52 THE entomologist's record. 



other islands of our western shores, and also those from the 

 Northern Shetlands and Orkneys, where moisture reigns 

 supreme. Professionals and amateurs alike have recorded 

 the variation and general tendency to melanism in the 

 Rannoch district. Aberdeen, Perth, Dundee, and Glasgow 

 have each their own body of active workers, and Lancashire 

 and Yorkshire have long boasted a large proportion of the 

 leading lepidopterists of the United Kingdom, and these 

 have given us an immense mass of information relative 

 to the melanic variation in their various districts. Most of 

 these districts have an exceedingly humid atmosphere, and 

 they produce a greater or less number of melanic forms, but 

 the most intense forms are undoubtedly from the west coast 

 of Ireland, the Scotch Islands and Highlands, where the 

 humidity of the atmosphere is most excessive. There is a 

 great deal of difference between the degree of melanism on 

 the east and west coasts of Scotland. Repeatedly we hear 

 that " the fauna of the east coast is less Alpine than that of 

 the west." With regard to the distribution of melanic forms 

 in Britain, I will again quote Dr. White. He writes : — " That 

 there is frequently a difference between South England and 

 Highland examples of the same species, will be admitted, I 

 think, by every one ; and that this variation is, in the majority 

 of cases, in the direction of melanism has been generally 

 taken for granted. That it really is so, the following brief 

 analysis^ of the Highland Lepidoptera will show. In it I have 

 compared the majority of the Macro-Lepidoptera of Scotland 

 north of the Tay, with South England (and a few cases 

 with South European) specimens of the same species ; for it 

 must be remembered that North and North-western English 

 specimens frequently exhibit the same or even a greater 

 tendency to melanism than the Highland specimens " {Ent. 

 Mo. Mag., vol. xiii., p. 146). Mr. Birchall also in the same 

 volume, p. 131, after referring to the melanism of the High- 

 lands of Scotland, writes : — " It must further be noted that 

 melanic varieties of Lepidoptera occur very commonly in 

 Ireland, the Isle of Man, Durham, South Lancashire, and the 

 West Riding of Yorkshire, under various conditions of climate 

 and soil." 



Now to turn from effects to probable causes. 



As I have pointed out above, the western coasts of our 



1 Dr. White [Ent. Mo. Mag., vol. xiii., pp. 145-147) gives a long list of 

 examples, as also does Dr. Birchall (vol. xiii., p. 133 of the same journal). 



