264 SCIENCE PROGRESS 



replaced by yellow in the female or young, as in Eos fuscata 

 and Charmosyna stellce. 



The Nectariniidae and Loriidae were chosen, because in the 

 first family there is great sexual dimorphism in colour, whereas 

 in the Loriidae the sexes are almost entirely alike. A comparison 

 of the colour distribution in these two families confirms that 

 which has already been shown to hold as regards sexual dimor- 

 phism in the Indian Lepidoptera, namely, that the differences 

 between males and females are entirely a matter of differences 

 in conspicuousness. In the Nectariniidse, the differences 

 between males and females appear to be exactly similar to the 

 differences between the colouration of the Loriidae and of an 

 inconspicuous group of birds like the Warblers. 



Fig. r. 



D. , dorsal area ; L. , lateral area ; V. , ventral area. 



The main features which have been brought out by this 

 consideration of animal colouration are : that the enemies of 

 insects have or have recently had only trichromic colour vision, 

 as instanced by the use of brown against green backgrounds, 

 and the use of yellow in association with inconspicuous arrange- 

 ments of pattern ; that in animals red is chiefly used to produce 

 conspicuousness at low illuminations, blue at high illuminations, 

 whereas in flowers the reverse occurs ; that patterns, composed 

 of complemental colours laid side by side, are inconspicuous 

 at long range, that is beyond their blending distance, but very 

 conspicuous at short range or within their blending distance ; 

 that sexual differences of colour in birds and insects when 

 considered from the point of view of colour vision can be entirely 

 accounted for on the basis of a difference in conspicuousness. 



