76 SCIENCE PROGRESS 



a factor of selective value. When, therefore, we find an animal 

 coloured yellow, it may well be that it appears inconspicuous 

 to its enemies who cannot distinguish yellow from green, though 

 to our eyes it may seem conspicuous. There is ample evidence, 

 especially amongst birds, that yellow is not a conspicuous 

 colour, though by reason of its high luminosity it is sometimes 

 used to produce conspicuousness, and in the vast majority of 

 these cases it is sharply cut off from the rest of the animal's 

 colouration by bands or large areas of black. 



The Consideration of Orange 



Orange comes next to yellow in frequency of occurrence. 

 It differs from yellow in that it is much less often found laid 

 down in large areas, and this is due to the fact that orange is 

 not found giving rise to conspicuousness in the Pierine as is 

 yellow (see diagram No. 7). The fact that the orange is not used 

 in this manner lends support to the conclusion that large 

 yellow in the Pierines is conspicuous by reason of its high 

 luminosity, rather than by its colour. Large orange is occasion- 

 ally used in a conspicuous manner in the Euploeinae with a 

 marginal band of black, and then is very light in tone and 

 approaches towards red rather than yellow. 



Large orange is chiefly found in the Argynninae occupying 

 the centre of the wings and surrounded by a pattern of black 

 spots. In the Satyrinae, centrally placed orange is also found, 

 but so encroached upon by marginal pattern that only moderate 

 areas are found (see diagram No. 4). Just as yellow with black 

 appears brown at a distance, so orange and black will become 

 copper-brown, simulating the colour of dying vegetation and 

 giving rise to an inconspicuous effect. Orange and yellow are 

 laid down in moderate areas chiefly in the forms of bars crossing 

 the wings, as in Kallima, or in apical blotches as in some of the 

 Pierines. The significance of these arrangements of colour is 

 not clear ; in Kallima the orange bar is in juxtaposition to an 

 area of blue, its complemental colour, and this will again be 

 referred to in Part II. 



Small orange is found in the vast majority of cases, as a 

 ground on which a pattern, usually of black spots or bars, is 

 laid, as in the Argynninae, evidently for purposes of conceal- 

 ment. Like yellow, the rarity with which orange is used con- 



