traced outlines of the wings, and helping all the faintly-patterned part of their 

 broad surface to 'melt away' into the background. (See Fig. 132.) The 

 sharply visible ocellus, therefore, either seems to be standing alone in air, or, 

 more characteristically, 'recedes' with the rest of the wings' surface, and passes 

 for a detail of the background. In either case, although in itself highly visible, 

 it looks like nothing edible to insectivores, while by its very brilliance it masks 

 and hides the organic forms of its wearer. Such is probably the main use of 

 major ocelli in the disguising costumes of butterflies. Minor ocelli are often 

 purely and simply details of background-picturing. Some, for instance, seem 

 closely imitative of gleaming dewdrops, and of dewdrops surrounded by shadow, 

 while others look like holes in leaves — dead or living, as the case may be. Some, 

 especially of moths, are actually transparent. Between minor and major ocelli 

 there is a smooth gradation, a complete chain of intermediates, and here as in 

 all such cases it is impossible to know just where one function ceases and the 

 next begins. Indeed, the two functions are more or less coordinate and inter- 

 woven throughout this whole gradation, for the biggest, most specialized 

 'dazzling' ocellus achieves its full service only when it passes for a detail of the 

 background, and, on the other hand, the smallest accessory detail-picturing 

 one has a share of intrinsic obliterative or 'dazzling' effect.* 



The multifarious obliterative devices of color and pattern worn by butter- 

 flies and moths are often seconded by modifications of external form, by 

 appendages, as in the case of birds and other animals. But the lepidopter's 

 appendages are much more limited in kind, consisting almost exclusively of 

 modifications of the outer edges of the wings. These are cut-in, in gentle 

 curves or sharp, angular notches, or extended outward in longer or shorter, 

 broader or narrower 'jags' or "tails," of many forms; in short, they are altered 

 much and variously from the simple, average butterfly-shape. On the other 

 hand, may it not be that even the 'normal' butterfly wings, so grotesquely 

 large for the body, and so wonderfully marked for obliteration, are themselves 



* This book aims to discuss only concealing-functions, though not forgetful of the obvious un- 

 limitedness of the uses that Nature must make of every detail.— A. H. T. 



230 



