Page:De Vismes Kane-European Butterflies.djvu/15

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INTRODUCTION.

of individuals is much more so. Though most will survive a surprising degree of cold in the chrysalis state, when they may be frozen hard with impunity, yet the rays of the sun are required to hatch and rouse them into activity.

In the sunny south, therefore, their swarms are only kept in check by the depredations of insect enemies and other hazards. But other causes are not less potent in regulating the distribution of species. Switzerland, for its extent of territory, has a more varied list by far than any other European State, partly owing to its geological and climatic conditions conducing to a variety of botanic and entomological products, but largely also by reason of its central position.

France, too, besides its continental position and latitude, in part owes the richness of its fauna to the varied character of its territory and climate. For, in addition to her widespread plains and sunny southern shores, she has mountain ranges which preserve most of the Alpine insects of Central Europe, and which are, moreover, of very diverse geological character, such as those of the Vosges, the Jura, and Savoy, the volcanoes of Auvergne, the Pyrenees stretching into Spain, and the Basses Alpes and Alpes Maritimes ranging along the sultry Mediterranean coast.

These two countries, therefore, but especially Switzerland, offer the most prolific hunting-grounds in Europe to the entomologist. I shall now proceed to describe:

The Butterfly : the Method of its Capture, and Preservation when Travelling.

For the benefit of those who are commencing the study of entomology for the first time, it is necessary to ofter a short prefatory explanation of the peculiar characteristics and