132 LEPIDOPTERA. 



black variety began to be reared, and obtained in greater 

 numbers, there appeared also an intermediate form, the 

 ground colour white, or greyish-white, but so much obscured 

 by spreading of the normal markings and spots into blotches 

 and clouds that it was almost obliterated. This "mulatto " 

 form, in greater or less intensity, seems at first to have been 

 as common as the black ; yet more recently, with the increase 

 in numbers of the latter, it has almost disappeared, or has 

 become comparatively rare, being apparently absorbed by 

 the black race. Even where the black insect has been inten- 

 tionally paired with the normal, the produce has often been 

 divided between the two extreme forms, without a single 

 specimen of the intermediate. Yet the latter still occurs out 

 ■of doors. I saw, a few weeks ago, a boxful of specimens of 

 this species, one hundred and eighty in number, which had 

 been taken by Mr. J. Arkle at an electric light at Chester. 

 'Of these, one hundred and fifty were black, twenty-four 

 normal, and six intermediate. 



A male specimen which scarcely falls iuto any of these 

 lines of variation exists in Dr. Mason's collection ; it has the 

 thorax and abdomen broadly black, and very large black 

 clouds along the costa of the fore wings ; moreover one of its 

 antenna) is darker than the other. 



On the wing in May and June, and sometimes even till the 

 middle of July ; but it has been taken as early as the end of 

 March. 



Larva twiglike ; slightly enlarged at each extremity ; there 

 are two lateral projections on the ninth segment, two dorsal 

 on the twelfth, and on the thirteenth two small projectiug 

 points ; also small ventral warts on the seventh, eighth and 

 ninth segments, appearing largest when the larva is half- 

 grown ; edges of the sides between the prolegs fringed with 

 small whitish bristles ; head large, strikingly bifid, ferrugi- 

 nous at the sides and back ; face truncate and indented, 

 ochreous, shaded with ferruginous ; body variable in colour, 



