i8o LEPIDOPTERA. 



brown variety is that in the South of England, where it 

 chiefly occurs, it emerges from pupa at large in March or 

 April, and produces a partial second generation in July or 

 August, which is smaller, paler, and very imperfectly fur- 

 nished with the usual markings ; while in the same localities, 

 as well as elsewhere, the paler typical race emerges in May 

 and the beginning of June, and has a very partial second 

 generation in August. It is thoroughly established that the 

 specimens on the wing in March and April are not the pro- 

 genitors of those which appear very much more commonly in 

 May and June ; and thus this species has the singular habit 

 of producing parallel races, constant in their emergence from 

 year to year. Also, after much investigation, it is now made 

 certain that in Midland localities and in Cheshire and York- 

 shire, where the brown form is unknown, in those woods in 

 which the parallel earlier and later races are found — as for 

 iu stance in Delamere Forest and in some of the Yorkshire 

 woods — the earlier as well as the later race was originally of 

 the crmmy-irhltc type. Here, however, another strain of 

 variation comes in — one in which the brown dusting almost 

 or wholly disappears, and is replaced by grey or black. This 

 in Derbyshire and other Midland districts is manifested in 

 grey dusting in every degree from greyish-white to grey- 

 black, the markings in all but the darkest specimens being 

 still visible ; and this occurs in both parallel races where 

 these exist. Some of the specimens have curious and quite 

 irregular and unsymmetrical blotches of whiter colouring, 

 sometimes on the fore, at others on the hind wings. In 

 specimens so much darkened that the markings begin to be 

 absorbed, the white subterminal line resists the darkening 

 tendency and begins to be noticeable. This is still more 

 conspicuously the case in specimens from Glamorganshire, 

 where a more deep and smoothly blackened variety early 

 appeared — at first in the April race, more recently also in 

 the other — the usual markings being quite absorbed, the 

 surface smoky-black, and the nervures more deeply black, 



