlin moth was imported in barrels of wormy apples from Tasmania and was a serious pest by 1874. In 1894 the Agricultural Department took steps to combat it, publishing literature with instructions about spraying and inspecting orchards and all fruit being imported into the country. An odd method of arrival was chosen by the Australian social wasp, Polistes: it came in the moss in which eggs were packed, in a shipment of salmon ova sent to Otago in 1869 in the Mindora. Although uninvited, this wasp has been welcomed as a predator on many species of insect pests; it is especially destructive of the pear-leech or sawfly.

A much less welcome intruder was the mite that caused the dreaded disease of scab on sheep. This arrived in a shipment of sheep from Australia, and the first public notice of its arrival in Canterbury was published in the Lytielton Times on 14 June 1851—it was known in Banks Peninsula in 1850. The mite burrowed into the sheep's hide, causing irritation and the eruption of pimples and dryness, leading to loss of wool and condition. The disease was considered so serious that in 1851 the Sheep Inspector, John Parkinson, advertised that anyone landing scabby sheep would be fined one hundred pounds. If any sheep-owner discovered scab in his sheep he had to report this to the sheep inspector, brand the sheep with a large 'S', and keep any affected sheep no less than half a mile from the boundary of his run. The disease was at its worst in 1863, when twenty percent of all sheep in Canterbury and Otago were page 218 affected with scab. Drovers were not supposed to take sheep from one part of the country to another without inspections for scab; they used to circumvent this by taking a bottle of poison along when they drove the sheep and quickly dispatching any animal that developed symptoms along the way; when the flock arrived at its destination, the inspector would not be able to find any animals with scab. Various dips and liniments were invented to cope with the disease, and a tax of two shillings per hundred sheep per year was levied on the run-holders to pay for the inspectors. About 1880 the country was declared free of scab, but the tax was not remitted until 1906, until which time close inspection of flocks was maintained. There has been no reappearance of the disease since then.

The tomato caterpillar arrived in consignments of tomatoes from Sydney, and was reported to the Agricultural Department by 1907. This is a very destructive insect, not only chewing its way through tomatoes, but attacking many other plants, with a particular fondness for eating away the centres of ornamental flowers. Similarly, the corn weevil arrived in produce. It was found in grain sheds at Timaru in 1894 and 1895, and in 1900 a rejected consignment of wheat was emptied on the beach and the weevils were seen crawling towards the town in thousands. Again, in 1916, vast numbers of corn weevils were accidentally imported in a shipment of barley from South Australia. Likewise, potatoes imported from New South Wales and Victoria were frequently infested with potato caterpillar.

The diamond-back moth arrived in turnips sometime shortly before 1879. It was noticed that various birds were very effective enemies of this pest, particularly starlings, and in areas where small birds were poisoned the diamond-back moth was particularly bad. Fruit scale insects, such as the red scale of orange, all arrived on shipments of fruit, as did the fruit fly, now a tool of the geneticist. A more unusual method of transport was chosen by the German wasp, which arrived at Te Rapa in 1944 in a crate of aeroplane parts for the war effort.

And so the list goes on: borer beetle arrived in timber before 1875, when it was first recorded by Captain Broun; the bacon beetle arrived in some geological-specimens, feeding on the paper wrapping, in 1884; the Australian locust arrived in vegetable material, probably rooted plant cuttings, before 1886. Many modes of transport were used by these accidental insect intruders, but in every case it was the human factor that made it possible. Settlement involves not only a great change to the environment, with building, cultivating and removal of plant cover, but also constant movement of people, stock and materials.

Early settlers had almost complete freedom to bring in seeds and plants for their useful or ornamental value. These plants were often carried with soil or moss packed around their roots. In this way horticultural imports provided a haven for insects, weeds and their seeds, snails, slugs and earthworms. Bulbs and tubers provided shelter for accidental insects also: the New Zealand Country Journal reported in 1863 that crops of turnips were heavily infested with pests from Europe. Many of these accidental intruders came from Australia, and had a good chance of survival merely because most ships unloaded in the warmer northern ports of New Zealand. A good South Island winter would have killed them off before they got established.

