Immense reduction has also taken place among aquatic species of Diptera, Neuroptera, etc.1

Among naturalists of the last half century there has been a strong belief that the introduced fauna and flora have been directly responsible for the diminution of many, and the disappearance of some indigenous animals and plants2.

Thus Darwin in the Origin of Species says:

From the extraordinary manner in which European productions have recently spread over New Zealand, and have seized on places which must have been previously occupied, we may believe, if all the animals and plants of Great Britain were set free in New Zealand, that in the course of time a multitude of British forms would become thoroughly naturalised there, and would exterminate many of the natives. On the other hand, from what we see now occurring in New Zealand, and from hardly a single inhabitant of the southern hemisphere having become wild in any part of Europe, we may doubt, if all the productions of New Zealand were set free in Great Britain, whether any considerable number would be enabled to seize on places now occupied by our native plants and animals. (The italics are mine.)

In examining this subject in connection with the introduced plant life I think it will be shown that where man does not interfere with the vegetation, the indigenous species can hold their own against the imported forms. It is human intervention—either direct or indirectwhich completely alters the conditions. The same probably holds good to some extent of the animal life, only the problem is more difficult to follow out.

Against the wholesale destruction of native animals which has taken place within the last half century, there have to be recorded some cases of increase in the native fauna, apparently due to some adaptation to the altered conditions.

One of the most interesting cases is that of the bell-bird or makomako (Anthornis melanura). This species has very largely disappeared from the North Island, though I cannot learn from any one why it

1 Mr Elsdon Best reports the disappearance of the grayling from the rivers on the east coast of the North Island. Mr O'Regan also records the same for the rivers on the west coast of the South Island. The latter says the popular belief is that the trout have exterminated them, but he says these fish disappeared from the Inangahua before trout were introduced, and he never heard of trout eating graylings. Though formerly they were very common on the west coast, he does not now know of any river where they may be found.

Mr Murray Campbell says the graylings come up the Cascade River in South Westland in great shoals for the greater part of the year. (April, 1910.)

2 A. R. Wallace (in Darwinism, 3rd edition, p. 34) says: "A native fly is being supplanted by the European house-fly." This kind of statement is the sort of terse sentence which is apt to be quoted by writers, but it is both utterly indefinite and quite misleading. No one can say what native fly is meant, nor is it certain what European house-fly is referred. It may however be stated definitely that no species of European fly has supplanted a native fly.

should have done so. It was common in Whangarei in 1860, and then began to get scarce. It was, however, common about the watershed of the Wanganui and Mangawhero rivers in 1909, and is also very abundant on some outlying islands, e.g. Mayor Island. But in the South Island it has certainly become more abundant in recent years, even though there has been very wholesale destruction of bush. It is many years since Mr W. W. Smith reported its increase in the forest belt of South Canterbury. I have myself noted it year by year in the neighbourhood of Dunedin, where it is found in the Town Belt and in suburban gardens during many months of the year, especially when certain trees are in flower. In Southland, Mr J. Crosby Smith and Mr Philpott also report the species as increasing. The case is certainly peculiar, for the tui (Prosthemadera) persists in the North Island, but has become comparatively rare in the settled districts in the South Island. The habits and food of the two birds are somewhat similar, only the tui is a much more conspicuous bird.

The harrier (Circus gouldii) is another bird which has certainly increased to a great extent.

Mr Richard Reynolds of Cambridge, Waikato, an enthusiastic sportsman and naturalist, writes me as follows (June 23rd, 1916):

The morning after £50 worth of partridges had been liberated here, my son found eight of them killed, with a hawk on each; he shot a rabbit, poisoned it with strychnine and secured eighteen hawks with it. In driving from here to Tepapa (24 miles) a few days ago I passed (within sight) 162 hawks, 17 of them in one bunch.

This gives some idea of the enormous abundance of this bird in the North Island. These hawks visit Stephens Island in Cook Strait apparently in pursuit of young petrels. But as the Island is a preserve for the Tuatara lizard, the lighthouse keepers are instructed to destroy all hawks met with. I am informed by Mr Newton of the Public Works Department that between 23rd January, 1917, and 28th February, 1919, no fewer than 1582 hawks were killed. They all seemed to come from the North Island via Kapiti. I have no corresponding figures for the South, but in open country the hawk is the bird most in evidence everywhere. They are protected birds on account of the damage they are supposed to do to rabbits, but even where they are very abundant the rabbit thrives without much hindrance from the hawk. In the North they are more destructive to hares than to rabbits.

Some of the introduced small birds attack the harrier, as their ancestors in Britain attacked kites and sparrow-hawks. Some larger birds also "go for" this hawk. Mr Holman of Whangarei tells me he has often seen guinea-fowls attacking and beating off the hawks from the chickens.

The increase of this bird has no doubt been due to the vast increase of rabbits, whose young are often caught by it, and of small birds; and also to the protection accorded to the species. A humourist could find excellent material on which to exercise his talents were he to summarise the literature and the oratory which has been expended on this hawk in New Zealand. The sheep-farmer protects it because it is more or less destructive to rabbits which are his great pest, though it is really too slow in its movements to keep down such an active and wary creature as the rabbit. Formerly it lived mainly on lizards and insects, but it has now a much larger menu. Wherever game fanciers prevailed, the bird was mercilessly destroyed, and rewards were offered for heads, as it certainly is a most active agent in keeping down pheasants, quail, wild ducks and other imported game. Where farmers grew grain crops the hawk was protected as an antidote to the small bird pest; but where poultry were largely kept, it was ruthlessly trapped and destroyed on account of its predilection for chickens. Altogether the record is a very mixed one, but on the whole the bird seems to have more than held its own, and is very common throughout New Zealand.

