IN THE BRITISH ISLANDS. 61 



black, the other, in which the opposite conditions take place, the central 

 area being black, and the basal and outer areas grey, unless 

 indeed a black form with a pale brown extreme outer margin is still 

 more striking. The grey and black varieties are not difficult to classify, 

 but the fuscous and brown forms are very puzzling. The hind wings 

 of the male vary from whitish-grey to dark grey ; nervures slightly 

 darker ; lunule variable in intensity but generally distinct. Those of 

 the female are dark grey ; nervures dark, lunule generally distinct. 

 Incidental varieties occur pretty freely, e.g., the dark forms generally 

 have the transverse strigae very indistinct, but occasionally one gets a 

 black form with the pale transverse lines standing out strikingly 

 pale, while again, some of the dark forms have the nervures very pale, 

 thus giving the specimens a very characteristic appearance. Classifying 

 the varieties we find the following are the most striking forms : 



A. Ground colour whitish-grey. 



1. Transverse lines more or less obsolete, sometimes entirely so, 



stigmata distinct, not irrorated with black scales = var. 



davigerus, Haw. 

 2. Transverse lines distinct, stigmata distinct, much irrorated with 



black scales especially along the costa = var. irrorata-pallida. 

 3. Basal and outer areas black, central area (containing stigmata) 



pale whitish-grey = var. virgata-pallida. 

 4. Basal and outer areas pale grey, central area black = var. sincerii, 



Frr. 



B. Ground colour fuscous or smoky-grey. 

 1. Transverse lines more or less obsolete, sometimes entirely so, 



stigmata distinct, not irrorated with black scales = var. obsoletd- 



fusca. 

 2. Transverse lines and stigmata distinct, much irrorated (especially 



costal area) with black scales = var. irrorata-fusca. 

 3. Transverse lines and stigmata suffused and almost lost in the 



unicolorous ground colour = var. subfuscus, Haw. 



C. Ground colour reddish-brown. 

 1. Transverse lines and stigmata distinct, slightly irrorated with 



black scales = var. brunnea. 

 2. Transverse lines and stigmata distinct, ground colour pale brown, 



costal area dark reddish-brown = corticea, Hb. (the type). 

 3. Much suffused with black scales, transverse lines and stigmata 



very indistinct = var. suffusa-brunnea. 

 4. With brown basal and outer areas and black central band = var. 



obscura, Freyer. 



D. Ground colour black. 

 1. Black, with pale brown extreme outer margin = var. brunnea- 



virgata. 



2. Black, with paler veins = var. venosa. 

 3. Black, with pale transverse lines = var. transversa. 

 4. Entirely black, with still more intense stigmata = var. nigra. 



The above list will be found to contain the greater number of our 

 varieties, but there are so many intermediate forms that it is impossible 

 to classify them all. Hiibner's type has the " anterior wings of the 

 ground colour pale brown, with a very slight reddish tinge. A tiny 