The imports of seeds, even the seeds of pasture plants, contained weed intruders. The thistles were introduced in this way, as stowaways in bags of grass and grain seeds; the common thistle was first recorded in Hooker's list in 1864. In the earliest days of cultivation, especially in the South Island, where huge areas were burned off and then sown with grass seeds, the thistle became extraordinarily abundant, taking absolute possession of the soil so that the casual observer would have gone away convinced that nothing but thistle seeds had been sown. Thomson travelled through hundreds of hectares of newly ploughed land in the Oamaru district in 1873, when the thistles covered the ground to the height of 1.8 metres and it was only possible for a horse to get through if a way had been slashed out for it. In 1864 Mr Macandrew had asked the Provincial Council of Otago if they were aware of the thistle problem. In response they requested the Government Gardener to make a Report which was read to the Council on 13th December 1865, stating, in part, 'In the northern part of the Province it appears that (the thistle plague) commenced about six years ago . . . and is now making its way to a distance of more than nine miles inland, generally avoiding the high lands, and following the course of the rivers and all the lowlands ... The growth of the Thistle,' declared the Government Gardener, 'is in some places five or six feet high, and as much as ten feet wide, being quite impervious to animals, and densely covering large patches of ground varying from ten to thirty acres in extent. When it is considered that in one patch of ground it commenced with Three thistles,' the gentleman exclaimed, 'and in the short space of three years ten acres have been densely covered, the magnitude of the evil cannot easily be exaggerated.'

The seeds of the thistle were a constant impurity in seed imports, particularly those of oats, so that in a very short time thistles were abundant from one end of the country to the other. It was initially most common in Otago and Southland, probably because of the Scottish loyalty to their native breakfast cereal, and for a while scurrilous stories went around the colony that the Scots were deliberately cultivating their national plant. Everywhere that the thistle grew, whether of the common, Scotch or Californian variety, it was ploughed, salted, burned or grubbed up; the only place it was left alone was along railway lines, so that in country areas the railway line could be traced by its bordering of thistles.

One of the kindest words said about that unpopular planned intruder, the sparrow, was uttered by Sir Walter Buller in connection with the thistle. 'If the sparrow is fond of ripe grain,' he remarked, 'it is still fonder of the ripe seeds of the variegated Scotch thistle. This formidable weed threatened at one time to overrun the whole colony. Where it had once fairly established itself it seemed well nigh impossible to eradicate it, and it was spreading with alarming rapidity, forming a dense growth which nothing could face. In this state of affairs the sparrows took to eating the ripe seeds. In tens of thousands they lived on the thistle, always giving it the preference to wheat or barley. They have succeeded in conquering the weed. In all directions it is dying out.' page 221 Ragwort was first recorded in 1874, when Thomson found it growing near Dunedin; it increased very rapidly and was declared a noxious weed in 1900. Guthrie-Smith claimed it was spread by horses, as he found it growing as seedlings sprouting from little heaps of horse-dung. Horses do not like to eat ragwort so they must have either picked up the seeds while browsing around the ragwort plants, or else the seed was a contaminant in horse-feed such as oats. Ragwort spread through New Zealand along the sides of roads and in closely cropped pasture, advertising its presence with its vivid yellow flowerheads. In the 1880s there was an outcry that ragwort was poisonous to horses. Such a fuss was made that the officers of the Veterinary Department were instructed to investigate and they found that the gossip was correct: that ragwort was killing horses, and, indeed, some cattle and sheep that were being fed on it, with cirrhosis of the liver.

One New Zealand native did benefit from the great spread of this accidental intruder—the magpie moth. The caterpillar feeds on the leaves of composite flowers such as the daisy, so the advent of European plants was a great boon. As well as ragwort it likes garden flowers such as the cineraria so it has done very well out of the European settlers. The ragwort grew too fast, though, even though the magpie moth worked valiantly to increase the moth population.

The horned poppy arrived in the packing material of the patent slip machinery at Wellington in the 1870s, and when it was recorded by Mr Kirk in 1877 it had become widely spread along the beach. It was carried to the South Island, being recorded by W. W. Smith at Ashburton in 1903, and also travelled north; it was found by Cheeseman from East Cape and Wanganui to Cook Strait. Cockayne collected it in Marlborough. Perhaps it was purposefully sown, as while its seeds are oily and adapted to float on water, they lose their buoyancy very quickly.

