CHAPTER I.

General Review of the Animal Kingdom.

At the outset it is advisable, by reviewing the animal kingdom as a whole, to secure in perspective the relationships of the animals with which the horticulturist has to deal.

To most people the animal kingdom is comprised chiefly of those animals commonly met with in everyday life or in general reading--the game and domestic animals and the fishes, all of which are similar in that they possess a backbone or vertebral column, and are consequently known as the vertebrates. Popularly, however, they are generally classed as the “lower” and “higher” animals; there is certainly some accuracy in such a haphazard classification, since, though all the vertebrates are, strictly speaking, the “higher” animals, some are “lower” (_e.g._, fish, frog, and bird) than others (_e.g._, kangaroo, dog, and man, the highest of all).

But when it comes to the true “lower” animals, that vast assemblage of less conspicuous creatures, the jelly-fish and corals, worms of all kinds, sea-urchins, crayfish, wood-lice, spiders and insects, shell-fish and snails, all characterised by the absence of a vertebral column and known as the invertebrates, they are not collectively visualised in a general sense as are the vertebrates. As a rule, these invertebrates are known individually as independent units, except, perhaps, in the case of worms, insects, spiders, wood-lice, etc., which are very often collectively and haphazardly referred to as “insects,” a term, in this sense, as ill-defined as it is unlimited.

That the average person should be more conversant with the vertebrates than the invertebrates is, to a great extent, the natural outcome of association and training; a possible influence is to be found at the outset of one’s career in the many illustrated nursery books depicting game and domestic animals, but seldom, if ever, any of the invertebrates; and this impression tends to be further fostered in later life by visits to the zoo, where we meet in person most of the nursery book animals, and perhaps some of the lower forms, such as insects; but the latter, in most cases, are there by chance, not design, and against the will of the authorities.

In recent years, however, more public attention has been given to the lower animals owing to the detrimental influence of many upon agricultural development as well as upon public health. That such animals are capable of ranking as fundamental factors hindering human progress, may be realised when it is considered that, of the invertebrates, insects alone comprise nearly four-fifths of the whole animal kingdom! This has been graphically illustrated as follows by F. E. Lutz, of the American Museum of Natural History:--Extend the arms and fingers at right angles to the body, and let the distance from the tip of the middle finger of one hand to that of the other represent the number of different kinds of living animals; then the last joint of the middle finger of the right hand will be proportionate to the number of mammals (kangaroos, hoofed animals, rabbits, man, etc.), the second joint to the reptiles and their relations, the first joint to the birds, and the distance between the knuckles and the wrist to the fishes. “In other words, you can hold the so-called zoological gardens and their aquarium annexes in one hand.” Finally, the distance between the wrist of the right arm and the tip of the middle finger of the left will proportionately represent all the known species of invertebrates, and of this section of the extended arms all except between a wrist and an elbow will be insects.

The zoologist classifies the animals under twelve main divisions, of which eleven contain the invertebrates and one the vertebrates; these divisions are arranged in a series, the first containing the simplest or lower animals, and the last the most complex or highest. A glance at this classification will serve to give some idea of the relative position in the animal kingdom of the animals which will be dealt with in the following pages. The very lowest forms, belonging to the first division, are micro-organisms known as the Protozoa; they inhabit water and soil, and live upon their own kind or upon minute plants, including bacteria, or are parasitic upon the higher animals, some of these parasites causing such diseases as malaria. The Protozoa are single units of living matter (protoplasm), and may be referred to as the one-celled animals; they are mostly microscopic, and lead an independent life, or are associated in colonies, but are capable, as a rule, of carrying on independently all the functions of life, though there are no organs such as those of digestion, respiration, and circulation, as we know them in the higher animals. It is amongst such simple forms that the distinction between the lowest animals and plants ceases to be clear. As will be discussed later, there is evidence that certain Protozoa have an important influence on soil fertility.

The remaining eleven divisions contain all other animals, ranging in size from mere specks to the mass of the elephant; the bodies of these are built up of a complex aggregate of countless cells of protoplasm arranged in groups to form the organs of digestion, circulation, respiration, reproduction, etc., each having its definite function in the animals’ lives. The following are some typical or well-known examples of each of these divisions, the technical names, with the exception of the Protozoa, not being given:--

The Protozoa (reference should be made here to Fig. 1) are followed by (2) sponges; (3) jelly-fish, sea-anemones, corals; (4) flat worms (tape-worms, etc.); (5) round worms (thread-worms, eel-worms); (6) sea-mats, lamp-shells; (7) wheel-animalcules; (8) star-fish, sea-urchins; (9) segmented worms (earthworms); (10) crayfish, woodlice, centipedes, millepedes, spiders, mites, insects; (11) shell-fish, slugs, snails; (12) fish, frogs, lizards, birds, hedgehogs, rabbits, man.

