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ON THE ORIGIN OF THE EUROPEAN RHOPALOCERA, 

 AND THE EFFECTS PRODUCED BY THE GLACIAL 

 PERIOD UPON THEIR PRESENT DISTRIBUTION 

 AND DIVERSITY. 



By W. Harcourt Bath. 



Geologists inform us that there was a period in the history 

 of this planet when the earth existed in a molten red-hot state, 

 analogous to that which holds sway at the present time in the 

 smaller mass of Mercury. During the course of many millions 

 of years its great heat gradually sublimed, until it was reduced 

 to a temperature capable of supporting animal and plant life. 



The two extremities of the earth were most probably the first 

 points where life first commenced to make its appearance, since 

 they were undoubtedly the first portions of this planet which 

 possessed a sufficiently low temperature for its production. But 

 whether the North Pole or the South Pole was actually the first 

 to evolve animals and plants, is a problem which requires 

 elucidating; likewise as to whether two identical or distinct 

 groups of fauna and flora came into existence at either extremity 

 independent of each other, and which for a long time were unable 

 to intermingle on account of the equatorial regions being still in 

 too thermal a state to enable them to do so. 



Butterflies are, however, geologically speaking, of compara- 

 tively very recent origin, according to the evidence furnished by 

 palaeontology, and the place where they were first produced was 

 most probably somewhere in the equatorial regions of the earth. 

 Tropical America very likely constitutes the cradle of their birth, 

 on account of the wonderful development they receive in this 

 region both as regards numbers and variety. In the basin of the 

 Amazon and adjacent countries to the north there exist about 

 5000 different species out of a total of 10,000 known to science, 

 that is, 50 per cent, of the rhopalocerous fauna of the globe. 



During the course of many thousands of years succeeding 

 they became disseminated through all portions of the earth, and 

 up to the commencement of the great glacial period there was 

 probably a rich rhopalocerous fauna found in most parts of 

 Europe. It is the influence of the above climatic conditions, as 

 afl'ecting the present distribution and diversity of the European 

 Rhopalocera, with which I propose to deal in the present paper. 



During the height of the glacial period, that is when the ice- 

 cap attained to its maximum dimensions, the major part of 

 Europe north of the Pyrenees, Alps, and Carpathians, was 

 covered by a vast field of snow and ice, which accumulated to 

 such an extent during the severe winters that the heat of each 

 succeeding summer was unable to sublime it. The butterflies 



