PROGRESSIVE MELANISM IN LEPIDOPTERA. 207 



in the surrounding counties, and at Swansea. Only light recorded 

 from Worksop (Alderson), Lynn (Baker, Atmore), Norwich (Pitman), 

 Bury (Norgate), Colchester (Harwood), Kent (Hewitt), Sussex (Christy), 

 Marlborough (Meyrick), Wigtownshire (Gordon), Berlin (Kloos). 

 Very dark recorded as occurring rarely, Sheffield (Brady, Doncaster), 

 Hereford (Hutchinson), London district (Fenn, Partridge), Bristol 

 (Prideaux), Chilwell (Notts) (Pearson), Market Drayton (Woodforde). 

 The darkest form occurs regularly at Halifax (Halliday), Hudders- 

 field (Porritt, Mosley), Bradford, Barnsley, Eotherham (Hewett). At 

 Huddersfield, 45 years ago, only lightish forms were known ; a dark form 

 appeared some 30 years ago, and the fully smoky form, with no 

 markings, became frequent about 1890 (Porritt, Mosley). This 

 form seems to have appeared at York between 1900 and 1903 (Hewett, 

 Adkin) ; it was recorded from Wharncliffe about 1884 (South), 

 Oainsborough in 1891 (Fowler), Sheffield, 1896 (Brady, Doncaster), 

 and occurs at Great Ayton (Lofthouse), Selby (Hewett), Lancaster 

 (Forsythe), Macclesfield (South), Derby (?) (Hill, 1886), Burnley 

 (Clutten, only recently) ; a quite similar form is found in the Swansea 

 district, and the Vale of Neath, where the prevalent form is rather 

 dark, as in Yorkshire (Llewelyn, Hewett). It is said to be more 

 frequent in some seasons, and to be increasing more rapidly in some 

 districts than in others, e.g., at Huddersfield it is said to be increasing 

 (Porritt), at Sheffield, it is no commoner than 10 years ago (Brady, 

 Doncaster). Breeding experiments show some discontinuity between 

 the darkest form and the type; a black 5 -giving 70%-80%, black 

 ^ s and ? s (Hewett) ; another giving 5 ? and 6 g black, 10 g light 

 (South, Knt., 1894, p. 138). 



Amphidasys betularia. — According to Barrett, the type form only 

 was known until about 1848. The var. douhledaijaria appeared in the 

 Manchester district in 1850, at Cannock Chase in 1878, in Berkshire, 

 1885, Cambridge, 1892, Norfolk, 1893, Suffolk, 1896, London, 1897. 

 Abroad at Hanover in 1884, in the Netherlands, before 1888, and has 

 now reached Thuringia, Saxony, Silesia, etc. At Newport (Mon- 

 mouth), the two forms were about equally common in 1870; now 

 the black is found almost exclusively. Intermediates between 

 the type and donhledayaria, are recorded from many localities 

 where the black var. is found. According to Barrett, they 

 were formerly more frequent than now, and he suggests that they 

 have been superseded by the fully black form. When records of 

 intermediates are examined more closely, it is found that they are 

 of two types. The majority are of the type form, but more thickly 

 .speckled with black than in normal hetidaria, they show the typical 

 markings, and are, probably, to be regarded as dark fluctuations of the 

 type. True intermediates do, however, occur, and although the number 

 seen has been small, it suggests that they are more frequently males 

 than females. They may either have the forewings almost completely 

 black, and the hindwings pale, as in betularia, or the forewings may be 

 very thickly speckled with dark scales, which obliterate all definite 

 markings. These specimens have a blurred, smoky appearance, the 

 pigment, like that of di>iibledai/aria, being apparently less intense than 

 in the black specks in hetidaria. When douhledaijaria is crossed 

 with the type, in general no intermediates are produced, bat the 



