PEOGRESSrVE MELANISM IN LEPIDOPTERA. 



225 



(Hewitt), Church Stretton (Newnham), Bristol (Prideaux), all forms 

 about equally common. In Lancashire, Yorkshire, Durham (Hewett), 

 Cheshire (Tait), Notts (Pearson), Birmingham (Jordan), Stroud (Davis), 

 -Cambridge (Farren), the London district (Mera, Fenn), and Berlin 

 {Berlin Entom. Verein), the dark forms predominate, and are reported 

 to be more frequent than formerly in London (Fenn), Hartlepool 

 .(Eobson), Huddersfield (Porritt). At Hartlepool (Robson), Burnley 

 (Clutten), only the dark form now occurs. At Sheffield, the light 

 form has a darker grey than in the south (Brady). In Ireland, in 

 rsome places the light, in others the dark, form predominates (Kane). 



PoLiA CHI. — -There are two distinct dark varieties, svffasa and 

 ■oUvacea. Both occur in the north of England ; in some districts both 

 are found, in others, only one or the other. The typical light form 

 ■occurs in the greater part of Scotland (Aberdeen, Forres, Kintyre, 

 Wigtownshire, Kincardine), Ireland, Cumberland, Yorkshire, Burnley, 

 Lincolnshire (Boston), Norwich, Notts (Chilwell), Market Drayton, 

 Hereford, Devonshire. The variety snffusa occurs at Newcastle, scarce 

 (Rosie), Durham (Robson), Bishop Auckland, Birtley, Chester-le-Street. 

 Yorkshire — Middleton, Cleveland (Robson), Huddersfield, Halifax, 

 Bradford, Rotherham, Sheffield (Pori-itt), Chester (Arkle), but is appar- 

 ently nowhere actually prevalent. Its distribution is somewhat capri- 

 cious, ejj., at Huddersfield, about 30% are reported as rather dark, and 

 perhaps 6-7% very dark, but at Saddleworth, 12 miles away, only the 

 pale form occurs (Porritt). So on the hills to the south of Sheffield, 

 very dark specimens are rare or absent, but are not infrequent a few 

 miles away (Brady, Doncaster). At Huddersfield, the very dark 

 form appeared suddenly about 1890, but forms darker than the 

 type had occurred for many years. The extreme Huddersfield 

 form is not identical with sufiisa (Porritt). Var. nlivacea was 

 first described from Edinburgh in 1831 (Barrett). It occurred 

 at Hartlepool, nearly 50 years ago (Robson). Around Newcastle 

 it is now not much less common than the type (Rosie); it occurs at 

 Sunderland (Brady), Birtley, Chester-le-Street, Bishop Auckland, etc. 

 It occurs also at Huddersfield, Bradford (scarce), Sheffield (rare) 

 (Porritt), Bolton (Lanes.) (Allen), Lancashire (both scarce) (Forsythe). 

 In Durham, olivacea occurs chiefly near large towns, suff'usa on the 

 moors (Robson). Both forms seem somewhat discontinuous from the 

 type, but some intermediates occur. 



Aplecta nebulosa. — In the southern counties only the palest form 

 is found. In the midlands, and even in some localities in Berkshire, 

 the ground becomes grey instead of white, and this darkening is 

 intensified further north. The pale form reappears in Scotland (Suther- 

 land, Argyle, Barrett), (Wigtownshire, Gordon). It occurs together 

 with the grey type at Bristol (Prideaux), in Shropshire (Newnham), 

 North Wales (Arkle), Worksop (Alderson). In Ireland, the pale type 

 is prevalent ; dark specimens recorded from Galway (Kane, Dillon). 

 Only the grey form, varying somewhat in intensity, recorded from 

 Market Drayton (Woodforde), Sheffield (Brady), York (Hewett), 

 Newcastle (Rosie). In addition to the prevalent grey, verj^ dark 

 specimens found at Huddersfield (Porritt), and apparently in the 

 South - west Riding generally and occasionally at Lancaster 

 (Forsythe) ; in south Yorks these are now commoner than formerly. 

 In Cheshire (Delamere), a rather dark form - is prevalent, and an 



