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atoms ; the base of the posterior wings is always more free from 

 them than are the other parts of the wings. In one form the 

 black atoms are so small and few in number that the insects 

 look entirely white ; at the other extreme specimens occur, in 

 which they are so numerous that the color appears black, cov- 

 ered with thinly scattered white specks ; in still others the black 

 atoms lose their identity and the ground color becomes uniform 

 gray or blackish gray ; but in a large series these extreme forms 

 are connected by so many intermediate links, that shade gradu- 

 ally into each other, that it is impossible to draw anywhere the 

 line which separates them from each other. In one curious 

 variety the black atoms are massed together into small blotches; 

 the nervules are black and contrasting and appear like a net- 

 work connecting the median lines. Individuals having the usual 

 ground color, but in which one or more of the nervules are 

 accompanied by a black band, are not infrequent. In one 

 remarkable male the ground is uniform blackish gray, and even 

 the fringe is gray and not chequered as usual ; the ordinary 

 lines are indistinct and diffuse, and each accompanied by a dis- 

 tinct white line which makes the specimen very conspicuous ; 

 in another, a female, the ground is the same, but the white lines 

 are absent. 



After the ground color, the median lines show the most vari- 

 ation. Ordinarily they are situated at a nearly equal distance 

 from one another and from the base and external margin ; some- 

 times they are connected by a fine submedian dash ; in one 

 strongly marked specimen they actually touch each other ; on 

 the other hand, in two females, they are so widely separated that 

 the median space occupies fully three-fourths of the surface of 

 the anterior wings. The exterior line is always sharply dentate 

 outwardly ; in some specimens it is narrow and clearly defined 

 inwardly, in others it is very thick and heavy, and in some 

 individuals of the latter form it is strongly suffused. The inte- 

 rior line is always thicker than the outer line, but it visually has 

 its lobes distinct ; occasionally, however, it is so much suffused 

 that the form of the lobes is lost ; in one pale specimen this 

 line, as well as the exterior, is thin, and both are nearly obso- 

 lete. 