So far we have reviewed the animal kingdom from one aspect only--that of classification, based on the resemblances and differences of the individuals. It is now necessary to look at the subject from the viewpoint of the horticulturist--that is, the relationships of the animals to their surroundings, or environment, and to the welfare of man. Of the two great life-groups--animals and plants--the plants are of fundamental importance; without them no animal could exist, since, of all living things, it is the green plants alone that are able to convert the inorganic chemical constituents in soil, air and water into living matter or protoplasm; and all animals, either directly or indirectly, are dependent upon plants for their food supply. Plants, therefore, may be looked upon as the primary producers of life, and animals as the consumers. It is in this respect that the horticulturist becomes interested, in that certain of these consumers destroy too many of the plants grown by him for other purposes; fortunately, not all of the consumers are destructive; many are of very great use to the horticulturist and mankind in general.

The last point is well illustrated by the following classification of the animal kingdom based upon the part it plays in human welfare; this is a modification of the scheme adopted by the British Museum of Natural History:--

_Group I._--Wild or domesticated animals used by man as beasts of burden, source of food, or in the manufacture of various products--_e.g._, sponges, crayfish, bees, silk-worms, shell-fish, and various vertebrates, as fish, birds and mammals.

_Group II._--Animals detrimental to man’s welfare, attacking man himself; animals and plants of value to him, or the products derived therefrom--_e.g._, Protozoa, parasitic worms, mites, insects, and such vertebrates as certain birds and mammals.

_Group III._--Animals aiding man’s welfare, as scavengers, or by pollinating flowers, or by attacking and checking such animals as are included in Group II.--_e.g._, Protozoa, parasitic worms, earthworms, parasitic insects, spiders, and such vertebrates as certain birds and mammals.

An analysis of the above classification shows that animals both aid and hinder the progress of man, hence the use of the terms “beneficial” and “destructive.” In nature, however, these terms are not altogether applicable in the same sense, since the balance maintained between animals and plants under natural conditions is an extremely fluctuating one, though sufficient for natural purposes; with man, however, the case is different. In order to compete in the world’s markets, and to supply the growing demands of increasing population, a much higher and dependable standard of productivity is required than is found in nature. Consequently, whilst utilising, and increasing the efficiency of the so-called natural enemies as auxiliaries in his fight against destructive animals, man has found it necessary to develop an effective system of artificial control, involving chemicals, resistant plants, cultivation, crop rotation, etc., for the purpose of maintaining a more stringent balance to meet his requirements.

Historical Review of New Zealand Conditions.

The animal population of European New Zealand is very different from that of pre-European times, a position brought about naturally enough by the changes resulting from agricultural development as practised in the Old World, and the consequent creation of an environment foreign to the country.

Though the official date of the settlement of New Zealand by Europeans is 1840, the influences, inaugurating that upheaval of the natural conditions which was later to have such a marked effect on the economic development of the country, had commenced many years earlier.

When the first Europeans set foot in New Zealand, they must have been impressed by their unique surroundings, totally different from anything to be met with in the Old World. They found the country dominated by a forest quite unlike the forests of any other land, and inhabited by an animal population presenting many unusual features. This terrestrial population was characterised by an abundance of insects and spiders, and a paucity of vertebrates excepting the birds; the vertebrates consisted of a species or two of frogs, a few species of lizards, some 200 species of birds, and two species of bats, the last being the only terrestrial mammals. In fact, the insects, spiders and birds were the dominant animals, a feature common to other parts of the world, but the scanty vertebrate population, other than birds, was a characteristic of primeval New Zealand.

New Zealand being a country fitted for agriculture, settlement by Europeans naturally resulted in extensive and rapid changes, since the settlers brought with them the knowledge, implements, animals and plants of the civilised world; and to make way for settlement, it was necessary to remove the forests and drain the swamps, and to replace them with cultivated crops and pastures. These activities have been so thorough, that, within a period of some 90 years practically the whole of the original North Island forests, and the greater part of those of the South Island, have been cleared.

An outstanding feature of these changes is that many of the pests associated with the agricultural animals and plants have been brought to New Zealand with the animals and plants they infest, and these exotic pests comprise by far the greater proportion of the destructive animal population, there being but few native species forming the balance. For example, 71 per cent. of the destructive insects are exotic, and 29 per cent. native, while all the parasitic worms of economic importance, all the destructive birds (_e.g._, sparrows) and mammals (_e.g._, deer, wild pigs, and goats) are introduced.

The exotic factors that have set up this new environment may be summarised as follows:--

(1) Clearing of the native vegetation.

(2) Introduced plants: _e.g._, grasses, forage crops, trees, etc.

(3) Introduced game animals: _e.g._, deer, pigs, rabbits, birds, etc.

(4) Introduced destructive animals, infesting animals and plants of economic value: _e.g._, parasitic worms, insects, etc.

(5) Animals imported to control pests, but which have become destructive themselves: _e.g._, weasels, birds.