TRIFIDM. 251 



The present species is also very much more variable in 

 ground colour than the last, from a whiter grey to a deep 

 slate-grey or grey-black, but the markings are always dis- 

 tinctly deeper black and, in the vast majority of instances, 

 the ground colour, whether darker or paler, is uniform. In 

 some specimens, and more particularly in the paler forms, 

 the two stigmata are completely outlined, in others the 

 orbicular only, and in some, dark varieties more especially, 

 the usual partial outlines are much restricted. Usually the 

 hind wings vary darker, in some degree in accordance with 

 the blackening of the fore wings, but this is not invariable, 

 there being in some instances a sharp contrast. The blackest 

 specimens are obtained in the outskirts of London. In a 

 brood, reared by Dr. Chapman at Hereford, a number of 

 specimens in both sexes have the dagger near the anal angle 

 so much shortened that its upper end hardly extends over 

 the inner side of the black second line ; in these the first line 

 is distinctly duplicated, and the enclosed pale stripe very 

 conspicuously and obliquely shows itself in crossing the wing ; 

 the second line is also more angulated and flattened in its 

 upper portion This is a very remarkable aberrant form ; 

 Dr. Chapman calls it var. hidens. 



On the wing in June, July, and August, in one generation 

 emerging over a long period. I have no knowledge of any 

 second emergence within the year. 



Larva cylindrical, with distinct segmental incisions ; on 

 the back of the fifth segment is a long, conspicuous, slender, 

 upright tubercle, and on the twelfth a much shorter and 

 broader dorsal hump. Head large, rounded, shining, slightly 

 hairy ; all the usual raised spots of the body emit a few 

 blackish or reddish hairs. Colour greyish-black on the sides, 

 a broad lemon-yellow dorsal stripe is interrupted on the fifth, 

 twelfth, and thirteenth segments ; spiracular stripe broad, 

 whitish ; between these stripes are two transverse bright red 

 dashes on each segment ; the long tubercle on the fifth 



