382 LEPIDOPTERA. 



beyond the inidiUe, and faint indicritions of others ; hind 

 niartrin sharply dotted with black : cilia greyish-white. 

 Female smaller, its thorax and abdomen thicker, all the 

 winos shorter and more ovate; the lines of the fore wings 

 usuallv formed into three narrow hands, much darker, and 

 frequently emphasised by l)lack blotches; the hind wings 

 more definitely banded. 



Underside of the fore wings smoke-colour ; costa spotted 

 with smoky-white; the transverse stripes of the upper side 

 faintly visible. Hind wings dusky white, witli two slender 

 grey transverse lines on the middle area, and a grey band 

 beyond. Body and legs pale brown ; tarsi black-brown 

 spotted with white. 



Variable in the deptli of ground colour, as already suggested, 

 from silvery white to grey or smoky-grey, sometimes even to 

 f|uite (lark grey, very often shaded therewith : the markings 

 •are more ri-liable. but in the speciiriens with dark ground 

 colour, are much obscured : occa.sionally, however, the sti'ipes 

 are drawn together and form a broad central dark band on a 

 pale ground ; in others they are partially obliterated — in 

 which case, sometimes, the black dashes u])on the subcostal 

 and median nervnres come out very sharply. Some of these 

 last, from the Isle of Lewis, have the stripes broken up into 

 dark wedges or spots, and are e.xceedingly pretty. It is a 

 very curious circumstance that where a birch wood occurs 

 npon tlie wild heathery moors frecpiented by this species, 

 a rather larger race is found, of great beauty, more than 

 usuallv clear white or ci'eamy-white, and with veiy clear 

 markintrs. This form has. like two different varieties of the 

 last species, lieen called l)y the name of ouhimvaria, and 

 supposed to lie a distinct species ; and it is very possible that 

 this actually is the form described by Guenee. The parallel- 

 ism of variation between this and 0. dilutata is remarkable, 

 and the onlv reliable distinctions in the wings seem to be in 

 their breadth and their degree of glossiness. ^Ir. L. 15. Prout 

 has specimens which structurally agree with this species, yet 



