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ECONOMICS

gardener are the Hymenopterous families of Ichneumon Flies (Ichneumonidae and Braconidae) ; the Dipterous families Syrphidce and Tachinidce; the Coleopterous families Coccinellidce and Carabidce ; and the Neuropterous Hemerobiidce, or Lace-Wing Flies. Ichneumon Flies lay their eggs either in the larvae or ova of other insects, and the parasites destroy their host. In this way the Hessian Fly is doubtless kept in check in Europe, and the Aphides meet with serious hindrance to their increase. If a number of plant-lice are examined, a few will be found looking like little pearls; these are the dried skins of those that have been killed by Ichneumonidce. The SyrphidcB, or Hover Flies, are almost exclusively aphis-feeders in their larval stage. Tachina flies attack lepidopterous larvae. One of the most notable examples of the use of insect allies is the case of the Australian Lady Bird, Adalia cardinalis, which, in common with all lady birds, feeds off Aphidce and Coccidce. The Icerya Scale {leerya purchasi) imported into America ruined the orange groves, but its Fig. 7.—Knapsack sprayer for liquid insecticides. enemy, the Adalia, was also imported from Australia, as parasites or by being insectivorous in habit; and (2) and counteracted its abnormal increase with such great insects of economic value, such as the bee and silkworm. results that the crippled orange groves are now once more (f v. T.) Amongst the most important friends to the farmer and profitable.

Beneficial Insects have also to be considered in Economic Entomology. They are of two kinds—(1) those that help to keep down an excess of other insects by acting either

ECONOMICS. IN a former article (see Political Economy, Ency. Brit., 9th edition, vol. xix. pp. 346-401), in which the growth of Economics from the earliest times was described, it was shown that, owing partly to the conditions affectA review ^ie industrial and commercial organization of recent and the economic policy of different countries, work on partly to the influence on economics of the economics, growth of other sciences, there were in Europe and America various schools of economists representing somewhat different views as to the aims, the subjectmatter, and the method of the science. This state of things was no doubt a symptom of vitality and progress, but it was associated with much destructive criticism of principles hitherto considered well founded, and diminished for a time both the practical usefulness of the science and the estimation in which it wras held by ordinary men. During the last few years there have been no new departures of fundamental importance, such as the application of the historical method to economic investigation ; the methods characteristic of the different groups of economists have been seen to be not mutually exclusive, but complementary to each other; and much of the work done has been constructive, in the sense that economic writers have devoted themselves to the solution of particular problems rather than the discussion of the method by which the problems should be attacked. The time has therefore now arrived when we can review the situation and attempt to combine the positive results of a period of active criticism and inquiry. Many years must elapse before we can survey the whole field of economic investigation, if indeed the time ever arrives when we can undertake so great a task. Present tendencies scarcely point to the creation of a complete .and well-rounded system of economics such as appealed to past generations. Like the world of business and commerce of which it is the reflex, economic thought resembles a great river. Its sources lie far back in the historic past. Its course has been determined by practical needs which are no longer felt, by ideals to which the present generation does not respond, and by systems of politics and philosophy whose day is over. The titles of an economic bibliography are a brief epitome of general history, and a complete survey of economic thought at the present time

would involve a careful examination of many of the important questions which now occupy the public mind in, at least, Europe and America. It is the spirit and the method of economic science which we may hope will be permanent. The more numerous the points of contact between economic science and the real world of business, the less possible will it be, at any rate for many years, to construct a complete system. In the present state of economic knowledge, generality can only be obtained by abstraction. But it is possible to describe the character and and subject-matter of economics, to indicate its relation to other sciences, to explain the methods by which economists reach their conclusions, to show within what limits a science which we may call General Economics is possible, to apply our reasoning to particular groups of practical questions; and that is the task we shall attempt in the following pages. Economics, as we understand it, is the science Avhich investigates the manner in which nations or other larger or smaller communities, and their individual mem- Definition bers, obtain food, clothing, shelter, and whatever else is considered desirable or necessary for the maintenance and improvement of the conditions of life. It is thus the study of the life of communities with special reference to one side of their activity. It necessarily involves the scientific examination of the structure and organization of the community or communities in question; their history, their customs, laws, and institutions; and the relations between their members, in so far as they affect or are affected by this department of their activity. At the root of all economic investigation lies the conception of the standard of life of the community. By this expression we do not mean an ideal mode of living, but the habits and requirements of life generally current in a community or grade of society at a given period. The standard of life of the ordinary well-to-do middle class in England, for example, includes not only food, clothing, and shelter of a kind different in many respects from that of a similar class in other countries and of other classes in England, but a highly complicated mechanism, both public and private, for ministering to these primary needs, habits of social intercourse, educational and sanitary organization, recreative arrangements, and many other