284 THE CAUSES WHICH 



black spots run into a band ; a specimen of the Yellow Shell 

 [Camptogramma Bilineata) in my possession has the lines run 

 together so as to form two black bands^ and some of Cerostoma 

 vittella have the dark markings extended from the inner margin 

 half over the wing ; but many more striking varieties occur from 

 time to time.* Nocfuina are notably blackish near towns ; for 

 example, Noctua glare osa taken near Barnsley had the fore- 

 wings chocolate-brown in place of pinkish grey. The isolation 

 of islands is no less congenial to the establishment of variety, and 

 these reproduce their like. In England and Scotland the aberra- 

 tions of three butterflies, two of which are scarce, the Large 

 Copper, the Purple-Edged Copper, and Blue Poli/ommatus 

 Artaxerxes are noticeable ; the second differing from the Conti- 

 nental type Eiirydice in having purple instead of black wing- 

 margins. Our yellow variety [Stramineola) of the Footman 

 {Lithosia griseola) is also not known to occur in Europe. Indi- 

 genous species are likewise distinguished by melanism. In 

 Ireland the Marsh Eritillary, for instance, is present as a variety 

 {Hibernica, Birchall) , which has the fulvous wing-colour replaced by 

 white ; and this kind is larger than the English type, and much 

 larger than the Scottish. On small islands butterflies have been 

 considered to have enlarged wings. This has been affirmed of 

 those of Madeira by Mr. Woolaston, and I find a note by Mr. 

 Butler to the effect that si:)eeimens of our Small White from 

 Japan were found to exceed the alar expanse of English examples 

 by one-third, and that Pale Clouded Yellows from the same 

 extreme outpost of the Old World were likewise larger. But it 

 should then be noticed these islands lay far south in latitude, a 

 consideration that might cause us to hesitate in accepting the 

 premises on Dr. Darwin^s explanatory theory that the wings are 

 acquired from battling with the winds. 



Albinism, the converse of melanism, where a pale ground 

 colour is increased at the expense of the darker tint, is attributed 

 to the species happening to frequent localities with light-coloured 

 soil. It is active on the English Chalk Downs, where it produces 



* A singular melanic variety of the Painted Lady, bred on September 3rd, 1879, 

 from a larva taken near the locks on the River Lea, at Clapton Park, had the 

 wings bordered with white spots, as regards the hind wing evidently caused by 

 replacement of the black. — Ji>itomologist for April, 1880. 



