PROTECTIVE COLOEATIOK'. 



11;3 



but this is a fact which may be made use of in several ways. 

 If Mr. Poulton* is right in assigning a protective value to the 

 bright-coloured wings of butterflies " as a conspicuous mark 

 easily seized by an enemy, and yet readily tearing without 

 much injury to the insect," it seems unnecessary to pay much 

 attention to the supposed utility of protective colours, such as 

 are shown by the Kallima or the Green Hairstreak. 



The conspicuousness of the white butterflies is, however, 

 diminished by their fondness for settling upon the yellow and 

 white flowers of cruciferous plants ; but they cannot be regarded 

 as good examples of protective coloration, as they fly much and 

 are, of course, conspicuous during flight. Both Mr. Wallace 



Fig. 6. —Bctiiliiaui delphln. 



and Mr. Poulton have dwelt upon the protective value of 

 white under certain circumstances. White eggs laid in an 

 open nest such as the pigeon builds, and the white under-side, 

 of many pelagic fish, of whales and dolphins (fig. 6), and even of 

 aquatic birds such as the penguin (fig. 7), are stated by these 

 writers to be inconspicuous when seen, as they would naturally 

 be, from below, and against a bright sky. It appears, however, 

 that this is really not the case. If snowflakes, which are of 

 a purer and brighter white than any egg, are watched as thej- 

 fall from the sky, which is naturally overcast and dull, they 

 appear almost black. If we can imagine for a moment the 

 * " Colours of Animals,"' p. -!05. 



