riUFID.E. 305 



marked variation ; often in the various shades of grey, these 

 remain conspicuously white, so that the slate-grey, or smoky- 

 gi-ey surface is broken up and beautifully set off, and in more 

 black-grey examples this results in producing remarkably 

 handsome specimens; but quite as frequently these lines 

 share the general suffusion of grey — light, slate, smoky or 

 blackened — producing a smooth, uniform, even gloomy, 

 appearance — which even the dark markings scarcely relieve. 

 Intermediates are of course found — one from Mr. G. T. 

 Porritt's collection is before me, a male black-grey to the sub- 

 terminal line, which is brightly white, with its edging of black 

 arrow heads also sharply defined ; another from the same collec- 

 tion is as smoothly and regularly blackish-slate colour as the 

 well-known London form of Acronyctapsi, and wonderfully like 

 it. These are both from South Yorkshire, as are many other 

 curious and interesting dark intermediate forms and also 

 those having all the white stripes conspicuous on a very dark 

 ground. In all cases the thorax agrees with the fore wings, 

 but the hind wings, though sometimes darkened, are by no 

 means always so. Stephens in his Illustrations describes as a 

 new species, under the name of olivacea, a specimen of this 

 species of an olive-green colour with the usual white lines 

 conspicuous. He states that it was taken at Cramond near 

 Edinburgh, and is the only specimen which he has seen. 

 Apparently it is a rare form, and I cannot say that I 

 have seen in any collection a specimen fully agreeing 

 with Stephens's description. A faint olivaceous tinge is 

 sometimes observed, but the name olivacea has often been 

 used for the slate-grey varieties. Another rare form is 

 yellowish-grey or brownish -grey, but in this the white lines 

 are seldom distinct. 



On the wing in August and September. 



Larva rather slender, cylindrical, though tapering a little 

 at either end, the head rounded and the antennal papillae well 

 developed ; the segmental divisions very delicately defined as 



VOL. IV. u 



