1889.] 199 



the fir shoot, would no doubt spin up where most convenient. But 

 there remains a third difficulty, which apparently Mr. Barrett has not 

 noticed. He argues all along about these Scotch forms. My two 

 Newmarket specimens, by which my attention was first directed to the 

 subject, are not Scotch ; so that the argument drawn from the mar- 

 vellous variations observable in other Scotch insects falls to the 

 ground. Is it not odd that, if the Scotch insect is merely a form of 

 turionella, it should occur unchanged 50 miles south of where Mr. 

 Barrett has found turionella with even whiter hind-wings than in its 

 Surrey haunts, and barely more than 50 miles north of those haunts 

 themselves ? 



13, Cheyne Bow, Chelsea, S.W. : 

 January, 1889. 



[Mr. "Warren has obligingly given me the opportunity of looking 

 over this paper before it goes to the printer, and of thus adding a few 

 words. 



I am unable to find the differences in the form of fore- and 

 hind-wings of which he speaks. To my eye there is no appreciable 

 difference between southern and northern specimens in this respect. 

 I should judge that the proportion of specimens obtainable in the 

 south, of the small size of those from the north, is extremely small. 

 The same may be said with reference to the analogous case of Ypsipetes 

 elutata. 



The obscuration of rusty colouring, and, indeed, of all light 

 colouring, by the substitution of black scales, is so familiar and usual 

 a process in higher altitudes and latitudes, that I really wonder that 

 it should be brought forward as a specific character. It is especially 

 observable in the fore-wings of Xylophasia polyodon and Noctua 

 glareosa, and in the hind-wings in -N. xanthographa, not to mention the 

 paramount instance of the constant black variety of Amphidasys 

 betularia. 



It did not occur to me to make any remark with reference to the 

 two specimens of the dark form obtained by Mr. Warren at New- 

 market. I do not know the exact conditions under which they were 

 found, but the case seems to me analogous to that of the sudden 

 extension southward of Miocodia rubiginosana (Bouchardana), which 

 is reasonably supposed to result from the extensive planting of young 

 fir trees obtained from Scotland. It could not be expected that their 

 dark colouring would disappear immediately.— C. G. B.] 



