54 THE entomologist's RECOiil). 



Romsdale Amt, close to the sea-shore, much darker than at 

 Dovrefjeld, about 2,000-3,000 feet above the sea ; Agrotis 

 candelaruin occurs at Bergen as dark as on the Jotiinfjelds 

 (var. jotunensis, mihi). But in the majority of species, the 

 darker colour is generally found, however, either at a greater 

 height above the sea, viz., on the mountains, or in a more 

 northern latitude. Yet this may also be chiefly caused by the 

 more humid condition of the atmosphere, for the mountains 

 are generally covered with masses of cloud, making the 

 atmosphere much more humid than in the valleys and low- 

 lands, and in the northern latitudes, large quantities of rain- 

 fall and fog and mist are prevalent. Under these circumstances 

 the grey colour of many moths will generally be more or less 

 darkened " {in litt. 18/3/go). I need not point out how 

 valuable this confirmation of my theory is. 



The melanism of Lancashire and Yorkshire deserves to be 

 considered separately. Mr. Dobree {Entom. xx., p. 28), con- 

 sidered the melanism of Yorkshire as " exceptional, and not 

 affecting the general question." Mr. Cockerell, on the other 

 hand {Entom. xx., pp. 58, 59), considered that the " melanism 

 of Yorkshire would follow the general rule, and that the 

 melanism of Yorkshire would be found coupled with a greater 

 degree of humidity in those localities where it occurs." 



I am inclined to agree partially with both these statements. 

 The melanism of Yorkshire is " exceptional," as many places 

 apparently more humid (because they have a greater rainfall) 

 do not produce such extreme cases of melanism, while there is 

 no doubt that the humidity of the atmosphere in Yorkshire is 

 greater than its rainfall would apparently lead one to suppose 

 it to be. Hence I consider Mr. Dobree correct in considering 

 it " exceptional, and not affecting the general question ;" while 

 there is no doubt that Mr. Cockerell's suggestion is in the 

 main also correct, and that the atmosphere is sufficiently 

 humid to account for a great deal of the melanism which 

 occurs there. But I agree with Mr. Dobree in considering the 

 melanism of these counties exceptional, for a reason which 

 will appear directly. I have been informed by Mr. Porritt, 

 that " the rainfall of West Yorkshire is about 33 inches, and in 

 Lancashire much the same"; but "the rainfall in Cum- 

 berland is much greater ; and yet there are not such striking 

 melanic forms, although probably the soil retains the moisture 

 more in Yorkshire " (zV/ litt?). If this be so, although the rain- 

 fall of Yorkshire is less heavy, the general humidity of the air 



