ARTICLES 



73 



Species. 

 EUPLOEINjE. 



9. Nemana simulatrix 



10. Tronga nicevillei . 



11. Penoa alcathoe 



12. „ menetriesii . 



13. Narmada montana . 



.Extent of Black Colouration. 



whole of both wings. 



centre of forewing, with margin of 



white spots, 

 whole of forewing. 

 whole of forewing. 

 whole of forewing, except for a few 



very small white spots. 



Large areas of black appear to be in almost every case laid 

 down in a manner which results in a conspicuous appearance. 

 Those examples found in the groups considered separately 

 (diagrams Nos. 3 to 7) are shown in table No. 1 ; with the excep- 

 tion of No. 10, there is a complete absence of an associated 

 marginal pattern ; either the whole wing is coloured black, or 

 a pattern is present as in No. 7, which cannot result in a con- 

 spicuous appearance. No pattern or colouration is thus found 

 associated with large areas of black which will in any way 

 counteract the conspicuous appearance which large areas of 

 black have against natural backgrounds. 



The Consideration of White 



White is the third most commonly used colour ; it is found 

 in small areas in 83 per cent, of the cases and almost entirely 

 in the form of marginal patterns, ocelli, and other small markings 

 associated with small areas of black. An advantage in con- 

 cealment, of the use of white in this way, depends upon the 

 following facts : 



If a red object be viewed against a yellow background, it 

 is seen that the red near the yellow becomes yellowish, and the 

 yellow near the red reddish. This diffusion of colour occurs 

 with all colours; it is, however, best seen when white is used, 

 because it changes from being colourless to becoming coloured. 

 If a narrow white line be drawn across red and blue back- 

 grounds, the white across the red will appear pale red, and 

 across the blue, pale blue. It follows that an insect presenting 

 a marginal pattern of black and white will at a distance be 

 seen to have a grey border fading on the one side into the colour 

 of the background and on the other into the colour of the 

 rest of the insect's wing. Not only in colour will this graduation 

 occur, but also in tone, as shown in previous papers (loc. cit.). 



