GEOGRAPHIC DISTRIBUTION OF NEUROPT£ROID INSECTS, WITH AN ANALYSIS OF THE AMERICAN INSECT FAUNA. By Nathan Banks. It is usual in general works on distribution to consider insects as widely dispersed by winds, and sea-currents, and therefore of little use in geographic studies. But every ento-mologist knows that the great majority of insects are more circumscribed in distribution than many of the higher animals. There are many insects of as wide distribution as the human species, but for each of these there are thousands that are con-fined to a very restricted range. Of our 15,000 known species of beetles only 500 or 600 are also known from Europe. Many of these belong to a few families of particularly northern dis-tribution, many are accidental captures, and many have been introduced by commerce. Insects, when properly investigated, are just as useful in studying distribution as any other animals. It has been remarked that there are two principal view-points from which to study geographic distribution. One is to consider what animals inhabit each country, and from these facts divide the world into a series of regions, subregions, etc. This, the static method, is, to my mind, extremely useful, and has been utilized by many, and may be followed to much advantage. It presents the facts that are to be accounted for by our theories. The other viewpoint is how the fauna of a country came to be what it is ; an attempted explanation of its various elements. This, the dynamic study of distribution, depends largely upon geology, palaeontology, and upon phil-osophic considerations regarding the origin, habits, and means of dispersal of the various groups of animals. In reality these two viewpoints are the beginning and end of the same thing. From this dynamic viewpoint one sees that the insect fauna of a country, as the United States for example, is partly due to what it has inherited from previous land-masses in this vicinity, partly to what has migrated to it in ancient times, and partly to what has reached it since the continents have existed in their present form. 125
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