BOARMID.'E-BIS TON. 1 29 



absent ; — or else the dusting and spotting is increased in 

 various degrees, sometimes on the fore wings only, often on 

 the hind also, and at the same time the transverse lines of all 

 the wings, which ordinarily are obscure, come out with great 

 sharpness and angularity, and indeed absence of grace. 



About another line of variation there is some perplexity. 

 In it all the usually black markings and dottings are yellowish- 

 brown ; and the perplexity arises from the circumstance that 

 this colour can be produced, in this species, with great ease 

 by exposure to the fumes of chlorine. Under this treatment 

 every black marking soon becomes pale brown ; and there 

 has been doubt whether some of the varieties known have 

 not been so produced. Yet it is positively asserted of some 

 specimens that they were captured, or reared, of this colour, 

 and I have seen one of quite a different hue, but yet with a 

 distinct tinge of brown, which was taken at Hawick by Mr. 

 J. G. Gordon. It is distinctly stated in the Entomolorjist, 

 1889, that this form — called there the buff variety — was reared 

 at Manchester, by local collectors, in considerable numbers 

 between 187i and 1880, and that then the strain died out, 

 and this statement is in accordance with that published in 

 Science Gossip, 1878, by the captor of the first specimen. 



Very different has been the fortune of a still more striking 

 variety, a form in which the ground colour of the fore wings, 

 and of the greater part of the hind wings, has changed com- 

 pletely from white to smoky-black; while the markings — 

 the transverse lines, the deep black spots, clouds, and dust- 

 ing — have totally disappeared, the fore wings having become 

 smooth smoky-black, with the nervures deep black ; and the 

 hind wings paler smoky-black, or smoky-grey, with frequently, 

 though not always, some white towards the front margin ; 

 the thorax and abdomen also have become black, and in some 

 instances the only white portion remaining is the face, or its 

 lower portion, and a round clear white spot at the extreme 

 base of the costa of the fore wings ; in other specimens this 

 spot also is absent, and the face or its lower portion, or even 



VOL. VII. J 



