190 



ARION ATER. 



(generally speaking, its distribution has been stated by the late Prof. 

 Von Martens to range witli tliat of the oak, about the isotherm of 42" 

 Fahrenheit, but it is probal)]e that this statement now needs revision, the 

 range of this s])ecies apparently extending beyond what was previously 

 known, wiiile it has also been recorded as ascending the Pyrennean Moun- 

 tains to a height of more than 6,000 feet. 



In Norway, the red variety only reaches as far as the fiftieth parallel, but 

 the black variety has been noted to extend to 68" north lat., while the var. 

 alba is recorded from Tromsdalen, 69° 50', its occurrence supporting 

 Gredler's view that albinism is often an indication that the sj)ecies has 

 reached the limit of its geographic or vertical range. 



It is known to occur in Germany, Belgium, Holland, France, Austro- 

 Hungary, Switzerland, Denmark, Norway, Sweden, North Italy, Spain, 

 Portugal, and the British Isles. 



It has also been recorded for Russia, from the Ukraine, Finland, the 

 Baltic provinces, and elsewhere, by Kaleniczenko, Nadjeschin, Kawall, and 

 other writers, but, according to Simroth, in every case erroneously. 



Geographical Distribution 



of 



Avion aler (L.). 



Recorded Distribution. 

 Probable Range. 



Fic. 206. 



BRITISH ISLES. 

 In the British Isles this species is universally distributed, being found 

 in all the one luuidred and forty-nine comital and vice-comital districts 

 into which the country lias been divided, and has even been collected by 

 Mr. W. K. Clarke on the Flannan Isles, the most westerly of the Outer 

 Hebridean islets. This coniprehensive survey of specimens has emphasized 

 the dull, dark forms as the characteristic colouring in these islands ; the 

 brighter coloured varieties being more plentiful in the soutiiern counties, 

 and during warm diy summers, while the greater prevalence of the fasciate 

 or juvenile colouring in Ireland shows the more primitive character of the 

 fauna and its greater remoteness from the theatre of the most evolutionary 

 activity. 