Mr Kirk, during his botanical rambles in both Auckland and Wellington, found the decaying heaps of ballast abandoned by long-departed ships a very profitable source of accidental plant arrivals. In this way he found paspalum on a heap of ballast from an Argentinian ship in Wellington in 1895. Cheeseman also found some in the North Cape districts in 1896. Yates and Co. claim they introduced it as a fodder plant from Australia in 1895, but it is a South American plant, not an Australian one. Introduced accidentally or not, it quickly declared itself to be a most aggressive plant and in the north became regarded as a pest; once established, its strong clumps made ploughing very difficult. Crab grass and twitch may have arrived in the same way, as they were first recorded on pieces of wasteland.

Thus the weeds of the world stole unnoticed into the new country. As Guthrie-Smith said, 'The proverbial sun that never sets upon the flag, never sets on the chickweed, groundsel, dandelion and veronicas that grow in every British garden and on every British garden path.' Hooker's Handbook of the New Zealand Flora, published in 1867, gave a list of 130 foreign plants naturalised in the country. Forty years later a similar book by Cheeseman listed over 500 plants that had arrived and made themselves comfortable. Guthrie-Smith recorded that hair-grass, crested dog's-tail, foxglove and vetch arrived as stowaways in sacks of legitimate seeds; corn thistle came in the chaff fed to the plough team; rape, white goose foot, evening primrose and buttercups arrived as seeds clinging to a dirty sack; goosegrass in a page 222 packet of spinach seed; wall mustard in a packet of Virginian stock; yellow pimpernel in a packet of verbena seed; a sunflower seed was found in a packet of French beeswax; speedwell grew from the soil around some rosebushes; pondweed arrived with water-lily roots; white dead-nettle came with a nursery-purchased daphne bush; bindweed arrived with a lilium plant. When Guthrie-Smith bought some red-hot poker plants, his bonus was some twitch grass. When his maid brought a canary along with her, the seed the canary threw out of the cage sprouted, not into canaries, but canary grass and cockspur grass. All these plants, once established, were dispersed around the country in mud on boots and hooves, in the folds of clothing, in the wool of sheep, in the intestines of horses and birds, and then, giving their spread an even wider range on the wheels of motor cars.

Plants and animals are still managing to sneak into the country by various back doors. Ten accidental bird species have arrived from Australia in the last hundred years. Two, the white-eyed duck and the Australian avocet, were frequent visitors in the nineteenth century, but have not been seen since. The silver-eye and grey teal became well established last century, and, unlike the duck and avocet, have managed to persist into modern times, the silver-eye being particularly successful. The white-faced heron, another recent arrival from Australia, is now widespread; the spur-winged plover and the royal spoonbill have adapted well to South Island conditions, and the Australian coot, the black-fronted dotterel and the welcome swallow are establishing themselves rapidly throughout New Zealand.

Similarly, the Monarch butterfly migrated from Australia and was first recorded in New Zealand in 1840. The real home of this attractive insect is Central America. Aided by air currents in the stratosphere, but nevertheless displaying an amazing feat of flying, the butterfly spread across the Pacific, hopping from island to island until it reached first Australia and then New Zealand. In order for the Monarch to thrive here, the growing of the introduced swan plant had to become widespread, and an Auckland nature-lover, Mr T. Skeates, made a project of promoting this, with very pleasing results.

An unusual Australian immigrant arrived in the Waikato in 1982—a golden orb-weaver spider, complete with an egg-sac. The spider, apparently, had 'ballooned' across the Tasman. The 'balloon' is a sort of web-construction, with which the spider disperses its numbers, but it is unusual for a golden orb-weaver to travel more than about fifteen kilometres in this way. This specimen must have been blown into the stratosphere and swept along until the air currents were dragged down by the Kaimai hills. When the baby orb-weavers hatch, Mr Gibbs, the spider expert on the staff of the Hamilton City Council, will probably release them, as they are, although large, completely harmless.

Much more unwelcome are three other recent accidental arrivals—the blue-green aphid, the white-fringed weevil, and the soldier fly. Aphids, being very light, are also often blown by high winds for immense distances. The blue-green variety, arriving in the early 1970s, quickly became a major threat to lucerne crops. As with so many new arrivals the build-up of numbers was phenomenal and any farmer who neglected to spray his lucerne was doomed to lose up to seventy percent of it. The white-fringed weevil was first found in New Zealand in the 1940s, and it also is a serious pest of page 223 lucerne crops, and attacks maize and potato fields into the bargain. The larvae are root feeders, and the adults feed on the leaves, so they divide up the plant between them. The adults, for the major part of the season, are females only, a form of reproduction taking place called parthenogenesis. These females contain about a thousand eggs each, all fertile without mating, and they produce fully-formed young at about the rate of one an hour for their entire existence. In this way, when the food supply is good, the rate of reproduction is horrifyingly fast.

