1S96.] Kane. — Melanism in Camptogranuna bilineata. 79 



black, with the usual white pattern obliterated excepting pale 

 outlines round the stigmata, and gre3^ish discontinuous traces 

 on the costa, subterminal band, and nervures, not however 

 inclining to ochreous as in D. carpophaga. This is a form of 

 great interest, as in all ni}^ experience of this species hitherto 

 I have found it but slightly variable in colour and markings 

 round the Irish coast. That a purely maritime species (in 

 Great Britain), maintaining a fairly constant character in its 

 distribution over all varieties of our rock-formations and 

 climatic conditions, should here develop well-marked melan- 

 ism would vsuggest the operation of some special local 

 influence. But on the cliffs of the mainland opposite, of 

 similar rock, a few miles distant onl};, I have taken specimens 

 of the type. Isolation therefore, as in the case of Campto- 

 gi'amma bi/i7ieata, seems to be the chief probable factor at 

 work. Xylophasia monoglypha also offers remarkable testi- 

 mony in the same direction. Hitherto I have been unable 

 to detect any topomorphism in the occurrence of the varieties 

 of this polymorphic species. But on two of these islands I 

 found no pale forms among over forty examples secured. 

 Most belonged to the v. brunnea, Tutt, and varied to black 

 forms. A few were of paler brown with the whitish markings 

 usually present in the commonest forms reproduced in paler 

 tone of the ground colour. The melanochroism is most ap- 

 parent in the absence from this series of any gre}' marked 

 specimens. 



Camptogramina bilineata shows a tendency to develop dark 

 scaling not only on the cliffs of Kerr}^ but also in the vast 

 tracts of bog and moor of Connemara. It is not found in the 

 wet swamps, but occurs on the broken banks of cut-out peat, 

 and on dry heather slopes of rising ground. Near Aasleagh 

 and Glendalough the varieties of the banded form with black 

 edges are very striking and numerous, and with them clouded 

 and black striated forms are frequent, similar to those of Unst. 

 A parallel phenomenon is presented by the dark variety scotica 

 of MelitcEa aurinia, which, in Ireland, I have only noticed to 

 occur on the margins of heathery bogs of ample extent ; while 

 the very brightly coloured v. prcsclara affects green marshes 

 and wet pastures. It therefore seems probable that a propor- 

 tion of the variable species that occur in any dark moorland 