The grey warbler (Pseudogerygone igata), yellow-breasted tit (Petræca macrocephala), the fan-tailed flycatchers (Rhipidura flabellifera and R. fuliginosa), and the pipit or ground lark (Anthus novazealandia) appear to have more than held their own. This may be due to a certain measure of protection accorded them by settlers, but they have been mostly left alone, and their most active enemy is the cat. Yet it is quite surprising how common the ground larks are in all open country, and especially in country districts, and how the others named penetrate into gardens, even in the larger towns. Their food supply consists mostly of small insects and other invertebrates, many of them introduced species, and these are very abundant.

The wax-eye or blight-bird (Zosterops cærulescens) has apparently increased very much since it was first recorded in 1832; the facts which are known as to its spread and increase are recorded at p. 161. These little birds are very fond of meat, and especially of fat, and come about houses and stock-yards for the sake of the animal food to be obtained. Dr Fulton says that many of his correspondents consider that the long-tailed cuckoo (Urodynamis taitensis) has become increasingly numerous during the past thirty years, and they attribute this to the increase of small European birds, on whose eggs and young they feed. In and about trout-hatcheries they do a great deal of mischief. They also destroy numbers of young birds, such as sparrows, wax-eyes (Zosterops), goldfinches, etc.

Recorded cases of increase among other groups of indigenous animals other than birds, are very few.

The two moths, whose larvæ are known as "flax-grubs”—Xanthorhoë præfectata and Melanchra steropastis—are both considered to be much more abundant now than they were formerly. It may be that by the clearing away of other native vegetation on which they formerly fed, their attacks are now made more persistently on flaxcovered areas, but the pest has assumed such serious proportions in recent years, as to lead to combined efforts to cope with it.

Another native moth-Eceticus omnivorus-appears to have increased also to a considerable extent. Within the last few years also very many complaints have been received of the steady increase of a moth Venusia verriculata, whose larva feeds on and occasionally nearly destroys the cabbage-tree (Cordyline australis).

The common magpie-moth (Nyctemera annulata) has certainly become extremely abundant wherever the introduced ragwort (Senecio jacobea) has become a common pest. Formerly Nyctemera appears to have fed chiefly on the indigenous Senecio bellidioides, S. Lautus and glabrous species of Erechtites, but it has transferred its attention now chiefly to the introduced species of Senecio (including S. vulgaris and S. mikanoides). Wherever ragwort has spread and become an abundant weed the Nyctemera has also increased enormously, and may be seen rising in vast swarms from the plants during the adult moth stage. I have never seen a bird catching the moths, and the hairy caterpillars appear to be very distasteful to them. I know chickens will not touch them. Hence they seem to increase almost without check from enemies. The only bird I have heard of as eating them is the shining cuckoo (Chalcococcyx lucidus); my informant is Mr Holman, Curator of the Whangarei Acclimatisation Society, who is a careful observer.

It is difficult to get any information as to changes in the abundance of native insects due to the introduction of foreign species of plants. One species of beetle, Odontria zealandica, the common grassgrub," has apparently greatly increased with the introduction and increase of European grasses. It is extraordinarily abundant in some pastures, and is most destructive to lawns. Two allied species, O. puncticollis and O. striata, have been found to be very destructive to seedling trees in the State nurseries. The former is most active in the North Island, destroying sometimes as much as 30 to 40 per cent. of the seedling larch (Larix Europæa). O. striata is most in evidence in the South Island, where it destroys both larch and Pinus laricio. The common longicorn beetle-Prionoplus reticularis-cannot be at all so common as it was before the wholesale destruction of forest trees

in which its larva used to bore. But it has now learned to bore into certain introduced plants, and I have received from Mr W. W. Smith of New Plymouth, specimens of oak trees (Quercus robur var. pedunculata), and of lilac (Syringa vulgaris) very freely tunnelled by these large grubs.

Changes in introduced Fauna since Naturalisation

In the introduction to this chapter I stated that the observations of naturalists thirty or forty years ago led to the prevalent belief that in this new country variation would proceed very rapidly among introduced species of animals and plants owing to the removal or rather absence of those checks which acted upon the species in their native habitats. After nearly fifty years of fairly close observation I have to state very definitely that such a belief has been absolutely dissipated. I am aware of no definite permanent change in any introduced species.

For a long time I collected all the information I could lay my hands on as to albinism in birds, expecting to find that it was greatly on the increase. Buller referring to this matter says:

A remarkable feature in the New Zealand avifauna is the inherent tendency to albinism. The condition itself is no doubt due to the absence of colouring pigment in the feathers; but the difficulty is to find any sufficient cause for this in a temperate climate like that of New Zealand. In India, as is well known, the tendency is in the opposite direction, melanism being of very frequent occurrence. Strange to say, there is the same tendency to albinism in the imported birds. Albino sparrows are far more common than they are in their native country, and even the skylark not unfrequently changes its sober dress for a yellowish-white one.

The italics are mine, but the statement shows that Buller-writing nearly fifty years ago was of opinion that colour changes were rapidly taking place.

Writing in 1891 I said:

Among house sparrows in particular, variation in colour and especially development of white feathers is extremely common, and is certainly on the increase. From evidence I have collected in Otago, I find that the development of white plumage, usually in the wings and tail, is a very common feature, and by no means confined to sparrows. I have numerous recorded cases of the occurrence of more or less complete albinism, as well as of the development of bright colours in thrushes, blackbirds, linnets, skylarks and starlings. Such variations are, of course, not uncommon in the original habitats of all these birds, but it never tends to increase. Here, on the other hand, it is of frequent occurrence, and seems to me to be very decidedly on the increase. My own observations lead me to think that birds with any bizarre or distinctly abnormal colouring are wilder and more shy than their normally coloured fellows; but as

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