6 THE entomologist's RECORD. 



attempted directly to connect certain forms of melanic varia- 

 tion with an excess of moisture, although in the Ent. Mo. Mag., 

 vol. xiii., p. 148, Dr. Buchanan White stated most explicitly 

 that he believed the exciting cause of melanism was to be 

 looked for in certain meteorological conditions. However, 

 a paper that Mr. Cockerell read before the members of the 

 South London Ent. and Nat. History Society {Transactions 

 S.L.E. and N.H.S., 1887, pp. 103, 104) caused me first to 

 give particular attention to it. It struck me at once that a 

 great deal of the melanism and melanochroism of our Islands 

 could be better explained by this theory — in combination with 

 " natural selection," — than by any other that had been pre- 

 sented to us. Our greatest authority on Continental Noctu^, 

 Mr. N. F. Dobree, wrote an article {Entoni. xx., pp. 25-28), 

 previously referred to, disproving the general notion that 

 melanism was characteristic of high latitudes, and pointing out 

 the following facts: — (i). That melanism scarcely ever occurred 

 in such latitudes. (2). That at any latitude, dry open areas 

 produced more brightly and clearly marked forms of lepidoptera, 

 and (3). That the North of Europe produced, practically, no 

 melanic forms, neither did the South, but that the melanism of 

 the Continent was confined almost entirel}^ to certain Alpine 

 districts. This was followed up {Entoni. xx., pp. 58, 59) by 

 a short article from Mr. Cockerell, who, of necessity accepting 

 Mr. Dobree's facts, disagreed with that gentleman's deductions 

 and conclusions, and suggested, that the areas where melanism 

 was prevalent were more or less humid, and that humidity 

 had probably more to do with melanism than food or any 

 other cause. Since I have devoted my attention to the matter, 

 the information I have been able to gather helps to confirm 

 Mr. Cockerell's view. 



Taking into account the physical geography of Europe, 

 what do we find are its broad, general, meteorological and 

 climatic characters? (i). That the great central plain, com- 

 prising Russia, Northern Germany, Holland, Belgium, and 

 Northern France, is swept by the prevalent east winds, which, 

 having traversed Siberia, are totally devoid of moisture, and 

 that consequently this area has a comparatively small rainfall, 

 and has exceptionally dry air. 



(2). That the great central mountain chain, the Alpine- 

 Carpathian range, running through Europe, east and west, 

 has a much heavier rainfall and moister atmosphere, due to 

 condensation, than the great central plain. 



