34 THE entomologist's record. 



will not apply in all cases. The imagines of our dark Alpine 



species appear in January and February, which are the clearest 



and hottest months in the year. Nothing is absolutely known 



of their economy and habits, yet we may surmise that the eggs 



are deposited soon after emergence, and the larvae feed up in 



March and April. In the latter months the autumnal rains 



set in, which are greater and more prolonged on the Ranges 



than in the lower country. It must be admitted that larvje 



feeding on high altitudes are subjected to a lower temperature ; 



but it will also be observed that they are subjected in our 



climate to a much greater degree of moisture than other or 



allied species existing on the lowlands. About the end of 



April or beginning of May, the snow begins to cover the higher 



parts of the Ranges, and continues, more or less, to fall until 



September, when the warm north-west wind generally begins 



to blow and melt it off the Ranges. The pupae thus deeply 



buried in snow through the winter, would experience no more 



cold on those high regions than other pupae exposed to all 



weathers on the plains, on which snow scarcely ever falls. 



The north-west winds which begin to blow in September, are at 



first slightly chilly, owing to their traversing the snow-fields of 



the Alps. As the snow lessens in quantity, the wind blows 



hotter and drier across the plains, causing the snow-fed rivers 



to flood, although the wind is cool before it impinges on the 



western summits of the Ranges. It absorbs great moisture in 



crossing the snow fields, which is frequently condensed in 



heavy rain showers over the lower hills and downs, and along 



the bases of the mountains ; here the lepidoptera are invariably 



darker than on the open plains, where the warm north-west 



rains rarely ever reach. The physical features of the country 



I have described, namely, high mountain ranges and extensive 



plains occurring contiguously, differ greatly from any districts 



as yet mentioned by Mr. Tutt, where he states melanism 



occurs. Nevertheless the cause of melanism and melanchro- 



ism appears to be identical in all cases. The very reverse 



meteorological conditions of climate are frequently observed 



here on the same day, for, although the day may be dry and 



hot on the plains, the Ranges are at the same time enveloped 



for days together in dense aqueous clouds condensing great 



moisture (see remarks by Professor Schoyen of Christiania, 



quoted by Mr. Tutt, Ent. Record, vol. i., 53). 



" The elucidation of any cause producing variation in animals 

 requires very careful study, and any theory advanced to 



