patterns. Dark is conspicuous against light, and vice versa — accordingly, 

 light-colored butterflies are apt to have dark tips and borders, with such in- 

 ternal contours as work to bely the insect's form when these markings 'merge' 

 with dusky backgrounds, while dark-colored butterflies are apt to have cor- 

 responding light-colored markings. (See Figs. 1 30-1 31.) As we have seen 

 in earlier chapters, a living animal in nature is subject to momentary vicissi- 

 tudes of dark and light 'relieving.' When one side of a bird shows dark 

 against its background, the other side, seen from the opposite direction, is 

 very apt to be 'relieving' light. Hence, in very many cases, the best a crea- 

 ture can have in the way of generalized disguise is the clearest development 

 of 'ruptive' pattern, made of sharply contrasting light and dark marks. It 

 is this 'ruptive' effect that seems chiefly aimed at in the costumes of many 

 butterflies, though the resultant appearance is nearly always of adequate 

 'picture '-pattern. Their background is to be a changing patchwork of 

 dark and light, and they themselves are to be both shadowed and lighted, in 

 rapid, ceaseless alternation; hence they must wear both dark and light in 

 sharply contrasted, form-belying patterns. 'Tip-clipping' bands of dusky 

 are very characteristic of light-colored butterflies, including some which bear 

 a mimetic likeness to single flowers. Of such mimics there are doubtless 

 many. But this flower-like-ness is seldom or never minutely perfect in the 

 sense of the leaf -like- ness of Kallima, though sometimes very effective. Cases 

 of this sort may be found among field butterflies, notably the Pierince. These 

 are usually yellow or white — the commonest colors of flowers — with scanty 

 markings. Their fore-wings, however, in the cases in point, are 'clipped 

 down' to a shape more normal to flower petals by diagonal dark tips. That 

 is, these tips, being of the regulation 'interstitial shadow color,' strongly 

 tend to look detached from the light-colored wings, and merged with the shade 

 beyond. Often these dark rims or tips — as also others of the larger shadow- 

 picturing patches of dark color on butterflies — contain small markings; dim 

 ones, like faint pictures of more or less distant plant-details in shadow; bright 

 ones, like lighted near details above the shadow; pure white dots which 



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