The Australian soldier fly became first established in the Opotiki district about 1940, but was not recognised as a major pest until widespread crop and pasture damage occurred in the Bay of Plenty, Waikato and South Auckland areas during the late 1960s. Feeding grubs of the fly suck nutrients from the roots of plants, causing loss of vigour in desired pasture, so that weeds and paspalum take over.

The problem today is to make sure that unwanted immigrants like these three pests do not keep arriving, faster and in greater numbers, on ships and on jet aircraft. An elaborate programme of quarantine and inspection has been established, along with a network of regulations.

Quarantine is deliberate and regulated isolation designed to prevent the spread of pests and diseases. The name comes from the French quarante (forty) which is the length of time of the original quarantine, when people and consignments from the Middle East were isolated for forty days to prove that they were not carriers of the dreaded bubonic plague. Nowadays the term applies to the process of fumigation and, if necessary, de-ratisation, as well as the period of isolation.

New Zealand's isolation was in its favour in the early days of quarantine; animals and plants with diseases showed symptoms before the journey was over. In the case of seeds, dormant plant material, dormant animals, or animals living on hosts or managing to survive in the cargo, this, of course, had no advantage. Today, with the swiftness of air travel, the officers who supervise the quarantine regulations are under even greater pressure. Laird, an entomologist attached to the RNZAF, demonstrated in 1951 that mosquitoes transported from this country to the Far East and back survived flights at 6 150 metres without any ill-effects. Because of this all incoming aircraft are inspected and fumigated, inside, including the cargo holds, and outside, including such places as the wheel bays. At ports all animals and plants entering the country are inspected and treated if necessary, and all machinery and dunnage is fumigated. Packing cases may be destroyed: memories of slaters, earwigs and cockroaches arriving in cases are long, and foot-and-mouth disease in Europe has been positively linked to packing materials such as straw and other animal bedding. All timber, both going out and coming in, is scrutinised and treated if this is required.

The Animals Act 1967 and the Plants Act 1970 give these policies 'teeth'. The Animals Act 1967 provides for the control of importation of animals and the prevention of introduction of diseases into New Zealand, through restriction or prohibition of unauthorised importation and liberation of animals or organisms. Regulations may be made to eradicate or prevent the spread of certain listed diseases. The Plants Act 1970 deals with the control of importing and exporting plant material and plant disease control. Quarantine stations may be set up on Crown Land if necessary, but not on parks or public reserves. The introduction of any plant page 224 material, disease, pest, soil, package, or any other thing may be restricted or prohibited by the publishing of a Notice in the Gazette, in order to prevent the introduction of any serious disease or pest into New Zealand. The Ministry of Agriculture and Fisheries has access to certain emergency powers to control a situation if they consider it sufficiently serious to warrant special measures. Offences under the Act include the possession or distribution of plant material, soil, insects etc. known to have been illegally imported, or known to be suffering from a disease or a pest.

The economy of New Zealand obviously would not survive if the dedicated staff of the Quarantine Service relaxed their watchfulness. At airports and seaports and in the post offices and freight terminals of inland centres they maintain a constant surveillance of the mass of imported material which may, and sometimes does, harbour prohibited immigrants. The Service is very dependent on public cooperation and goodwill, particularly when people return to New Zealand from countries overseas, but also during their day-to-day activities. A Waikato sports goods store noticed that one cricket bat in a new consignment had a hole in it. Closer examination revealed that the plastic bag it was packed in had fine sawdust at the bottom and, in the dust, was scuttling a healthy-looking borer-beetle. Bat and borer were quickly reported and then dispatched to the MAF Diagnostic Laboratory in Levin—the beetle proved to be a longhorn borer, native of the Indian sub-continent, an accidental intruder definitely not welcome in the country.

The Agricultural Quarantine Service is made up of a staff which numbers less than two hundred. Their vigilance, and the assistance of citizens like the sports-store owner, guard against the invasion of New Zealand by 'little accidents' that could cause an agricultural economy incalculable harm.