waving leaves, sunlit and bright above dark shadowy interstices. Again, 

 when the Heliconius is quietly perching, its yellow marks may produce the 

 effect, additional to that described by Beebe, of vistas through shadows or 

 dark twigs to a more distant sunny background. In fact, this effect is inter- 

 changeable with the other (that of light details or marks laid on or standing 

 above a shadowy background) in almost all the numberless obliterative pat- 

 terns of this general character, both on butterflies and on other animals. 

 According to the creature's position and the character of its background, at 

 any given moment, its pattern will incline toward one or the other of these 

 two equally deceptive and obliterative effects. 



The beautiful South American Metamorpha dido, already mentioned 

 among 'close-folding sedentaries' wears on its upper side a bolder green- 

 and black-laced pattern, which makes it extremely 'dim' and elusive in its 

 flight amidst foliage. But this pattern must also on occasions serve the but- 

 terfly at rest, for though cruder than that of the underside, it is too delicate 

 in detail to be merely a flight-pattern. For flight of course tends to cancel 

 the visibility of markings, blurring and blending forms and colors, and even 

 on the most slow-moving butterflies only big, bold patterns can maintain 

 a clear effect in flight. Many of the more aerial butterflies have such big, 

 bold patterns, however. In addition to the t5^es described and figured 

 above, those represented by some of the other HeliconidcB, and some of the 

 South American green and black and red PapilionidcE, are notable. A but- 

 terfly thus patterned with black and yellow (e. g., Heliconius sara), or with 

 black and green and red (e. g., Papilio gargasus), will never at any point in 

 its airy course relieve clearly, in full contour. As it passes across shadowy 

 interstices amidst vegetation, its black will disappear, leaving in sight only a 

 skeleton pattern of yellow, or green and red; and while it is passing brightly 

 lighted leaves and flowers only the black will show. Thus the watching eye 

 is condemned to see only flickering glints of color, instead of seeing the whole 

 form of the moving insect, as it would were the insect monochrome. Such 

 constantly repeated metamorphoses of aspect, amid the vegetation's varying 



222 



