its vigilance and is sitting more or less inert, that the pattern of its under- 

 side is displayed in full. Also, the side view is apt to have a somewhat more 

 distant background than the full top view,* and hence requires a more deli- 

 cate pattern for ' obliteration.' 



Sun-flecks are another important feature in these picture-patterns of the 

 NymphalidcE, etc. They are big circular marks of yellow or whitish, some- 

 times rimmed with violet or blue, and set in leaf-shadow color. The blue 

 border is a mere intensified rendering of the sky-tinged rim around real sun- 

 flecks, which are in fact camera-obscura images of the sun surrounded by 

 blue sky. Such markings are worn for instance by Nymphalis bolina and by 

 the male of Hypolymnas misippus. Usually, as in the case of H. misippus, 

 the encompassing dark tone (with or without a skyey rim) ends in sharp 

 contrast against the spot; sometimes, however, it is blended into it, as is the 

 case with real sun-flecks also. Then there are sun-streak pictures — mark- 

 ings that depict sharp ribbons of sunlight alternating with bands of dusky 

 shadow. Patterns of this kind are a most characteristic element of some 

 woodland scenes, particularly in tropical woods, amid fringed palm leaves, 

 and other, smaller, finely pinnate foliage,— and bright pictures of them are 

 worn by some of the butterflies inhabiting these forests. Heliconius chari- 

 tonia, of the West Indies, etc., is a fine example. Indeed, the disguising- 

 coloration of this or a closely allied butterfly has been, ere now, in part, well 

 and accurately analyzed and described — by Mr. C. W. Beebe, of the New 

 York Zoological Park. But such a costume as Heliconius charitonia wears 

 is not limited to the single function of still-sun-stripe-and-shadow picturing 

 described by Mr. Beebe, admirably though it serves that function. It is also 

 highly ' obliterative ' as the Heliconius flies about rather slowly amid feath- 

 ery, sunlit foliage. The irregular and not rapid motion of the butterfly's vividly 

 striped wings fits into and merges with the mazy scintillations of the fine-cut, 



* Because the butterfly is likely to be in closer contiguity with the nearer details of its back- 

 ground when flatly outspread, than when folded and projecting outward perpendicularly from its 

 perch. 



221 



